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Quest towards the design and synthesis of functional metal-organic materials

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Title:
Quest towards the design and synthesis of functional metal-organic materials a molecular building block approach
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Book
Language:
English
Creator:
Sava, Dorina F
Publisher:
University of South Florida
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Tampa, Fla.
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Subjects / Keywords:
Single-metal-ion based molecular building block
Zeolite-like metal-organic frameworks
Porosity
Hydrogen storage
Topology
Dissertations, Academic -- Chemistry -- Doctoral -- USF   ( lcsh )
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bibliography   ( marcgt )
non-fiction   ( marcgt )

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Summary:
ABSTRACT: The design of functional materials for specific applications has been an ongoing challenge for scientists aiming to resolve present and future societal needs. A burgeoning interest was awarded to developing methods for the design and synthesis of hybrid materials, which encompass superior functionality via their multi-component system. In this context, Metal-Organic Materials (MOMs) are nominated as a new generation of crystalline solid-state materials, proven to provide attractive features in terms of tunability and versatility in the synthesis process. In strong correlation with their structure, their functions are related to numerous attractive features, with emphasis on gas storage related applications. Throughout the past decade, several design approaches have been systematically developed for the synthesis of MOMs.Their construction from building blocks has facilitated the process of rational design and has set necessary conditions for the assembly of intended networks. Herein, the focus is on utilizing the single-metal-ion based Molecular Building Block (MBB) approach to construct frameworks assembled from predetermined MBBs of the type MNx(CO2)y. These MBBs are derived from multifunctional organic ligands that have at least one N- and O- heterochelate function and which possess the capability to fully saturate the coordination sphere of a single-metal-ion (of 6- or higher coordination number), ensuring rigidity and directionality in the resulting MBBs. Ultimately, the target is on deriving rigid and directional MBBs that can be regarded as Tetrahedral Building Units (TBUs), which in conjunction with appropriate heterofunctional angular ligands are capable to facilitate the construction of Zeolite-like Metal-Organic Frameworks (ZMOFs).ZMOFs represent a unique subset of MOMs, particularly attractive due to their potential for numerous applications, arising from their fully exploitable large and extra-large cavities. The research studies highlighted in this dissertation will probe the validity and versatility of the single-metal-ion-based MBB approach to generate a repertoire of intended MOMs, ZMOFs, as well as novel functional materials constructed from heterochelating bridging ligands. Emphasis will be put on investigating the structure-function relationship in MOMs synthesized via this approach; hydrogen and CO2 sorption studies, ion exchange, guest sensing, encapsulation of molecules, and magnetic measurements will be evaluated.
Thesis:
Dissertation (Ph.D.)--University of South Florida, 2009.
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Includes bibliographical references.
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Statement of Responsibility:
by Dorina F. Sava.
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Title from PDF of title page.
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Document formatted into pages; contains 298 pages.
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Includes vita.

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aleph - 002317257
oclc - 659866847
usfldc doi - E14-SFE0003005
usfldc handle - e14.3005
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Quest Towards the Design and Synthesis of Functional Metal-Or ganic Materials: A Molecular Building Block Approach by Dorina F. Sava A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemistry College of Arts and Sciences University of South Florida Major Professor: Mohamed Eddaoudi, Ph.D. Julie P. Harmon, Ph.D. Brian Space, Ph.D. Michael J. Zaworotko, Ph.D. Anthony W. Coleman, Ph.D. Date of Approval: June 29, 2009 Keywords: single-metal-ion based molecular building block, zeolite-like metal-organic frameworks, porosity, hydr ogen storage, topology Copyright 2009 Dorina F.Sava

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Dedication To my beloved mother, Maria, for her lo ve, wisdom, optimism, and for her tireless unconditional support.

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Acknowledgements First and foremost, I would like to expr ess my sincere gratitude to my mentor professor, Dr. Mohamed Eddaoudi, for giving me the opportunity to approach exciting discoveries in his research lab, and for f acilitating my professi onal development. At the same time, I would like to ack nowledge Dr. Julie P. Harmon, Dr. Brian Space, and Dr. Michael J. Zaworotko, for th eir time, and helpful advice throughout my graduate career. Many thanks to Dr. Ant hony Coleman (IBCP), for recommending me to conduct my doctoral work at USF, and for serving as chairperson. Additionally, my deepest recognition to Dr. Juergen Eckert (UCS B) for his help with INS experiments and for the positive input at all levels. I woul d also like to extend my appreciation to Dr. Lukasz Wojtas, Dr. Victor Kravtsov, a nd Dr. Derek Beauchamp, for performing the invaluable crystal data analysis. Many thanks go to all past and pr esent fellow labmates, and especially to Dr. Jarrod Eubank, Jaci Br ant, Farid Nouar, Ryan Luebke, and Dr. Yunling Liu, who were directly involved in di stinct aspects of the work described herein. Finally, I would like to express my deepes t appreciation to my dear close family, for their endless love and encouragement, and to my friends Silvana, Adriana, and Daniel, for their constant support throughout these challenging years.

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Note to Reader The original of this document contains color that is necessary for understanding the data. The original dissertat ion is on file with the USF library in Tampa, Florida.

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i Table of Contents List of Tables v List of Figures vi List of Abbreviations xvii Abstract xx Chapter 1. An Introduction to Meta l-Organic Materials (MOMs) 1 1. 1. Preamble and Scope in the Design and Synthesis of Metal-Organic Materials 1 1. 2. Historical Perspective on MOMs 3 1. 3. Topological Analysis of MOMs 6 1. 4. MOMs Constructed from Nitrogen-donor Ligands 9 1. 5. MOMs Constructed from Carboxylate-based Ligands 12 1. 6. MOMs Constructed from Heterofunctional Ligands: the Single-Metal-Ion-based Molecular Building Block (MBB) Approach 20 1. 7. Zeolites 23 1. 8. Design Strategies for the Construction of MOMs with Zeolitelike Topologies and Properties 24

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ii 1.8.1. Zeolite MOMs Constructed via Organic Tetrahedral Nodes 27 1.8.2. Edge Expansion Approach to MOMs with Zeolitic Features 27 1.8.2.1. Zeolite MOMs Derived from Angular Ditopic N-donor Ligands: Pyrimidine and Imidazole-based Linkers 27 1.8.2.2. Zeolite -like Metal-Organic Frameworks (ZMOFs) Constructed via the SingleMetal-Ion-based MBB approach 31 1. 9. Functionality in MOMs 35 1.10. References 38 Chapter 2. MOMs Derived from Angular Th iophenedicarboxylate Bridging Ligands 2.1. Introduction 49 2.2. Experimental Section 52 2.3. Results and Discussions 54 2.4. Summary 70 2.5. References 71 Chapter 3. MOMs Constructed via the Single-Metal-Ion-based MBB Approach 73 3.1. Metal-Ligand Directed Assembly of MOMs from Iron and 2,5-H2PDC 73 3.1.1. Introduction 73 3.1.2. Experimental Section 74 3.1.3. Results and Discussion 76 3.1.4. Summary 87 3.2. MOMs Derived from Heterofunc tional Bis-Chelating Bridging Pyrimidinecarboxylate Ligands 88

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iii 3.2.1. Introduction 88 3.2.2. Experimental Section 90 3.2.3. Results and Discussion 95 3.2.4. Summary 116 3.3. Novel MOMs Constructed from Singl e-metal-ions with High Coordination Number and Multifunctional Pyrimidinecarboxylate Ligands 117 3.3.1. Introduction 117 3.3.2. Experimental Section 118 3.3.3. Results and Discussion 120 3.4. Summary 136 3.5. References 137 Chapter 4. Design Strategies and Synthesis of Materials with Large and Extra-Large Cavities 141 4.1. The Single-metal-ion-based MBB Approach to Target ZMOFs 141 4.1.1. Introduction 141 4.1.2. Experimental Section 143 4.1.3. Results and Discussion 146 4.2. ZMOFs Constructed from the Assembly of Metal-Organic Cubes (MOCs) 159 4.2.1. Introduction 159 4.2.2. Experimental Section 160 4.2.3. Results and Discussion 160

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iv 4.3. Mixed Ligands Approach Towa rds Accessing Functional Materials with Extra-Large Cavities 166 4.3.1. Introduction 166 4.3.2. Experimental Section 166 4.3.3. Results and Discussion 168 4.4. Summary 178 4.5. References 180 Chapter 5. Gas sorption Investig ations in Porous MOMs 183 5.1. Hydrogen Storage Methods in Solid-State Materials 183 5.1.1. Hydrogen storage in MOMs 189 5.1.2. Results and Discussions 195 5.2. Carbon Dioxide: Separation, Capture and Storage 219 5.2.1. Results and Discussion 222 5.3. Summary 233 5.4. References 235 Chapter 6. Summary and Future Outlook 239 6.1. Summary 239 6.2. Future Outlook 242 Appendices 245 Appendix A. Single-Crystal Structural Analysis and Refinement Data 246 Appendix B. X-ray Powder Diffraction Spectra 282 About the Author End page

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v List of Tables Table 5.1. DOE Technical Targets for On -board Hydrogen Storage systems 185 Table 5.2. Hydrogen uptake at various temperat ures and pressures in select MOMs 192 Table 5.3. Comparative case study in compounds 27 28 and 29 206 Table 5.4. Rotational transitions (meV) fo r hydrogen adsorbed on various sites in compound 36 214 Table 5.5. Hydrogen and CO2 uptake in compounds 27 28 29 35 36 37 38 233

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vi List of Figures Figure 1.1. Histogram highlighting the number of publications containing the terms “Coordination polymers” (red) and “Metal-Organic Frameworks” (green) 2 Figure 1.2. Example of the Werner complex, Ni(SCN)2(4-phenylpyridine)4; packing efficiency and inclus ion of dimethylsu lfoxide guest molecules 3 Figure 1.3. Example of the Hofmann Clat hrate: (a) single 2periodic layer outlining the square planar Ni(CN)4 and the octahedral Cd(CN)4(N(CH3)2)2; (b) benzene guest molecules trapped in between layers 4 Figure 1.4. Example of the first X-ray cr ystal structure of a Prussian blue analogue, Mn3(Co(CN)6)2(H2O)x 5 Figure 1.5. Fragment of diamondoid nets constructed from (a) CN and (b) 4,4’-bipy bridging ligands 9 Figure 1.6. Examples of pol ytopic N-based ligands 10 Figure 1.7. Polytopic N-donor organi c ligands and (a) dinuclear M2(N4CR)3 paddlewheel-like cl uster (b) trinuclear M3(N4CR)6 (c) trinuclear oxo-centered triazolate-bridged cluster M3(3-O)(N3CR)3 and (d) tetranuclear M4(4-Cl)(N4CR)8; (e) example of a net built from tetranuclear cube-like cluster 11 Figure 1.8. Examples of polytopic carboxylic acids 13 Figure 1.9. Commonly empl oyed carboxylate-based MBBs: (a) dimetal tetracarboxylate “paddle wheel” M2(RCO2)4L2, (b) basic chromium acetate trimerM3O(RCO2)6L3 and (c) basic zinc acetate, M4O(RCO2)6 13

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vii Figure 1.10. 1,3-BDC and 3,5,3’,5’-TCQP and (a) 2D Kagom layer and (b) 3D pillared Kagom layers (h ighlighted in blue and magenta) 14 Figure 1.11. X-ray single crystal structur e representation of IRMOF-1 (MOF-5) and the corresponding organic ligands that generate the isoreticular series of IRMOFs: (a) IR MOF-1, (b) IRMOF-2, (c) IRMOF-3, (d) IRMOF-6, (e) IRMOF-8,(f) IRMOF-9,(g) IRMOF-11, (h) IRMOF-13, (i) IR MOF-18, (j) IRMOF-20 15 Figure 1.12. Supertetrahedral building un its in (a) MIL-100 and (b) MIL-101 17 Figure 1.13. Example of a small rhombihe xahedron (nanoball) regarded as a SBB 17 Figure 1.14. Examples of multifunctional li gands resulted from functionalizing the 5-position of 1,3-BDC to derive extended nets based on nanoball SBBs: (a) 5-sulfoisophthalic acid, (b) 1,3-bis(5-methoxy-1,3-benzen edicarboxylic acid)benzene and (c) 5-(4-tetrazolyl)isophthalic acid 18 Figure 1.15. Tiling representation of a net with rht topology 19 Figure 1.16. Examples of hetero functional organic linkers 20 Figure 1.17. Single-metal-ion-based MBBs of the type MNx(CO2)y: (a) MN4O4; two conformational isomers of MN4O2-based MBBs (b) cis MN4O2 and (c) trans MN4O2; two conformational isomers of MN3O3-based MBBs, (d) fac -MN3O3 and (e) mer -MN3O3 and two conformational isomers of MN2O4-based MBBs, (f) cis -MN2O4 and (g) trans MN2O4 21 Figure 1.18. Tetrahedral nodes (T) bridged by ox ygen at an angle T-O-T of approximately 145 23 Figure 1.19. mtn -like framework based on HMTA organic tetrahedral nodes 27 Figure 1.20. sod -like frameworks based on 2-Hpymo (left) and 4-Hpymo (right) 29 Figure 1.21. Schematic representation of lta -net constructed from three different types of tiles 3[46]+[412.68.86]+[46.68] 30 Figure 1.22. MN4(CO2)4 and MN4(CO2)2 MBBs regarded as TBUs for the construction of rho -ZMOF (bottom left) and sod -ZMOF (bottom right) 33

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viii Figure 1.23. Two different types of cages and tiling representation of usf -ZMOF ( med ) 2[49.62.83] + [410.64.84] 34 Figure 2.1. Prototype 144 angle in a) 2,5H2TDC and b) 3,4-diphenyl-2,5-H2TDC 55 Figure 2.2. Common binding modes afforded by 2,5-TDC 56 Figure 2.3. (a) M(CO2)4 type MBB representing a (b) tetrahedral node, TBU in compound 1 57 Figure 2.4. (a) Ball and stick representa tion and (b) cubic diamond topology in compound 1 58 Figure 2.5. M2N2(CO2)6 type MBB, regarded as a 6-connected node 59 Figure 2.6. HMTA-based MBB, regarded as a 3-connected node 60 Figure 2.7. Representative fragment of topology in compound 2 outlining the hetero-coordinative nature of the framework based on (6,3) nodes 61 Figure 2.8. Representa tive tiles in compound 2 61 Figure 2.9. Representative MBB in compound 3 regarded as a tetrahedral node, acting as a TBU 62 Figure 2.10. Ball-and stick representation of three-member ring (left) and schematic representation of ten-member ring (right) in compound 3 63 Figure 2.11. (a) CPK representation of single framework, (b) schematic representation of lcv topology and (c) repres entative tiles in compound 3 64 Figure 2.12. Magnetic measurements on compound 3 : (a) magnetization vs. applied magnetic field, (b) magnetization vs. temperature. 65 Figure 2.13. Representative MBB in compound 4 regarded as a square building unit 66 Figure 2.14. Ball-and-stick depiction of simplified framework, (b) schematic representation of lvt topology and (c) repres entative tiles in compound 4 67

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ix Figure 2.15. Magnetic measurements on compound 4 : (a) magnetization vs. applied magnetic field, (b) magnetization vs. temperature 68 Figure 2.16. (a) MBBs in compound 5 regarded as three-connected T-shaped nodes; (b) ball-and-stick (left) and schematic representation of hcb topology (right) in compound 5 69 Figure 3.1. Prototype 120 angle in 2,5-H2PDC 76 Figure 3.2. Common binding modes afforded by 2,5-PDC 77 Figure 3.3. MN2(CO2)3 type MBB (left), regarded as a MNO bent BU (right) in compound 6 78 Figure 3.4. X-ray single crystal structure of compound 6 outlining one-periodic zig-zag chain motif 78 Figure 3.5. Detailed view of unidimensional chains in 6 held together by hydrogen bonded piperazi ne guest molecules 79 Figure 3.6. MN2(CO2)4 type MBB (left), regarded as a square planar trans -MN2O4 4-connected BU (right) in compound 7 80 Figure 3.7. X-ray single-cry stal structure of compound 7 : ball-and-stick (left) and CPK (right) representation of Kagom layer 81 Figure 3.8. (a) Magnetization vs. temp erature and magnetization vs. applied magnetic field in compound 7 at (b) 300K and (c) 2K 82 Figure 3.9. MN2(CO2)4 type MBB (left) in compound 8 regarded as a see-saw-like cis -MN2O4 4-connected BU (right) 83 Figure 3.10. (a) X-ray single-crysta l structure fragment, schematic (b) topological and (c) ti ling representation of diamondoid topology in compound 8 84 Figure 3.11. MN2(CO2)4 type MBB (left) in compound 9 regarded as a square planar cis -MN2O4 4-connected BU (right) 85 Figure 3.12. View of the X-ray sing le-crystal structure of compound 9 along (a) X direction (b) Y direction; (c) lvt topological analysis 86 Figure 3.13. Prototype 120 angle in 4,6-H2PmDC 88

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x Figure 3.14. Common coordination m odes afforded by 4,6-PmDC 89 Figure 3.15. (a) One step oxidation of 4,6dimethylpyrimidine for the synthesis of (b) 4,6-PmDC, divalent anion upon deprotonation in situ 90 Figure 3.16. (a) One step oxidation of 2-amino-4,6-dimethylpyrimidine for the synthesis of (b) 2-amino-4,6PmDC, divalent anion upon deprotonation in situ 90 Figure 3.17. (a) One step oxidation of 2-hydroxy-4,6-dimethylpyrimidine for the synthesis of (b) 2-hydroxy4,6-PmDC, divalent anion upon deprotonation in situ 90 Figure 3.18. (a) MN2(CO2)2 type MBB (top left), regarded as a MN2 bent BU (top right) in compound 10 ; (b) Zig-zag chains in compound 10 95 Figure 3.19. (a) MN2(CO2)2 type MBB (top left), regarded as a MN2 bent BU (top right) in compound 11 ; (b) Zig-zag chains in compound 11 95 Figure 3.20. (a) MN2(CO2)3 type MBB (top left), regarded as a MN2 bent BU (top right) in compound 12 ; (b) Zig-zag chains in compound 12 96 Figure 3.21. (a) Representative MBB in compound 13 M2N4(CO2)4 (top left) regarded as (b) see-saw like 4-connected MN4 BU (top right); (c) X-ray single-crystal st ructure of a layer in compound 1 3 98 Figure 3.22. (a) Representative MBB in compound 14 M2N7(CO2)3, regarded as (b) see-saw like 4-connected MN4 BU ; (c) X-ray single-crystal structure of a layer in compound 14 ; (d) layers stacking in an ABAB fashion 99 Figure 3.23. (a) Representative MBB in compound 15 M2N4(CO2)4, and alternative ways of analyz ing the connectivity and topology : (b) 3-connected MN2O3 BU, resulting in hcb herringbone-like topology (top right) and 4-connected M2N4O2 BU, resulting in sql topology (bottom right); (c) X-ray singl e-crystal structure of a layer in compound 15 101 Figure 3.24. (a) Representative MBB in compound 16 MN2(CO2)4 (top left) regarded as square planar cis -MN2O2 4-connected BU (top right); (b) X-ray single-crystal structure of layer in compound 16; (c) layers stacking in an ABAB fashion 103

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xi Figure 3.25. (a) MBB1 in compound 17 MN2(CO2)5 (left), regarded as trans MN2O2 see-saw-like 4-connected BU (right) ; (b) MBB2 in compound 17 MN3(CO2)5 (left), regarded as MN3O see-saw-like 4-connected BU (right) 105 Figure 3.26. (a) X-ray single-crystal structure of a layer in compound 17 ; (b) CPK representation of layer in compound 17 ; (c) Alternating layers stacking in an ABAB fashion in compound 17 106 Figure 3.27. MN2(CO2)4 type MBB (left) in compound 18 translated into a square planar trans -MN2O2 4-connected BU(right) 109 Figure 3.28. (a) Ball-and-stick represen tation of the X-ray single-crystal structure of a squa re grid layer in compound 18 and (b) Piperazine guest molecules intercalated in-between the layers 109 Figure 3.29. Representative MBB in compound 19 MN2(CO2)4 (left), regarded as a see-saw-like cis -MN2O2 4-connected BU (right) 110 Figure 3.30. Ball-and-stick representation of (a) Kagom laye r; (b) herringbonetype layer; (c) square grid and (d) schematic representation of layers arrangement in compound 19 111 Figure 3.31. Tiling representation of smc topology in compound 19 112 Figure 3.32. Alternative wa y of analyzing compound 19 based on (a) ligand connectivity, regard ed also as a 4-connected node, (b) tiling representation of nbo topology 113 Figure 3.33. Representative MBB in compound 20 MN3(CO2)3 (left), regarded as fac -MN3O3, 3-connected BU 114 Figure 3.34. Ball-and-stick representation of metal-organic cube in compound 20 115 Figure 3.35. Representative MBB in compound 21 MN2(CO2)4 (left), regarded as a cis -MN2O2 see-saw-like 4-connected BU (right) 120 Figure 3.36. (a) Hydrogen bonding interactions between two MBBs of distinct layers and (b) Ball-and-stic k representation of hydrogen bonded layers in compound 21 121

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xii Figure 3.37. (a) MBB in compound 22 MN4(CO2)4 (top left), regarded as a see-saw-like MN4O4 4-connected BU (top right) and (b) Dimetal cluster in compound 22 M2N4(CO)12 (bottom left), regarded as a MN4O8 8-connected BU (bottom right) 123 Figure 3.38. (a) Ball-and-stick and (b) CPK representation of single crystal structure in compound 22 ; (c) flu (4,8)-net topology and d) tiling representation of flu topology 124 Figure 3.39. (a) Representative MBB in compound 23 MN3(CO2)3 (left), regarded as MN3O3 3-connected BU 125 Figure 3.40. (a) Ball-and-stick representati on of the single crystal structure of a honeycomb layer in compound 23 ; (b) AAAA packing modes of distinct layers 126 Figure 3.41. (a) MBB in compound 24, MN4(CO2)4(top left), regarded as a tetrahedral MN4O4 TBU (top right); (b) Meta l cluster in compound 24 MN2(CO2)12 (bottom left), regarded as a eight-connected BU 128 Figure 3.42. (a) Ball-and-sti ck (left) and CPK (right) representation of X-ray single-crystal structure in compound 24 129 Figure 3.43. Tiling representation of unprecedented topology of a (4,8) heterocoordinated net in compound 24 130 Figure 3.44. (a) MBB1 in compound 25 MN3(CO2)3 (top left), regarded as a T-shaped MN3O3 3-connected BU (top right); (b) MBB2 in compound 25 MN4(CO2)4 (bottom left), regarded as a tetrahedral MN4O4 TBU (bottom right) 132 Figure 3.45. (a) Ball-and-stick representati on of a fragment of the single crystal structure in compound 25 ; (b) Ball-and-stick and (c) graphical representation of unprecedented cage constructed from (d) 4-MR, (e) 5-MR a nd (f) 6-MR; (g) 9-MR 133 Figure 3.46. Tiling representation of unprecedented topology of a (3,4) heterocoordinated net in compound 25 135 Figure 4.1. MBB in compound 27, MN4(CO2)4 (left), regarded as a tetrahedral MN4O4 TBU (right) 148

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xiii Figure 4.2. (a) Ball-and-stick represen tation of 4-MR(left) and 6-MR (right), assembled to form (b) Truncated octahedron ( -cage), ball-and-stick (left) and CPK spacefilling (right); (c) Fragment of the X-ray single-crystal structure in 27 outlining zeolite-like sod topology 149 Figure 4.3. XRPD spectra of compound 27 ; red= calculated, blue= experimental; compound 28 green=calculated, experimental= olive; compound 29 pink= calculated, experimental= violet 151 Figure 4.4. MBB in compound 32 MN2(CO2)4 (left), regarded as a (b) see-saw-like trans-MN2O4 4-connected BU (right) 152 Figure 4.5. Ball-and-stick representation of (a) 4-MR, (b) 6MR, (c) 6-MR and (d) schematic view of -cage, outlining two types of 6-MRs (blue and red) in compound 32 153 Figure 4.6. Ball-and-stick (lef t) and CPK representation (r ight) of X-ray singlecrystal structure in compound 32 155 Figure 4.7. Solid-state UVvis spectra of compound 32 after exchange with AO (green) vs. AO (red) and as-synthesized 32 (blue) 156 Figure 4.8. XRPD spectra of compound 32 ; red = calculated, blue = experimental; compound 33 experimental= wine; compound 34 experimental=green 157 Figure 4.9. MBB in compound 35, MN4(CO2)4 (left), regarded as a tetrahedral MN4O4 TBU (right) 157 Figure 4.10. (a) Ball-and-stick representati on of 4-MR left) and 6-MR (middle), 8-MR (right), assembled to form (b) Truncated cuboctahedra ( -cages), ball-and-stick (left) and CPK space-filling (right); (c) Fragment of the sing le-crystal structure in compound 35 outlining zeolite-like rho -topology 159 Figure 4.11. (a) Ball and stick (left) and schematic representation (right) of a metal-organic cube; (b) Thr ee O-HO intermolecular hydrogen bonds linking the vertices of two neighboring cubes; (c) Schematic representation of ACO topology; (d) X-ray single-crystal structure of compound 36, ball-and-stick (left) and CPK representation (right) 163

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xiv Figure 4.12. Ball-and-stick representation of single-crystal st ructure (left) and schematic representation of AST topology (right) in compound 37 165 Figure 4.13. Schematic representation of the ammonium cation interacting with the vertices of four neighboring cubes (left) and ammonium cations sustaining trifurcated Hbonding mode (right) in compound 37 166 Figure 4.14. Four different MBBs in compound 38 : (a) MN2(CO2)2, regarded as 4-connected MN2O2 BU, (b) M(CO2)6, regarded as 4-connected MO4 BU, (c) MN(CO2)5, regarded as 5-connected MNO4 BU and (d) MN(CO2)6, regarded as a 6-connected MNO5BU 171 Figure 4.15. Ball-and-stick representation of (a) 3-MR, (b) first type of 4-MR, (c) second type of 4-MR, (d) th ird type of 4-MR, (e) 6-MR and (f) unique assembly of one 3-MR and three distinct 4-MR in compound 38 172 Figure 4.16. Ball-and-stick (left) and sc hematic representation (right) of unprecedented mesoporous cage in compound 38 ; (b) Fragment of the X-ray single-crystal structure in compound 38 173 Figure 4.17. Tiling representation of unprecedented topology of a (4,5,6) heterocoordinated net in compound 38 175 Figure 4.18. Alternative way of interpreting 38 : (a) MN2(CO2)6, regarded as 4connected MN2O2 4-connectedBU; (b) Ball-a nd-stick, schematic and tiling representation of mesoporous cage 176 Figure 4.19. Solid-state UVvis spectra of compound 38 after AO sensing (red) vs. as-synthesized (blue) 177 Figure 4.20. Solid-state UVvis spectra of compound 38 as-synthesized (green) and after free-base TTMAPP encapsulation (blue), and metalated-TMAPP (red) 177 Figure 5.1. (a) Argon and Nitrogen adsorp tion isotherms measured at 77 and 87K, on compound 27 (b) Hydrogen sorption isotherms measured at 77 and 87K (left), and Isoste ric heat of adsorption (right) on compound 27 198 Figure 5.2. (a) Hydrogen molecules sorbed per metal, measured at 77K on Liand Na-exchanged Insod -ZMOF (top left) and enlarged region at lower pressure (top right), and (b) Isosteric heat of adsorption on the Liand Na-exchanged Insod -ZMOF 200

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xv Figure 5.3. Hydrogen sorption isothe rms measured on Na-exchanged Insod -ZMOF at 77 and 87K, upon ac tivation at different temperatures: (a) 85C, (b) 150C, (c) 200C, and (d) corresponding isosteri c heats of adsorption 204 Figure 5.4. Hydrogen uptake measured at 77 and 87K (left) and Isosteric heat of adsorption (right) in compounds (a) 28 and (b) 29 205 Figure 5.5. Isosteric heat of adsorption in the Li-exchanged Insod -ZMOFs ( 27 ), Ybsod -ZMOFs ( 28 ), and Ersod -ZMOF ( 29 ) 207 Figure 5.6. (a) Argon and Nitrogen adsorp tion isotherms measured at 77 and 87K, on compound 35 (b) Hydrogen sorption isotherms measured at 77 and 87K and (c) Isoste ric heat of adsorption in compound 35 209 Figure 5.7. (a) Argon and Nitrogen adsorption is otherms measured at 77 and 87K, (b) Hydrogen sorption isotherms measured at 77 and 87K, (c) Isosteric heat of adsorption and (d) INS spectra obtained at 15K on the quasielastic neutron spect rometer (QENS) at the intense pulsed neutron source (IPNS) at Argonne National Laboratory (ANL) for loadings of 1, 2 and 3 H2/In, in compound 36 212 Figure 5.8. (a) Argon adsorption isotherm measured at 87K, (b) Nitrogen adsorption isotherms measured at 77K, (c) Hydrogen sorption isotherms measured at 77 a nd 87K and (d) Isosteric heat of adsorption, in compound 37 216 Figure 5.9. (a) Nitrogen sorption isot herms measured at 77K, (b) Argon sorption isotherms measured at 87K in 38 217 Figure 5.10. (a) Langmuir equation fitting curve for Ar isotherm (adsorption branch data points, P/P0 = 0 1–0 14). Surface area 1476 m2 g 1, linearity 0.9997; (b) BET equation f itting curve for Ar isotherm (adsorption branch data points, P/P0 = 0 1–0 14). Surface area 1018 m2g 1, linearity 0.99999 218 Figure 5.11. Pore size dist ribution histogram calcula ted with a DFT/MonteCarlo model using the Argon gas adsorption data at 87 K (zeolite/silica NLDFT eq) 219 Figure 5.12. (a) Hydrogen sorption isotherms measured at 77 and 87K, and (d) Isosteric heat of adsorption in compound 38 220

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xvi Figure 5.13. CO2 sorption isotherms measured at 0C and 25C, on compound 27 224 Figure 5.14. CO2 sorption isotherms measured at 0C and 25C, on compound 28 225 Figure 5.15. CO2 sorption isotherms measured at 0C and 25C, on compound 29 225 Figure 5.16. CO2 sorption isotherms measured at 0C and 25C, on compound 35 227 Figure 5.17. CO2 sorption isotherms measured at 0C and 25C, on compound 36 228 Figure 5.18. CO2 sorption isotherms measured at 0C and 25C, on compound 37 229 Figure 5.19. CO2 sorption isotherms measured at 0C and 25C, on compound 38 229 Figure 5.20. CO2 sorption isotherms measured at 0C, on compounds 27 35 36 and 38 231

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xvii List of Abbreviations Acronym Full Name 2-PmCN 2-Cyanopyrimidine 4,5-DcIm 4,5-Dicyanoimidazole 3,4-diphenyl-2,5-H2TDC 3,4-Diphenyl-2,5-Thiophen edicarboxylic acid 3,4-diphenyl-2,5-TDC 3,4-Dipheny l-2,5-Thiophenedicarboxylate 2,5-H2PDC 2,5-Pyridinedicarboxylic acid 2,5-PDC 2,5-Pyridinedicarboxylate 4,6-H2PmDC 4,6-Pyrimidinedicarboxylic acid 4,6-PmDC 4,6-Pyrimidinedicarboxylate 2,5-H2TDC 2,5-Thiophenedicarboxylic acid 2,5-TDC 2,5-Thiophenedicarboxylate AO Acridine Orange CH3CN Acetonitrile BU Building Unit Dabco 1,4-Diazabicyclo[2.2.2]octane DEF N,N’-Diethylformamide DMA N,N’-Dimethylacetamide

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xviii DMA+ Dimethylammonium cations DMF N,.N’-Dimethylformamide EtOH Ethanol En Ethylenediamine FT-IR Fourier Transform Infrared HMTA Hexamethylenetetramine H2O Water Imi Imidazole MBB Molecular Building Block MOC Metal-Organic Cube MOF Metal-Organic Framework MOM Metal-Organic Material MOP Metal-Organic Polyhedron n MRs n Member Rings HNO3 Nitric acid Pip Piperazine SBB Supermolecular Building Block TEA Triethylamine TBU Tetrahedral Building Unit TMAN Tetramethylammonium nitrate TMDP 4,4’-Trimethylenedipiperidine TTMAPP 5,10,15,20-Tetrakis(4-(trimethyl ammonio)-phenyl)-21H,23Hporphinetetratosylate

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xix UV-Vis Ultraviolet-visible XRPD X-Ray Powder Diffraction ZMOF Zeolitelike Metal-Organic Framework ZIF Zeolitic Imidazolate Framework

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xx Quest Towards the Design and Synthesis of Functional Metal-Org anic Materials: A Molecular Building Block Approach Dorina F. Sava ABSTRACT The design of functional materials for specific applications has been an ongoing challenge for scientists aiming to resolve pr esent and future societal needs. A burgeoning interest was awarded to developing methods for the design and synthesis of hybrid materials, which encompass superior functi onality via their multicomponent system. In this context, Metal-Organic Materials (MO Ms) are nominated as a new generation of crystalline solid-state materials, proven to provide attractive features in terms of tunability and versatility in the synthesis process. In st rong correlation with their structure, their functions are related to numerous attractive features, with emphasis on gas storage related applications. Throughout the past decade, several design approaches have been systematically developed for the synthesis of MOMs. Thei r construction from building blocks has facilitated the process of rational design and has set necessary conditions for the assembly of intended networks.

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xxi Herein, the focus is on utilizing the si ngle-metal-ion based Molecular Building Block (MBB) approach to construct framewor ks assembled from predetermined MBBs of the type MNx(CO2)y. These MBBs are derived from multifunctional organic ligands that have at least one Nand Oheterochelat e function and which possess the capability to fully saturate the coordination sphere of a single-metal-ion (of 6or higher coordination number), ensuring rigidity and directional ity in the resulting MBBs. Ultimately, the target is on deriving rigid and directional M BBs that can be regarded as Tetrahedral Building Units (TBUs), which in conjunction with appropriate hete rofunctional angular ligands are capable to facilita te the construction of Zeolitelike Metal-Organic Frameworks (ZMOFs). ZMOFs represent a unique subset of MOMs, particularly attractive due to their potential for numer ous applications, arising from their fully exploitable large and extra-large cavities. The research studies highlighted in this dissertation will probe the validity and versatility of the single-metal-ion-based M BB approach to generate a repertoire of intended MOMs, ZMOFs, as well as novel functional materials constructed from heterochelating bridging ligands. Emphasis wi ll be put on investigating the structurefunction relationship in MOMs synthesized via this approach; hydrogen and CO2 sorption studies, ion exchange, guest sensing, en capsulation of molecules, and magnetic measurements will be evaluated.

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1 Chapter 1. An Introduction to Metal-O rganic Materials (MOMs) 1.1. Preamble and Scope in the Design a nd Synthesis of Metal -Organic Materials For several decades, synthetic chemists have been trying to systematically develop new routes for the design of co mpounds which possess desired properties. Research studies are dynamically adapting in or der to meet current societal and industrial needs, suggesting that superior functionality can be provided by materials with multiple components. Metal-organic materials (MOMs), represent a new generation of crystalline solid-state materials built form metal ions and bridging organic linkers, proven to possess exceptional potential for numerous applicati ons in many areas: ga s storage/separation, catalysis, selective sensing, magnetism, non-linear optics etc.1-14 The repertoire of the organic-inorgani c assemblies ranges from discrete zeroperiodic (metal-organic polygons or polyhedra) to one-, twoand th ree-periodic extended frameworks, commonly referred to as coor dination polymers and/or metal-organic frameworks (MOFs). The interest shown in th is research field has grown exponentially in the past twenty years, highlighted by the remarkable upsurge in the number of publications (Figure 1.1.) over this time frame.

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2 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 20080 500 1000 1500 2000 2500 Number of publicationsPublication year Coordination polymers Metal-Organic Frameworks Figure 1.1. Histogram highlighting the number of publications containing the terms “Coordination polymers” (red) and “Metal-O rganic Frameworks” (green) (source: ISI Web of Science, 02/26/09). MOMs are modular and very attractive due to the tunability and versatility of both the metal and organic ligand involved in thei r synthesis. Metal i ons that can adopt a variety of coordination geometries are gene rally employed, such as transitional metals, and lanthanides, while the expanded librar y of available organic ligands highlights various sizes of the linkers and inherent asso ciated functionalities. In this context, it becomes evident that the combinations betw een the two chemical components may lead to a very large set of materials. Rational de sign strategies have been therefore devised and developed to facilitate the synthesis of targeted compounds. This chapter will focus on the historical perspective, along with severa l strategies for the design and synthesis of functional MOMs.

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3 1.2. Historical Perspective on MOMs Examples of crystalline materials co nstructed from metal centers bridged by organic linkers emerged and were fully characterized by X-ray studies15 as early as 1943.16 Initial discoveries of metal-ligand co mplexes underscore various types of inclusion compounds, such as Werner-type co mplexes, Hoffmann type clathrates, and Prussian blue analogues. Early investigations of metal-nitrogen ba sed systems, lead to a specific class of compounds, Werner-type complexe s, generally expressed by MX2A42G where M is a divalent octahedral metal i on, X is an anionic ligand (NCS-, CN-, NCO-, Cl-, Br-, I-,NO3 -), A represents a pyridine-based coordinating mo lecule and G, the guest molecules present in the lattice (Figure 1.2.). Figure 1.2. Example of the Werner complex, Ni(SCN)2(4-phenylpyridine)4;17 packing efficiency and inclusion of di methylsulfoxide guest molecules. Ni= green, C= gray, S= yellow, and N= blue. The diverse packing modes afforded by these complexes may translate into potential accessible void spaces, correspondent of the pl ace where guest molecules reside. A great

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4 variety of inclusion compounds were deri ved from this multi-component system; the potential for fine tuning needs to outlined, es pecially when considering the multitude of compounds synthesized by substituting th e neutral pyridine-based ligands. In the late 1960s, Iwamoto and cowork ers initiated the work on a series of derivatives on the Hoffman-type clathrate, named after K. A. Hofmann, who discovered the parent compound, Ni(CN)2NH3C6H6, in 1897.18 The analogous complexes are differentiated by various guest molecules th ey accommodate, highlighting the host-guest selectivity of the compounds defined by the general formula M(NH3)2M'(CN)42G (M = Mn, Fe, Co, Ni, Cu, Zn: M' = Ni, Pd, Pt; G = pyrrole, thiophene, benzene, aniline).19-22 Figure 1.3. Example of the Hofmann Clathrate:23 (a) single 2-periodic layer outlining the square planar Ni(CN)4 and the octahedral Cd(CN)4(N(CH3)2)2; (b) benzene guest molecules trapped in between layers. Hydrogen atoms have been omitted for clarity; Cd= green, Ni= magenta, C= gray, and N= blue. Another category of early inclusion com pounds is underlined by the Prussian blue analogues, originally composed of octahedr al mixed valance iron metal ions, bridged by cyanogroups. A great variety of such c oordination compounds were synthesized and detailed, although characterized by X-ra y studies only in 1970 (Figure 1.4.).24 (a) (b)

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5 Furthermore, the work was extended to othe r mixed valence transitional metals-cyanide complexes, represented by the general formula Mx[My(CN)6]n xH20. The synthesis of these materials was mainly pursued due to th eir capability to act as a molecular sieves, while maintaining the integr ity of their crystalline st ructure upon desolvation and resolvation; further studies are now referring to their magnetic properties.25,26 Figure 1.4. Example of the first X-ray crystal st ructure of a Prussian blue analogue,24 Mn3(Co(CN)6)2(H2O)x: Mn= green, Co= magenta, C= gray, N= blue; water molecules were omitted for clarity. It wasn’t until the late 1980s, when pioneering work by Robson and Hoskins introduced the conceptual approach to wards the rational construction of open coordination polymers.27-29 The following subchapters will de tail the structural analysis of MOMs and will provide an overview of most prominent design strategies, frameworks derived upon their implementation, as well as highlighting their functionality. The focus will be put on the insights of the design r outes for construction of MOMs with zeolitelike topologies and properties.

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6 1.3. Topological Analysis of MOMs The topological evaluation of frameworks expressed by mathematical descriptors, and its relevance to crystal chemistry was detailed and pursued by Wells, who describes nets in terms of nodes connected by spacers.30,31 This type of analys is also enables the materials designer with the use of geometrical principles for the construction of materials with intended topologies. A net is said to be n-periodic structures if it maintains its symmetry when translated in n-independent di rections. It is significant to outline this aspect in the light of common terminology used to describe MOMs (for example, polygons and polyhedra are generally referred to as being zero dimensional, even though they should be really categoriz ed as 0-periodic, as they ar e in fact three dimensional). The geometrical “fingerprint” of a net is by given by the coordination sequence 32,33 and vertex symbol.34 For each n coordinated node in a net, there are N = n ( n -1)/2 angles associated with the node. For ex ample, in the diamond topology there are six angles correspondent to each vertex, as the net is based on a 4-connected node. A unique net is described by distinctive point (Schlfl i) symbols and vertex symbols (O’Keeffe). These notions are introduced with resp ect to the i) size and ii) number of cycles and rings that meet at a given vertex; the number of cycles and rings is denoted by a superscript (point symbol) or subscript (vertex sy mbol). In this context, the terms cycle and ring need to be distinguished. A (strong) ring is the shorte st cycle or closed ci rcuit that is not the sum of two smaller cycles (it does not allow shortcuts). According to these criteria, the point symbol of a given node is re presented by a general expression Aa Bb…Nn, where “A, B,.., N” correspond to the size of the shortest cycle at each angle, while superscripts

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7 “a, b,…, n”, to the number of such cycles. For diamond, the short point (Schlfli) symbol is 66, meaning that for each of the six angles correspondent to the 4-connected node, the size of the shortest cycle is 6 and there are 6 cycles meeting at a vertex. A more elaborate depiction is given by the long (e xtended) Schlfli and the vertex symbol of a net. The sequence contains all an gles of the n-connected net, expressed as AaBb…Nn, where A, B, …,N represent the sizes of the smallest cycle (long point symbol) and ring (vertex symbol) at an angle; a, b,…,n are the numbers of these rings (the only difference between the extended point symbol and the vertex symbol lies therefore in the consideration of cycles vs. rings). In the case of diamond, the vertex symbol is 6262 62626 62, indicating that there are two 6-rings fo r each one of the six angles. Utilizing vertex symbols is highly useful in nets with two types of nodes, for example, that indicate the same short point symbol for each node. A sp ecial case is considered for nets based in 4-connected nodes only where a constraint is introduced that allows opposite pairs of angles that are not sharing edges. At the same time, each node has a corresponding coordination sequence, which outlines the infinite extensi on of the net based on that given connectivity, where the sequence of neighboring vertices is rega rded. For example, the diamond net is constructed from 4-connected nodes, and the coordination sequence is 4, 12, 24, 42, 64, 92, 124, 162, 204, 252, 981,…; that represents each of the 4-connected nodes, which are linked to 12 nodes, further ex tended to 24 nodes, and so on. Hence, unique coordination sequences and vertex symbols are equivalent for each net and these descriptors are informative to fully confirm the identity of the framework. The most occurring topologies to date are collected in the RCSR database;35 O’Keeffe

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8 designates a three letter code for each ne t; for example, the correspondent topology for the 3-periodic diamond structure is referred to as dia The correlation between the geometrical principles and the design of materials with intended topologies can al so be regarded when consid ering the net’s transitivity, which represents to a certain extent, the regu larity of that structure. Transitivity is expressed by a list of four figures, pqrs ( p kinds of vertices, q kinds of edges, r kinds of faces and s kinds of tiles, where a tile is defined as a polyhedra that cont ains at least two edges that meet at each vertex and two faces that meet at each edge);36,37 for example, structures with just one kind of vertex/edge (p=1/q=1) are called vertex/edge transitive and are easier to target. As a general statemen t, the lower the mathematical descriptors in the pqrs sequence, the more regular the net is, and therefore, a more facile to access synthetically. As a result, each n-connected node has a default net associated with it; for the 4-connected nodes, the most occurring net is the diamond structure. When targeting porous materials with zeolite topologies base d on 4-connected nodes, it is therefore impetuously necessary to employ superior at tributes in order to avoid the default dia net, with 1111 transitivity. This aspect will be fu rther discussed in the section dedicated to various design strategies to c onstruct materials with zeolitelike topologies. In conclusion, the topologi cal description of the diamond net can be characterized by the notions introduced in this section, as follows: dia has the corresponding Coordination sequence: 4, 12, 24, 42, 64, 92, 124, 162, 204, 252, 981; Point (short Schlfli) symbol: {66}; Extended (long Schlfli) symbol: [6262 62626 62]; Vertex symbol: [6262 62626 62] and Transitivity: 1111.

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9 1.4. MOMs Constructed from Nitrogen-donor Ligands The “node-and-spacer” strategy commenced by Robson and Hoskins27,28 identified the rich possibility to construct solid-state materials derived from metals centers of known coordination geometry, br idged by organic struts, and its utmost importance to crystal chemistry. Some of th e earliest examples of MOMs were based on cyanide linkers, an approach further extended to longer N-donor organic ligands, such as 4,4’-bipyridine (4,4’-bip y) and its analogues. Figure 1.5. Fragment of diamondoid nets constructed from (a) CN28 and (b) 4,4’-bipy38 bridging ligands. Hydrogen atoms and solvent molecules have been omitted for clarity; (a) Cu= green, Zn= magenta, C= gray, N= blue; (b) Cu= green, C= gray, N= blue. Figure 1.5. reveals two examples of diamond topologies, constructe d from mixed Cu/Zn and cyano ligands,28 and also Cu and (4,4’-bipy).38 The topological equivalence between the two structures highlights the modularity in MOMs, and validates the early attempts for the design of these materials. The relatively ease in the crystallization of MOMs based on this system promoted the continuous interest in these material s. The primary aim became associated with establishing reliable synthetic pathways, while a subsequent focus was put on their (a) (b)

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10 function. Due to the neutral nature of th ese N-based ligands, the resulting MOMs are cationic and require the presence of anions in the crystal lattice, for the insurance of the charge balance. As a result, the exploitation of their propert ies is severely hindered, as many of the structures co llapse upon guest removal. The library of N-based organic ligands has largely expanded, and relevant factors for the design of intended materials relate with the positioning of the nitrogen atoms on the aromatic ring, and the overall geometry and length of the ligand. Figure 1.6. exemplifies a variety of N-based linkers employed for the construction of functional MOMs. Figure 1.6. Examples of polytopic N-based ligands. Angular polytopic Nbased linkers such as pyrimidine, imidazole and hexamethyletetraamine (HMTA), possess geometri cal attributes that make them suitable to be employed in the design of nets with zeolitelike topologies and features. The propensity of nets derived from these linkers will be detailed he rein, in the section dedicated to zeolitelike nets. A possible pathway directed toward s increasing the robustness of these assemblies, and hence their functionality, is to introduce polytopic expanded N-based N N N N N N N N N N NN NN N N N N N N N

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11 linkers, which in conjunction with metal ions with higher coordination numbers are capable to direct the formation of metal clus ters, regarded as Molecular Building Blocks (MBBs). Figure 1.7. Polytopic N-donor organic li gands and (a) dinuclear M2(N4CR)3 paddlewheel-like cluste r (b) trinuclear M3(N4CR)6 (c) trinuclear oxo-centered triazolatebridged cluster M3(3-O)(N3CR)3 and (d) tetranuclear M4(4-Cl)(N4CR)8; (e) example of a net built from tetranuclear cube-like cluster. Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, Cl= magenta, and O= red. N NH N N N HN N N N NH N N N NH N N N HN N N (a) (b) (c) (d) (e)

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12 Figure 1.7. depicts various N-base d polynuclear metal clusters and the example of a very well studied porous MOF based on the tetranucl ear cube-like cluster, derived from Mn and 1,3,5-benzenetristetrazolate (BTT, Figure 1.7. top right).39,40 It is thus inferred that the overall rigidity of the structure is reinforced by the MBBs generated in situ a factor that significantly aids the process of de sign and formation of intended structures. 1.5. MOMs Constructed from Carboxylate-based Ligands A significant amount of work in the area of coordination polymers is dedicated to materials derived from polycarboxylic acids (Figure 1.8.), which accommodate a variety of bridging modes upon coordination to metal io ns. From a historical perspective, the transition to linkers containing carboxylic acid donating groups can be regarded as significantly important, especially in the context of improving the rigidity of the frameworks. The anionic bridging linkers ensu re the necessary net charge balance, and thus the presence of charged guest molecules is often precluded. In this context, the potential to improve stability upon guest rem oval is increased, as compared to early compounds constructed from monodentate ne utral pyridine and cyano donating groups. Concomitantly, these linkers possess the desi rable attributes (bis-monodenate bridging modes) to facilitate the formation of metal clusters, regarded as rigid MBBs, generated in situ The main challenge is associated with fi nding the exact reaction conditions that will consistently permit the generation of the intended molecular clusters.

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13 Figure 1.8. Examples of polytopic carboxylic acids. Some of the most commonly occurring carboxylate-based MBBs are portrayed in Figure 1.9.; it is denoted that carboxylates bind the metal centers in a bis-monodentate fashion, giving rise to robust nodes. Figure 1.9. Commonly employed carboxyl ate-based MBBs: (a) dimetal tetracarboxylate “paddle wheel” M2(RCO2)4L2, (b) basic chromium acetate trimerM3O(RCO2)6L3 and (c) basic zinc acetate, M4O(RCO2)6. Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. From their points of extension, the MBBs can be regarded as Secondary Building Units, (SBUs, terminology borrowed from zeolite materials), based on the geometry of the MBBs: the “paddlewheel” dimetal cluster is translated into a square building block, the trimer into a trigonal prismatic building bl ock, while the tetranuc lear zinc acetate is O OH HO O O OH O HO O OH OH O O HO OH O O HO O OH OH O OH O O HO OH O OH O O HO (b) (a) (c)

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14 regarded as an octahedral building block. Indeed, by exploiting the consistency in generating these MBBs, 41-51 and by gaining enough contro l over these new valuable design tools, a new generation of a repertoire of novel materials has been pursued and detailed. Supramolecular isomerism in MOMs repres ents a particular case of structural diversity promoted by carboxylate-based MBBs; the concept refers to the occurrence of more than one framework from the same building block.4 For instance, the Cu or Zn dimetaltetracarboxylate cluster derived from 1,3-benzenedicarboxylate (1,3-BDC)affords the formation of distinct supram olecular isomers: discrete 0-periodic “nanoballs”,52 2-periodic tetragonal sheets53 and Kagom lattices54 and 3-periodic extended nets.55,56 Figure 1.10. 1,3-BDC and 3,5,3’,5’-TCQP and (a) 2D Kagom layer and (b) 3D pillared Kagom layers (highlighted in bl ue and magenta). Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. OH O O HO HO O O OH O OH HO O (a) (b)

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15 Figure 1.10. depicts one layer of a twoperiodic Kagom layer; by using the tetracarboxylate linker, 3 ,5,3’,5’-tetracarboxylatequaterphe nyl (3,5,3’,5’-TCQP), the layers are pillared to result in a three-pe riodic framework with NbO topology and with high apparent surface area and gas storage capacities.57 In the same context, groundbreaking work pioneered by Yaghi and co-workers, established the foundation of a new generation of functional materials. MBBs based on the basic zinc acetate, bridged by ditopic terephtal ic acid struts result in the formation of a highly porous material with cubic topology, MOF-5 (IRMOF-1),58 Figure 1.11. Figure 1.11. X-ray single crystal structure repr esentation of IRMOF-1 (MOF-5) and the corresponding organic ligands that generate the isoreticular series of IRMOFs: (a) IRMOF-1, (b) IRMOF-2, (c) IRMOF-3, (d) IRMOF-6, (e) IRMOF-8,(f) IRMOF-9,(g) IRMOF-11, (h) IRMOF-13, (i) IRMOF-18, (j) IRMOF-20. Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. Yellow sphere represents the largest sphere that can be fit inside the cavity, considering the van der Waals radii of the nearest atoms. O OH HO O O OH HO O Br O OH HO O H2N O OH HO O O OH O HO O OH HO O CH3 CH3 H3C H3C O OH O HO O OH O HO O OH O HO O OH S S O HO ( a ) ( b ) ( c ) ( f ) ( e ) ( d ) ( g ) ( h ) ( i ) ( j )

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16 The material exhibits permanent porosity a nd a surface area higher than most zeolitic materials, representing also the first ex ample of a hydrogen study on a metal-organic material.59 MOF-5 is one of the most studied MOMs to date, mainly due to the potential applications related to its permanent porosity. Furthermore, the discovery of this functi onal material lead to the development of a series of Isoreticular MOFs (IRMOFs), t opological analogs constructed from the same zinc acetate octahedral building units, but where the linear ligands are substituted with longer and/or functionalized correspo ndents, IRMOF 1-13 (Figure 1.11. a-h),58 IRMOF18, (Figure 1.11. i),60 IRMOF-20(Figure 1.11.j).61 This factor ultimately affects the tunable metrics, where the increase in the le ngth of the linkers results in a gradual increase of the pore size. The importance of th ese findings highlights the reliability of the MBBs formed in situ that maintain unaltered their pr e-designed function throughout the assembly process, proving the exceptional potential for design and tunability of the resulting materials. The approach based on rendering rigid car boxylate-based metal clusters derived from trimeric units constructed from three octahedra meeting at a vertex, were largely explored by Frey and co-workers (Figure 1.12.). Their recent work reports on the synthesis of two porous solid -state materials, MIL-10062 and MIL-101,63 with augumented mtn zeolite topology, assembled with th e aid of trimesic acid, or 1,3,5benzenetricarboxylate (1,3,5-BTC), and1,4-be nzenedicarboxylic acid (1,4-BDC), respectively. Both materials exhibit hi gh porosity, accompanied by a breadth of properties associated with their complex structures.

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17 Figure 1.12. Supertetrahedral building units in (a) MIL-100 and (b) MIL-101. Hydrogen atoms and solvent molecules have been omitted for clarity; M = green, C = gray, N =blue, and O = red. A hierarchically superior design stra tegy considers the construction of MOMs from Metal-Organic Polygons and Polyhedra (MOPs). At the scale of the molecular assembly, the discrete MOPs can be rega rded as Supermolecular Building Blocks (SBBs), which permit extension to threeperiodic frameworks through peripheral functionalities.64 Figure 1.13. Example of a small rhombihexahedr on (nanoball) regarded as a SBB. Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. (a) (b)

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18 Zaworotko et. al carried out extens ive research towards the synthesis of molecular assemblies with the formula [M2(bdc2)L2]12, regarded as the small rhombihexahedron polyhedron, and ge nerically referred to as the nanoball .65a,b The 5-position of the benzenedicarboxylate moiety allows for linkage of the discrete architectures into periodic assemblies. A ccordingly, the group reported the successful linkage of the SBBs through coordination bonds when using 5-sulfoisophthalic acid (Figure 1.14.a), which resulted in a 3D net with bcu -like topology.65c At the same time, the covalent cross-linkage of the BDC liga nds (Figure 1.14.b) resulted in a net with pcu -like topology.65d Figure 1.14. Examples of multifunctional ligands resulted from functionalizing the 5position of 1,3-BDC to derive exte nded nets based on nanoball SBBs: (a) 5-sulfoisophthalic acid, (b) 1,3-bis(5-methoxy-1,3-benzene dicarboxylic acid)benzene and (c) 5(4-tetrazolyl)isophthalic acid. More recent investig ations by Eddaoudi et. al. highlight a reli able design strategy with targeted built-in in formation. The novel net has rht topology (Figure 1.15.), and is based on the assembly of 24-connected na noball SBBs and 3-c onnected trinuclear trimeric clusters MBBs.66 This advancement was aided by the heterofunctional linker 5(4-tetrazolyl)isophthalic acid (H3TZI), where the 5-position of the isophtalic acids is OH O O HO N N HN N O O HO O OH O O OH HO O O OH O HO S O O HO ( a ) (b) ( c )

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19 modified with a tetrazolate moiety. The surface area and gas storage capacities are remarkable, making this material one of the mo st promising candidates in its class; at the same time, this approach offers potential to target the same net built from similar heterofunctional extended ligands. Figure 1.15. Tiling representation of a net with rht topology. Therefore, the construction of MOMs from MBBs has facilitated the process of design and has set necessary conditions fo r the assembly of intended networks.67 By gaining enough control over these design tools, a new generation of a repertoire of novel materials has been pursued and detailed. Th e periodic assembly of intended MBBs has permitted access to expected nets, as well as allowed for the discovery of novel materials.

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20 1.6. MOMs Constructed from Heterofunction al Ligands: a Single-Metal-Ion-based MBB Approach In recent years, our group implemente d a single-metal-ion-based MBB approach which has been identified as a reliable pathway for the cons truction of functional MOMs based on predetermined building blocks.68,69 The concept involves the use of an organic ligand that has Nand Oheterochelating moieties (the nitrogen atom is positioned on the aromatic part of the ring, ha ving carboxylates located in the position relative to the nitrogen), as shown in Figure 1.16. Figure 1.16. Examples of heterofunctional organic linkers. The main advantage of this approach as compared to solely carboxylic acid or nitrogen based ligands is the rigidity and di rectionality reinforced by the chelating ring that locks the metal in its position and mainta ins intact the geometric requirements that facilitate the design of targeted frameworks Within the net to be, the nitrogen atoms direct the topology, while the car boxylates lock the metal in its position. Hence, the main attributes of our approach are the rigidity a nd the directionality em bedded in these singlemetal-ion based MBBs which preserve intact the geometric specific ities of the organic ligands utilized. N O HO HO O N HO O OH O N HN O HO N N HO O OH O

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21 Figure 1.17. Single-metal-ion-based MBBs of the type MNx(CO2)y: (a) MN4O4; two conformational isomers of MN4O2-based MBBs (b) cis MN4O2 and (c) trans MN4O2; two conformational isomers of MN3O3-based MBBs, (d) fac -MN3O3 and (e) mer -MN3O3 and two conformational isomers of MN2O4-based MBBs, (f) cis MN2O4 and (g) trans MN2O4. M= green, C= gray, N= blue, and O= red. (f) (g) (c) (b) (a) (e) (d)

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22 The polytopic nature of such ligands possesses the leading role as to fully saturate the coordination sphere of the single metal i on, in such a way that unwanted coordination of solvent or guest molecules is avoided. The hetero-functionality provided by the organic ligands results in the generation of molecular building blocks of the type MNx(CO2)y (where x represents participating N-, O-chelating moieties, while y is translated to the functionality offered bridgi ng ligands at the availabl e metal sites; M is a commonly a 6-, 7-or 8-coordi nate metal ion), Figure 1.17. This strategy has utterly little limitations in term of the repertoire of materials that it can generate. In such systems, it is enhan ced the role played by the Structure Directing Agents (SDAs), as our group previously repo rted on the synthesis of supramolecular isomers derived from indium metal i ons and 2,5-pyridinedicarboxylic acid (H2-2,5-PDC): discrete octahedron, 2D layered Kagom lattice,70 and 3D diamondoid net.68 The same method has been utilized to target metalorganic polyhedra (MOPs), i.e. metal-organic cube.71 The great majority of the work conducte d in this dissertation focuses on this approach to construct functional materi als, and specifically towards Zeolitelike MetalOrganic Frameworks (ZMOFs).

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23 1.7. Zeolites Purely inorganic materials, zeolites represent a reference point in the area of porous solid-state materials. They possess homogeneously sized and shaped pores and have notable major economic significance with applications in catalysis, ion exchange (ion removal, water softening), separation, gas storage etc.72-85 These materials are comprised of Si and/or Al tetrahedral metal ions (T), linked by oxygen atoms, at approximately 145 T-O-T angles (Figure 1.18.). Figure 1.18. Tetrahedral nodes (T) bridged by oxygen at an angle T-O-T of approximately 145. Si= magenta, Al= yellow, and O= red. The attractiveness of these compounds relies in part on their porosity and forbidden interpenetration. These confined spaces permit their conventional use par excellence as shapeand size-selective catalysts, ion exchangers and adsorbents. Moreover, the access to a multitude of networks makes zeolitic materials highly valuable in function. The diversity of these compounds is reflected in the extended number of framework types (over 170 Zeolit es as recognized by the IZA),86 each differentiated by a specific profile: size of member rings (M R), window/aperture opening, cages dimensions, charge density, framework density (FD, nu mber of tetrahedra l vertices per 1000 3), types of pores etc. The diverse nature of these materials is also influenced by the

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24 synthetic conditions, and of th e utilization of influential Structure Directing Agents (SDAs). However, limitations in their desi gn and tunability restrict these functional materials to certain pore sizes and channel di mensionality and consequently, to smaller molecule applications. Additionally, a general trend implies that increasing pore sizes may lead to unidimensional pore system s and hence, limit the applications. In this context, considering the relevance of the functions associated to solid-state porous materials on a societal and industr ial level, it has become prominent and encouraging to pursue the avenue of di scovering MOMs based on zeolitic topologies. The control of th e MBBs generated in situ has facilitated bett er access to design strategies. Therefore, the set target become s associated with the ability to construct materials in which great emphasis is placed on deriving frameworks possessing large and extra-large cavities, along with readily tuna bility aided by intra and/or extra framework organic components. 1.8. Design Strategies for the Construction of MOMs with Zeolitelike Topologies and Properties Among metal-organic assemblies, emphasis is placed on 3-periodic nets due to their potential for applications Analysis of prevalence of 3D MOMs is evidence that the most occurring of such framework types are based on 4-connected nodes, such as dia nbo cds lvt .87 These reference three letter codes ar e generally associated with the structural features/building blocks, as impl emented by O’Keeffe. In this context, it is denoted that the assembly of simple building blocks, in the absence of a superior reaction

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25 environment (such as a template or SDA), w ill most likely lead to the construction of these default structure relative to those sp ecific building blocks, and, therefore, the efficiency of the design methods that impart directionality and rigidity is strongly impaired. Rational construction of tetr ahedrally connected porous ma terials, related in their topology and function to zeolites, with extralarge cavities and periodic intraand/or extra-framework organic functionality, is an ongoing synthetic challenge, and it is of exceptional scientific and tec hnological interest. The large and extra-large cavities offer great potential for innovative ap plications serving as nanore actors, becoming a platform for a variety of alternative applications pertaining to large molecules, nanotechnology, optics, sensor-technology, medici ne etc., enhancing the correl ation between structure and function. Within the last years, MOMs with zeolitic topologies have become a major focus for research groups in materials chemistr y community, particularly interested in the attractive properties associated with this uni que subset of MOMs. These materials lack interpenetration; hence the accessibility to their porous channel systems is fully exploitable. In principle, the two basic necessa ry conditions in order to target zeolite-like topologies are related with: i) the generation of tetrahedral-based bu ilding blocks and ii) the capability of positioning the tetrahedra l building blocks at approximately 145 (resembling the T-O-T angle in i norganic zeolites of ~145). Up to date, the synthesis of zeolite-like MOMs has proven to be challenging and not trivial, as the complexity associated w ith these structures cannot be easily overcome. Moreover, the assembly of simple tetrahed ral nodes correlates most often with the

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26 formation of the cubic diamond topology, the so-cal led “default” structure for this type of node. 88 Therefore, multiple routes have been e xplored for targeting tetrahedral building blocks associated with the in tended angle connectivity in or der to access non-default nets, and furthermore, to generate MOMs with zeolite topologies. Amongst metal-organic materials analogues to zeolites, sodalite ( sod ) net has the highest occurrence, as its vertices possess high symmetry, while the st ructure accommodates a wide range for the T-O-T angle.67 Over the years, othe r MOMs with zeoli te-like topologies have been encountered, such as: aco89, ana90,91, crb (BCT),90,92-104 dft, 90,92,105-107 gis,90,92,106,108-113 gme,90 lta,114 mer, 90,92 mtn,62,63, 115, 116 sod,117,90,91,92,118-128 rho,117,90,91,92 but only recent studies consider an in depth systematic appr oach for the construction of these materials. Of targeted networks, the number of encounter ed frameworks can be considered as to being limited. In order to access a large num ber of frameworks, including unrevealed topologies, it is necessary to consider multip le variables, including SDAs, nature of the tetrahedral or supertetrahedral building blocks, along with the angularity/additional functionality of the organic component. Theore tically, the number of possible structures to construct from these set conditions is ye t vast, as reflected in the high number of zeolite-like frameworks from hypothetical databases.129

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27 1.8.1. Zeolite MOMs Constructed via Organic Tetrahedral Nodes One possible strategy to c onstruct zeolite MOMs is th rough a so-called “inverted” approach, which introduces the use of organic molecules to act as tetrahedral nodes. This concept involves metal ions with various coor dination numbers required to act as ditopic linkers, while auxiliary weakly coordinating ligands satisfy the re maining coordination sites of the metals. Ultimately, the organic Te trahedral Building Units (TBUs) have to be positioned at suitable angles (average of ~145 ) in order to facilitate structures with zeolite-like features. Figure 1.19. mtn -like framework based on HMTA orga nic tetrahedral nodes. Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. Yellow sphere repres ents the largest sphere that can be fit inside the cavity, considering the van der Waals radii of the nearest atoms. The four nitrogen atoms situated in a tetr ahedral arrangement in HMTA, attribute the desired features to qualify this molecule as an organic tetrahedral nod e. From the work of Qiu et al comes the example of a MOM with mtn topology (Figure 1.19.), constructed from HMTA TBUs, and trigonal bypira midal Cd metal ions which reinforce directionality to the net through the av ailable equatorial coordination sites.130 N N N N

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28 1.8.2. Edge Expansion Approach to MOMs with Zeolitic Features 1.8.2.1. Zeolite MOMs Derived from Angular Ditopic N-donor Ligands: Pyrimidine and Imidazole-based Linkers The search for constructing functional hybrid solid-state porous materials with topologies akin to inorganic zeolites has b een investigated by implementing a top-down approach. By deconstructing the nets into sm all components, it is di stinguished that the materials are built by corner shar ing tetrahedral bridged by an O2anion (T-O-T of ~145). Accordingly, the “edge expansion” refers to a principle that consists of replacing the oxygen atom with an organic functiona lity that preserves the desired angle connectivity. The strategy is based in choosing single-me tal ions with preferred tetrahedral geometry, in combination with a ngular ditopic Nbased organic ligands. Such candidates have been imidazole and pyrimidine based molecules. Given these guidelines, several other paradigms outline derivations of the approach described above. One example is illustrated in Figure 1.20., where a metalorganic framework with the zeolite sod topology, is built from 2-hydroxypyrimidine (2Hpymo) ligands which are bridging square planar copper (II) metal ion centers.120 Correspondingly, a topologically equivalent net is constructed from yet another pyrimidine derivative, 4-hydroxypyrimidine (4-H pymo) and copper (II), with octahedral geometry.125

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29 Figure 1.20. sod -like frameworks based on 2-Hpym o (left) and 4-Hpymo (right). Hydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. More recent studies from Yaghi and co-workers, 90,92 among others,91, 106,124 furthermore reinforce the ability of imidazole -based linkers to yield MOMs with zeolitic topologies and properties. Synt hetically, the challenges are associated with a reaction environment which lacks SDAs, thus limiting the variety of the zeo lite-like topologies that can be derived solely from imidazole. The alternative route in favor of structure diversity is portrayed by linker functionalizat ion. In accordance with this approach, they report on the synthesis of various Zeolitic Imidazolate Frameworks (ZIFs), including ana, crb (BCT) dft, gme, gis, lta, mer, sod and rho The overall topological features resemble the ones encountered in the trad itional inorganic zeolites, howev er, on a larger scale, as a result of introducing th e organic functionality. NN HO NN OH

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30 As the goal of producing zeotype archite ctures based on metal ions and organic ligands has been successfully pursued, the di fficulty of accessing hierarchically complex structures with more than one type of cage remains a challenge. In this context, Yaghi et.al recently highlight on the organic ligand functionalization effect While when using benzimidazole, they obtain two materials with zeolitic sod and rho topologies, by replacing the carbon atom with a nitrogen atom in the 4-position of benzimidazole, the ubiquitous diamond structure is favored. C onversely, by replacing the carbon atom(s) with nitrogen atom(s) in 5or 5and 7position on benzimidazole, a framework with lta (Linde Type A or zeolite A) topology is c onstructed, consisting of two types of cages truncated cuboctahedra ( cage) and truncated octahedra ( cage) (Figure 1.21.).114 The inorganic LTA has an internal free diamet er of 11.4, while in its metal-organic analogue it increases to 15.4 ; hence, numerous studies were conducted towards exploiting its porosity for gas storag e/separation related applications. Figure 1.21. Schematic representation of lta -net constructed from th ree different types of tiles 3[46]+[412.68.86]+[46.68]. NH N N NH N N N

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31 1.8.2.2. Zeolite -like Metal-Organic Frameworks (ZMOFs) Constructed via the Single-Metal-Ion-based MBB approach Introduced earlier in this chapter, th e single-metal-ion-based MBB approach has shown potential to be suitable also for targeting Zeolitelike metal–organic frameworks (ZMOFs).117,131 ZMOFs represent a unique subset of MOMs that are t opologically related to the purely inorganic zeolites and exhi bit similar properties: (i) forbidden selfinterpenetration which allows for the design of readily accessible extra large cavities; (ii) chemical stability, where the structural integrity is maintained in water (not common in MOMs), permits potential ZMOF applications for heterogeneous cat alysis, separations, and sensors, especially in aqueous media; (iii) ion exchange capab ility permits (a) the ability to control and tune extraframework ca tions toward specific applications such as catalysis or gas storage and (b) the rem oval/sequestration of toxic metal ions. In this context, the edge expansion stra tegy qualifies as appropriate for the design and synthesis of very open ZMOFs. The key factors are related with the ability of generating rigid and directional Tetrahedra l Building Units (TBUs), which are to be positioned at intended angle through the aid of rigorously chosen heterofunctional organic ligands. These angular ditopic organic linkers will th erefore serve to replace the oxygen bridges in traditional zeolites, while maintaining the placement of TBUs at similar angles T-O-T (~145). Consequently, it is evident that build ing information into the MBB is vital, and it is of broader intere st to use the MBB approach based on rigid and directional single-metal-ion TBUs as a so lid platform and basis for developing new design strategies to construct and functionaliz e novel ZMOFs for specific applications.

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32 Having these set conditions, our group employed imidazoledicarboxylates (ImDC) as potential attractive candidates to serve our purposes (possessing both desired angularities and he terofunctionality).117 From the metal ion choice perspective, metal ions that have primarily six or eight available coordination sites were targeted, that should further allow the formation of the in tended building blocks of the type MN4(CO2)2, MN2(CO2)4, MN4(CO2)4, MN2(CO2)6 to ultimately render TBUs. Accordingly, when four ImDc ligands saturate the coordination sphere of a single-metal ion (divalent or trivalent), an anionic ZMOF can be realized. Accordingl y, we successfully reported the synthesis of two anionic ZMOFs with rho and sod topologies, which possess large and extra-large cavities, up to 8 times larger than their inor ganic analogs (Figure 1.22.). As in the case of 2,5-H2PDC-based supramolecular isomers menti oned previously, the anionic nature allows for the utilization of ca tionic SDAs, as well as explorat ion of applications akin to traditional zeolites. rho -ZMOF is synthesized in th e presence of 1,3,4,6,7,8-hexahydro2 H -pyrimido[1,2a ]pyrimidine (HPP), while sod -ZMOF is formed in the presence of imidazole (Imi).

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33 Figure 1.22. MN4(CO2)4 and MN4(CO2)2 MBBs regarded as TBUs for the construction of rho -ZMOF (bottom left) and sod -ZMOF (bottom right). H ydrogen atoms and solvent molecules have been omitted for clarity; M= green, C= gray, N= blue, and O= red. Yellow sphere represents the largest sphere that can be fit inside the cavity, considering the van der Waals radii of the nearest atoms. Additionally, our group’s findings lead to the discovery of a novel zeolitelike net, usf -ZMOF,132 with unprecedented topology, referred to in the RCSR database as med (Figure 1.23.). The synthetic protocol invol ves similar starting materials as for and rho ZMOFs and sod -ZMOF detailed above, yet in the presence of another SDA, 1,2diaminocyclohexane (1,2-H2DACH) N HN O HO HO O

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34 Figure 1.23. Two different types of cage s and tiling representation of usf -ZMOF ( med ) 2[49.62.83] + [410.64.84]. In this context, some of the challenges a ssociated with the work conducted for this dissertation are directly ta rgeting the construction of ZMOFs and other functional materials with extra-large cavities, and will be thoroughl y detailed in Chapter 4.

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35 1.9. Functionality in MOMs The great majority of studies on functi onal MOMs are directed towards exploiting their permanent porosity, and therefore, thei r relevance for hydroge n storage, selective gas sorption and separation. At the same time, MOMs are considered promising candidates in the areas of catalysis,133a magnetism,134 and luminescence and sensors135 related applications. More recently, investig ations are also targeting post-covalent modifications,136 thin films related functions,137 and even can even be found in industrial setting.138 MOMs are well suited for catalysis as th ey are very diverse and amenable to allow modifications that would be appropria te for targeting certain reactions; however, these features are only relevant in regimes that do not require stability at very high temperatures, and where zeolites are cu rrently outperforming MOMs. Catalytic investigations account for their porosity and/ or the presence of metal centers, while a concern is related with resp ect to establishing the exact source responsible for the catalytic activity. One of the earliest repor ts in this area comes from Fujita and coworkers in 1994, who probed the cyanosilyla tion of aldehydes usi ng a two-periodic square grid constructed from Cd and 4,4 ’-bipy, outlining size and shape selectivity.139 Several other investigations were carried out on the most studied compounds, such as MOF-5, Friedel–Crafts tert -butylation of bi phenyl and toluene.140 Cyanosilylation of aldehydes was also probed in MOMs with coor dinative unsaturated metal centers, such as HKUST-1141 and MIL-101. 142

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36 Porphyrins are well recognized as molecu lar catalysts, and in the context of MOMs they were implemented as linkers,143 and more recently as pillars to extend twoperiodic layered structures.144 Our group has considered th e incorporation of free base porphyrin, [H2TMPyP][ p -tosyl]4+, in the extra-large cavities of rho -ZMOF, followed by post-synthetic metallation by various transiti on metal ions to produce a wide range of encapsulated metalloporphyrins.145 The assessment of the catal ytic activity consisted of oxidation of cyclohexane, performed in th e presence of Mn-met alated version. Homochiral MOMs are primarily targeted for enantioselective separations related applications.146-152 Achiral components can be imple mented to form homochiral frameworks; however, emphasis is placed on using chiral building block approaches, including bridging linkers that may possess catalytically active sites. Lin and co-workers have reported a number of relevant examples possessing these properties 153-159 and recently reviewed the state-of -the-art in heterogeneous as ymmetric catalysts for the production of enantionmeric pure products.133b Molecular magnetism160 represents another attrac tive property encountered in certain MOMs.7, 11,161-173 At such, an important role is especially played by the transitional metal, since most of the organi c linkers possess diamagnetic properties, and consequently, very low magnetization propertie s. Hence, the magnetic centers need to favor cooperative interactions in order to generate an overall magnetic moment.8 These types of interactions are usua lly ordering at low temperature that is most of the times referred as critical temperature, Tc. One of the goals in this di rection is to be able to design materials that possess a pe rmanent magnetization at a high Tc and at zero-field current.

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37 Gas sorption related properties in MOMs represent by far the most extensive studies conducted with MOMs.174-177 Specifically, hydrogen and recently CO2 storage, along with selective gas storage for gas separation purposes178 is also a much researched aspect. These capabilities will be thorough detailed in Chapte r 5, in the context of novel synthesized and characterized porous materials, and whic h make the objective of a consistent part of this dissertation. Therefore, the hybrid nature of MOMs ma kes them suitable for a repertoire of applications, and concerted efforts are direct ed towards enhancing the structure-function relationship in these materials.

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38 1.10. References 1. Yaghi, O. M.; Li, H. L.; Davi s, C.; Richardson D. and Groy, T. L. Acc. Chem. Res. 1998 31 474-484. 2. Kondo, M.; Okubo, T.; Asami, A.; Noro, S.-I.; Yoshitomi, T.; Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Seki, K. Angew. Chem. Int. Ed 1999 38 140-143. 3. Kahn, O. Acc. Chem. Res. 2000 33 647-657. 4. Moulton, B.; Zaworotko, M. J. Chem.Re v 2001 101 1629-1658. 5. Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O'Keeffe, M.; Yaghi, O. M. Science 2002 295, 462-472. 6. Evans, O. R.; Lin, W. Acc. Chem. Res. 2002 35 511-522. 7. James, S. L. Chem. Soc. Rev. 2003 32 276-288. 8. Janiak, C. Dalton Trans. 2003 2781-2804. 9. Chae, H. K.; Siberio-Perez, D. Y.; Kim, J.; Go, Y.; Eddaoudi, M.; Matzger, A. J.; O'Keeffe, M. and Yaghi, O. M. Nature 2004 427 523-527. 10. Frey, G.; MellotDraznieks, C.; Serre C. and Millange, F. Acc. Chem. Res. 2005 38 217-225. 11. Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem. Int. Ed. 2004 43 2334 – 2375. 12. Rao, C. N. R.; Natarajan S. and Vaidhyanathan, R. Angew. Chem. Int. Ed. 2004 43 1466-1496. 13. Frey, G. Chem. Soc. Rev. 2008 37 191-214. 14. Dinc M. and Long, J. R. Angew. Chem. Int.Ed. 2008 47 6766-6779. 15. Keggin, J. F. Nature 1936 137 577-578. 16. Griffith, R. L. J. Chem. Phys. 1943 11 499-505. 17. Nassimbeni, L. R.; Papanicolaou, S.; Moore, M. H. J. Inclusion Phenom. 1986 4 31-42. 18. Hofmann, K. A. and Kiispert, F. Z. Anorg. Chem. 1897 15 204-207.

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49 Chapter 2. MOMs Derived from Angular Thiophe nedicarboxylate Bridging Ligands 2.1. Introduction Given the significant importa nce of zeolites in the area of porous materials related applications, the attempt for the design a nd synthesis of their metal-organic expanded analogues, represents a relevant research endeavor within th e last two decades. A major topic of this dissertation, the most significant examples, design strategies and challenges were thoroughly discussed in Chapter 1. In the early stages, the primary target was related to establishing reliable design plans that would eventually lead to the synthesis of materials with similar topologies and properties with zeolite. Accordingly, by deconstructing the repertoire of inorganic ne tworks, it is revealed that the tetrahedral units are bridged by oxygen atoms (T-O-T), positioning the two nodes at approximately 144 Therefore, this top-down approach enables the materi al designer with sufficient information towards the bottom-up synthetic route. That is to incorporate the same amount of information, but on a larger scale, replacing the oxygen atom by the organic functionality, approach referre d to as the “edge expansion” Accordingly, the two major

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50 conditions that concomitantly have to be met are related to: i) the rational choice of the organic ligand and ii) control over the generation of tetrah edral building units (TBUs). In this chapter, the focus is on MOMs generated from angular carboxylate-based ligands with such attributes: 2,5 -thiophenedicarboxylic acid (2,5-H2TDC) and its derivative, 3,4-dipheny l-2,5-thiophenedicarboxylic acid (3,4-diphenyl-2,5-H2TDC). Experimental Section Unless otherwise noted, all MOMs discu ssed in the following chapters were synthesized and characterized by Dorina F. Sava in Prof. Mohamed Eddaoudi’s group, Department of Chemistry at the University of South Florida accord ing to the following: Materials and Methods All chemicals were used as received fr om Fisher Scientific, Sigma-Aldrich, and TCI America chemical companies. Single-crystal X-ray diffraction (SCD) da ta were collected on a Bruker SMARTAPEX CCD diffractometerusing MoK radiation ( = 0.71073 ) operated at 2000 W power (50 kV, 40 mA). The frames were in tegrated with SAINT software package1 with a narrow frame algorithm. The structures were solved using direct methods and refined by full-matrix least-squares on| F |2. All crystallographic calcul ations were conducted with the SHELXTL 5.1 program package,2 and performed by Dr. Lukasz Wojtas, Dr. Derek Beauchamp, Dr. Gregory J. McManus in the De partment of Chemistry at the University

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51 of South Florida and Dr. Victor Kravtsov at the Institute of Applied Physics of Academy of Science of Moldova. Crystallographi c tables are included in Appendix A. X-ray Powder Diffraction (XRPD) meas urements were carried out on a Bruker axs D8 Advance 50kV, 40mA for CuK ( = 1.5418 ), with a scan speed of 1/min and a step size of 0.02 in 2 at room temperature. Calculated XRPD patterns were produced using PowderCell 2.4 software3 and/or Materials Studi o MS Modeling version 4.0.4 XRPD patterns are included in Appendix B. The graphical structural analysis wa s performed using Ma terials Studio MS Modeling version 4.0.4 Olex5 and Topos6 software were used to evaluate the topological sequences of all compounds; RCSR database was utilized as primary resource for comparison purposes related to topological analyses. For all known topologies the three-letter symbols code implemented by Prof. Michael O’Keeffe (e.g. sql represents a square lattice) is used. Tiling representations were ev aluated using 3dt software.7 Total solvent-accessible volumes were determined using PLATON8 software by summing voxels more than 1.2 away from the framework. Atomic Absorption experiments were conducted on a Varian Spectra AA 100 instrument, with the help and supervision of Mr. Farid Nouar at Department of Chemistry at the University of South Florida. Volumetric gas sorption studies were performed on a Quantachrome Autosorb-1 instrument; gravimetric gas sorption studies were performed on a VTI MB-300 GHP

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52 (Gravimetric High Pressure Analyzer) by Mr Ryan Luebke, in the Department of Chemistry at the University of South Florida. 2.2. Experimental Section Synthesis of {[Cd3(2,5-TDC)6]( 2H -Dabco)2( H -Dabco)(DMA+)(H2O)0.5}n, 1 The reaction mixture containing Cd(NO3)24H2O (0.02175mmol, 0.0067g ), 2,5-H2TDC (0.0435mmol,0.0075g), DMF (1mL), CH3CN (1mL), Dabco (0.15mL, 1.78M in DMF) and HNO3 (0.15mL, 3.5M in DMF) wa s placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and 115 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. Polyhedral colorless crysta ls were collected and air-dried and were determined to be insoluble in water and common organic solvents. Synthesis of {[Cd2(H2O)(2,5-TDC)2(HMTA)2/3(DMF)2](CH3CN/H2O)1/3]}n, 2 The reaction mixture containing Cd(NO3)24H2O (0.02175mmol, 0.0067g ), 2,5-H2TDC (0.0435mmol, 0.0075g), DMF (1mL), CH3CN (1mL), HMTA (0.15mL, 1.42M in H2O) and HNO3 (0.15mL, 3.5M in DMF) wa s placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. Parallelepipedic colorless crystals were collected and air-dried and were determined to be insoluble in water and common organic solvents.

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53 Synthesis of {[Co(3,4-diphenyl-2,5-TDC)2](DMA+)2(H2O)3.3}n, 3 The reaction mixture of Co(NO3)26H2O (0.02175mmol, 0.00633g) 3,4-diphenyl-2,5H2TDC (0.0435mmol,0.007g) DMF (1.5mL), CH3CN (1mL), Pip (0.30mL, 0.58M in DMF) and HNO3 (0.15mL, 3.5M in DMF) was placed in a 20mL scintillation vial and heated to 85 C for 12 hours, followed by additional heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Purple cubic crystals were collected and air-dried and were determined to be insoluble in water and common organic solvents. Synthesis of {[Co(3,4-diphenyl-2, 5-TDC)(Dabco)](H2O)0.5}n, 4 A mixture of Co(NO3)26H2O (0.02175mmol, 0.00633g) 3,4-diphenyl-2,5-H2TDC (0.0435mmol, 0.007g), DMF (1.5mL), CH3CN (1mL), H2O (1mL), Dabco (0.20mL, 1.78M), was placed in a 20 mL scinti llation vial and was heated to 85 C for 12hours, which was followed by subsequent heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Green octahedral crystals were collected and air-dri ed and were determined to be insoluble in water and common organic solvents. Synthesis of [Cd2(3,4-diphenyl-2,5-TDC)3(NO3 -)DMF](DMA+)3(DMF)2, 5 A mixture of Cd(NO3)24H2O (0.02175mmol, 0.0067g) a nd 3,4-diphenyl-2,5-H2TDC (0.0435mmol, 0.007g), DMF (1 mL), CH3CN, (1mL), Pip (0.2mL 0.58M in DMF) and HNO3 (0.15mL, 3.5M in DMF) was heated to 85 C for 12hours, followed by additional

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54 heating at 105 C for 23 hours and 115 C for 23 hours at a heating rate of of 1.5 C/minute and cooled to room temperat ure at a cooling rate of 1 C/minute. Polyhedral crystals were collected and air-dried and were determined to be insoluble in water and common organic solvents. 2.3. Results and Discussion 2, 5H2TDC and 3,4-diphenyl-2,5-H2TDC (Figure 2.1.) represent organic linkers that hold potential to serv e the purpose towards the constr uction of MOMs with zeolitic features, due to their inherent geometry that positions the carboxylat es functional groups at about 144 Combining these capabilities with the variety of metal coordination geometries, an arsenal of complexes can be constructed. The focus of the current studies is on generating frameworks based on 4-c onnected nodes, and speci fically on materials with zeoliteslike topologies. Figure 2.1. Prototype 144 angle in a) 2,5H2TDC and b) 3,4-diphenyl-2,5-H2TDC. S O HO OH O S O HO OH O

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55 Both angular ligands possess two carboxy lic acids functionalities in the 2 and 5 positions to generate a divalent anion br idging linker, available for coordination upon deprotonation. Based on the specif ic experimental conditions (pH, ionic strength, solvent system, temperature) and vari ous coordination modes afforded by the metal ions sources with various geometries/oxidation states, a repe rtoire of neutral and/or charged (anionic or cationic) nets can be obtained.9,10 Figure 2.2. highlights several binding modes afforded by 2, 5-TDC, upon binding to the metal ion. Figure 2.2. Common binding modes afforded by 2,5-TDC. S O O O O M S O O O O M M S O O O O M M M S O O O O M M M M S O O O O M M S O O O O M M M S O O O O M M

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56 As mentioned earlier, the emphasis is placed on targeting networks based on 4connected nodes, and specifically, framework s derived from TBUs, which hold potential for the generation of ZMOFs. The choice of me tal ions is regarding primarily those that can predominantly adopt tetrahedral geometri es, case in which the ligands should bind solely in a monodentate fashion. Benefiti ng the other bridging capabilities of the thiophenedicarboxylate linker, metal ions w ith higher coordination numbers are also suitable to facilitate the formation of tetr ahedral building blocks. Although the rationale is feasible and should yield th e intended outcome, it is antici pated that the generation of the most occurring structures based on 4connected nodes would be favored primarily: tetragonal sheets for two-periodic nets and diamondoid-type networks11 for the threeperiodic frameworks. Accordingly, the reaction between Cd(NO3)34H2O and 2,5-H2TDC, under mild solvothermal conditions results in the form ation of polyhedral crystalline material, characterized and formulated by crystallographic studies as {[Cd3(2,5-TDC)6]( 2H Dabco)2( H -Dabco)(DMA+)(H2O)0.5}n,, 1 In the crystal structure of 1 Cd adopts a heptacoordinated geometry, where a ll the available binding sites are fully saturated by four thiophenedicarboxylate ligands.

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57 Figure 2.3. (a) M(CO2)4 type MBB representing a (b) tetrahedral node, TBU in compound 1 Hydrogen atoms are omitted for clar ity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. The representative MBB is expressed by Cd(CO2)4, Figure 2.3.a, in which three ligands bind the metal ion in a bis(bidentate) fash ion, while the forth one coordinates in a monodentate way, giving rise to a tetrahedra l node, regarded as a TBU, Figure 2.3.b. The overall arrangement of the MBBs results in an anionic three-periodic net that triply selfinterpenetrates, and in which protonated Da bco guest molecules and dimethylammonium cations are ensuring the net’s charge ba lance. The resulting framework possesses diamond topology, Figure 2.4., highlighting to some ex tent an expected result, as it is the most likely net to form from a tetrahedral node.12 (a) (b)

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58 Figure 2.4. (a) Ball and stick representati on and (b) cubic diamond topology in compound 1 Hydrogen atoms are omitted for clar ity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. In this context, an alternative route towards targeting novel frameworks based on 4-connected nodes consists of introducing strong competitive terminal ligands/templating molecules in order to generate a complex react ion environment that could potentially lead to the generation of non -default structures. Compound 2 forms upon heating a reaction mixture of Cd(NO3)24H2O and 2,5TDC in a DMF/CH3CN solution, resulting in parallelepi pedic colorless crystals. Upon single-crystal X-ray crystallography st udies, the compound was formulated as {[Cd2(H2O)(2,5-TDC)2(HMTA)2/3(DMF)2](CH3CN/H2O)1/3]}n, 2 Detailed structural i nvestigations reveal a M2N2(CO2)6 MBB, Figure 2.5., consisting of a cadmium dimetal cluster (r esembling the paddle wheel-type molecular cluster) generated by four independent thi ophenedicarboxylate ligands, two of which are bridging the metal in a monodentate fashion, while the other two adopt a bis-monodentate binding mode. The 2-bridging water molecule forms two intermolecular O-HO hydrogen bonds with the non-coordinate d oxygen atoms of the carboxylic groups.

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59 Figure 2.5. M2N2(CO2)6 type MBB, regarded as a si x-connected node. Hydrogen atoms are omitted for clarity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. In the same time, two DMF molecules ar e completing the coor dination sphere of the metal ions in the cluster, while two HM TA molecules occupy the apical position in this MBB. In this case, the HMTA plays a more elaborate role because it is not acting solely as a terminal ligand, but also as bridgi ng linker, as it further connects three distinct MBBs at this position (depicted in Figure 2.6.) Disordered acetonitrile and water solvent molecules of partial occupancy are re siding in the crystalline lattice. The complex structure consists to two types of nodes: a six-connected, corresponding to the overall connectivity associated with the cl uster, Figure 2.5., and a three-connecting node, associated with HM TA’s capabilities, Figure 2.6. Topological analysis performed with the aid of TOPOS software,6 confirms the framework’s unprecedented topology (Figure 2.7.). The hete rocoordinated net is defined by unique coordination sequences and vertex symbols. The coordination sequence for the 3connected node is 3, 12, 31, 64, 107, 160, 220, 293, 373, 466, while for the 6connected node is: 6, 18, 42, 78, 122, 176, 240, 314, 398, 492.

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60 Figure 2.6. HMTA-based MBB, regarded as a three-connected node. Hydrogen atoms are omitted for clarity; Cadmium =green, carbon =gray, nitrogen = blue, oxygen = red, sulfur= yellow. The corresponding vertex symbols for the 3connected node, [4.4.4], and for the 6connected node, [4.4.4.4.4.4.6(2).6(2).6(2).6 (2).6(4).6(4).8(28).8(28).8(8)]. The superior reaction environment did not yield expected results, however very interesting materials could be arising from serendipitous discoveries as well, as we encountered in this case a ma terial possessing a novel topology.

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61 Figure 2.7. Representative fragment of topology in compound 2 outlining the heterocoordinative nature of the fr amework based on (6,3) nodes. The net’s transitivity is [2233], while the tiling representation is depicted in Figure 2.8. Figure 2.8. Representative tiles in compound 2 The use of thiophene-based organic ligands as means to construct nets based on 4connected nodes was further ex tended to a derivative of 2,5-H2TDC, namely 3,4diphenyl-2,5-H2TDC. The bulkier phenyl groups in th e 3 and, respectively, 4 position of [46] + 3[4.62]+ [66] [46] 3[4.62] [66]

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62 the thiophene core may stabilize the aver age angle range associated with the two carboxylate groups in the 2 and 5 positions, upon coordination to metal ions. The novelty of this work is also reflected by the fact that it has not been yet employed for the synthesis of MOMs, as no reports are found in Cambridge Structural Database (CSD) to date.13 The reaction between Co(NO3)2H2O and 3,4-diphenyl-2,5-H2TDC under mild solvothermal conditions yields purple cubi c crystals characterized and formulated by crystallographic studies as {[Co(3,4-diphenyl-2,5-TDC)2](DMA+)2(H2O)3.3}n, 3, where DMA represents the dimethylammonium extraframework cations generated in situ from decomposition of DMF, which balance out the ch arge in the anionic material. Analysis of the crystal structure of 3 reveals a material that consis ts of two doubly interpenetrated frameworks, resulting in a densely packed net. Figure 2.9. Representative MBB in compound 3 regarded as a te trahedral node, acting as a TBU. Hydrogen atoms are omitted for clarity; Cobalt= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow.

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63 Cobalt adopts a tetrahedra l geometry, and it’s coordi nated by four monodentate thiophene ligands, giving rise to a tetrahedral MBB of the type M(CO2)4, Figure 2.9. The phenyl rings are skewed out of the plane of the aromatic ring with an average of 68 and are pointing inside the cavities, filling up th e potential available space. The overall threeperiodic framework consists of alternating three and ten member rings (Figure 2.10.). The latter is made up by one “edge” of te n individual three member rings. Figure 2.10. Ball-and stick representation of thre e-member ring (left) and schematic representation of ten-memb er ring (right) in compound 3 Hydrogen atoms are omitted for clarity; Cobalt= green, carbon= gray, nitr ogen= blue, oxygen= red, sulfur= yellow. Topological evaluation reveals a net with lcv topology, which stands for lattice complex vertex (Figure 2.11.). This denomination is correl ated with the fact th at it is the only uninodal 4-connected framework that has two three member rings meeting at a vertex.14 The corresponding coordination sequence for the lcv net with 1121 transitivity: 4, 8, 16, 32, 54, 70, 102, 128, 158, 212, and the long vertex symbol: [3.3.10(2).10(2).10(3).10(3)].

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64 At the time of the synthesis, the compound represented first example of a metal-organic material possessing this topology, while since th en just one example has been reported.15 Figure 2.11. (a) CPK representation of single framew ork, (b) schematic representation of lcv topology and (c) repres entative tiles in compound 3 Hydrogen atoms, guest and phenyl rings are omitted for clarity; Coba lt= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. Cobalt complexes are well studied for th e potential relevant magnetic properties.16 Magnetic measurements conducted on 3 monitored the temperature dependence of the magnetization vs. applied magnetic field (in a range from -50 KOe to 50 KOe), as shown in Figure 2.12.. At temperatures close to ambi ental conditions, 300 K the plotted straight [32.103] (a) (b) (c)

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65 line depicts the paramagnetic behavior in the material. Ferromagnetic interactions are occurring at a critic al temperature of Tc =20K phenomenon outlined by the sinusoidal shape measured at 2K. Figure 2.12. Magnetic measurements on compound 3 : (a) magnetization vs. applied magnetic field, (b) magnetization vs. temperature. Further experiments conducted on a system based on the same starting materials, Co(NO3)26H2O and 3,4-diphenyl-2,5-H2TDC, but in the presence of slightly dissimilar SDA/solvent system resulted in 4 formulated as {[Co(3,4-diphenyl-2,5TDC)(Dabco)](H2O)0.5}n by single-crystal X-ray diffractio n studies. The three-periodic net is assembled from M2(CO2)8 type MBBs, representative of the dimetal tetracarboxylate “paddle wheel”, Figure 2.13. The coordination sphere of the metals is completed by terminal Dabco molecules, lo cated in the apical position of the MBB. 020406080100 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 H = 1 kOeM (emu)T (K)-60000-40000-200000200004000060000 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 M (emu)H (Oe) 2 K 20 K 25 K 300 K (a) (b)

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66 Figure 2.13. Representative MBB in compound 4 regarded as a square building unit. Hydrogen atoms are omitted for clarity; C obalt= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. Unidimensional channels of ~6 (when considering the wan der Waals radii of the nearest atoms) are potentially exploitable, while in the other two directions, the voids are obstructed by the phenyl rings tilted out of the thiophene core by an average angle of ~ 63.44 Analysis of the vertex symbol [ 4.4.8(4).8(4).8(8).8(8) ] and coordination sequence 4, 10, 24, 44, 72, 104, 144, 188, 240, 296, 1127, confirms the fact that the 4connected framework possesses lvt topology,17-20 depicted in Figure 2.14, also with 1121 transitivity.

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67 Figure 2.14. Ball-and-stick depiction of simplified framework, (b) schematic representation of lvt topology and (c) represen tative tiles in compound 4 Hydrogen atoms, guest and phenyl rings are omitted for clarity; Cobalt= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. The magnetic measurements conducted on 4 outline a very similar behavior as in the case of 3 That is, ferromagnetic interactions are ordering at very low temperatures (2K), Figure 2.15., when plotting magnetization vs applied magnetic field in the range (a) (b) (c) [ 42 .8 4 ]

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68 50 KOe to 50 KOe, while typical linear para magnetic behavior is observed at room temperature. Figure 2.15. Magnetic measurements on compound 4: (a) magnetization vs. applied magnetic field, (b) magnetization vs. temperature. Furthermore, the solvothermal reaction between Cd(NO3)2H2O and 3,4diphenyl-2,5-H2TDC yields a two-periodic MOM, fo rmulated by crystallography studies as {Cd2 (3,4-diphenyl-2,5-TDC)3(NO3 -)DMF](DMF)2(DMA+)3}n. Analysis of the crystal structure reveals that the two crystallographically independent cadmium cations are coordinated by three ligands in a bis(bident ate) fashion, generating a M(CO2)6 type MBB. The coordination sphere of the metal ion is completed by either NO3 anion or neutral DMF molecules, as shown in Figure 2.16.a. The resulting building unit is regarded as a T-shaped three connector, which sustains th e assembly of undulated bricks-wall like sheets, Figure 2.16.b.. The thiophenedicarboxyla te ligands are alternating up and down, where the dihedral angles vary between 50.512-78.578, correspondent to the steric torsion of the phenyl rings out of the thi ophene core. The overall character of the -60-30 0 30 60 -2 -1 0 1 2 -006 -003 000 003 006 M(emu)H(k Oe) 2 K 300 K020406080100 0.0 0.4 0.8 1.2 M'(emu 10-3)T(K)

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69 framework is anionic, with three dimet hylammonium cations providing the charge balance. Concomitantly, the guest mol ecules are bridging the sheets via N-H…O hydrogen bonds, within the range 2.699-2.923. Figure 2.16. (a) MBBs in compound 5 regarded as three-conn ected T-shaped nodes; (b) ball-and-stick (left) and sc hematic representation of hcb topology (right) in compound 5 Hydrogen atoms and guest molecules are omitted for clarity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red, sulfur= yellow. As compared to the two other structures derived from the same organic ligands, 3 and 4 nets based on 4-connected nodes, in 5 we note the differences introduced by the terminal ligands (NO3 -/DMF) which restrain the occu rrence of a net based of a 4connected node. (a) (b)

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70 2.4. Summary Herein it has been remarked the potentia l of the design strategy based on angular thiophenedicarboxylates, 2,5-TDC and 3,4-diphenyl -2,5-TDC, to generate frameworks constructed from 4-connected nodes. Novel materials were obtained upon implementation of this approach, and primar ily the emphasis is put on the significant effect of the SDA directed synthesis, howev er not resulting in intended ZMOFs. One possible reason regarded for this outcome is the degree of flexib ility of the carboxylic functional groups, which alter the indended positioning of the building units within the desired angle range. Nevertheless, upon finding the appropriate experi mental conditions, the goal of deriving nets with zeolitelike features should still be at tainable via this route, as well. In the same time, these findings offer valuable insights towards targeting similar angular organic ligands, with superior built-in functionalit y. Such organic ligands are represented by heterofunctional angular N-donor based linkers that have carboxylic acid functionalities in the position relative to the nitrogen. This new pathway is to be thoroughly discussed in the following chapters.

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71 2.5. References 1. Saint Plus, v. 6.01, Bruker Analytical X-ray, Madison, WI, 1999 2. Sheldrick, G. M. SHELXTL, v. 5.10; Bruker Analytical X-ray, Madison, WI, 1997 3. Powder Cell for Windows, Versi on 2.4 (programmed by W. Kraus and G. Nolze, BAM Berlin, 2000). 4. Accelrys MS Modeling 4.0, 2005, Accelrys Software Inc. 5. OLEX (v. 2.55, Release 10.09.2004): Do lomanov, O. V; Blake, A. J.; Champness, N. R.; Schrder, M. J. Appl. Cryst. 2003 36 1283-1284. 6. TOPOS (v. 4.0 Profesional) Blatov, V. A., Carlucci, L., Ciani, G., Prosperpio, D. M. Cryst. Eng. Comm. 2004 6, 378-395. 7. 3dt Delgado-Friedrichs, O. The Gavrog Project http://gavrog.sourceforge.net/ 8. PLATON, 1980-2007 A.L.Spek, Utrech t University, Padualaan 8, 3584 CH Utrecht, The Netherlands. http://www.cryst.chem.uu.nl/platon/. Spek, A. L. J. Appl. Cryst. 2003 36 7-13. 9. Eddaoudi, M.; Kim, J.; Vodak, D.; S udik, A.; Wachter, J.; O'Keeffe, M.; Yaghi, O. M. Proc. Nat. Acad. Sci. U.S.A. 2002 99 4900-4904. 10. Sun, X.-Z.; Sun, Yi-F.; Ye, B.-H.; Chen, X.-M. Inorg. Chem. Commun. 2003 6 1412-1414. 11. Moulton, B.; Zaworotko, M. J. Chem.Re v 2001 101 1629-1658. 12. O'Keeffe, M.; Eddaoudi, M.; Li, H.; Reineke, T.; Yaghi, O. M. J. Solid State Chem. 2000 152 3-20. 13. Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993 8 31-37. CSD Cambridge Structural Database of organic and metal-or ganic structures (v1.10, including a Jan. 2009 update). 14. M.O’Keeffe, Acta Cryst 1992 A48 670-673. 15. Solntsev, P. V.; Sieler, J.; Kr autscheid, H.; Domasevitch, K. V. Dalton Trans. 2004 8 1153-1158.

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72 16. Kurmoo, M. Chem. Soc. Rev. 2009 38 1353-1379. 17. Kurmoo, M.; Kumagai, H.; Green, M. A.; Lovett, B. W.; Blundell, S. J.; Ardavan, A.; Singleton, J. J. Solid State Chem. 2001 159 343-351. 18. Evans, O. R.; Manke, D. R.; Lin, W. Chem. Mater. 2002 14 3866-3874. 19. Rather, B.; Moulton, B.; Bailey Walsh, R. D.; Zaworotko, M. J. Chem. Commun. 2002 7 694-695. 20. Carlucci, L.; Cozzi, N.; Ciani, G.; Mo ret, M.; Proserpio, D. M.; Rizzato, S. Chem. Commun. 2002 13 1354-1355.

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73 Chapter 3 MOMs Constructed via the Single-Metal-Ion-based MBB Approach 3.1. Metal-Ligand Directed Assembly of MOMs from Iron and 2,5-H2PDC 3.1.1. Introduction The rational design of solid-state mate rials from single-metal-ion based MBBs derived from heterofunctional or ganic linkers, has been proven reliable and of particular interest in recent years.1-3 In this subchapter, the focus is on MOMs derived from a heterochelating multifunctional ligand, namely 2,5-pyridinedicarboxylic acid (2,5-H2PDC), and octahedral single metal ions capable to rende r rigid and directional MBBs of the type MNx(CO2)y (where x represents participating N-, O-chelating moieties, while y is translated to the functionality offered bridgi ng ligands at the availabl e metal sites; M is a 6-coordinate metal ion).

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74 3.1.2. Experimental Section Materials and Methods All materials and methods are described in Chapter 2, unless otherwise noted. Static and dynamic magnetic susceptibility and magnetizat ion loop measurements were performed by the Hariharan group in the Physics Depa rtment at USF using Physical Property Measurement System (PPMS) by Quantum Design on dried crystals filled in gelatin capsules. Synthesis of {[Fe(2, 5-PDC)2(H2O)]( 2H -Pip)(H2O)2}n, 6 The reaction mixture containing FeSO4 7H2O (0.0435mmol, 0.012g), 2,5-H2PDC (0.087mmol, 0.0145g), DMF (1mL), CH3CN (1mL), H2O (0.75mL), Pip (0.15mL, 0.58 M in DMF) was placed in a 20 mL scintillat ion vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Parallelepipedic red crystals were collected and air-dried. Synthesis of {[Fe(2, 5-PDC)2]7(H20)}n, 7 The reaction mixture containing Fe rrocene (0.0435mmol, 0.008g), 2,5-H2PDC (0.087mmol, 0.0145g), DMF (1mL), CH3CN (1mL), TEA (0.15mL, 1.43M in DMF), HNO3 (0.15mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a heating

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75 rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Slight brown hexagonal crystals were collected and air-dried. Synthesis of {[Fe(2, 5-PDC)2]( H -HMTA)(H2O)2}n, 8 The reaction mixture containing Fe(NO3)3 9H2O (0.0435mmol, 0.017g), 2,5-H2PDC (0.087mmol, 0.0145g), DEF (1.5mL), CH3CN (1mL), H2O (0.75mL), HMTA (0.15mL, 1.42M in H2O) was placed in a 20 mL scintill ation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Pale yellow polyhedral crystals were collected and air-dried. Synthesis of {[Fe(2, 5-PDC)2](H2O)}n, 9 The reaction mixture containing Fe rrocene (0.0435mmol, 0.008g), 2,5-H2PDC (0.087mmol, 0.0145g), DEF (3mL), Morpho line (0.05mL, 1.2M in DEF), HNO3 (0.15mL, 3.5M in DEF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and 115 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Pale yellow polyhedral crys tals were collected and air-dried.

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76 3.1.3. Results and Discussion Upon the deprotonation of the two car boxylic acids functional groups in 2,5H2PDC, Figure 3.1., the corresponding divale nt anion, 2,5-pyridine dicarboxylate (2,5PDC) is resulted. Thoroughly described in Chapter 1, the single-metal-ion-based MBB approach addresses for one of carboxyl ates to be purposely located in the -position relative to the aromatic nitrogen, in such a manner to promote N-, Oheterocoordination to a single metal ion. In the resultant five-membered chelate ring, the Natom directs the topology of the assembly, while the Oatom locks the metal in its position. In this instance, the carboxylate in the 5-position serves as bridging ligand, extending the dimensionality of the potential networks to be formed, maintaining intact the intended functions of this linker. Figure 3.1. Prototype 120 angle in 2,5-H2PDC. The extended number of robust assemblies generated from MBBs derived from this organic ligand is also highli ghted by the several coordina tion modes it affords, Figure 3.2.. N HO O OH O

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77 Figure 3.2. Common binding modes afforded by 2,5-PDC. Reaction between iron (II) sulfate and 2,5-H2PDC, under mild solvothermal conditions yields a 1D zig-zag chain, formulated by crysta llography studies as {[Fe(2, 5PDC)2(H2O)]( 2H -Pip)(H2O)2}n, 6 Each iron metal ion adopts an octahedral geometry being coordinated by three independent pyr idinedicarboxylate ligands, generating a MN2(CO2)3 type MBB, Figure 3.3.. Upon deprotonati on of the carboxylic acids, two of the ligands are heterocoordinating through Nand O-, forming two coplanar five member chelation rings, while the third ligand is binding in a monodentate fashion, through the N O O O O M N O O O O M M N O O O O M M N O O O O M M M N O O O O M M M N O O O O M M N O O O O M M M N O O O O M M M M

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78 oxygen atom of the carboxylate in the 5 position. The coordination sphere of the metal is completed by a terminal water mo lecule in the axial position. Figure 3.3. MN2(CO2)3 type MBB (left), regarded as a MNO bent BU (right) in compound 6 Hydrogen atoms are omitted for clarit y; Iron= green, carbon= gray, nitrogen = blue, oxygen= red. In the resultant anionic coordination polymer Figure 3.4., the charge balance is ensured by doubly protonated piperazine molecules, stacked in betwee n the alternating unidimensional chains. Figure 3.4. X-ray single-cryst al structure of compound 6 outlining one-periodic zig-zag chain motif. Hydrogen atoms and guest molecules are omitted for clarity; Iron =green, carbon =gray, nitrogen = blue, oxygen = red. In the same time, the guest molecules fo rm three NHO hydrogen bonds with the oxygen atoms of the pyridinedicarboxylate ligands (1.976 , 1.859, and 1.789), bridging the unidimensional polymer. The chains are sta ggered in alternating ABAB fashion, Figure

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79 3.5.. Each of the MBBs is alternating up-down, and stacking interactions in the range of 3.476 are occurring between the aromatic rings of the ligands. Figure 3.5. Detailed view of unidimensional chains in compound 6 held together by hydrogen bonded piperazine guest molecules; Iron= green, car bon= gray, nitrogen= blue, oxygen= red, hydrogen= white. The reaction between Ferrocene and 2,5-H2PDC, in a 1:2 molar ratio under solvothermal conditions and in the presence of TEA yields a two-periodic Kagom net, formulated by preliminary crystall ographic studies as{[Fe(2, 5-PDC)2]7(H20)}n, 7 The octahedral metal ion is coordinated by four ditopic ligands, two of each are heterocoordinating, while the other tw o are bridging through the monodentate carboxylate, resulting in a MN2(CO2)4 type MBB, Figure 3.6.. Within the square planar BU, MN2O4, the N atoms are trans, regarding one of the tw o available conformational isomers for this type of MBB. In this context, it is important to remark that we have we have previously reported this lattice constr ucted from indium-based the square planar cis MN2O4 BUs.2

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80 Figure 3.6. (a) MN2(CO2)4 type MBB (left), regard ed as a square planar trans -MN2O4 BU (right) in compound 7 Hydrogen atoms and guest molecules are omitted for clarity; Iron= green, carbon= gray, nitrogen= blue, oxygen= red. In the resulting anionic material, presumably DMA cations are balanc ing out its inherent charged nature; however, poor crystallographic da ta in not enabling for detailed analysis, and further data collection would be appropr iate to confirm the current hypothesis. The material is built from alternatin g three and six membered rings, Figure 3.7., resulting in undulating layers, which are packing in an ABCABC fashion. Kagom lattices represent a well studied class of mate rials, especially for the potential they hold for magnetic-related applications,4-10 due to spin frustration arising from the arrangement of the metal center as vertices of the triangular rings.

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81 Figure 3.7. X-ray single-crystal structure of compound 7 : ball-and-stick (left) and CPK (right) representation of Kagom layer. Hydrogen atoms and guest molecules are omitted for clarity; Iron= green, carbon= gr ay, nitrogen= blue, oxygen= red. In this instance, it was specifically targ eted to construct th e iron-based net when accessing the MN2O4 BU, given the fact we had al ready obtained the In-parent compound. Magnetic measurements on 7 reveal a similar behavior to the one observed in 3 and 4 That is, ferromagnetic interactions ar e ordering at low temperatures, Figure 3.8.b., while the expected stronger interactions around room temperature are not present, Figure 3.8.a.. However, more in-depth inves tigations are deemed appropriate to be conducted on this sample, while considering additional techniques used for its characterization.

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82 Figure 3.8. (a) Magnetization vs. temperature and magnetization vs applied magnetic field in compound 7 at (b) 300K and (c) 2K. The difficulty in assessing and unders tanding the magnetic behavior in these complexes is still an ongoing research ch allenge, and was also addressed by Rao et.al 11,12 in their report of sulfate-based iron Kagom lattices, where they specifically highlight the effect induced by the oxidation state of the iron metal ion (+2 vs. +3, or mixed valence compounds), and its correlations with magnetic measurements. Therefore, further investigations are deemed necessary to make definite conclusion with regards to the properties associat ed with the iron-based Kagom lattice. -20020406080100120140160180 0.0 0.1 0.2 0.3 0.4 0.5 0.6 M (emu)Temperature, K Magnetization vs. Temperature in 2 Tesla Field-60-40-200204060 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 M (emu)H (kOe) MH 2K-60-40-200204060 -0.020 -0.015 -0.010 -0.005 0.000 0.005 0.010 0.015 0.020 M (emu)H (kOe) MH 300K (a) (b) (c)

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83 Reaction between iron (III) nitrate and 2,5-H2PDC, under mild solvothermal conditions generates a 3-periodic framew ork with diamondoid topology, formulated by crystallography studies as {[Fe(2, 5-PDC)2]( H -HMTA)(H2O)2}n, 8 .3 The material is comprised of MN2(CO2)4 type MBBs, resulting into a see-saw-like cis -MN2O4 BU, Figure 3.9.. The molecular arrangement consis ts of four independent 2,5-PDC ligands which coordinate to the octahedral iron metal ion as follows: two of the pyridinecarboxylates are forming two five -member chelating rings through N-,Oheterochelation, reinforcing the rigidity and directionality of the assembly. The other two bridging ligands are binding in a monodentat e fashion solely though the oxygen atoms of the carboxylate, completing the coor dination sphere of the metal ion. Figure 3.9. MN2(CO2)4 type MBB (left) in compound 8 regarded as a see-saw-like cis MN2O4 BU (right). Hydrogen atoms and guest molecules are omitted for clarity; Iron= green, carbon= gray, nitrogen= blue, oxygen= red. Monoprotonated HMTA molecules are providi ng the charge balance for the anionic framework. The structure exhibits diamond topology, Figure 3.10., the most occurring net for the 3D frameworks based on 4-connected nodes.13,14 It is to be noted the same

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84 MN2(CO2)4 type MBBs as in 7, but an overall different coor dination geometry of the BU, cis -MN2O4 a see-saw-like vs. square planar trans -MN2O4. Figure 3.10. (a) X-ray single-crystal structure fragment, schematic (b) topological and (c) tiling representation of diamondoid topology in compound 8. Hydrogen atoms and guest molecules are omitted for clarity; Iron = green, carbon= gray, nitrogen= blue, oxygen= red. Further experiments involving ferrocene and 2,5-H2PDC, in the presence of morpholine, and under mild solvothermal conditions results in a 3D anionic MOM, characterized and formulated by single crys tal X-ray diffraction st udies as {[Fe(2, 5PDC)2](H2O)}n, 9. In 9 four independent pyridinedicar boxylate ligands coordinate the [64] (a) (b) (c)

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85 octahedral iron metal ion, rendering a MN2(CO2)4 type MBB, translated into a square planar cis -MN2O4 BU; it resembles the coordination geometry encountered in 7 revealing a second type of constitutional isomer for the square planar MN2O4 BU, where the Natoms are in the cis position with respect to each other, Figure 3.11.. Figure 3.11. MN2(CO2)4 type MBB (left) in compound 9 regarded as a square planar cis -MN2O4 BU (right). Hydrogen atoms and guest molecules are omitted for clarity; Iron= green, carbon= gray, nitrogen= blue, oxygen= red. Therefore, two of the ligands form two chel ate rings through hete rocoordination of the aromatic Nof the pyridine core and the Oatom situated in the -position relative to the nitrogen. In this arrangement, the topology is directed by the two n itrogen atoms, while the oxygen locks the metal in its pos ition. The other two independent pyridinedicarboxylates are bridging through the available oxygen atom in the 5-position of the carboxylate. Overall, each independent pyridinedicarboxylate is an integral part of two independent MBBs: in one, it forms the chelate rings, while extends to the second MBB through the bridging oxygen atoms.

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86 Figure 3.12. View of the X-ray single-c rystal structure of compound 9 along (a) X direction (b) Y direction; (c) lvt topological analysis; Ir on= green, carbon= gray, nitrogen= blue, oxygen= red. The assembly of the BUs are gene rating an anionic 3D network with lvt topology,15,16 which consists of alternating 4 a nd 8 member rings, where uncoordinated oxygen atoms from the chelate rings are point inside, embedding a hydr ophilic specificity to the small openings (Figure 3.12.). Similar to the case of 7 dimethylammonium guest molecules that are balanci ng out the charged nature of the compound were not fully localized. (a) (b) (c)

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87 3.1.4. Summary The work conducted in this section of Ch apter 3 represents a step forward towards made-to-order materials by implementing the si ngle-metal-ion based MBBs strategy. It is essential to highlight that compounds 7 8 and 9 represent examples of supramolecular isomers17 which refers to “the existence of more than one type of network superstructure for the same molecular building blocks”, as described by Zaworotko.13 It is important to mark the distinction between isomerism and polymorphism (the exis tence of a substance in more than one crystalline state), which can be regarded as a t ype of supramolecular isomerism. This phenomenon is interfering to some degree with gaining enough control over the predictability of the to-be materials. Ho wever, this can be regarded also as an advantage, especially if intended molecula r-building blocks are generated under certain experimental conditions. A successful example is represented by compound 7 which outlines the iron-Kagom lattice, intentiona lly targeted to be constructed upon the synthesis of the parent indium compound. Further investigations for the construction of f unctional MOMs based on singlemetal-ions MBBs are to be further discussed in the remaining of this chapter, as well in Chapter 4.

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88 3.2. MOMs Derived from Heterofunc tional Bis-Chelating Bridging Pyrimidinedicarboxylate Ligands 3.2.1. Introduction This subchapter also conveys the use of multifunctional, rigid and directional heterochelating ligands as means to faci litate the formation of intended MBBs in situ upon coordination to single metal ions. Pr imarily, the approach is extended to pyrimidinedicarboxylate-based organic ligands capable to generate MBBs that maintain intact the geometric attributes of the orga nic ligand, Figure 3.13., a nd thus contribute to the synthesis of networks of interest. Figure 3.13. Prototype 120 angle in 4,6-H2PmDC. Therefore, the focus is on MOMs de rived from such a heterochelating multifunctional ligand, 4,6-pyrimidinedicarboxylate (4,6-PmDC), and two of its functionalized derivatives, namely 2-am ino-4,6-pyrimidinedicarboxylate (2-amino-4,6PmDC) and 2-hydroxy-4,6-pyrimidinedicar boxylate (2-hydroxy-4,6-PmDC). 4,6-PmDC possesses the necessary characteristics to rend er rigid and directional MBBs of the type MN2(CO2)x, MN3(CO2)x or MN4(CO2)x (in which x stands for th e bridging ligands at the NN O O OH OH

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89 available metal sites), which can lead to the generation of a diversity of BUs, including TBUs, which represent the key elements for ta rgeting ZMOFs. Foremost, the structural diversity afforded by 4,6-PmDC is explore d, reporting on the desi gn and synthesis of materials based on a multitude of MBBs, along with outlining various coordination modes of the heterofunctiona l organic ligand, Figure 3.14.. Figure 3.14. Common coordination mode s afforded by 4,6-PmDC. Emphasis will be also put in the role introduced by Structure Directing Agents (SDAs), in reactions derived from similar starting materials, and their influence in targeting non-default structures. N N O O O O M M NN O O O O M N N O O O O M M M N N O O O O M M M NN O O O O M M NN O O O O M M M M NN O O M M O O NN O O O O M M M N N O O O O M M M M NN O O O O M M M M NN O O O O M M M M M NN O O O O M M M M M M d) j) c) b) g) a) e) h) k) f) i) l)

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90 3.2.2. Experimental Section Synthesis of 4,6-PmDC Figure 3.15. (a) One step oxidation of 4,6-dime thylpyrimidine for the synthesis of (b) 4,6-PmDC, divalent anion upon deprotonation in situ Synthesis of 2-amino-4,6-PmDC Figure 3.16. (a) One step oxidation of 2-am ino-4,6-dimethylpyrimidine for the synthesis of (b) 2-amino-4,6-PmDC divalent anion upon deprotonation in situ Synthesis of 2-hydroxy-4,6-PmDC Figure 3.17. (a) One step oxidation of 2-hydr oxy-4,6-dimethylpyrimidine for the synthesis of (b) 2-hydroxy-4,6-Pm DC, divalent anion upon deprotonation in situ (a) (b) NaOH KMnO4, H2O NN H3C CH3 NH2 NN NH2 OH O O OH (b) (a) NaOH KMnO4, H2O NN OH H3C CH3 NN OH O O OH OH (b) (a) NaOH KMnO4, H2O NN H3C CH3 NN O O OH OH

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91 Materials and Methods All materials and methods are described in Chapter 2, unless otherwise noted. 4,6-PmDC, 2-amino-4,6-PmDC and 2-hydroxy-4,6-PmDC were synthesized according to literature procedures18 from the 4,6-dimethylpyrimidine, 2-amino-4,6-dimethylpyrimidine and 2hydroxy-4,6-dimethylpyrimidine, respectively, schematically depicted in Figure 3.15., Figure 3.16. and Figure 3.17.. Synthesis of {[Cd(4,6-PmDC)(H2O)3](H2O)2}n, 10 Cd(NO3)24H2O (0.0435mmol, 0.0134g) and 4,6PmDC (0.087mmol,0.016g), H2O (1mL) was placed in a 20 mL scintil lation vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The colorless block-shaped cr ystals were collected and air-dried. Synthesis of {[Yb(4,6-PmDC)(H2O)3( CO2H)]}n, 11 Yb(NO3)39H2O (0.087mmol,0.040g) and 4,6-Pm DC (0.0435mmol,0.008g), H2O (1.5mL), DMF (0.75mL) and HNO3 (0.2mL, 3.5M in DMF) was placed in a 20 mL scintillation vial a nd was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temperat ure at a cooling rate of 1 C/minute. The colorless blockshaped crystals were collected and air-dried.

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92 Synthesis of {[Y2(4,6-PmDC)4](DMA)2( HPip)}n, 12 Y(NO3)36H2O (0.0084g, 0.02175mmol) and 4,6-P mDC (0.008g, 0.0435mmol), H2O (1mL), DMA (1mL) and Pip (0.1mL, 0.58M in DMF) was placed in a 20 mL scintillation vial a nd was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temperat ure at a cooling rate of 1 C/minute. The colorless polyhedral crystals were collected and air-dried. Synthesis of {[Cd(4,6-PmDC)2K2(H2O)6]}n, 13 The reaction mixture containing Cd(CH3COO)22H2O (0.0435mmol, 0.0116g) and 4,6PmDC (0.087mmol, 0.016g), in DMF (1mL), H2O (1mL), En (0.2mL, 3M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The colorless block-shaped crystals were collected and air-dried. Synthesis of {[Cd2(4,6-PmDC)2(En)2(H2O)](H2O)2}n ,14 The reaction mixture containing Cd(CH3COO)22H2O (0.0116g, 0.0435mmol) and 4,6PmDC (0.016g, 0.087mmol), in DMF (1mL), H2O (1mL), En (0.1mL, 1.5M in DMF ) was placed in a 20 mL scintillat ion vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The colorless block-shaped crystals were collected and air-dried.

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93 Synthesis of [Mn2(4,6-PmDC)2(H2O)2]n, 15 Mn(NO3)36H2O (0.0435mmol, 0.008g) and 4,6PmDC (0.087mmol,0.016g), H2O (1.5mL), Isopropanol (0.5mL), HNO3(0.15mL, 3.5M in DMF) was placed in a 20 mL scintillation vial a nd was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. The pale yellow block shaped crystals were collected and airdried. Synthesis of {[In(4,6-PmDC)2K(H2O/DMF)(H2O)0.5]H2O}n, 16 The reaction mixture containing In(NO3)35H2O (0.02175mmol, 0.0085g), 4,6-PmDC (0.0435mmol, 0.008g), DMF (0.75mL), H2O (1mL), HNO3(0.2mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The colorless block-shaped crystals were collected and air-dried. Synthesis of {[In2(4,6-PmDC)4](Imi)(H2O)9}n, 17 The reaction mixture containing In(NO3)35H2O (0.02175mmol, 0.0085g) and 4,6-PmDC (0.0435mmol, 0.008g), in DEF (0.5mL), H2O (1.5mL), Imi (0.1mL, 1.46M in DMF ) HNO3(0.2mL, 3.5M in DEF ) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Colorless polyhedral crystals were collected and air-dried.

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94 Synthesis {[Fe(2-amino-4,6-PmDC)2] ( 2 HPip)}n, 18 The reaction mixture containing Fe(NO3)39H2O (0.0435mmol, 0.017g), 2-amino 4,6PmDC (0.087mmol, 0.016g), DMF (1mL), H2O (1.5mL), Pip (0.2 mL, 0.58M in DMF), was placed in a 20 mL scintillat ion vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Dark brown block-shaped crystals were collected and air-dried. Synthesis {[Yb(2-OH-4,6-PmDC)(H2O)2] ( NO3 -)(H2O)1.5}n, 19 The reaction mixture containing Yb(NO3)39H2O (0.02175mmol, 0.01g), 2-hydroxy 4,6PmDC (0.0435mmol, 0.008g), DMF (1mL), H2O (1mL) and HNO3(0.1mL, 3.5M in DMF) was placed in a 20 mL scintil lation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. Colorless rhombohedral crystals were collected and air-dried. Synthesis of {[In8(2-hydroxy-4,6-PmDC)12K6] (NO3 -)6(H2O)24, 20 The reaction mixture containing In(NO3)35H2O (0.0435mmol, 0.017g) and 2-hydroxy4,6-PmDC (0.087mmol, 0.016g) in DEF (1mL), H2O (1mL), TMAN (0.1mL, 1.29M in H2O), HNO3(0.1mL, 3.5M in DEF ) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Colorless polyhedral crys tals were collected and air-dried.

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95 3.2.3. Results and Discussion Examples of metal-organic zig-zag ch ains were resulted upon the solvothermal reaction of Cd(NO3)24H2O, Yb(NO3)39H2O, and Y(NO3)36H2O and 4,6-PmDc, 10 11 12 Figure 3.18. (a) MN2(CO2)2 type MBB (top left), regarded as a MN2 bent BU (top right) in compound 10 ; (b) Zig-zag chains in compound 10 Hydrogen atoms are omitted for clarity Cadmium= green, carbon= gr ay, nitrogen= blue, oxygen= red. The choice of metal ions that have higher coordination numbers as means to target MN4O2 or MN4O4 TBUs, lead in fact to one-pe riodic assemblies, where undesired coordination of guest molecules complete the coordination sphere of the metals. Figure 3.19. (a) MN2(CO2)2 type MBB (top left), regarded as a MN2 bent BU (top right) in compound 11 ; (b) Zig-zag chains in compound 11 Hydrogen atoms are omitted for clarity Ytterbium= green, carbon= gr ay, nitrogen= blue, oxygen= red. (a) (b) (a) (b)

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96 Therefore, in compounds 10 and 11 a similar metal to ligand coordination is observed, resulting in MN2(CO2)2 type MBBs, where two ligands ar e heterochelating to the single metal ions. Nevertheless, the angle between the two chelate rings that direct the assembly are quite different, 79.188 in 10 and 123.352 in 11. This feature is directly dependent on the slightly dissimilar coordination environment of the single metal ions, also depicted by the resulting bent BUs, Figure 3.18.a. a nd Figure 3.19.a. (three water molecules in 10 vs. three water molecules and a formate in 11 ). Figure 3.20. (a) MN2(CO2)3 type MBB (top left), regarded as a MN2 bent BU (top right) in compound 12; (b) Zig-zag chains in compound 12. Hydrogen atoms are omitted for clarity Yttrium= green, carbon= gr ay, nitrogen= blue, oxygen= red. In the crystal structure of 12, the resulting zig-zag chain is also assembled from bent MN2 BUs, derived from a MN2(CO2)3 type MBB, where three pyrimidinedicarboxylate ligands are forming 5-membered rings of chelat ion, Figure 3.20.; however, similar to the coordination modes observed in both 10 and 11, only two ligands are contributing to the assembly of the chains, while the third one acts solely as a terminal ligand, fulfilling the coordination sphere of the yttrium metal ion. Th e balance charge in th is anionic assembly (b) (a)

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97 in ensured by protonated pipera zine guest molecules, which are also linking the chains through NHO hydrogen bonds (1.910). Further experiments introduced a superi or reaction environment and focused on employing SDAs/competitive ligands as means to access targeted MBBs. Reaction between cadmium acetate, 4,6-PmDC and ethyl enediamine (En) results in compounds 13 and 14 where slight differences in the concentrat ion of En, directs the formation of one structure over the other. In the crystal structure of 13 {[Cd(4,6-PmDC)2K2(H2O)6]}n, as formulated by crystallographic studies, the 8-coordination s phere of the cadmium metal ion is fully satisfied by four independent he terochelating 4,6-PmDc ligands, resulting in the formation of the intended M2N4(CO2)4 type MBB, Figure 3.21.a.. However, the deviation from planarity of the chelate rings, in a range from 26.688-32.354 regard a see-saw like 4-connected MN4 BU, rather than the expected TBU. As a result, the assembly of the BUs gives rise to tw o-periodic tetragona l sheets, Figure 3.21.b.. Potassium cations are bridging th e layers, in the same time en suring the balance charge of the anionic framework.

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98 Figure 3.21. (a) Representative MBB in compound 13 M2N4(CO2)4 (top left), regarded as (b) see-saw like 4-connected MN4BU (top right); (c) X-ray si ngle-crystal structure of a layer in compound 1 3 Hydrogen atoms and guest molecules were omitted for clarity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red Interestingly, very similar qua ntities of the reactants as in 13 but just a slight variation in the concentration of the species present in the reaction environment, reveals the formation of 14 {[Cd2(4,6-PmDC)2(En)2(H2O)](H2O)2}n, as formulated by crystallographic studies. In the resulting materi al, both potential ligands are present in the crystal structure, where two independent metal ions are present, as well. One 7coordinated independent cadmium metal ion is bound in its availa ble apical sites by bridging ethylenediamine ligands, while in the ecuatorial positions is coordinated by two pyrimidinedicarboxylates ligands through N-, Oheterochelation and water molecule that saturates the coordination sphe re of the metal. Furthermore, a similar coordination environment is noted for the second cadmiu m metal ion, which adopts an octahedral geometry. In this instance, only one indepe ndent pyrimidinedicarboxylate ligand binds to (b) (a)

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99 the metal ion through the Nand Omoieties, forming a rigid 5-member chelating ring, while the two bridging ethylenediamine ligands coordinate the open metal sites in the axial positions. In this circumstance, the representative MBB is expressed as M2N7(CO2)3, pseudo-cluster consisting of two bis-oxo bridged cadmium metal ions, Figure 3.22.a. Even though this MBB is not a single-metal-ion-based type, according to its connectivity, it can be vi rtually interpreted as a 4-c onnected node based on the points of extension, resulting into a see-saw-like BU, MN4 (Figure 3.22.b). Topologically, the structure is equivalent to compound 13 consisting in the ABAB packing of the tetragonal sheets (Figure 3.22. c and d). Figure 3.22. (a) Representative MBB in compound 14 M2N7(CO2)3, regarded as (b) seesaw like 4-connected MN4 BU ; (c) Single-crystal stru cture of a layer in compound 14 (d) layers stacking in an ABAB fashion. Hydr ogen atoms and guest molecules were omitted for clarity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red. ( a ) ( b ) ( c ) ( d )

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100 Compound 15 highlights another instance when a si ngle-metal-ion-based MBB has not been accessed, an argument in favor of structural diversity afforded by this organic ligand. On the other hand, the degree of predictability is impaired, and more experiments are deemed necessary to be conducted in order to narrow down exact reaction conditions that would allow the c onstant access to intended single-metal-ionbased MBBs. Solvothermal reaction between manganese nitrate and 4,6-PmDc, yields crystalline material, formulated by singlecrystal X-ray diffraction studies as {[Mn2(4,6PmDC)2(H2O)2}n, 15 In the crystal structure of 15 two manganese metal ions are coordinated by four pyrimidined icarboxylate ligands to result in a two-pe riodic neutral layered MOF, Figure 3.23.c.. Each metal ion with slightly distorted octahedral geometry is coordinated by three pyrimidine liga nds, two binding thro ugh N-, Oheterocoordination, forming rigid and directional five-member rings of chelation, while the third ligand coordinates through the remaini ng available site of the bridging oxygen of the carboxylate, Figure 3.23.a.. The coordination sphere of th e metals is completed by water molecules. The angle between the two ch elating rings in the MBB is approximately 101.575.

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101 Figure 3.23. (a) Representative MBB in compound 15 M2N4(CO2)4, and alternative ways of analyzing the connectivity and topology : (b) 3-connected MN2O3 BU, resulting in hcb herringbone-like topology (top right) and 4-connected M2N4O2 BU, resulting in sql topology (bottom right); (c) X-ray single-cr ystal structure of a layer in compound 15 Hydrogen atoms and guest molecules were omitted for clarity; Manganese= green, carbon= gray, nitrogen= blue, oxygen= red. From a topological perspective, this net can be interpreted in two different ways: (i) if solely considering the point of extensions, a network with sql topology is derived, (ii) in the same time, if the actual connectivity of the metals is considered, the topology is based on 3-connected nodes, outlining an hcb herringbone-like topo logy, as schematically represented in Figure 3.23.b.. Conse quently, the generic BU is MN2O3 if considered a 3( a ) (b) (c)

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102 connected BU, while in the case in which the pseudo-cluster is viewed as a square point of extension, the representative BU is M2N4O2. Compound 16 {[In(4,6PmDC)2K(H2O/DMF)(H2O)0.5]H2O}n, as characterized and formulated by X-ray single-crystal di ffraction studies, was generated under mild solvothermal conditions, by reacting In(NO3)35H2O and 4,6-PmDC. In the crystal structure of 16, two bis(bidentate) 4,6-PmDC ligands coordinate to the indium metal ion through Nand Oheterochelation, forming tw o five-member rings situated in the same plane with the aromatic pyrimidine ring. The remaining two available coordination sites of the metal ion are saturated by othe r two independent monodentate bridging pyrimidinecarboxylate ligands, giving rise to the formation of a MN2(CO2)4 type MBB, which translates into a cis -MN2O2 (Figure 3.24.a) BU. The BUs are regarded as square planar 4-connected nodes, with an approxima te 89.720 angle between the planes of the two ligands that heterochelat e the metal ion. The In-N distance is approximately 2.299 , while the In-O distances range between 2.135-2.148 . The dihedral angles (viewed down an axis from the oxygen atom of the carbo xylate in the 4-position to the carbon of the adjacent pyrimidine core carbon atom) ar e in the range of 2.725 for the bridging pyrimidinecarboxylate ligands, and 23.480 for the ligands that heterocoordinate the metal ion.

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103 Figure 3.24. (a) Representative MBB in compound 16 MN2(CO2)4 (top left) regarded as square planar cis -MN2O2 4-connected BU (top right); (b) X-ray single-crystal structure of layer in compound 16; (c) layers stacking in an AB AB fashion. Hydrogen atoms and guest molecules were omitted for clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. The directed assembly of the 4-connected BU s leads to the generation of two dimensional square grids, the expected motif corresponding to the ge ometry of the MBB (Figure 3.24.b.), packing in an alternating ABAB fa shion (Figure 3.24.d.). The overall anionic character of the framework is balanced out by potassium cations positioned in between the two-periodic layers. ( a ) ( b ) ( c )

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104 By the slight alteration of th e experimental conditions from 16 combined with the effect introduced by the presence of a SDA in the reaction environment, a new material from the same starting materials is obtai ned, formulated by crystallographic studies as{[In2(4,6-PmDC)4](Imi)(H2O)9}n, 17 In the crystal structure of 17 two different types of MBBs are generated under mild solvot hermal conditions, associated with two independent indium metal ions. The metalligand directed assembly consists of one MN2(CO2)5 MBB1, regarded as a trans -MN2O2 see-saw-like BU, delineating three different coordination modes of the organi c linker: two ligands bind a 7-coordinated indium metal ion in a bis(bi dentate) fashion, forming two chelate rings, while the other two pyrimidinecarboxylates bind in a bident ate and, respectively, monodentate fashion, only through the bridging carboxylates, Figure 3.25.a. The second type of MBB consists of three pyrimidinecarboxylates which heteroch elate the 8-coordinated indium metal ion through Nand Ocoordination bonds, while th e fourth ligand is bi nding in a bidentate fashion, saturating the coordination sphe re of the metal. Accordingly, a MN3(CO2)5 type MBB2 is generated, translated into a see-saw-like 4-connected MN3O BU.

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105 Figure 3.25. (a) MBB1 in compound 17 MN2(CO2)5 (left), regarded as trans -MN2O2 seesaw-like 4-connected BU (right) ; (b) MBB2 in compound 17 MN3(CO2)5 (left), regarded as MN3O see-saw-like 4-connected BU (right); Hydrogen atoms were omitted for clarity; Indium= green, carbon= gray, ni trogen= blue, oxygen= red. It is worth mentioning that in both MBB1 and MBB2 it is observed a slight deviation from of the planarity of the ca rboxylates, leading to their slight torsion out of plane of the pyrimidine aromatic ring. The resulting dihe dral angles (again, viewed down the axis from the oxygen atom of the carboxylate in th e 4-position to the ca rbon of the adjacent pyrimidine core carbon atom) in MBB1 vary from just 1.526 to 12.158, while in MBB2 they average between of 11.571 to17.987. (a) (b)

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106 Figure 3.26. (a) X-ray single-crystal stru cture of a layer in compound 17 ; (b) CPK representation of layer in compound 17 ; (c) Alternating layers stacking in an ABAB fashion in compound 17 Hydrogen atoms and guest molecules were omitted for clarity; Indium= green, carbon= gray, ni trogen= blue, oxygen= red The asymmetric part of unit cell co ntains two indium metal ions, four pyrimidinedicarboxylates ligands, one imidazole and nine water molecules of partial occupancy. This arrangement results into an anionic framewor k, which requires two protons in order to satisfy the charge ba lance. In accordance with these findings, two hydrogen atoms are present in the formula unit, statistically redistribu ted over five places: ( b ) (a) (c)

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107 four on the nitrogen atoms of four pyrimidine rings and one on the imidazole guest molecules, which are disordered over two close positions. The two types of 4-connected nodes are id entical from a topol ogical perspective, with a coordination sequence 4, 9, 15, 21, 27, 33, 39, 45, 51, 57 corresponding long vertex symbol, [4.6(2).4.6(2).4.6(2)]. This network can be referred to as a bilayered (pillared) hcb with a scarce occurrence in the field. To the best of our knowledge, this is only the second example of this topological type to date,19 being classified originally by E.Koch & W.Fischer as a 2-periodic net ( 6,3)Ia corresponding to a 2-periodic sphere packing.20 In the same time, the material possesses a zeolitic topology, based on double 6-member rings (d6R), entry currently hi ghlighted only in the Hypothetical Zeolites Database.21 The total solvent-accessible volume for 17 was obtained using PLATON software by summing voxels that are more than 1.2 aw ay from the framework; the potential accessible free volume corresponds to approximately 39.4% of the unit cell volume. The diameter of the largest sphere that can be fit inside the cag e without interacting with the van der Waals atoms of the framework is a pproximately 1nm. However, the layers are packing in an ABAB fashion, each layer be ing slipped with resp ect to the precedent layer, thus preventing the full access to the en tire cage. The potentia l accessible channels along z axis are obstructed by the imidazole guest molecules. Conversely, unidimensional potential accessible channels with a dimens ion of approximately 6.63 are exploitable along y axis. Preliminary sorption studies were not consistently confirmed, and better activation methods need to be pursued in orde r for its porosity to be fully exploited.

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108 Furthermore, several new experiment s were set in parallel with other pyrimidinedicarboxylate derivatives, functionalize d in the 2-position with either an amine or hydroxyl group (the work has a high degr ee of novelty, as no other materials were reported with these bridging orga nic ligands, to date). In a fi rst instance, reaction between iron nitrate and 2-amino-4,6-PmDC, in th e presence of pipe razine and under solvothermal conditions, yields a crystallin e material characterized and formulated by crystallographic stud ies as{[Fe(4,6-PmDC)2](2 HPip)}n. In the crystal structure of 18 four independent pyrimidine ligands coordi nate around the octahedr al iron metal ion center, generating a MBB of the type MN2(CO2)4, Figure 3.27. Two ligands are binding through the carboxylate functional ity in a monodentate way, while the other two ligands fully exploit their hetero-coordinative nature generating two rigid and directional fivemember rings through N-, Oheterochelation to the single-metal-ion. The two chelating rings are situated in the same plane, while the ligands adopt alte rnating conformations with respect to the functionalized 2-position.T he directed metal-ligand assembly results into a square planar trans -MN2O2 BU, aiding the formation of the tetragonal two-periodic sheets.

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109 Figure 3.27. MN2(CO2)4 type MBB (left) in compound 18 regarded as a square planar trans -MN2O2 4-connected BU (right); Hydrogen atoms are omitted for clarity; Iron= green, carbon=gray, nitrogen= blue, oxygen= red. Protonated piperazine molecules have a collabor ative effect on the formation of the net, lying in between layers pack ing in an AAA fashion. In the same time, they provide the positive balance charge needed to neutralize the anionic nature of the square grids. Figure 3.28. (a) Ball-and-stick representation of the X-ray single-crystal structure of a square grid layer in compound 18 and (b) Piperazine guest mo lecules intercalated inbetween the layers. Hydrogen atoms are omitte d for clarity; Iron= green, carbon= gray, nitrogen= blue, oxygen= red. (a) (b)

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110 Interestingly, extended investigations of the system involving the reaction between 2-amino-4,6-PmDC and several metals with 3+ oxidation st ate resulted in a series of novel materials, that will be further de tailed in the next sec tion of this chapter. Initial research studi es involving 2-hydroxy-4,6-Pm DC, in conjunction with ytterbium nitrate, resulted in 19 {[Yb(2-OH-4,6-PmDC)(H2O)2](NO3 -)(H2O)1.5}n. In the crystal structure of 19 the metal-ligand directed assembly outlines a MN2(CO2)4 type MBB, regarded as a see-saw-like cis -MN2O2 4-connected BU, Figure 3.29.. The representative MBB is comprised of the Yb single metal ion, which is coordinated by four independent hydroxypyrimidine organic linkers. Two distinct binding modes are noted, one in which two ligands are utilizing both N-,Oheterochela ting sites, fulfilling their function upon coordination to the metal a nd ensuring directionality of the assembly through the formation of five-member rigi d chelating rings. Additionally, two other pyrimidine ligands are bridging solely th rough the carboxylate functionality, while two water of coordination are completed the 8-c oordinated sphere of the single metal ion. Figure 3.29. Representative MBB in compound 19 MN2(CO2)4 (left), regarded as a seesaw-like cis -MN2O2 4-connected BU (right). Hydrogen atoms are omitted for clarity; Ytterbium= green, carbon= gra y, nitrogen= blue, oxygen= red.

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111 Interestingly, the complex framework is made up of three different t ypes of two-periodic layers: i) a Kagom layer (Figure 3. 30.a), ii) a herringbonetype sheet running perpendicular to the Kagom layer (Figure 3.30.b), and iii) a te tragonal sheet (Figure 3.30.c), that runs through the diagonal of th e six-member ring of the Kagom layer. Figure 3.30. Ball-and-stick representation of (a ) Kagom layer; (b) herringbone-type layer; (c) square grid and (d) schematic representation layers arrangement in compound 19 ; Hydrogen atoms are omitted for clarity ; Ytterbium= green, carbon= gray, nitrogen= blue, oxygen= red. (a) (b) (c) (d)

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112 The complexity of the framework allows for two different ways of interpreting its topology. When accounting for the metal connec tivity, the representative metal of each MBB connects further onto six other distinct metal centers, therefore acting as a sixconnected node. In this instance, the t opological analysis outlines a coordination sequence 6, 22, 50, 88, 134, 198, 260, 352, 428, 550, associated with a short (Schlfli) point symbol of {32;44;55;64} and a long (O’Keeffe ) vertex symbol [3.3.4.4.4.4.5.5.5(2).5(2).5(2) .6.6(2).6(3).6(3)]. The corresponding topology is smc with [1353] transitivity. The tiling re presentation of the net’s topology outlines three different types of tiles (Figure 3.31.). The novelty of th is discovery is also reflected by the fact that this is the first structure to date to possess this connectivity. Figure 3.31. Tiling representation of smc topology in compound 19 3[4.52] [32.43] [32.56]

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113 The alternate way of analyzing the framewo rk accounts for the liga nd connectivity, that acts as a 4-connected node, as depicted in Figure 3.32.a. In this instance, the net possesses nbo topology. Figure 3.32. Alternative way of analyzing compound 19 based on (a) ligand connectivity, regarded also as a 4-conn ected node, (b) Tili ng representation of nbo topology; Hydrogen atoms are omitted for clarity; Ytterbium= green, carbon= gray, nitrogen= blue, oxygen= red. The reaction between indium nitrate and 2-hydroxy-4,6-PmDC, under mild solvothermal conditions resulted in colorless crystallin e material with polyhedral morphology. Upon X-ray single crystal diffraction studies, it was formulated as {[In8(2-hydroxy-4,6PmDC)12]K6(NO3 -)6(H2O)24, 20 In the crystal structure of 20 two independent octahedral indium metal ions are coordinated by three 2OH-4,6-PmDC ligands, forming an MBB of the type MN3(CO2)3, regarded as a MN3O3 BU, Figure 3.33.. This example represents the first kind of such a MBB afforded by heterofunctional pyrimidinedicarboxylate-based organic linkers, a nd thus enlarges the library of available (b) (a)

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114 MBBs, and consequently, of the to-be-made materials. The bis(bi dentate) ligands are forming three rigid and directional five-mem ber rings though N-,Oheterochelation upon coordination to the metal ion, in which th e metal-nitrogen bonds are directing the topology of the assembly (each ligand heterochelates two metal ions). Figure 3.33. Representative MBB in compound 20 MN3(CO2)3 (left), regarded as fac MN3O3, 3-connected BU. Hydrogen atoms are om itted for clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. The periodic assembly of these BUs gives rise to a discrete MetalOrganic Cube (MOC), Figure 3.34., in which the indium metal ions ar e occupying the vertices of the cube, while the organic linkers are constituting its edges. Accordingly, this material represent first example of an edge-directed assembly of MOC from pyrimidine-based ligands, while the imidazole-based analogue was detail ed by us in a previous instance.1 Pyrimidinecarboxylate-based molecules are ditopic angular organic ligands, inherently possessing an angle of approximately 120. The range of the afforded angles can be influenced upon coordination to singl e-metal-ion and/or by the position of the carboxylate function /additional f unctional groups. When consid ering an ideal cube, the

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115 chelating rings should be coplanar with the pyrimidine aromatic core, while the ligands should act as nearly linear connectors. Figure 3.34. Ball-and-stick representation of metal-organic cube in compound 20 .Hydrogen atoms are omitted for clar ity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. In this case, the deviation from planarity of the rings is within the range 6.521-6.757, while the coordination angles are in the range 126.621127.623. However, the regular geometry of the cube is evidenced by the InInIn angles, 88.872, 90.694, 91.736, 92.175 and InIn distances of 6.313 and 6.370 . The inner cavity of the cube in not accessible, as all hydroxyl groups are pointi ng to its interior (a distance of 3.706).

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116 3.2.4. Summary In this subchapter, the focus was put on investigating the accessi bility of rigid and directional single-metal-i on-based MBBs resulted from implementing angular heterofunctional pyrimidinedicarboxylatebased organic ligands. The library of obtainable MBBs has been thus further ex tended, when considering the work conducted with 2,5-PDC, thoroughly detailed in th e first section of this chapter. Predominant molecular entities associated with a simplified reaction environment have consistently directed to BUs of the type MN2O2, MN4O4, MN3O and MN2O3, and resulted in the assembly of repertoire of two-periodic frameworks. This occurrence is anticipated to a certain extent, as the forma tion of simple nets with high regularity is known in crystal chemistry. However, examples of discrete metal-organic cube or zig-zag chains are also remarked, derived from MN3O3 and MN2 type BUs. It is highlighted the effect of the SDA-directed synthesis, whic h poses a tremendous consequence in favor of structural diversity.

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117 3.3. Novel MOMs Constructed from Single -metal-ions with High Coordination Number and Multifunctional Pyrimidinecarboxylate Ligands 3.3.1. Introduction Supported by results detailed in the prev ious section, the single-metal-ion MBB approach based on pyrimidinecarboxylate ligands has been proven to be a successful effective and versatile strategy for the cons truction of MOMs. Linke r functionalization is portrayed as an alternative route to be expl ored in favor of structure diversity, as well function of the to-be materials. In accorda nce with this approach, the focus on this chapter will be put on structures construc ted from pyrimidinecarboxylate derivatives: 2amino-4,6-PmDC and 2-hydroxy-4,6-PmDC. In the same time, metals with high coordination numbers will be employed, in order to facilitate the access to targeted MBBs of the type MN4(CO2)4, where an 8-coordinate metal woul d be ideal to result in such an arrangement, when envisioning four hete rochelating rings necessary for imparting directionality and rigidity in the BU. Ne vertheless, high coordination metal complexes may also result in nets with higher transitivi ties, hence containing more than one type of building block/node. Concomitantly, this stra tagem will also be considering an SDAdirected synthesis, therefore outlining an ove rall complex synthetic level in the quest for targeting functional materials.

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118 3.3.2. Experimental Section Materials and Methods All materials and methods are described in Chapter 2, unless otherwise noted. Synthesis of {[Tb(2-amino-4,6-PmDC)2(H2O)2](TMA+)(H2O)2}n, 21 The reaction mixture containing Tb(NO3)35H2O (0.02175mmol, 0.0095g), 2-amino 4,6PmDC (0.0435mmol, 0.008g), DMF (1mL), H2O (1.5mL), TMAN (0.1mL, 1.76M in H2O), HNO3(0.1mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. The colorless cubic crysta ls were collected and air-dried. Synthesis of {[Tb(2-amino-4,6-PmDC)2K0.15]( H -Imi)0.5(DMA+)0.35(H2O)5}n, 22 The reaction mixture containing Tb(NO3)35H2O (0.0435mmol, 0.0188g), 2-amino 4,6PmDC (0.087mmol, 0.016g), DMF (1mL), H2O (1.5mL), Imi (0.1mL, 1.46M in DMF), HNO3(0.1mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. The colorless cubic crysta ls were collected and air-dried. Synthesis of {[Y2(2-amino-4,6-PmDC)3(H2O)6](H2O)18.5}n, 23 The reaction mixture containing Y(NO3)36H2O (0.0435 mmol, 0.0168g), 2-amino 4,6PmDC (0.087 mmol, 0.016g), DMF (1mL), H2O (2 mL), TMAN (0.1mL, 1.76M in H2O) was placed in a 20 mL scintillat ion vial and was heated to 85 C for 12hours, at a rate of

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119 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Colorless block crystals were collected and air-dried. Synthesis {[Y9(2-amino-4,6-PmDC)9(OH-)8(H2O)15(DMF)] ( NO3 -)(H2O)6}n, 24 The reaction mixture containing Y(NO3)36H2O (0.0435 mmol, 0.0168g), 2-amino 4,6PmDC (0.087 mmol, 0.016g), DMF (1.5mL), H2O (1.5mL), TMDP (0.1mL, 0.95M in H2O) was placed in a 20 mL scintilla tion vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Colorless polyhedral crystals were collected and air-dried. Synthesis of {[Er6(2-amino-4,6-PmDC)11(H2O)3](DMA+)4(H2O)12}n, 25 The reaction mixture containing Er(NO3)39H2O (0.0435mmol, 0.0193g), 2-amino 4,6PmDC (0.087mmol, 0.016g), DMF (1mL), H2O (1mL), En (0.1mL, 3M in DMF), HNO3(0.1mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The pale pink polyhedral cr ystals were collected and air-dried. Synthesis of {[Yb6(2-amino-4,6-PmDC)11(H2O)3](Yb)0.34(DMA+)3(H2O)5}n, 26 The reaction mixture containing Yb(NO3)39H2O (0.0435mmol, 0.0195g), 2-amino 4,6PmDC (0.087mmol, 0.016g), DMF (1mL), H2O (1mL), En (0.2mL, 3M in DMF),

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120 HNO3(0.15mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The brown polyhedral crystals were collected and air-dried. 3.3.3. Results and Discussion The reactions between terbium and 2-amino-4,6-PmDC, under similar solvothermal conditions, but when employi ng different SDAs, yield two different materials, 21 and 22 Accordingly, in the presence of TMAN, the resulting crystalline material was characterized and form ulated by crystallographic studies as {[Yb(2-amino4,6-PmDC)2(H2O)2](TMA+)(H2O)2}n, 21 In the crystal structure of 21 four 2aminopyrimidinedicarboxylate lig ands coordinate to the i ndependent terbium metal ion, through two N-, Oheterochelating rings, wh ile the other two linke rs are binding in a monodentate fashion, where water molecules are satisfying the remaining available coordination sites. Figure 3.35. Representative MBB in compound 21 MN2(CO2)4 (left), regarded as a cis MN2O2 see-saw-like 4-connected BU (right) ; Hydrogen atoms are omitted for clarity; Terbium= green, carbon= gray, nitrogen= blue, oxygen= red.

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121 (a) (b) The resulted MBB is MN2(CO2)4, translated into a cis -MN2O2 BU, regarded as a distorted see-saw-like BU, Figur e 3.35, leading to the formati on of a two-periodic square layered structure. Further anal ysis of the resultan t BU, conveys that similar topologies were also noted in two other transand cis MN2O2 examples in 16 and 18 respectively. Given the anionic nature of the framework, th e SDA employed in this particular case, provides the necessary charge balance. Tetramethylammonium (TMA) molecules are laying in the middle of the la rge four member rings resulted from linking the metal centers, 15.792 X 10.893 (point to point, a nd without considering the van de Waals radii of the terbium atoms). Symmetrical hydrogen bond interac tions, 2.035, are occurring between the carboxylate functionali ty of one layer and the hydrogen atoms from the functionalized 2-amino position of the pyrimidinedicarboxylate ligand, and vice versa (Figure 3.36.), respectively, leading to a three-periodic fram ework. The material becomes a candidate for exchange with sma ller ions that could furthermore favor the potential accessibility to gas sorption properties, as the laye rs pack in an AAA fashion, stacking on top of each other. Figure 3.36. (a) Hydrogen bonding interac tions between two MBBs of distinct layers and (b) Ball-and-stick representation of hydrogen bonded layers in compound 21 Guest molecules are omitted for clarity; Terbiu m= green, carbon= gray, nitrogen= blue, oxygen= red.

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122 The reaction environmental involvi ng the same protocol as in 21 but in the presence of Imi instead of TMAN, resu lted in a new material, {[Tb(2-amino-4,6PmDC)2K0.15]( H -Imi)0.5(DMA+)0.35(H2O)5}n, 22 as formulated by single crystal diffraction analysis studies. In the crystal structure of 22 a different metal to ligand coordination is observed than in 21 ; hence, two independent terbium metal ions are coordinated by the angular di topic hetero-functio nal pyrimidine linkers, generating two different molecular building blocks. In the fi rst MBB, the eight available sites of the terbium metal ion are fully coordinated by f our ligands through N-, Ofive-membered heterochelating rings, generating a MN4(CO2)4 type MBB, translated into a MN4O4 BU, regarded as a MN4 TBU (Figure 3.37.a.). Concomitantly, a dimetal terbium cluste r based also on eight-coordinated metal ions, generates the second MBB, of the type M2N4(CO)12, Figure 3.37.b., a MN4O8 BU, regarded as an eight connect ed node. CSD analysis of the prevalence of this dimetal cluster with the exact coordina tion environment found in the M2N4(CO)12 type MBB reveals that it is unprecedented in meta l-organic coordination compounds. However, similar overall connectivity has been observed in discrete complexes based on Gd, Pr, La, Nd, Sm and Tb.22-26

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123 Figure 3.37. (a) MBB in compound 22 MN4(CO2)4, regarded as a see-saw-like MN4O4 4-connected BU and (b) Dimetal cluster in compound 22 M2N4(CO)12, regarded as a MN4O8 8-connected BU; Hydrogen atoms are omitted for clarity; Terbium= green, carbon= gray, nitrogen= blue, oxygen= red. Accordingly, in addition to four “axia l” linkers binding the metal ion through N-, Ohetero-chelating moieties, other four pyrimidinedicarboxylates are bridging the two metal centers only through the carboxylate f unctions in a bis-monodentate fashion, in the “equatorial” positions. The periodic arrangement of the two types of MBBs generates a three-periodic anionic framework, Figure 3.38.a., in which the charge balance is ensured by protonated Imi, DMA and potassium cations. Topological analysis revealed that the binodal (4,8)-net topology is characterized by the coordination sequences: 4, 22, 24, 82, 64,182,124, 322, 204, 502 for the 4-connected node, and 8, 12, 48, 42,128, 92, 248, (a) (b)

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124 162,408, 252 for the 8-connected node, respectivel y; the correspondent short (Schlfli) point symbols {46} and {412;612;84} reveal that the framework’s connectivity is equivalent to flu (fluorite)27,28 topology. The regular ity of the net is also reflected by its 2111 transitivity, construc ted from unique [412] tiles. Figure 3.38. (a) Ball-and-stick and (b) CPK repres entation of single crystal structure in compound 22 ; (c) flu (4,8)-net topology and d) tiling representation of flu topology. Hydrogen atoms and guest molecules are omitted for clarity; Terbium= green, carbon= gray, nitrogen= blue, oxygen= red. Elongated rhombododecahedron cavities have an internal diameter of approximately 11.12, when considering th e van de Waals radii on the surrounding atoms. However, the potential accessibility of these unidime nsional channels is hindered by the windows aperture of only 1.44 , distan ce measured considering the van de Waals radii of the near est oxygen atoms. (b) (c) (d) (a)

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125 The important role played by the SDAs is once again evidenced by in compounds 23 and 24 where the same reagents, under mild solvothermal conditions, but in the present of different SDAs yields 23 (TMAN) and 24 (TMDP). In the crystal structure of 23 {[Y2(2-amino-4,6-PmDC)3(H2O)6](H2O)18.5}n, the yttrium metal ion possesses a 9-coordinati on sphere environment, satisfied by three pyrimidine ligands and three water molecules, acting as terminal ligands. The metalligand directed assembly outlines a MBB of the type MN3(CO2)3, Figure 3.39., based on three independent hetero-functional aminopyr imidinedicarboxylate ligands which are binding the metal ion through both N-, Of unctional available sites, forming fivemember rings of chelation, ri gid and directional, reinfo rcing the robustness of the assembly. Figure 3.39. (a) Representative MBB in compound 23 MN3(CO2)3 (left), regarded as MN3O3 3-connected BU; Hydrogen atoms are om itted for clarity; Yttrium= green, carbon= gray, nitrogen= blue, oxygen= red. The MBB is further on translated into a 3-connected trigonal MN3O3 BU, where their assembly gives rise to the forma tion of two-periodic sheets, with hcb honeycomb (6,3) topology, Figure 3.40.. A similar ar rangement was noted in 20 where a discrete metal-

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126 organic cube was obtained also from the MN3O3 type BU, fact that therefore infers two supramolecular isomers afforded by this MBB. Figure 3.40. (a) Ball-and-stick representation of the single crystal structure of a honeycomb layer in compound 23 ; (b) AAAA packing modes of distinct layers. Hydrogen atoms are omitted for clarity; Iron= green, carbon= gr ay, nitrogen= blue, oxygen= red. Distorted non-planar six-member ri ngs, consisting of alternating up-down pyrimidine ligands lead to the forming a “conve x” cavity with an internal diameter of 9.39 X 11.069. The undulating layers are pack ing in an alternating AAAA fashion; however, the potential unidimensional channe ls are obstructed as each subsequent twodimensional sheet is slipped half-way with respect to the previous layer. (b) (a)

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127 Crystal chemistry has allowed for the in situ formation of readily “available” metal clusters (dimetal carboxylate, trimer basic zinc acetate), which have become reliable building blocks in targ eting a variety of structures.29-38 Lanthanides possess high coordination numbers, and as a consequence of satisfying all the available sites, they have the capability of favoring the formation of metal clusters, in which the metal ions are bridged by carboxylate, oxo or hydroxo gr oups; one example of such molecular arrangement has been encountered in 22 Nevertheless, these types of MBBs are not generated on a common basis and, moreover, their control in situ has to be targeted, in order to become accessible design tools. Reaction between yttrium n itrate and 2-amino-4,6-PmDC, under the same molar ratio and solvothermal environment as in 23 but in the presence of TMDP afforded crystalline material with polyhedral mo rphology, characterized and formulated by crystallography studies as, {[Y9(2-amino-4,6-PmDC)9(OH-)8(H2O)15(DMF)](NO3 -)(H2O)6}n, 24 In the crystal structure of 24 there are nine independe nt yttrium metal ions, which upon coordination by 2-amino-pyrimidinedi carboxylates give rise to two chemical and geometrically distinct MBBs. One type c onsists of an yttrium metal ion that is bridged by four ligands, thr ough N-, Ohetero-coordinati on, generating an MBB of the type MN4(CO2)4, translated into a MN4O4 BU and a MN4 TBU. In the same time, the complex metal-ligand directed assembly give s rise to a heptanuclear metal-cluster,39 an MBB of the type M7N4(CO)10, generating an overall ei ght-connected node. The pyrimidinedicarboxylate ligands comprised in the cluster afford various coordination

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128 modes: bis-bidentate through N-, Oheterochel ation, as well as br idging solely through the carboxylic function in bis-monod entate and monodentate fashion. Figure 3.41. (a) MBB in compound 24, MN4(CO2)4(top left), regarded as a tetrahedral MN4O4 TBU (top right); (b) Me tal cluster in compound 24 M7N4(CO2)10 (bottom left), regarded as a eight-connected BU. Hydr ogen atoms are omitted for clarity; Yttrium= green, carbon= gray, ni trogen= blue, oxygen= red. A CSD search regarding the incidence of th is dicubane-like cluster reveals that up to April 2009 there are 16 entries in which this arrangement is encountered.40-53 The occurrence evidences examples of various d-block metals (Ni, Zn, Cu, Mn, Co, Cd) or even s-block metals (Ca, Li), and just three example deri ved from lanthanide metal ion sources (Eu, Ho, Yb). In this context, 24 represent the first example of an extended framework from such an yttrium-based metal cluster. Even though a d-block metal, it has (b) (a)

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129 properties in close resemblance with lantha nides, as in nature it has been found in minerals containing rare earth metals. The arrangement of the MBBs generate s a three dimensional heterocoordinated (4,8) framework, with unidimensional explo itable channels with a 11.153 diameter, when considering the van de Waals of the inner oxygen atoms pointing inside the voids. The total solvent-accessible volumes for 24 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework, revealing it accounts for approximately 53.4% of the unit cell volume. Figure 3.42. (a) Ball-and-stick (left) and CP K (right) representation of X-ray singlecrystal structure in compound 24 ; Hydrogen atoms and guest molecules are omitted for clarity; Yttrium= green, carbon= gr ay, nitrogen= blue, oxygen= red. Topological analysis of the heterocoordinated (4,8) net reveal the following coordination sequence and vertex symbol s: for the four connected node, the corresponding coordination sequenc e is 4,18, 40, 63, 115, 171, 198, 286, 389, 409, with(Schlfli) point symbol of {46} and long (O’Keeffe) vertex symbol [4.4.4.4.4.4],

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130 while for the 8-connected node the c oordination sequence is 8, 19, 40, 79, 112, 154, 232, 287, 344, 467, with a short (Schlfli) point symbol of {413;612;83}, along with an elaborate long (O’Keeffe ) vertex symbol [4.4.4. 4.4.4.4.4.4.4.4.4.4.6(2).6(2).6(2).6(2). 6(3).6(3).6(4).6(4).6(4).6(4).8(19).8(19).8(33 ).6.6], outlining an unprecedented topology, Figure 3.43.. Figure 3.43. Tiling representation of unprecedented topology of a (4,8) heterocoordinated net in compound 24 In the same time, the complexity of this mate rial is also reflected by its 2464 transitivity, having four different types of tiles: 2[42.82], 4[46], 2[44.82], [414]. Furthermore, the reaction between er bium nitrate and 2-amino-4,6-PmDC, under solvothermal conditions, and in the presence of En, yields crystalline material with polyhedral morphology, characteri zed and formulated by X-ray single-crystal diffraction studies as {[Er6(2-amino-4,6-PmDC)11(H2O)3](DMA+)4(H2O)12}n, 25 Interestingly, very similar experimental conditions as in 25 but when the erbium metal ion is substituted 2[44.82] 2[44.82] 4 [ 414 ] 4[46]

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131 with ytterbium, crystalline material with polyhedral morphology is obtained, 26 Upon crystallographic analysis,{[Yb6(2-amino-4,6-PmDC)11(H2O)3](Yb)0.34(DMA+)3(H2O)5}n 26 was determined to be isostructural to 25 In the crystal structure of 25 are identified two crystallographically independent Er metal ions. In a first instance, the heptacoordinate erbium metal ion is bri dged by three pyrimidined icarboxylate ligands through N-, Oheterochelation, while the api cal position is occupied by a water molecule which contributes to the completion of th e coordination sphere of the metal. The generated MBB is of the type MN3(CO2)3, regarded as a T-shaped MN3O3 BU, Figure 3.44.a.. Similarly, the second erbium metal i on has a 8-coordination environment; four ligands contribute to the satu ration of all available sites, forming four N-, O-, fivemembered chelate rings, which are ensuring the rigidity and dire ctionality of the MN4(CO2)4 type MBB, translated into a tetrahedral MN4O4 BU, Figure 3.33.b.. The overall arrangement of the two kinds of MBBs results into a binodal (3,4) heterocoordinated anionic fram ework, where DMA guest molecules are balancing out the charge.

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132 Figure 3.44. (a) MBB1 in compound 25 MN3(CO2)3 (top left), regarded as a T-shaped MN3O3 3-connected BU (top right); (b) MBB2 in compound 25 MN4(CO2)4 (bottom left), regarded as a tetrahedral MN4O4 TBU (bottom right). Hydrogen atoms and guest molecules are omitted for clarity; Erbium =green, carbon =gray, nitrogen = blue, oxygen = red. Detailed structural analysis of the unique features in 25 Figure 3.45.a., reveals four different types of windows, regarded as 4-, 5-, 6and 9-MRs. Thus, the 4-MR (Figure 3.45.d.) has of a non-planar square geometry (1.931 deviation from the ideal 90), where all corners consist of MN4O4 BUs. It is depicted that the ligands which define the edges of the square are alternating updown. The aperture of the window is very small, ~0.651, when considering the van de r Waals radii. In th e case of the 5-MR, Figure 3.45.e., the four vertices of the pent agon are based on tetrah edral nodes, derived from the same MN4O4BUs, while the fifth node is T-shaped, outlined by the MN3O3 type BU. Opposite to the coordination mode s observed in the square window, all (b) (a)

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133 (a) (b) (c) (d) (e) (f) (g) pyrimidinedicarboxylate ligands in the 5-MR are pointing with the functional amino group inside the aperture (3.507 , consider ing the van der Waals radii). The 6-MR, Figure 3.45.f., is comprised of four tetr ahedral vertices derived from the MN4O4 BUs, while the two remaining nodes are based on the MN3O3 BU. These particularities are evidenced in the slight differences reflected by the distances between metal centers, for example (7.040 between two erbium metal ions which originate the MN4O4 BUs vs. 7.156 between the two erbium metal ions that are forming the MN3O3 BU). Similarly to the 4-MR, it is encountered an up-down alte rnating conformation of the 2-amino-PmDC ligands. When considering the van der Waals radii, the window has an accessible 5.458 aperture. Figure 3.45. (a) Ball-and-stick representation of a fragment of the X-ray single-crystal structure in compound 25 ; (b) Ball-and-stick and (c) gr aphical representation of unprecedented cage constructed from (d) 4MR, (e) 5-MR, (f) 6-MR and (g) 9-MR. Hydrogen atoms and guest molecules are omitted for clarity; Erbium= green, carbon= gray, nitrogen= blue, oxygen= red.

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134 Figure 3.45.g. depicts the 9MR, which is based on three subunits composed at their turn from three alternating BUs, (two MN4O4 –like BUs linked by a MN3O3-type BU) situated in the same plane. The transi tion to each subsequent coplanar three BUsbased “family” is ensured through a 2-amino4,6-pyrimidinedicarboxylate that possesses an opposite orientation as the adjacent ligands. As a result it is derived an ad-hoc “cavitand” with a hydrophilic character, as al l oxygen atoms are pointing inside it, with a 6.396 accessible opening, when considering the van der Waals radii (the largest of all discussed rings). The overal l arrangement of 4-, 5-, and 6-MRs results in an unprecedented cage, 44.54.64 as shown in Figure 3.45. b. and c., having an approximate internal diameter of 6.34 X 8.412 , when considering the van der Waals of the nearest atoms. Topological analysis outlines the foll owing coordination sequence for the 3connected node: 3, 8, 18, 32, 48, 68, 100, 132, 166, 205, with a short (Schlfli) point symbol of {5;62} and the long (O’Keeffe) vertex sy mbol [5.6.6]. For the 4-connected node, the characteristic coordination sequence is 4, 10, 18, 32, 49, 74, 105, 134, 169, 209, with a short Schlfli symbol {4;52;62;9} and the long O’Keeffe vertex symbol [4.9(3).5.5.6.6], resulting in an unprecedente d (3,4) topology for heterocoordinated MOMs.

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135 Figure 3.46. Tiling representation of unpr ecedented topology of a (3,4) heterocoordinated net in compound 25 As in the case of 24 the net’s complexity is outlined by the 2442 transitivity, highlighted by two types of tiles: 3[44.54.64] and [512.612.98], Figure 3.46.. The [512.612.98] type cages are fused together by the [44.54.64] tile. Interestingly, the structural feature in this framework seem to be closely related to the clathrasil family,54 assumption supported also by the tiling representation in MEP [512] + 3[512.62],55 and MTN, 2[512] + [512.64],56-59 zeolite nets. The total solvent-accessible volume for 25 was obtained using PLATON software by summing voxels that are more than 1.2 aw ay from the framework. Accordingly, the potential accessible free volume corresponds to approximately 55% of the unit cell volume. [512.612.98] [44.54.64] 3[44.54.64] + [512.612.98]

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136 3.4. Summary In this subchapter, the focus was put on MOMs derived from metal ions with higher coordination number, juxtaposed with pyrimidinedicarboxylate-based ligands. The deliberate targeted TBUs of the type MN4 were resulted in severa l instances, however in the same time, a second type of MBB was al so obtained. The overall heterocoordinated nets possess complex transitivities and exhibit rare or unprecedented topologies. The role played by SDAs in the synthesis process is also delineated, where di fferent materials are resulted from similar starting reagents, but in the presence of different SDAs. In summary, this chapter demonstrat ed that the single-metal-ion-based MBB represents an appropriate route towards the co nstruction of a repertoire of MOMs. In this context, trends can be established as to what structure will most likely occur from a type of MBB, even though the synthetic pathway still represents a gr eat challenge, with respect to finding the exact experimental conditions to yield the targeted MBB in situ at all times. Nevertheless, the successful im plementation of this strategy, where the multitude of coordination modes afforded by directional and angular heterofunctional ligands, in conjunction with appropriate metal ions, resulted in a la rge set of available rigid and directional MBBs, that lead to a series of expected, as well as novel materials. Once again, the single-metal-ion-based MBB approach represents a valuable design tool in order to facilitate the forma tion of targeted MBBs, which can then aid the synthesis of metal-organic materials akin to zeolite topologies and f unctions; this aspect, primarily important, will be further discu ssed in the following chapter, Chapter 4.

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137 3.5. References 1. Liu, Y.; Kravtsov, V.; Walsh, R.D.; Poddar, P.; Srikanth, H. and Eddaoudi, M. Chem.Commun. 2004 24 2806-2807. 2. Liu, Y.; Kravtsov, V. Ch.; Beauchamp, D. A.; Eubank, J. F. and Eddaoudi, M. J. Am. Chem. Soc. 2005 127 7266-7267. 3. Brant, J. A.; Liu, Y.; Sava, D. F.; Beauchamp, D. and Eddaoudi, M. J. Mol.Struct. 2006 796 160-164. 4. Moulton, B.; Lu, J. J.; Hajndl, R.; Hariharan, S.; Zaworotko, M. J. Angew. Chem. Int. Ed. 2002 41 2821-2824. 5. Greedan, J. E. J. Mater. Chem. 2001 11 37-53. 6. Ramirez, A. P. Annu Rev. Mater. Sci. 1994 24 453-480. 7. Wills, A. S.; Harrison,A. J. Chem. Soc., Faraday Trans. 1996 92 21612166. 8. Inami, T.;Nishiyama, M.; Maegawa, S.; Oka, Y. Phys. Rev. B 2000 61 12181-12186. 9. Reimers, J. N.; Berlinsky, A. J. Phys. Rev. B 1993 48 9539-9554. 10. Frunzke, J.; Hansen, T.; Harrison, A. ; Lord, J. S.; Oakley, G. S.; Visser, D.; Wills, A. S. J. Mater. Chem 2001 11 179-185. 11. Rao, C. N. R.; Sampathkumaran, E. V.; Nagarajan, R.; Paul, Geo; Behera, J. N.; Choudhury, A. Chem. Mater. 2004 16 1441-1446. 12. Rao, C. N. R.; Paul, G.; Choudhury, A.; Sampathkumaran, E. V.; Raychaudhuri, A. K.; Ramasesha, S.; Rudra, I. Phys. Rev. B: Condens. Matter. 2003 67 134425/1-134425/5. 13. Zaworotko, M.J. Chem. Soc. Rev. 1994 23 283-288. 14. Moulton, B.; Zaworotko, M. J. Chem.Rev 2001 101 1629-1658. 15. Evans, O. R.; Manke, D. R.; Lin, W. Chem. Mater. 2002 14 3866-3874.

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138 16. Rather, B.; Moulton, B.; Bailey Walsh, R. D.; Zaworotko, M. J. Chem.Commun. 2002 7 694-695. 17. Hennigar, T. L.; MacQuarrie, D. C. ; Losier, P.; Rogers, R. D.; Zaworotko, M. J. Angew. Chem., Int. Ed. 1997 36 972-973. 18. Hunt, R. R.; McOmie, J. F. W.; Sayer, E. R. J. Chem. Soc. 1959 525-530. 19. Wang, X.-W.; Chen, J.-Z.; Liu, J.-H. Cryst. Growth Des. 2007 7 1221-1229. 20. Koch, E.; Fischer, W. Z. Kristallogr. 1978 148 ,107-152. 21. Foster, M. 2004 Hypothetical Zeolites Database http://www.hypotheticalzeolites.net/ DATABASE/SILVER/XYZ/viewer.php ?file=166-2_1_61 22. Song, Y.-S.; Yan, B.; Chen, Z.-X. J. Solid State Chem. 2004 177 3805-3814. 23. Romanenko, G. V.; Podberezs kaya, N. V.; Bakakin, V. V. Dokl. Akad. Nauk. 1979 248 1337-1341. 24. Aslanov, L. A.; Ionov, V. M.; Kiekbaev, I. D. Koord. Khim. 1976 2 1674-1680. 25. Moore, J. W.; Glick, M. D.; Baker, W. A., Jr J. Am. Chem. Soc. 1972 94 1858-1865. 26. Yin, M.-C.; Ai, C.-C.; Yuan, L.-J; Wang, C.-W.; Sun, J.-T. J Mol. Struct. 2004 691 33-37. 27. Poojary, D. M.; Zhang, B.; Bellinghausen, P.; Clearfield, A. Inorg. Chem. 1996 35 4942-4949. 28. Cao, D.-K.; Gao, S.; Zheng, L.-M. J. Solid State Chem. 2004 177 2311-2315. 29. Frey, G. J. Solid State Chem. 2000 152 37-48. 30. Cotton, F.A.; Lin, C.; Murillo, C.A. Acc. Chem. Res. 2001 34 759-771. 31. Eddaoudi, M.; Moler, D.B.; Li, H.; Chen, B.; Reineke, T.M.; O'Keeffe, M.; Yaghi, O.M. Acc. Chem. Res 2001 34 319-330.

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139 32. Moulton, B.; Lu, J.; Hajndl, R.; Hariharan, S.; Zaworotko, M.J. Angew. Chem. Int. Ed 2002 41 2821-2824. 33. Eddaoudi, M.; Kim, J.; Vodak, D. ; Sudik, A.; Wachter, J.; O’Keeffe, M.; Yaghi, O.M. Proc. Natl. Acad. Sci. USA 2002 99 4900-4904. 34. Moulton, B.; Abourahma, H.; Bradner, M. W.; Lu, J.; McManus, G. J. and Zaworotko, M. J. Chem. Commun. 2003 1342–1343. 35. Cotton, F. A.; Lewis, G. E. and Mott, G. N. Inorg. Chem. 1982 21 3127–3130. 36. Sudik, A. C.; Ct, A. P. and Yaghi, O. M. Inorg. Chem. 2005 44 2998–3000. 37. Liu, Y.; Eubank, J. F.; Cairns, A. J. ; Eckert, J. ; Kravtsov, V. Ch.; Luebke, R.; Eddaoudi, M. Angew. Chem. Int. Ed. 2007 46 3278-3283. 38. Li, H.; Eddaoudi, M.; O’Keeffe, M. and Yaghi, O. M. Nature 1999 402 276–279. 39. Ziegler, M.L.; Weiss, J. Angew.Chem.Intl. Ed. 1970 9 905-906. 40. Keene, T. D.; Hursthouse, M. B. and Price, D. J. New J. Chem. 2004 28 558 – 561. 41. Fromm, K. M. Chem. Commun. 1999 1659 – 1660. 42. Fromm, K. M.; Gueneau, E. D.; Bern ardinelli, G.; Goesmann, H.; Weber, J.; Mayor-Lpez, M.-J.; Boulet, P. and Chermette H. J. Am. Chem. Soc. 2003 125 3593–3604. 43. Liu, X.; McAllister, J. A.; Miranda, M. P. de; McInnes, E. J. L.; Kilner, C.A.; Halcrow, M. A. Chem.-Eur.J. 2004 10 1827 – 1837. 44. Maudez, W.; Haussinger, D.; Fromm, K.M. Z. Anorg.Allg.Chem. 2006, 632 2295 – 2298. 45. Boyle, T.J.; Bunge, S.D.; Andrews, N.L.; Matzen, L.E.; Sieg, K.; Rodriguez, M.A.; Headley, T.J. Chem. Mater. 2004 16 3279–3288. 46. Fleming, S.; Gutsche, C.D.; Harrowf ield, J.M.; Ogden, M.I.; Skelton, B.W.; Stewart, D.F.; White A.H. Dalton Trans. 2003 3319 – 3327.

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140 47. Charette, A.; Beauchemin, A.; Francoeur, S.; Belanger-Gariepy, F.; Enright G.D. Chem. Commun. 2002 466 – 467. 48. Li, X.; Cao, R.; Guo, Z.; Lue, J. Chem.Commun. 2006 1938-1940. 49. Ishimori, M.; Hagiwara, T.; Tsuruta, T.; Kai, Y.; Yasuoka, N.; Kasai, N. Bull.Chem.Soc.Jpn. 1976 49 1165-1166. 50. Clerk, M.D.; Zaworotko, M.J. Chem.Commun. 1991 1607-1608. 51. Ray-Kuang Chiang, Chi-Chun Huang, Ching-Shuei Wur Inorg. Chem. 2001 40 3237–3239. 52. Buesching, I.; Strasdeit, H. Chem.Commun. 1994 2789-2790. 53. Herrmann, W. A.; Egli, A.; Herdtweck, E.; Alberto, R.; Baumgaertner, F. Angew.Chem.Intl. Ed. 1996 35 432-434. 54. van Koningsveld, H. ; Gies, H. Z. Kristallogr. 2004 219 637-643. 55. Delgado-Friedrichs, O.; Foster, M. D.; O’Keeffe, M.; Proserpio, D. M.; Treacy, M.M.J.; Yaghi, O. M. J. Solid State Chem. 2005 178, 2533-2554. 56. Frey, G.; Serre, C.; Mellot-Draznieks, C.; Millange, F.; Surble, S.; Dutour, J. Margiolaki, I. Angew. Chem.Intl. Ed. 2004 43 6296-6301. 57. Frey, G.; Mellot-Draznieks, C.; Serre C.; Millange, F.; Dutour, J.; Surble, S.; Margiolaki, I. Science 2005 309 2040-2042. 58. Park, Y. K.; Choi, S.; Kim, H. B.; Kim, K.; Won, B.-H.; Choi, K.; Choi, J.S.; Ahn, W.-S.; Won, N.; Kim, S.; J ung, D.H.; Choi, S.-H.; Kim, G.-H.; Cha, S.-S.; Jhon, Y. H.; Yang, J. K. Angew. Chem.Intl. Ed 2007 46 8230-8233. 59. Fang, Q.; Zhu, G.; Xue, M.; Sun, J.; Wei, Y.; Qiu, S.; Xu, R. Angew. Chem.Intl.Ed. 2005 44 3845-3848.

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141 Chapter 4. Design Strategies and Synthe sis of Materials with Large and Extra-Large Cavities 4.1. The Single-Metal-Ion-based MBB Approach to Target ZMOFs 4.1.1. Introduction In the ongoing quest for the design of functional materials, the deliberate construction of porous periodic solids can addr ess pertinent scientific and societal needs via particular integrated func tions and is of great interest across discipli nes. Our group has successfully implemented rational design st rategies for the synthesis of functional materials from single-metalion-based MBBs, comprehensively detailed in Chapter 3, where the desired functionality and direct ionality are embedded prior the assembly process. We have utilized heterofunc tional organic ligands that are rigid and directional, which allow the formation of rigid five-m embered rings of chel ation through N-,Ohetero-coordination to a single-metal ion, to facilitate the synthe sis of intended MOMs. Accordingly, the judicious selection of organic linkers (e.g. imidazolecarboxylates) has allowed for the saturation of singlemetal ions to generate MBBs (MN4O2, MN4O4) regarded as rigid and directional TBUs (MN4) necessary for the construction ZMOFs.1-4

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142 A detailed subchapter in th e introductory material of th is dissertation was entirely dedicated to the design strategies to access MOMs possessing zeolitelike features. To reiterate the importance of targeting ZM OFs, some of their unique features are highlighted: (i) The access to their large a nd extra-large cavities is fully exploitable, as they don’t allow interpenetration; (ii) They possess superior attributes as co mpared to common MOMs, as their chemical stability in aqueous media facilitates their use in many areas, such as heterogeneous catalysis, separations, and se nsing-related applications; (iii) ZMOFs typically have anionic characte r, which allows for tuning of the extraframework cations toward specific applications such as gas storage, catalysis, and the removal/sequestration of toxic metal ions, to enumerate just few of the most promising functions. In addition, ZMOFs are constructed usi ng metal-ligand directed assembly and encompass periodic arrays of organic functionality, allowing for the tunability of both inorganic and organic component s, features that permit fac ile alteration of pore size and/or organic functionality and hence the e xpansion of zeolite a pplications to large molecules.1,5 MOMs having zeolite-like topologies are atypi cal as a direct c onsequence of their intricate structures, and therefore systematic design strategies are necessary for their deliberate construction. That is zeolite topologies are not ar ising from the assembly of simple TBUs (i.e. not rigid nor directional), which, in combination with flexible ditopic

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143 organic linkers, have consistently lead to MOMs having the default cubic diamond topology.6,7 Therefore, building information into th e MBB is vital, and it is of broader interest to use the MBB approach based on rigid and directional single-metal-ion TBUs as a solid platform and basis for developi ng new design strategies to construct and functionalize novel ZMOFs for specific applications. Herein, the quest towards ZMOFs will be attempted by implementing the singlemetal-ion-based MBBs approach derived from pyrimidinecarboxylate bis-chelating bridging ligands. 4.1.2. Experimental Section Materials and Methods All materials and methods are described in Chapter 2, unless otherwise noted. Synthesis of {[In(4,6-PmDC)2Na0.36K1.28](NO3)0.64(H2O)2.1}n, Insod -ZMOF, 27 The reaction mixture containing In(NO3)35H2O (0.0435mmol, 0.017g), 4,6-PmDC (0.087mmol, 0.016g), DMF (0.75mL), H2O (1.5mL), HNO3(0.2mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and 115 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The pale yellow polyhedral crystals were collected and air-dried.

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144 Synthesis of {[Yb(4,6-PmDC)2K](H2O)7.73}n, Ybsod -ZMOF, 28 The reaction mixture containing Yb(NO3)39H2O (0.0435mmol, 0.0195g) and 4,6-PmDC (0.087mmol, 0.016g), H2O (1mL), DMF (1mL) and HNO3 (0.1mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The colorless crystals with dodecahedron mo rphology were collected and air-dried. Synthesis of {[Er(4,6-PmDC)2K]}n, Ersod -ZMOF, 29 The reaction mixture containing Er(NO3)39H2O (0.0435mmol, 0.01928g) and 4,6-PmDC (0.087mmol, 0.016g), H2O (1mL), DMF (1mL) and HNO3 (0.2mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. Pale yellow polyhedral crystals were collected and air-dried. Synthesis of {[Y(4,6-PmDC)2K](H2O)9.65}n, Ysod -ZMOF, 30 The reaction mixture containing Y(NO3)36H2O (0.02175mmol, 0.0084g) and 4,6-PmDC (0.0435mmol, 0.008g), H2O (1mL), DMF (1mL) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by a dditional heating at 105 C for 23 hours and 115 C for 23 hours at a heating rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. Colorless crystals with dodecahedron morphology were collected and air-dried.

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145 Synthesis of {[Cd2(4,6-PmDC)2](H2O)8.42}n, Cdsod -ZMOF, 31 The reaction mixture containing Cd(CH3COO)22H2O (0.0435mmol, 0.0116g) and 4,6PmDC (0.087mmol, 0.016g), in DMF (0.5mL), H2O (1.5mL), En (0.1mL, 3M in DMF) was placed in a 20 mL scintillat ion vial and was heated to 85 C for 12hours, at a heating rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. The colorless block-shaped crystals were collected and air-dried. Synthesis of {[In(2-amino-4,6-PmDC)2]( H -Pip)(DMF)(H2O)4}n, In-aminosod -ZMOF, 32 The reaction mixture containing In(NO3)35H2O (0.0435mmol, 0.017g), 4,6-PmDC (0.087mmol, 0.016g), DMF (1mL), H2O (1.5mL), Pip (0.1mL, 0.58M in DMF), was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Red faceted polyhedral crystals we re collected and air-dried. Synthesis of Ga-aminosod -ZMOF, 33 The reaction mixture containing Ga(NO3)35H2O (0.0435mmol, 0.0167g), 2-amino 4,6PmDC (0.087mmol, 0.016g), DMF (1.5mL), H2O (1mL), En (0.1mL, 3M in DMF), was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of

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146 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Colorless faceted polyhedral crystals we re collected and air-dried. Synthesis of Fe-aminosod -ZMOF, 34 The reaction mixture containing Fe(NO3)39H2O (0.02175mmol, 0.0085g), 2-amino 4,6PmDC (0.0435mmol, 0.008g), DMF (1mL), H2O (1.5mL), En (0.1mL, 3M in DMF), was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Red faceted polyhedral crystals we re collected and air-dried. Synthesis of {[Cd(2-PmC)2](Pip)0.35(H2O)5.36}n, Cdrho -ZMOF, 35 The reaction mixture containing Cd(NO3)24H2O (0.0435mmol, 0.0134g), 2-PmCN (0.087mmol, 0.0092g), DMF (1mL), H2O (1mL), Pip (0.1mL, 0.58M in DMF) were added to a 20mL glass scintillation vial and heated to 85 C for 12 h at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Colorless polyhedral crystals were collected and air-dried.

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147 4.1.3. Results and Discussion This subchapter focuses on demonstrating the utility of the single-metal-ion-based MBB strategy to synthesize novel ZMOFs by ta rgeting rigid and directional TBUs built from suitable heterofunctional organic linke rs, such as pyrimidine derivatives with carboxylate substituents in the 2-, or 4,6positions. Reaction between 4,6-PmDC and In(NO3)35H2O in a solution of DMF and water affords pale yellow homogenous crystals with polyhedral morphology, referred to as Insod -ZMOF. The as-synthesized compound, stable a nd insoluble in water and common organic solvents, was characterized and fo rmulated by single-crystal X-ray diffraction studies as {[In(4,6-PmDC)2Na0.36K1.28](NO3)0.64(H2O)2.1}n, 27 .8 In the crystal structure of 27 (Figure 4.2.c.), four bis(bi dentate) 4,6-PmDC ligands fully saturate the coordination sphere of each indium metal ion through Nand Obonds, forming a chelate ring that locks the metal in its position and reinforces the rigidity of the TBU. Hence, each ligand chelates two i ndividual indium ions, forming two fivemembered rings coplanar with the pyri midine ring. The MBB is represented by InN4(CO2)4, which translates into a 4-connect ed node regarded as a TBU, InN4 (Figure 4.1.).

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148 Figure 4.1. MBB in compound 27, MN4(CO2)4 (left), regarded as a tetrahedral MN4O4 TBU (right). Hydrogen atoms are omitted fo r clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. The building units assemble in a fashi on that gives rise to the formation of truncated octahedra ( -cages), Figure 4.2.b., that are fu rther connected through shared square windows, Figure 4.2.a. forming a net with sodalite topology, Figure 4.2.c..1,9-22 The as-synthesized 27 Insod -ZMOF, unit cell contains 12 indium metal ions, 24 ligands, 15 potassium cations disordered over 24 posi tions, 4 sodium cations disordered over 12 positions, 5 nitrate anions disordered over 16 positions and approximately 25 disordered water molecules. The framework is anionic, where the overall charge is balanced by the K and Na cations.

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149 Figure 4.2. (a) Ball-and-stick representation of 4MR (left) and 6-MR (right), assembled to form (b) Truncated octahedron ( -cage), ball-and-stick (left) and CPK space-filling (right); (c) Fragment of the X-ray single-crystal structure in compound 27 outlining zeolite-like sod topology; Hydrogen atoms and guest molecules are omitted for clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. Yellow sphere represents the largest sphere that can be fit inside the cage, considering the van der Waals radii. (a) (c) (b)

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150 The approximate diameter of the largest sphere that can be fit inside the cage, considering the van der Waals radii of the nearest atoms, is 9.6. The total solventaccessible volume for 27 was obtained using PLATON soft ware by summing voxels that are more than 1.2 away from the framework, and it was found to correspond to approximately 46% of the unit cell volume. In order to inves tigate the ion exchange capabilities of 27 and also to exploit its porous nature, the K cations, pr esent in the as-synthesized 27 that prevent pore access, were fully exchanged with smaller Na and Li cations, respectively; the process was carried out at room temperature for 24 hours in aqueous media and was monitored by atomic absorption studies as follows. In a first step, the as synthesized Insod -ZMOF sample was rinsed several times with a solution of Sol1= EtOH and H2O to remove any impurities. Subsequently it was washed and let to soak for 24 hours in a 1M sol of NaNO3 in Sol1. Upon ion exchange the sample was washed again several times with Sol1; the atomic absorption studies reveal a In to Na ra tio= 1:1.31 found vs. In to Na = 1:1.41 calculated. Further on, the Na-exchanged Insod -ZMOF sample was further tested for ion exchange of the Na cations with an even smaller cation, Li, whic h we considered a more attractive candidate for gas storage purposes. The protocol outli ned for the Na-exchanged sample was also implemented for the ion exchange with a 1M LiNO3 in Sol1; the atomic absorption studies reveal a In to Na ratio= 1:0.0788 found vs. In to Na=1:0 calculated. The investigation pertinent to gas sorption capabi lities were conducted on this sample and the

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151 results will be discus sed in the following Chapter 5, entire ly dedicated to these types of investigations. Compounds 28 31 were synthesized under mild solvothermal conditions, as detailed in the experimental section. XRPD studies outli ne similar powder patterns, Figure 4.3., indicating the fact th at the materials are isostruc tural. The significance of these results is reinforcing the reliability and versatility of the single-metal-ion-based MBBs to construct a repertoire of ZMOFs, which has been shown to be not trivial in previous instances. The relevance of these findi ngs is also strictly correlated with their function, as several investigati ons can be carried out on the suitable platform of anionic sod-ZMOFs. The effect of intraand/or extra-framework metal ions upon the hydrogen sorption and its energetics will be detailed in Chapter 5. Figure 4.3. XRPD spectra of compound 27 ; red= calculated, blue= experimental; compound 28 green=calculated, experimental= olive; compound 29 pink= calculated, experimental= violet. 510152025303540 0 250 500 750 1000 1250 1500 Intensity2-theta/0 Insod -ZMOF, calculated Insod -ZMOF, experimental Ybsod -ZMOF, calculated Ybsod -ZMOF, experimental Ersod -ZMOF, calculated Ersod -ZMOF, experimental

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152 By functionalizing the two-position of 4,6PmDc, the geometric attributes of the linker are preserved, complementing its charac teristics with the am ino functional groups, in this instance. Similar reagents and reac tion environments as the ones implemented for 4,6-PmDC were pursued when utilizing 2amino-4,6-PmDC as linker, targeting the construction of materials with similar properties and features. Reaction between indium nitrate and 2amino-4,6-PmDC, in the presence of Pip yields polyhedral crystalline ma terial, referred to as In-aminosod -ZMOF, {[In(2-amino4,6-PmDC)2]( H -Pip)(DMF)(H2O)4}n, 32 as formulates by X-ray crystallography studies. In the crystal structure of 27 the indium metal ion adopts an octahedral geometry, being coordinated by four independent pyrimidin edicarboxylate ligands, giving rise to a MN2(CO2)4 type MBB, regarded as a trans -MN2O2 see-saw-like 4-connected BU, Figure 4.4.. The resultant MBB is comprised of a different metal-ligand assembly than in 27 where the environment of the 8-coordinate i ndium metal ion is satu rated by four heterocoordinating bis-chelating pyrimid inedicarboxylate bridging ligands. Figure 4.4. MBB in compound 32 MN2(CO2)4 (left), regarded as a (b) see-saw-like trans-MN2O4 4-connected BU (right). Hydrogen atoms are omitted for clarity; Indium= green, carbon= gray, ni trogen= blue, oxygen= red.

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153 The periodic arrangement of the MBBs gi ves rise to an anionic material with overall sod topology, in which the charge balanc e is provided by protonated guest Pip molecules. Albeit regarded as a sod -ZMOF though metal conn ectivity, the compound does not crystallize in the highest symmetry crystal system (hexagonal R-3 vs. cubic Im3m as in compounds 27 31 ), deriving a slightly distorte d version of the net. The structural features of the fr amework are influenced by this factor, observed also in the geometry of the truncated octahedra ( -cages), comprised of 4MR and two types of 6MRs, Figure 4.5.. Figure 4.5. Ball-and-stick representati on of (a) 4-MR, (b) 6-MR, (c) 6-MR and (d) schematic view of -cage, outlining two types of 6-MRs (blue and red) in compound 32 Hydrogen atoms are omitted for clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. (a) (b) (d) (c)

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154 Four distinct MBBs constitute the ver tices of the 4MR, Figure 4.5.a., generating a square with very slight devi ation from planarity and with InIn distances in the range 9.204 -9.232 . The pyrimidine ligands define the edges of the square, with the functional amino group pointing to its interior. Concomitantly, two different types of 6MRs are encountered: a plan ar elongated parallelogram -like, Figure 4.5.b., and a distorted hexagonal chair-like, Figure 4.5.c.. In the first instance, the arrangement of the MBBs outlines alternating quasi-orthogonal amino-pyrimidinedicarboxylate ligands, defining two types of edges: a short one, in which only one linker is bridging two distinct MBBs, and an elongated edge which encompa sses two ligands connecting to two MBBs, which constitute the vertices of the para llelogram. The distorted hexagonal rings highlight a chair conformation, in which one independent angular ligand bridges alternating MBBs, delineating an edge with of 9.232 (InI n distances between the two MBBs). One reason that could be accounted for the deviation from planarity relies on the coordination mode afforded by the linker: one site hetero-chelates through Nand Ometal bonds, while on the symmetrically equivale nt position, the coordination is ensured solely by carboxylate functionality. The framework, Figure 4.6., possesses uni dimensional accessible channels of approximately 12.587 X 13.878, considering th e van der Waals radi i of the nearest oxygen atoms.

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155 Figure 4.6. Ball-and-stick (left) and CPK repres entation (right) of X-ray single-crystal structure in compound 32 Hydrogen atoms are omitted for clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. The total solvent-accessible volume for 32 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework, and it was found to correspond to approximately 60% of the unit cell volume. As the anionic material possesses large apertures (~10 ), it allows for the diffusion of N,N,N’,N’-tetramethyl-3,6-acridinediamine (AO), acting as a cationic probe sensor. The successful AO encapsulation in In-aminosod -ZMOF was probed by UV studies, as shown in Figure 4.7..

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156 Figure 4.7. Solid-state UV-vis spectra of compound 32 after exchange with AO (green) vs. AO (red) and as-synthesized 32 (blue). Furthermore, reaction between Ga(NO3)35H2O and Fe(NO3)39H2O and 2amino-4,6-PmDC, under mild solvothermal cond itions yields crystalline material with polyhedral morphology, 33 and 34 XRPD studies indicate that the materials are isostructural with 32 as depicted in Figure 4.8.. 300400500600700 0.0 0.5 1.0 1.5 2.0 Absorbance (a.u.)Wavelength, nm AO In-aminosod -ZMOF + AO In-aminosod -ZMOF

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157 Figure 4.8. XRPD spectra of compound 32 ; red = calculated, bl ue = experimental; compound 33 experimental= wine; compound 34 experimental=green. Reaction between Cd(NO3)24H2O and 2-PmCN in a solution of DMF and water yields colorless polyhedral crystals w ith dodecahedron morphology, referred to as rho ZMOF, 35 The as-synthesized compound was char acterized and formulated by X-ray crystallography diffraction studies as {[Cd(2-PmC)2](Pip)0.35(H2O)5.36}n.8 Figure 4.9. MBB in compound 35, MN4(CO2)4(left), regarded as a tetrahedral MN4O4 TBU (right). Hydrogen atoms are omitted fo r clarity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red. 510152025303540 0 200 400 600 800 1000 1200 1400 1600 Intensity2-theta/0 Fe-aminosod -ZMOF, experimental Ga-aminosod -ZMOF, experimental In-aminosod -ZMOF, experimental In-aminosod -ZMOF, calculated

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158 In the crystal structure of 35 (Figure 4.10.), four indepe ndent bis(bidentate) 2PmC ligands, generated in situ from 2-PmCN, hetero-coordina te through Nand Oto the eight-coordinate cadmium metal ion. As a re sult, four chelating rings are formed around the metal ensuring the rigidity of the MBB represented by CdN4(CO2)4, regarded as a 4connected TBU, MN4 (Figure 4.9.). Consequently, the pe riodic arrangement of these TBUs generate the formation of truncated cuboctahedra ( -cages, Figure 4.10.b.) that are connected via double-eight-member rings (d8R) to yield rho -ZMOF (Figure 4.10.c.), with analogous topological features to the inorganic rho zeolite net.1,9,10,11 Each -cage consists of 48 cadmium ions and 96 2–PmC ligands, with piperazine and water guest molecules residing inside the cavity. Upon their removal open ch annels are exploitable in all three directions, the diameter of the larg est sphere that can be fit inside the cage without interacting w ith the van der Waals atoms of the framework being approximately 16.4 . The total solvent-accessible volume for 35 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework, and it was found to correspond to approximately 58% of the unit cell volume. Gas sorption investigations were conducted on the fully evacuated sample, a nd the results of thes e investigations will be detailed in Chapter 5.

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159 (a) (b) (c) Figure 4.10. (a) Ball-and-stick representation of 4-MR(left) and 6-MR (middle), 8-MR (right), assembled to form (b Truncated cuboctahedra ( -cages), ball-and-stick (left) and CPK space-filling (right); (c) Fragment of the X-ray single-crystal structure in compound 35 outlining zeolite-like rho -topology. Hydrogen atoms and guest molecules are omitted for clarity; Cadmium= green, carbon= gray, nitrogen= blue, oxygen= red. Yellow sphere represents the largest sphere that can be fit inside the cage, considering the van der Waals radii.

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160 4.2. ZMOFs Constructed from the Assembly of Metal-Organic Cubes (MOCs) 4.2.1. Introduction Thoroughly detailed in the fi rst part of this chapter, the single-metal-ion-based MBB approach has shown potential for targ eting ZMOFs, a subset of MOMs that exhibits properties and topol ogies akin to inorganic zeolit ic materials. Here, a new approach to derive ZMOFs is presented, base d on the assembly of metal-organic cubes (MOCs) which may be regarded as double four-member rings, d4R. As these are viewed as composite building units in traditional zeolitic materials,23 they should also be targeted as suitable MBBs to construct ZMOFs based on d4R. Our group has in fact succeeded in obtaining MOCs by implementing the singlemetal-ion-based-MBB approach. We previ ously reported the synthesis of MOC-1,24 a robust assembly in which ditopic hetero -functional imidazoledi carboxylate ligands constitute the edges of the cube, while the MBB comprising the single metal ions occupy its vertices. The additional pe ripheral coordination sites in MOCs offer the potential for coordination and/or hydrogen bonds or a combin ation thereof, whereby materials with zeolitelike topologies based on d4R may be targeted. Herein, an alternative avenue toward intended ZMOFs is probed by means of the introduction of a superior leve l of built-in information prior to the assembly process.

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161 4.2.2. Experimental Section Materials and Methods All materials and methods are described in Chapter 2, unless otherwise noted. Synthesis of {[In8(HImDC)12](DMF)6}n, MOC-2, 36 The reaction mixture containing In(NO3)35H2O (0.087mmol, 0.034g), 4,5-DCIm (0.1305mmol, 0.0206g), DMF (2mL), Pip (0.1mL, 0.58M in DMF) and HNO3 (0.075mL, 3.5M in DMF) were placed in a 20mL scintillation vi al and heated to 85 C for 12h, followed by additional heating at 105 C for 23h. at a rate of 1.5 C/minute and cooled to room temperatur e at a cooling rate of 1 C/minute. The pale yellow pure homogeneous microcrystalline material with dodecahedron morphology was collected and air dried Synthesis of {[In8(HImDC)12][In8(HImDC)11(ImDC)]-NH4 +}n, MOC-3, 37 The reaction mixture containing In(NO3)35H2O (0.0435mmol, 0.017g), 4,5-DCIm (0.1305mmol, 0.0206g), EtOH (3mL), and HNO3 (0.2mL, 3.5M in DMF) were placed in a 20mL scintillation vial and heated to 85 C for 12h. Colorless polyhedra were collected and air dried.

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162 4.2.3. Results and Discussion Reaction of In(NO3)35H2O with 4,5-DCIm in a DMF solution and in the presence of Pip, affords pale yellow hom ogeneous microcrystalline material with dodecahedron morphology, referred to as MOC-2, 36 The as synthesized compound, stable in water and most organic solvents was characterized and formulated by X-ray crystallography diffract ion studies as {[In8(HImDC)12](DMF)6}n. Each cube, Figure 4.11.a., consists of twelve doubly deprotonate d imidazoledicarboxylate ligands generated in situ,25 which coordinate in a bis(bi dentate) fashion to eight In3+ metal ions though N,Ohetero-coordination, forming a rigid 5-membered chelate ri ng that locks the metal in its position and reinforces the rigidity and directio nality of the assembly. The discrete cubes reside around special pos ition with site symmetry m-3 which corresponds to a Th molecular symmetry of cube. Indium (III) metal ions occupy the vertices of an ideal cube with InIn distan ces 6.675(1) and 90 InInIn angles. The cubes are connected vertex to ve rtex via intermolecu lar hydrogen bonds, OHO, 2.786. The oxygen atoms pointing outward of each cube form three intermolecular hydrogen bonds with the corr esponding oxygen atoms of the neighboring cube, Figure 4.11.b.. That is, each metal-organi c cube concomitantly connects to eight neighboring cubes through 24 hydrogen bonds.

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163 (c) (d) (b) (a) Figure 4.11. (a) Ball and stick (left) and schema tic representation (right) of a metalorganic cube; (b) Three O-H O intermolecular hydrogen bonds linking the vertices of two neighboring cubes; (c) Schematic repres entation of ACO topology; (d) X-ray singlecrystal structure of compound 36 ball-and-stick (left) and CP K representation (right). Hydrogen atoms and guest molecules are omitted for clarity; Indium= green, carbon= gray, nitrogen= blue, oxygen= red. Yello w sphere represents the largest sphere that can be fit inside the cage, c onsidering the van der Waals radii.

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164 It should be noted that all the carboxy lic groups are symmetri cally equivalent in the structure in accordance with the sy mmetry of the space group, but only one carboxylate can bear the labile proton, so an obvious frustra tion in the position of the hydrogen atoms involved in th e intermolecular hydrogen bon ds takes place. One can assume that in each pair of H-bonded vert ices, one vertex donates two protons and accepts one from the neighbor vertex and vice versa, for another vertex of the cube. Moreover, the OO intramolecular distance of 2.70(1) indicates the possibility of intramolecular H-bonds and thus flip-flop mode l of switching over tw o possible positions (intermolecular and intramolecular) of the single labile proton on the imidazoledicarboxylate ligand can be addressed. Consequently, the periodic arrangement of the discrete molecules results into an open framework that resembles the zeolite ACO topology (Figure 4.11.c.). The framework exhibits two types of infinite ch annels, having similar f eatures and properties with a compound previously reported by us, with soc topology and high hydrogen storage.26,27 The first type of channels has small openings with an approximate diameter of 3.333 , while the second type of accessibl e channels can accommodate a sphere with the largest diameter of 11.782, when consider ing the van der Waals radii of the nearest atoms. The reaction between the same starting reagents, In(NO3)35H2O and 4,5-DCIm, but in an EtOH solution yield colourless pol yhedral crystals, referred to as MOC-3, 37 The as-synthesized compound was charac terized and formulated by X-ray crystallography diffract ion studies as {[In8(HImDC)12][In8(HImDC)11(ImDC)]-NH4 +}n, in

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165 which it is assumed the proton transfer from the carboxylic group to ammonia and, therefore, inferring each other cube to be monoanionic. In the crystal structure of 37 Figure 4.12., the same ligand coordinati on to the metal is observed as in 36 Thus, eight In+3 ions occupy the vertices of an ideal cube with InIn distances of 6.576(2), coordinated by twelve exo-ligands in a bis( bidentate) fashion. Figure 4.12. Ball-and-stick representation of X-ra y single-crystal structure (left) and schematic representation of AST topology (right) in compound 37 Hydrogen atoms and guest molecules are omitted for clarity. Indium= green, carbon= gray, nitrogen= blue, oxygen= red. Yellow sphere represents the larges t sphere that can be fit inside the cage, considering the van der Waals radii. The vertices of four neighboring cu bes form a tetrahedron arrangement, generating a cavity in which the ammonium cation resides (Figure 4.13.). The distance from the centre of the cavity to th e twelve surrounding oxygen atoms is 3.207, indicating weak charge assi sted trifurcated N-HO hydr ogen bonding. In this instance, the discrete cubes generate a structure with the zeolite AST topology (Figure 4.12).

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166 Figure 4.13. Schematic representation of the a mmonium cation interacting with the vertices of four neighboring cubes (left) and ammonium cat ions sustaining trifurcated Hbonding mode (right) in compound 37 The total solvent-accessible volumes for 36 and 37 were obtained using PLATON software by summing voxels that are more th an 1.2 away from the framework. For 36 this was estimated to be 56.1%, while for 37 it represents approximately 31% of the unit cell volume. Investigations regarding their ga s sorption capabilities are to be revealed in the next chapter.

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167 4.3. Mixed Ligands Approach Towards Acce ssing Functional Materials with Extra-Large Cavities 4.3.1. Introduction Targeting materials with hi gh surface area has been of tremendous interest in the area of porous solid-state materials. In this context, concerted e fforts were dedicated towards the design of extended organic liga nds; this strategy is capable to render materials that go beyond the microporous regi me characteristic to most MOMs, and recent reports have highlighted a numbe r of very promising such compounds.28-35 An alternative strategy towards this scope is portrayed by inco rporation of more than one appropriate organic functionality in the synthesis process. This approach implies a very high degree of complexity, and the capacity of anticipating the exact outcome when employing such a strategy is rather limite d, at this point. However, materials with exceptional properties may be accessed from already predetermined building blocks, when implementing this synthetic route. Hitherto, very few attempts were dir ected towards this novel approach. Matzger et.al have reported very intere sting results when using H3BTB (1,3,5-tris(4carboxyphenyl) benzene), in co njunction with 1,4-H2BDC (terephtalic acid) to result in UMCM-1,36 while the same H3BTB utilized in combination with T2DC (thieno[3,2b]thiophene-2,5-dicarboxyl ate), yields UMCM-2.37 Both materials possess exceptional features, porosity in the mesoporous regime, a nd the latter material qua lifies as one of the MOMs having the highest surf ace area reported to date.

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168 Herein, the goal is to incorporate two poten tial bridging ligands in the synthesis of functional MOMs, in which at least one linker has shown poten tial to result in materials with zeolitelike features. Among the many advantages of targeting such materials with extra-large cavities that resemble the structures of zeolites, a major attribute is represented by their forbidde n interpenetration, which may be a primary concern when using linkers with extended lengths. 4.3.2. Experimental Section Materials and Methods All materials and methods are described in Chapter 2, unless otherwise noted. Synthesis of {[Y(2-amino-4,6-PmDC)0.85(oxalate)0.57(H2O)1.42](DMA+)0.14(H2O)2.68}n, 38 The reaction mixture containing Y(NO3)36H2O (0.0168g, 0.0435 mmol) 2-amino 4,6PmDC (0.016g, 0.087 mmol), Oxalic acid ( 0.00195g, 0.02175mmol), DMF (1 mL), H2O (2mL), and HNO3 (0.1mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, at a rate of 1.5 C/minute and cooled to room temperature at a cooling rate of 1 C/minute. Colorless polyhedral crystals were collected and airdried. Encapsulation of 5,10,15,20-Tetrakis(4(trimethylammonio)-phenyl)-21H,23Hporphinetetratosylate (TTMAPP) Protocol 1 : The reaction mixture containing Y(NO3)36H2O (0.0168g, 0.0435 mmol) 2amino 4,6-PmDC (0.016g, 0.087 mmol), Oxalic acid (0.00195g, 0.02175), TTMAPP

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169 (0.00055g, 0.35mol), DMF (1 mL), H2O (1.5 mL), and HNO3 (0.1mL, 3.5M in DMF) was placed in a 20 mL scintillat ion vial and was heated to 85 C for 12hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. Protocol 2 : The reaction mixture containing Y(NO3)36H2O (0.0168g, 0.0435 mmol) 2amino 4,6-PmDC (0.016g, 0.087 mmol), Oxalic acid (0.00195g, 0.02175), TTMAPP (0.0022g, 1.4 mol), DMF (1 mL), H2O (1 mL), and HNO3 (0.1mL, 3.5M in DMF) was placed in a 20 mL scintillation vial and was heated to 85 C for 12hours, followed by additional heating at 105 C for 23 hours and at 115 C for 23 hours, at a rate of 1.5 C/minute and cooled to room temp erature at a cooling rate of 1 C/minute. 4.3.3. Results and Discussion As previously shown in this subchapt er, pyrimidinedicarboxylate ligands have shown to possess high potential as to facilita te the formation of complex materials with zeolite-like topologies and features. One possible avenue that would assist with the increase in the size of the large cavities, and hence the available surf ace area, is regarded by the use of a secondary ligand in the reacti on environment. Albeit difficulty to control these experimental conditions, materials with highly interesting properties can be pursued via this route. Accordingly, solvothermal reaction between Y(NO3)36H2O, 2-amino 4,6-PmDC and oxalic acid, in a 1.5: 1.5:1 ratio and in a DMF/H2O based system, yields crystals with polyhedral morphology, characte rized and formulated by Xray single-crystal data

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170 as{[Y(2-amino-4,6-PmDC)0.85(oxalate)0.57(H2O)1.42](DMA+)0.14(H2O)2.68}n, 38 The resulting crystalline material is anionic, where the 24+ necessary balance charge is provided by DMA cations, resulted as a c onsequence of the decomposition of DMF. In the crystal structure of 38 the complex metal to ligands directed assembly comprises a variety of MBBs, and hence BU s, Figure 4.14., that are finally resulting a heterocoordinated net based on 4, 5, 6-connected nodes. Four distinct types of MBBs are present in 38 In Figure 4.14.a., four pyrimidinedi carboxylate ligands are binding the 8coordinate Y metal ion, thr ough two hetero-coordinating N-, Ochelate rings, while the other two linkers ar e bridging in a monodentate fash ion, solely thr ough the carboxylate functionality. Two water molecules are completing the remaining available sites, resulting in an MN2(CO2)4 type MBB, regarded as 4-connected MN2O2 BU. Similarly, the second type of MBB resembles the conn ectivity encountered in the one described above. However, in this case, the two chela ting rings are ensured by the second type of organic ligand, the oxalate. The remaining site are occupied by two monodentate carboxylate bridging 2-amino-4,6-Pm Dc, and two terminal water molecules, resulting in an M(CO2)6 type MBB, regarded as a MO4 4-coonected BU, Figure 4.14.b.. In the MN(CO2)5 type MBB, a 5-connected MNO4 BU, Figure 4.14.c., the ce ntral Y metal ion is bridged to two other metals by oxalates linkers, while a hetero-coordinating aminopyrimidinedicarboxylate aids the connectiv ity to two other metal ions. Lastly, a MN(CO2)6 type MBB is encountered, rega rded as a 6-connected MNO5BU, Figure 4.14.d., where each of the two hetero-chelating pyrimidinedicarboxylate further enable

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171 the linkage to other two individual metal cente rs. Two oxalate bridgi ng units are assisting the connectivity to two distinct metal centers. Figure 4.14. Four different MBBs in compound 38 : (a) MN2(CO2)4, regarded as 4connected MN2O2 BU, (b) M(CO2)6, regarded as 4-connected MO4 BU, (c) MN(CO2)5, regarded as 5-connected MNO4 BU and (d) MN(CO2)6, regarded as a 6-connected MNO5BU. Hydrogen atoms and guest molecules are omitted for clarity; Yttrium= green, carbon= gray, nitrogen= blue, oxygen= red. (a) (b) (c) ( d )

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172 The periodic assembly of these molecular components result in a complex novel cage, with extra-large cavities, com posed of 3-MR, three different types of 4-MR and a 6-MR, Figure 4.15. Figure 4.15. Ball-and-stick representation of (a) 3MR, (b) first type of 4-MR, (c) second type of 4-MR, (d) third type of 4-MR, (e) 6-MR and (f) unique assembly of one 3-MR and three distinct 4-MR in compound 38 Hydrogen atoms and guest molecules are omitted for clarity; Yttrium= green, carbon= gray, nitrogen= blue, oxygen= red. The extra-large cages, Figure 4.16.a., resemb le the profile of the ones encountered in zeolites, however with a superior co mplexity, and on a much larger scale. Each cage contains 168 Y metal ions and a to tal of over 3500 atoms, with the internal diameter of 38 (when considering the van de r Waals radii of the n earest atoms), and an outside diameter of 48 X 53 . (a) (b) (c) (d) (e) (f)

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173 Figure 4.16. Ball-and-stick (left) and schematic representation (right) of unprecedented mesoporous cage in compound 38; (b) Fragment of the X-ray single-crystal structure in compound 38 Hydrogen atoms and guest molecules are omitted for clarity; Yttrium= green, carbon= gray, nitrogen= blue, oxygen= re d. Yellow sphere represents the largest sphere that can be fit inside the cage, considering the va n der Waals radii. (b) (a)

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174 The unprecedented cag e is described by [372.4114.68], where there superscripts represents the number of each distinct MR a nd their overall distribution in the cavity. For example, the descriptors 4114 delineates the total number of 4-MR encountered in the cage, even though there are ther e three idiosyncratic such MR present in the extra-large cavity. The profile of this cag e is similar to the one enc ountered in ZIF-100, where the moz cage is depicted as [34841081226] .38 Topological analysis rev eals that the two 4-connect ed nodes are topologically identical and they have the followi ng point symbol (short Schlfli){3;42;52;6}, and corresponding coordination sequence: 4, 12, 27, 45, 64, 86, 116, 154, 202, 261; the 5connected node outlines the unique seque nce and point symbols 5, 13, 25, 40, 58, 85, 124, 163, 198, 249, {3;47;52}. The coordination sequence fo r the 6-connected node: 6, 16, 28, 42, 63, 93, 127, 163, 206, 256, associated with the following {32;47;55;6} point symbol.

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175 Figure 4.17. Tiling representation of unprecedented topology of the (4,5,6) heterocoordinated net in compound 38 The (4,5,6) trinodal net has an overall point symbol (short Schlfli) {3;42;52;6}{3;47;52}{32;47;55;6}2, which confirms also the uniqueness of the net as having an unprecedented topology to date. The t iling representation is depicted in Figure 4.17. The extra-large cavities [372.4114.68] are fused together by 2[32.43]+21[46] tiles, while the framework’s transitivity is: 39(11)5. [372.4114.68] 12[32.43]+21[46] [372.4114.68]+ 12[32.43]+21[46]

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176 (a) ( b ) Interestingly, an alternative analysis ca n be regarded, where the complexity of the framework is reduced. The newly described ne t has a hypothetical natu re, of course, as we are not accounting for any of the yttrium metal ions and ligands that are not really contributing to the skeleton of the net, a nd which, if not present are not impeding the overall integrity/profile of the net. That is we do not account for any of the metal ions that are forming the first type of 4-MR, and the one that are found in the 6-MR. The resulting framework is based solely of 4-connected nodes, Figure 4.18., with the following coordination sequence 4, 8, 13, 20, 29, 41, 56, 73, 93, 116, 454 and corresponding vertex symbol [4.4.4.8.4.12]. The two topolog ical parameters indicate wse topology, also regarded as zeolite-like net, ye t to be synthesized, as it is found listed only in the hypothetical zeolite atlas.39 Figure 4.18. Alternative way of interpreting 38 : (a) MN2(CO2)6, regarded as 4-connected MN2O2 4-connectedBU; (b) Ball-and-stick, sc hematic and tiling representation of mesoporous cage; Hydrogen atoms and guest molecules are omitted for clarity; Yttrium =green, carbon =gray, nitrogen = blue, oxygen = red.

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177 The total solvent-accessible volume for 38 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework, and it was found to correspond to approximately 62.7% of the unit cell volume. In 38 all windows have very small openings, that do not allow di ffusion of any molecules, while the only accessible aperture is the 6MR (~5.9X 7.3 ). Preliminary UV studies probe the successful diffusion and anchorage of AO in 38 as evidenced in Figure 4.19., upon exposure to an ethanolic solution, for just 30 minutes. The deeply orange crystals were washed several times to remove any ex cess AO, before recording the UV spectra. Figure 4.19. Solid-state UV-vis spectra of compound 38 after AO sensing (red) vs. assynthesized (blue). Further investigations regarded the encapsulation of cationic porphyrin, TTMAPP in the extra-large cavities of 38 as means to access the multitude of possible host-guest related applications.5 The protocol was designed as “one -pot synthesis”, as the window 300400500600700800 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 AbsorbanceWavelength, nm me737 as-synthesized me737+ Acridine Orange

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178 apertures are too small to allow the diffusion of large molecules, in spite of very large accessible cavities. In order to attempt this application, the reaction was conducted under the same experimental conditions as the tr aditional synthetic route detailed in the experimental section. Initial investigations considered ju st a very slight amount of TTMAPP, 0.35mol, which result ed in slightly brown colore d crystals. The UV profile is depicted in Figure 4.20., solid blue line, wh ere the five characteristic absorption bands are noticed, confirming the pres ence of the free -base porphyrin. Figure 4.20. Solid-state UV-vis spectra of compound 38, as-synthesized (green) and after free-base TTMAPP encapsulation (blue), and metalated-TMAPP (red). The slight alterations in the experimental protocol, outlined by increasing the concentration of TTMAPP to 1.4mol, as well as of the incubation temperature and time, results in uniform green polyhedral material where XRPD studies confirmed the identity of 38. The solid-state UV-vis spec trum (Figure 4.19. red solid line), was collected after washing the crystals several times with DMF, where the shift of the Soret bands and 300400500600700800 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 AbsorbanceWavelength, nm me737-TTMAPP low conc. me737-TTMAPP-metalated high conc. me737-as synthesized

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179 collapse of the Q-bands indicate the metalla tion of the free-base porphyrin with the excess yttrium metal ion. 4.4. Summary Here it was delineated the successful im plementation of various strategies to result in metal-organic materials that possess periodic intr aframework organic functionality and zeolitelike topologies and properties. In the light of the considerable efforts directed at the synthesis of such comp lex materials, proven to be very challenging and difficult to pursue, the re sults are highly significant. Hence, it was probed that the singlemetal-ion approach conveys rigid and directional TBUs, which utilized in comb ination with appropri ate angular heterofunctional ditopic organic ligands, are capable to lead the assembly of targeted ZMOFs. Furthermore, a novel approach to construct ZMOFs was considered, by utilizing metalorganic cubes as building blocks generated in situ thus introducing a superior level of built-in information prior to the assembly process. Lastly, a mixed ligands approach towards accessing functional materials w ith extra-large cavities wa s pursued, resulting in an exceptional complex material with zeolitelike features, constructed from mesoporous unprecedented cages. Solid-state materials with large and extr a-large cavities allow for a multitude of diverse studies that complement areas where zeolites encountered limitations. Ipso facto innovative functions are arising from the specificity associat ed with their porous nature, along with readily tunability aided by intra and/or extra framework organic components. Preliminary results demonstrate the ability of the anionic materials to serve as periodic

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180 porous platform as (host-guest)-guest sensors, as well as encapsulat ion and metallation of porphyrins. Gas storage related functions of these solid-state porous materials will be thoroughly covered in th e next chapter. In conclusion, the developed strategies were proven to offer great potential to access other complex structures that are not readily constructed from the conventional assembly of simple building blocks. It was demonstrated that complex structures, based on non-default nets, such ZMOFs can be desi gned and assembled by rational choice of rigid and directional building blocks containing the require d hierarchal information.

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181 4.5. References 1. Liu, Y.; Kravtsov, V. Ch.; Larsen, R.; Eddaoudi, M. Chem.Commun. 2006 14 1488-1490. 2. Eddaoudi, M.; Eubank, J. F.; Liu, Y.; Kravtsov V. Ch. and Brant, J. A. in Proceedings of the 15th International Zeolite Conf erence, Stud. Surf. Sci. Catal .; Xu, R.; Gao, Z.; Chen, J. and Yan, W., Eds.; Elsevier: New York 2007 2021-2029. 3. Eddaoudi, M.; Eubank, J. F. Organic Nanostructures 2008 251-274. 4. Liu, Y.; Kravtsov, V. Ch.; Eddaoudi, M. Angew. Chem. Int. Ed. 2008 47 8446-8449. 5. Alkordi, M. H.; Liu, Y.; Larsen, R. W.; Eubank, J. F. and Eddaoudi, M. J.Am.Chem. Soc. 2008 130 12639–12641. 6. Zaworotko, M.J. Chem. Soc. Rev. 1994 23 283-288. 7. Moulton, B.; Zaworotko, M. J. Chem.Re v 2001 101 1629-1658. 8. Sava, D. F.; Kravtsov, V. C.; Nouar, F.; Wojtas, L.; Eubank, J. F.; Eddaoudi, M. J. Am. Chem. Soc 2008 130 3768-3770. 9. Banerjee, R.; Phan, A.; Wang, B.; K nobler, C.; Furukawa, H.; O'Keeffe, M.; Yaghi, O. M. Science 2008 319 939-943. 10. Huang, X.-C.; Lin, Y.-Y.; Zhang, J.-P.; Chen, X.-M. Angew. Chem.Intl.Ed. 2006 45 1557-1559. 11. Park, K. S.; Ni, Z.; Cote, A. P.; C hoi, J. Y.; Huang, R.; Uribe-Romo, F.J.; Chae, H. K.; O'Keeffe, M.; Yaghi, O. M. Proc. Nat. Acad. Sci. U.S.A. 2006 103 10186-10191. 12. Post, M. L. and Trotter, J. J. Chem. Soc., Dalton Trans. 1974 17 1922-1995. 13. Dawes, H. M.; Waters, J. M.; Waters, T. N. Inorg. Chim. Acta 1982 66 29-36. 14. Masciocchi, N.; Bruni, S.; Cariati, E.; Cariati, F.; Galli, S.; Sironi, A. Inorg. Chem 2001 40 5897-5905.

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182 15. Tabares, L. C.; Navarro, J. A. R.; Salas, J. M. J. Am. Chem. Soc. 2001 123 383-387. 16. Naumov, P.; Ristova, M.; Soptrajanov, B. ; Kim, M. J.; Lee, H. J.; Ng, S. W. Acta Crystallogr. Sect. E: Struct. Rep. Online 2001 E57 m14-m16. 17. Abrahams, B. F.; Haywood, M. G.; Robson, R.; Slizys, D. A. Angew. Chem.Intl. Ed. 2003 42 1112-1115. 18. Huang, X.; Zhang, J.; Chen, X. Chin. Sci. Bull. 2003 48 1531-1534. 19. Barea, E.; Navarro, J. A. R.; Salas, J. M.; Masciocchi, N.; Galli, S.; Sironi, A. Polyhedron 2003 22 3051-3057. 20. Solntsev, P. V.; Sieler, J.; Chernega, A. N.; Howard, J. A. K.; Gelbrich, T.; Domasevitch, K. V. Dalton Trans 2004 5 695-696. 21. Barea, E.; Navarro, J. A. R.; Salas, J. M.; Masciocchi, N.; Galli, S.; Sironi, A. J. Am. Chem. Soc 2004 126 3014-3015. 22. Abrahams, B. F.; Hawley, A.; Haywood, M. G.; Hudson, Ti. A.; Robson, R.; Slizys, D. A. J. Am. Chem. Soc 2004 126 2894-2904. 23. Baerlocher, Ch. and McCusker, L.B. 2008 Database of Zeolite Structures: http://www.iza-structure.org/databases/ 24. Liu, Y.; Kravtsov, V.; Walsh, R. D.; Podda r, P.; Srikanth, H.; Eddaoudi, M. Chem. Comm. 2004 24 2806-2807. 25. The in situ hydrolysis of reac tants containing cyano groups is known in MOF chemistry: Evans, O. R.; Lin, W. Chem. Mater 2001 13 3009-3017. 26. Liu, Y.; Eubank, J. F.; Cairns, A. J.; Ec kert, J. ; Kravtsov, V. Ch.; Luebke, R.; Eddaoudi, M. Angew. Chem. Int. Ed. 2007 46 3278-3283. 27. Belof, J. L.; Stern, A. C.; Eddaoudi, M.; Space, B. J. Am. Chem. Soc 2007 129 15202-15210. 28. Nouar, F.; Eubank, J. F.; Bousquet, T.; Wojtas, L.; Zaworotko, M. J.; Eddaoudi, M. J. Am. Chem. Soc. 2008 130 1833–1835. 29. Yan, Y; Lin, X.; Yang, S.H.; Blake, A.J.; Dailly, A.; Champness, N.R.; Hubberstey, P.; Schrder, M. Chem. Commun. 2009 9 1025-1027.

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183 30. Chae, H. K.; Siberio-Perez, D. Y. ; Kim, J.; Go, Y.-B.; Eddaoudi, M.; Matzger, A. J.; O’Keeffe, M.; Yaghi, O. M. Nature 2004 427 523-527. 31. Lin, X; Telepeni, I; Blake, A.J.; Dailly, A., Brown, C.M.; Simmons, J.M.; Zoppi, M.; Walker, G.S.; Thomas, K.M .; Mays, T.J.; Hubberstey, P.; Champness, N.R.; Schrder, M. J.Am.Chem. Soc. 2009 131 2159-2171. 32. Choi, H. J.; Dinc M. and Long, J. R. J. Am. Chem. Soc. 2008 130 7848– 7850. 33. Wang, X.-S.; Ma, S.; Sun, D.; Parkin, S. and Zhou, H.-C. J.Am.Chem. Soc 2006 128 16474-16475. 34. Ma, L.; Lin, W. J.Am.Chem. Soc 2008 130 13834-13835. 35. Park, Y.K.; Choi, S.B.; Kim, H.; Kim, K.; Won, B.H.; Choi, K.; Choi, J.S.; Ahn, W.S.; Won, N.; Kim, S.; Jung, D.H. ; Choi, S.H.; Kim, G.H.; Cha, S.S.; Jhon, Y.H.; Yang, J.K.; Kim, J. Angew. Chem. Int. Ed. 2007 46 8230–8233. 36. Koh, K.; Wong-Foy, A.G.; Matzger, A.J. Angew. Chem. Int. Ed. 2008 47 677-680. 37. Koh, K; Wong-Foy, A.G.; Matzger, A.J. J. Am. Chem. Soc. 2009 131 41844185. 38. Wang, B.; Cote, A. P.; Furukawa, H.; O'Keeffe, M. and Yaghi, O. M. Nature 2008 453 207-211. 39. Foster, M. 2004 Hypothetical Zeol ites Database http://www.hypotheticalzeolite s.net/DATABASE/BRONZE/ XYZ/viewer.ph p?file=229_1_1

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184 Chapter 5. Gas Sorption Investigations in Porous MOMs 5.1. Hydrogen Storage Methods in Solid-State Materials Hydrogen is nowadays the focus of in -depth theoretical and experimental investigations due to its potential usag e as a clean energy source for vehicular applications and portable systems. “Towards a hydrogen economy” is an expression that now is becoming familiar outside the scientific community, on a societal level, worldwide. Primarily, emphasis has been put on transportation re lated purposes. While hydrogen production strategies have been already developed and implemented, the storage and delivery still requi re substantial efforts; idea lly, its storage should be achieved in light-weight, safe and compact reservoirs. Cu rrently, the most efficient storage methods require either large volume tanks at ambien t temperature, and very high pressures (which brings up safety considera tions) or storage at ve ry low temperatures, 20K (implying very high costs of operations). Cooling systems to the critical temperature of hydrogen require very good insulating vessels; in spite of certain deficiencies, this method was shown to have potential and ha s been used in space technology related applications.1

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185 Other hydrogen storage approaches are related to finding materials that have affinities towards hydrogen, aimed to improve so me of the drawbacks associated with the techniques mentioned above. The Energy E fficiency and Renewable Energy (EERE) program, implemented by the US Department of Energy (DOE), deals with hydrogen production, delivery, storage, technology valida tion and safety. In accordance with these factors, DOE has set tec hnical targets for the onboard storage of hydrogen,2 criteria that have to be met in order for these applicati ons to be considered viable as alternative fueling systems. Table 5.1. DOE Technical Targets for Onboard Hydrogen Storage systems.2 Hydrogen storage in solid state materi als is currently ac complished through chemisorption (chemical adsorption) techni ques, physisorption (physical adsorption) methods and by spillover. Extensive research studies have been devoted to systems based on metal hydrides and hydrides complexe s. Promising results are obtained on a Storage parameter Units 2007 2010 2015 System Gravimetric Capacity (net useful energy/max system mass) kWh/kg (kg H2/kg system) 1.5 (0.045) 2 (0.06) 3 (0.09) System Volumetric Capacity (net useful energy/max system volume) kWh/L (kg H2/L system) 1.2 (0.036) 1.5 (0.045) 2.7 (0.081) Min/max delivery temperature C -30/85 -40/85 -40/85 Max. delivery pressure from tank atm 100 100 100 Refueling rate for 5kg min 10 3 2.5

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186 volumetric basis, and currently lighter metals are targeted to improve the gravimetric capacities, as well. On the other hand, concerns arise from elevated temperature required for the desorption of hydrogen (in the context in which the actual formation of the metal hydride is an exothermic reaction). Some co mplex hydrides have superior performances, such as LiBH4, Ca(BH4)2 and Mg(BH4)2, however the desorption temperatures are higher than 300C, while their kinetics are very low.3 Alternatively, physisorption techniques possess certain advantages in direct comparison to chemisorption methods, mainly due to these factors: fast kinetics, full reversibility of and low energy associated with the sorption-desorption cycles (lower than 10 kJ mol-1). On the lower end, all experiment s are carried out at relatively low temperatures (77 and 87K), which is not a desi rable aspect in the premises of commercial effectiveness and meeting the DOE targets. According to the pore size, porous materi als are classified as: ultramicroporous (pore size <5 ), microporous (pore size 520 ), mesoporous (pore size 20-500 ), and macroporous (pore size >500 ). Gas adso rption studies are commonly regarded techniques to evaluate the porosity of so lid-state materials. Based on the pore size criteria, the International Un ion of Pure and Applied Chemistry (IUPAC) has established 5 types of adsorption isotherms: type characteristic to micropor ous materials; type II, III and IV encountered in macroporous solid s and type IV and V associated with mesoporous compounds (usually exhibiting hysteresis upon desorption). An adsorption isotherm for a given adsorbate on a surface is regarded as the amount of substance adsorbed at equilibrium of the adsorptive in the gas phase, over a constant temperature

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187 regime. The great majority of MOMs are microporous, for which the characteristic isotherm is type I (or Langmuir isotherm). In this context, porous MOMs qualify as potential candidates in areas related to hydr ogen storage, reducti on of the emission of green house gases (CO2) and gas separation. Nitrogen and argon sorption isotherms are us ed to evaluate the specific surface area and pore volume, which are important pa rameters to monitor in porous materials. The specific surface area (area between two pha ses divided by the mass of the relevant phase) is an important factor, aiming for a high surface to volume ratio. One of the most employed methods to evaluate surface ar ea is Brunauer-Emmett-Teller (BET) method.4 A standard BET measurement requires at leas t 3 points to fit a linear plot, in a P/P0 range of 0.05 to 0.35 (slightly lower relative pressu re regime for microporous materials) on a nitrogen adsorption isotherm. A particulate case of the BET method is represented by the Langmuir method,5 employed only to evaluate the su rface area of microporous solids, considering the adsorption of a monolayer of the adsorbate. In this model, the coverage is not dependent on the adsorption energy; it is assumed there are no interactions between the adsorbed molecules, and that the ad sorption enthalpy is does not depend on the number of molecules adsorbed on the surface. The pressure range close to unity allo ws for the calculation of the total pore volume based on the amount of vapor adsorbe d, assuming that the liquid adsorbate is filling the pores. The Dubinin-Radushkevich (DR) method6 is based on the Polanyi potential theory of adsorption7 and states that the frac tion of the adsorption volume occupied by liquid adsorbate at various adsorption potentials can be expressed as a

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188 Gaussian function. The concept of pore size distribution describes th e direct relationship between the distribution of the pore volume w ith respect to the pore size. In order to calculate the pore size distribu tion, it has been established th at the desorption isotherm is more appropriate than the adsorption isothe rm. Surface area and pore volume are directly correlated, as well as is the surface area a nd the hydrogen uptake at 77K, as shown by Zhou et.al .8 Inelastic Neutron Scattering (INS) is regarded as a usef ul technique that aims to gather a better understanding of the favorable sorption sites within physisorbed hydrogen materials. Neutron scattering is very sensitive to hydrogen and th e hindered rotations of the hydrogen molecule can be assigned to spec ific interactions co rresponding to certain adsorption sites within the studied material.9 Low temperature thermal desorption spectroscopy (TDS) represents another usef ul technique that monitors the hydrogen desorption upon temperature dependence. Scientis ts in the University of Stuttgart have developed an experimental setup where the sample is primarily subjected to hydrogen sorption; subsequently, the sample is cooled down to 20K, followed by a second evacuation. The hypothesis relies on the fact that at such a low temperature, the physisorbed hydrogen will stick onto the materi al, and only potential other free guests are evacuated. The cell is gradually heated and it is measured the quantitative response of desorbed hydrogen by mass spectroscopy. Resu lts are interpreted also in terms of hydrogen affinity towards the material, just like in the case of INS; the higher the temperature at which the signal response is received, the stronger the interactions

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189 between the dihydrogen molecule and material. In the case of expected different sorption sites, it should be equivalent to more than one maximum peaks in the plot. Carbon-based materials, zeolites, and of course, porous MOMs represent the most studied classes of compounds amenable to physisor bed hydrogen approaches. Carbon materials include carbon nanot ubes, activated carbons, fullerene s, graphite nanofibers; all these materials are related, but differ mainly in the degree of order and of the actual shape of the nanostructures. Disadvantages attribut ed to carbon-based materials in the context of hydrogen storage are related to high produc tion cost and low binding affinities. The high costs are directly correla ted with the quality of the materials, evidently; as the degree of purity is incr eased (free of defects, byproducts, remains of catalysts), so is their performance in terms of storage (as we are looking at per wei ght storage, it is clear that those impurities are affecting the performan ce of the material). The highest specific surface areas associated w ith this class of comp ounds do not exceed 1000 m2g-1 for carbon nanotubes, and up to 3000 m2g-1for activated carbon materi als, associated with hydrogen uptake up to 4.5 % at 77K10 and 3.2% at ambient temperatures and very high pressures (200 bar).11 Zeolites, also described in chapter on e of this dissertati on, represent porous materials with attractive properties, associat ed with elevated temperature resistance, along with stability in extreme chemical conditions. Studies on their hydrogen storage capabilities are not very promising though, mainly due to their relative small surface area (maximum up to 800-900 m2g-1), and therefore a relatively low saturation capacity

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190 reached at low or moderate pressure. Langmi et. al reported one of the highest values in Ca exchanged Zeolite X, at 77K and 15 bar, 2.19 wt %.12 5.1.1. Hydrogen storage in MOMs Porosity qualifies as one of the most advantageous characteristics attributed to MOMs, regarded as a very unique class of hydrogen storage materials; many research studies are now focusing on designing bette r candidates for this purpose. Equally important, investigations are targeted to wards understanding the fundamentals of hydrogen storage mechanism in these materi als. Comprehensive reviews have been recently entirely dedicated to this topic, covering the wide range of experimental results,8,13-18 along with theoretical approaches.19,20 Since MOMs are primarily synthesized solvothermally, a highly porous structure may accommodate guest solvent/counterions in its voids. The activat ion procedures of very open MOMs require substantial efforts main ly due to the fact th at “one size doesn’t fit all”; the material’s stability and specificity need to be accounted for each particular framework. Generally, in a primary step, exchan ge of guests molecule s is facilitated by using a volatile solvent, most commonly at room temperatures for as little as 12 hours. In a second step, relatively hi gh activation temperatures are required in order to attempt full guest evacuation, parameter maintained within limits that will not damage the integrity of the framework. Particle size and am ount of sample may also have an impact in the direct measurement of the hydrogen isothe rms; it is generally believed that smaller

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191 particle sizes favor a more rapi d gas diffusion; as far as amou nt of sample used, the range between 25-100 mg can be considerable suita ble. Repetitive tests on the same materials need to be employed to verify the accuracy of the measurements and probe the reproducibility of the results. Table 5.2. summarizes the most promising hydrogen storage results in select MOMs.

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192 Table 5.2. Hydrogen uptake at various temperatures and pressures in select MOMs. Material ref Surface area (m2g-1) Pore vol. (cc g-1) Max. H2 uptake (% wt) Experimental conditions: T, P BET Langmuir MOF-177,21 Zn4O(BTB)2 4750 5640 nr. 7.6 11.4 77K, 66 bar 77K, 78 bar IRMOF-122 (MOF-5), Zn4O(1,4-BDC)3 3800 4400 nr. 7.1 10 77K, 40 bar 77K, 100 bar MIL-10123, Cr3O (1,4-BDC)3F n.r. 5500 1.9 2.5 6.1 0.43 77K, 1 atm 77K, 60 bar 298K, 80 bar CUTET,24 Cu6O (TZI)3NO3 2847 3223 1.01 2.4 77K, 1 atm UMCM-150,25 Cu3(BHTC)2 2300 3100 1 2.1 5.7 77K, 1 atm 77K, 45 bar Cu2(QPTC),26 2932 n.r. 1.138 2.24 6.07 77K, 1atm 77K, 20 bar PCN-11,27 Cu2(SBTC) 1931 2442 0.91 2.55 5.05 77K, 1 atm 77K, 20 bar Cu2(TPTC) 26 2247 n.r. 0.886 2.52 6.06 77K, 1atm 77K, 20 bar Mn4Cl(BTT)3/8 28 2100 n.r. nr. 2.2 5.1 6.9 77K, 1atm 77K, 50 bar 77K, 90 bar Co3(NDC)3 dabco29 1502 2293 0.822 2.45 4.2 77K, 1 atm 77K, 20 bar Cu4Cl(BTT)3/8 28 1710 1770 nr. 2.42 4.2 5.7 77K, 1atm 77K, 30 bar 77K, 90 bar MOF-50526 Cu2(BPTC) 1670 n.r. 0.68 2.59 4.02 77K, 1 atm 77K, 20 bar soc -MOF, In3O(ABTC)3/2NO3 n.r. 1417 0.5 2.61 77K, 1atm HKUST-1,31 Cu3(BTC)2 1154 1958 nr. 2.54 3.6 77K, 1atm 77K, 10 bar PCN-10,27 Cu2(ABTC) 1407 1779 0.67 2.34 4.33 77K, 1 atm 77K, 20 bar

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193 Acronyms : ABTC= azobenzene-3,3’,5,5’-tetracarboxylate 1,4-BDC = 1,4-benzenedicarboxylate; BHTC= biphenyl-3,4’,5tricarboxylate; BPTC= 3,3’,5,5’-biphenyltetracarboxylate; BTB = 1,3,5benzenetribenzoate; BTC= 1,3,5-benzenetricarbox ylate; BTT= 1,3,5-benzenetristetrazolate; NDC= naphthalenedicarboxylate; QPTC= quater phenyl-3,3’’,5,5’’-tetracarboxylate; SBTC= trans-stilbene-3,30,5,50-tetracarboxylate; TPTC= te rphenyl-3,3’’,5,5’’-tetracarboxylate TZI= 5tetrazolylisophthalate; n.r.= not reported. The great majority of hydrogen sorption studies on MOMs are primarily performed at 77K, and atmospheric pressure s. Outstanding candidates have revealed record surface areas above 5000 m2 g-1,32,33 and uptakes as high as 7.6 wt% were measured at moderate pressures ( 66 bar), but low temperatures, 77K.21 The great majority of high pressure studies on MOMs report on what is generically termed the “excess wt%”, which does not account for the gas that could potentially be adsorbed independently of the MOF, and just due compressibility in the accessible volume. Absolute wt % measurements are estimated ju st theoretically, and are a good measure to evaluate the practical performance of these materials. A recent report proposes an equation for the expression of the absolute va lue, considering the excess wt%, the pore volume and the bulk density of the hydrogen.21 Hydrogen sorption measurements at 77K a nd 87K, allow for the calculation of the isosteric heat of adsorption (adsorption enth alpy), using either the Clausius-Clapeyron34,35 or the virial equation.36An important ongoing challenge is to attempt the in crease of these binding affinities, as even the best materials en gineered so far, are unable to maintain the high amount sorbed closer to the room temp erature regime. Consequently, a desirable material capable to deliver in close pr oximity of the set targets around ambient

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194 temperatures would presumably have ve ry high surface area and the high binding energetics. Since MOMs are highly tunable, they possess the capability to facilitate modifications that can improve the capacities of the as-synthesized materials. One aspect relates to the generation of coordinatively unsaturated intra-framework exposed metal sites, in order to allow for a direct interac tion with the hydrogen molecules. This fact can potentially lead to binding energies toward s a range of 15-20kJ/mol, amount calculated as optimal for a material operating at room temperature, at pressures up to 30bar.37 The access to the intraframework open metal sites can be achieved primarily by removal of weakly coordinated/axial guest solvent mol ecules, where applicable. Concurrently, the overall trend is to reduce the weight of the materials, so therefore the target is to use lighter metals to build intended frameworks th at have already shown great capabilities in terms of hydrogen storage. Charged frameworks, and especially an ionic MOMs with large and extra-large cavities, hold great potential to attempt the increase of the hydrogen-material affinity as they are pertinent to incorporate various species that can tune the in teractions to optimal ranges. Specifically, extraframework me tal ions represent suitable avenues to investigate possibilities regarding this aspect as increased polariz ability in the pores enhances the affinity between the hydrogen and material. Recent studies in our group showed improved values for the heats of ad sorption in metal-exchanged frameworks vs. neutral materials, especially at low loadings.38 However, these findings were not in accordance with expected values, mainly due to the fact that the extraframework metal

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195 cations were fully hydrated, and were not di rectly accessible to the hydrogen molecules, as it was intended. Some of the experiments conducted and reflected in this chapter for this work, also focus on this aspect and will be detailed later on. In the same time, cationic frameworks show also potential for increase hydrogen intera ctions, as shown in recent calculation studies on fluoride-based anions.39 Alternative research studies aim to inco rporate open metal sites within MOMs via the organic linker itself by utilizing metallol igands, such as porphyrins, crown ethers, salen-type ligands, or by thei r incorporation in materials with extra-large cavities. Interestingly, new attempts are relate d to less conventional methods, such as hydrogen adsorption by spillover. New perspectives evidence the possibility of enhancing the uptake of H2 by bridged hydrogen spillover, where by this method was investigated for all classes of materials discusses above: carbon-based materials, zeolites and MOMs. The spillover phenomenon is related to the tr ansport of a dissociated hydrogen molecule from a metal substrate to a support surf ace through surface diffusion. Even though the actual mechanism is not fully understood, extensive studies done by R. T. Yang et. al. at University of Michigan have shown si gnificant improvements in the amounts of hydrogen stored on modified adsorbents, by hyd rogen spillover (at va rious pressures and ambient temperature). A so called “secondary spillover” is intermediated through carbon bridges and it leads to even be tter performances. Using this a pproach, the best results in the MOMs category is represented by IRMOF-177 which stores ~1.5 wt%,40 and by the bridged catalyst/ IRMOF-8 which stores >3 wt .%, ~20 kJ/mol, both measured at 100 bar and 298K.41

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196 5.1.2. Results and Discussion All sorption isotherms included in this chapter were measured on a volumetric basis at low temperatures (77K and 87K) and atmospheric pressures (for N2, Ar and H2), and gravimetrically, where the conditions are somewhat reversed: temperatures in the 273K-293K range and high pressure (up to 25atm) for CO2. The work described in this chapter will highlight the porosity in select compounds, and provide reliable experimental data targeted to ch aracterize the hydrogen and CO2 sorption uptake. A case study will be de vised to discuss the capabilities of neutral vs. anionic frameworks, materials with narrow vs. large pores and will investigate the possible effects of all these factors upon the gas uptake, and its affinity to the parent materials. In order to examine the ion exchange cap abilities of the isostructural series of anionic sod -ZMOFs, compounds 27 (Insod -ZMOF), 28 (Ybsod -ZMOF) and 29 (Ersod -ZMOF) and also to exploit their porous nature, the fully exchange of the K cations (present in the as-synthesized samples and which prevent the pore access), with smaller Li cations, respectively, was attempted. The pr ocess was carried out at room temperature for 24 hours in aqueous media, while the full cations exchange was monitored and confirmed by atomic absorption studies. One of the key aspects that makes ZMOFs desirable is the fact that they stable in air, and do not modify their properties upon air/water exposure (discussed in this chapter require water as part of the solvent system). In this context, it is appropriate to highlight a very important aspect with respect to a great number of porous MOMs which are moistu re sensitive (e.g. MOF-5), and therefore,

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197 in spite of very large surf ace areas and very good perfor mances in terms of hydrogen storage, their eventual practical applicability is questionable. With respect to this feature, among other aspects that will be further de tailed, anionic ZMOFs derived from singlemetal-ion-based rigid and directional TBUs, represent reliable platforms suitable to investigate the hydrogen storage capabilities. The total solvent-accessible volume on In-sod-ZMOF, 27 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework; the potential accessible free volum e corresponds to approximately 46% of the unit cell volume. In the same time, the appr oximate diameter of th e largest sphere that can be fit inside the cage, c onsidering the van der Waals radi i of the nearest atoms, is 9.6 ; however, this value is not accoun ting for guests occupancy. Gas sorption experiments were performed on the Li-excha nged sample which wa s outgassed at room temperature for 12 hours; it was proven that the Li+-exchanged and fully evacuated Insod -ZMOF exhibits permanent microporosity, as evidenced by the reversible type I N2 and Ar adsorption isotherms (Figure 5.1.a). The apparent Langmuir surface area is estimated to be 616 m2g-1 and the pore volume is determined using DubininRadushkevich (D-R) equation to be equal to 0.245 cm3g-1. The dual character of ZMOFs, anioni c frameworks and/or containing large accessible cavities, represent suitable platforms to evaluate the effect of pore size and/or intra-/extra-framework charge density on th e hydrogen uptake and its sorption energetics. Accordingly, hydrogen sorption studies were conducted on compound 27 Li exchanged, at 77K and 87K and atmospheric pressures. H ydrogen sorption isotherms revealed that it

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198 can store up to 0.9% weight H2 at 77K and 1 atm, (Figure 5.1.b left) with an associated isosteric heat of adsorption estimated at lower loadings to be 8.4 kJmol-1 (Figure 5.1.b right). Figure 5.1. (a) Argon and Nitrogen adsorption is otherms measured at 77 and 87K, on compound 27 (b) Hydrogen sorption isotherms measured at 77 and 87K (left), and Isosteric heat of adso rption (right) in compound 27 ZMOFs are unique porous materials that co mbine the ability to readily alter pore size, charge density, and surface area. Th e deliberate enhancement of the framework(a) (b) 0.00.20.40.60.81.0 40 60 80 100 120 140 160 180 200 220 Amount sorbed (cm3/g)P/P0 Argon adsorption @ 87K Nitrogen adsorption @ 77K0.0020.40.6081.0 000 025 050 0.75 100 % Weight of H2 sorbedP/P0Insod -ZMOF, Li exchanged H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K000.10.20.30.4050.60.70.8 0 1 2 3 4 5 6 7 8 9 Heats of adsorption (kJ/mol)% Weight of H2sorbed Insod -ZMOF, Li exchanged

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199 hydrogen interactions is an ongoing challenge. Herein, it is important to emphasize that the isosteric heat of adsorpti on reveals relatively large values, in the context of MOMs, despite the fact that the hydr ogen uptake is not considerab ly high. We have previously postulated that the pore dimensions (around 1n m) and the presence of high local charge density, in combination with large surface areas, are key elements to enhance the H2 uptake at moderate pressures and elevated temperatures.30 It can be noted that the uptake at lower pressures is steepened, which can be correlated to the charge effect and the pore size on the H2 sorption. This is supported by the fact that the constancy of the isosteric heat of adsorption is maintained up to 0.4% H2 sorbed. As discusses in the preamble of this chapter, recent studies indicate that an increase in the polarizability may lead to higher binding affinitie s and hydrogen storage in MOMs.42 Preliminary studies on a previous anionic ZMOF reported by us, with rho topology and based on imidazoledicarboxylate linkers was utilized to st udy the effect of various metal ions in the hydrogen uptake and energetics. It was found that ion exchanged rho -ZMOF clearly demonstrates that the pr esence of an electrostatic field in the cavity is largely responsible for the obser ved improvement in th e isosteric heats of adsorption, however the ion’s identity did not influence greatly the overall results.38 In this context, similar experiments were conducted on 27 to verify this hypothesis and gather more information with respect to this important aspect. Moreover, compounds 28 29 30 and 31 represent isostruc tural variants of 27 constructed from Yb ( 28 ), Er ( 29 ), Y( 30 ) and Cd ( 31 ) intra-metal ions. Therefore, these pyrimidinedicarboxylate sod ZMOFs represent an ideal platform to study the effect of the pore size and the effect of

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200 ( a ) ( b ) 0.00.20.40.60.81.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 H2 per metalP/P0 Insod -ZMOF, Li exchanged H2 adsorption @ 77K Insod -ZMOF, Li exchanged H2 desorption @ 77K Insod -ZMOF, Na exchanged H2 adsorption @ 77K Insod -ZMOF, Na exchanged H2 desorption @ 77K0.000.010.020.030.040.05 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 H2 per metalP/P0 Insod -ZMOF, Li exchanged H2 adsorption @ 77K Insod -ZMOF, Li exchanged H2 desorption @ 77K Insod -ZMOF, Na exchanged H2 adsorption @ 77K Insod -ZMOF, Na exchanged H2 desorption @ 77K0.00.51.01.52.02.53.0 0 1 2 3 4 5 6 7 8 9 Insod -ZMOF, Na-exchanged Heats of adsorption (kJ/mol)H2 per metal Insod -ZMOF, Li-exchanged the extraand/or intra-frame work cations on the hydrogen isosteric heats of adsorption and uptakes. In a first instance, experiments focused on the studying the effect of identity of the introduced ion species, Livs. Na-exchanged Insod -ZMOF on the hydrogen uptake. Figure 5.2. (a) Hydrogen molecules sorbed per me tal, measured at 77K on Liand Naexchanged Insod -ZMOF (top left) and enlarged region at lower pressure (top right), and (b) Isosteric heat of adsorpti on on the Liand Na-exchanged Insod -ZMOF. Pyrimidinedicarboxylate sod -ZMOFs represent an ideal platform to study the effect of the pore size and the effect of th e extraand/or intra-framework cations on the

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201 hydrogen isosteric heats of adsorption and uptak es. In-depths studies are targeted towards the enhancement of the binding affinities between the framework and the hydrogen molecules sorbed, along with improving the ove rall hydrogen storage capacity. In a first instance, experiments focused on the studying the effect of id entity of the introduced ion species, Livs. Na-exchanged Insod -ZMOF on the hydrogen uptake. In this context, the anionic sod -ZMOFs platform allows for consideri ng the effect introduced by the narrow pore sizes (around 1nm), in combination with a close monitoring of the effect of the extraand/or intra-framework cations on the adsorption enthalpies. The hydrogen sorption measurements conducted at 77 and 87K, on the Liand Na-exchanged Insod ZMOF enable us to establish whether the id entity of the extra-framework metal ions plays an influencing role with respect to asso ciated enthalpy of adsorption of the material. The hydrogen sorption isotherms measured at 77K highlight a slightly better performance of the Na-exchanged sample as compared to the Li-exchanged Insod ZMOF, in terms of overall hydrogen molecu les stored per metal, 3.45 vs. 2.9 (15% increase), as shown in Figure 3a (top left). This finding is to some extent unexpected, as one would rather infer the reverse scenari o, given the correspondent volume occupied by the two hydrated complexes. That is, the Na-hexaaqua complex takes up more space inside the -cages as compared to the Li-tetr aaqua complex, resulting in a smaller available volume; it is important to mention the same amount of cations, 12 per cage, as both are monovalent single metal ions. Experimentally, we observe this is not the case, and we can potentially attribute this behavior to an increase in the electrostatics inside the pore, due to less available space, which is reflected in an increased number of hydrogen

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202 molecules stored per cage. In terestingly, in the low pressure regime (below 0.05 atm), a steeper rise in the amount sorbed by the Li -exchanged sample vs. the Na-exchanged one is noted (Figure 3, top right). The same scenario is reflected in the is osteric heat of adsorption of these two compounds; the binding affinity of the Li-e xchanged sample is higher than the Naexchanged one initially, while the opposite is recorded at higher loadings. Although these findings are informative, no definite conclu sive remarks can be drawn unless a full refinement of the occupancy of the hydrat ed complexes will be crystallographically evidenced The results of these preliminary investig ations are somewhat comparable to the ones gathered in the rho -ZMOF system, where a similar behavior of the Livs. Mgexchanged and as-synthesized (dimethylammoni um sample) was observed. In the present case study, a “control” test with regards to this aspect was not pursued since the sample’s porosity is exploited only upon full exchange of the K ions with smaller Li or Na cations. Studies on the Mgand Li-exchanged rhoZMOF revealed that extra-framework cations are fully coordinated by aqua ligands, and also are not directly accessible to the H2 molecules.38 Therefore, open-metal sites do not cont ribute to a dramatically increase in the overall binding energies. Continuing this comparative case study, we further attempted for at least a partial dehydration of the extra-framework cations as means towards reaching high adsorption enthalpies. As the integrity of the frame work upon ion-exchange was maintained at higher temperatures than in the rho -ZMOF system, as shown by TGA studies, the Na-

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203 exchanged Insod -ZMOF sample was gradually h eated to 85C, 150C and 200C. Hydrogen sorption isotherms were measured at 77 and 87K, for each activation temperature (Figure 5.3.), and the results accounted for 1.01 wt% H2 at the 85C, 1.24 wt% H2 at 150C and, again, 1.01 wt% H2 for the sample outgassed at 200C. Figure 5.3. Hydrogen sorption isotherms measured on Na-exchanged Insod -ZMOF at 77 and 87K, upon activation at different temperat ures: (a) 85C, (b) 150C, (c) 200C, and (d) corresponding isosteri c heats of adsorption. 0.00.20.40.60.81.0 0 1 2 3 4 5 6 7 8 9 Heats of adsorption (kJ/mol)% Weight of H2 sorbedInsod -ZMOF, Na exchanged outgassed @ 850C outgassed @1500C outgassed @2000C0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 % Weight of H2 sorbedP/P0Insod -ZMOF, Na exchanged, sample outgassed @850C H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 % Weight H2 sorbedP/P0Insod -ZMOF, Na exchanged, outgassed @1500C H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 Weight % H2 sorbedP/P0Insod -ZMOF, Na exchanged, outgassed @ 2000C H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K ( a ) ( b ) ( c ) ( d )

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204 The highest amount of hydrogen sorbed was therefore achieved in the 150C activation step. In the same time, the corre sponding values for th e isosteric heats of adsorption did not show significantly high values, nor trends; at low loadings, the adsorption enthalpies measure 8 kJ mol-1 (85C), 7.91 kJ mol-1 (150C) and 8.35 kJ mol-1 (200C). These values and overall similar behavior over the whol e pressure range, suggested that the partial dehydr ation of the extra-framework metal ions was in fact not achieved, not even at 200C and could not help in establishing a direct relationship of the activation temperature dependence influence upon the isosteric he at of adsorption. Continuing the in depth-studies initiate d on the sod-ZMOFs platform, we further investigated the possible effect of various intra-framework cations on the capabilities associated with this prototype anionic compound. Hydrogen sorption studies at 77 and 87K were conducted on the Li-exchanged Yb sod -ZMOFs, 28 and Ersod -ZMOFs, 29 (Figure 5.3.). The corresponding isosteric heat s of adsorption were also evaluated. It was revealed that 28 stores up to 1.12 wt% H2, while 29 adsorbs 1.15 wt% H2, with associated heat of adsorption of 8.29 kJ mol-1 and 8 kJ mol-1, respectively.

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205 Figure 5.4. Hydrogen uptake measured at 77 and 87K (left) and Isosteric heat of adsorption (right) in compounds (a) 28 and (b) 29 (a)0.00.20.40.60.81.0 0 1 2 3 4 5 6 7 8 Heats of adsorption (kJ/mol)Weight % of H2 sorbed Er-sod-ZMOF, Li exchanged0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Weight % of H2 sorbedP/P0Ersod -ZMOF Li-exchanged;sample outgassed @ 250C Hydrogen adsorption @ 77K Hydrogen desorption @ 77K Hydrogen adsorption @ 87K Hydrogen desorption @ 87K0.00.20.40.60.81.0 0.00 0.25 0.50 0.75 1.00 1.25 Weight % H2P/P0Ybsod -ZMOF Li-exchanged;sample outgassed @ 250C Hydrogen adsorption @ 77K Hydrogen desorption @ 77K Hydrogen adsorption @ 87K Hydrogen desorption @ 87K0.00.20.40.60.81.0 0 1 2 3 4 5 6 7 8 9 Heat of adsorption (kJ/mol)Weight % of H2 sorbed Ybsod -ZMOF, Li-exchanged ( b )

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206 Table 5.3. Comparative case study in compounds 27 28 and 29 In this context, Table 5.3. reflects a direct comparison of the three targeted compounds, Li-exchanged, InYband Ersod -ZMOFs. Upon close inspection of the various parameters, it is apparent that there are slight differences recorded in the overall performance among these materials, mainly in terms of amount of hydrogen sorbed per metal and on a volumetric basis, as well. That is, slightly be tter amounts of hydrogen molecules per metals are stored up to atmo spheric pressures in the lanthanide-based ZMOFs. It is clearly depi cted that a higher density of hydrogen and consequently, hydrogen per metal sites are enc ountered in the Yband Ersod -ZMOFs, as compared to the parent In compound. Further studies are nece ssary to clearly assess this behavior as function of certain parameters (such as available surface area, or the location of the extrametal ions in the slightly larger cages in 28 and 29 ). In the same time, a very similar perfor mance in terms of the isosteric heat of adsorption measured is noted, parameter which does not seem to depend on the identity of the intra-framework metal ion, since the ac cess to those metal sources is not facile. Material Weight (% H2) Volumetric uptake (kg H2 L-1) H2/metal Qst, kJ mol-1 Insod -ZMOF 0.95 0.013965 2.88 8.4 Ybsod -ZMOF 1.12 0.017024 3.72 8.3 Ersod -ZMOF 1.15 0.01771 3.78 8

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207 Generally, the values are in a very clos e range (Figure 5.5.), with the In-sod-ZMOF having the highest affinity, 8.4 kJ mol-1. Figure 5.5. Isosteric heat of adsorption in the Li-exchanged Insod -ZMOFs ( 27 ), Ybsod ZMOFs ( 28 ), and Ersod -ZMOF ( 29 ). To conclude, it was shown that pyrimidinedicarbxylate-based s od -ZMOF anionic materials represent a reliable platform to gather information about the hydrogen storage/energetics in such systems. It was observed that higher binding affinities are associated with charged systems, as compared to neutral MOMs. In the same time, it was investigated the direct effects on targeted parameters of the extraand/or intra-framework metal ions. Several other experiments can be devised based on this approach, in which the focus can be put on introducing several ot her highly polarizable molecules, either solely organic or just based on metal clusters The potential for exploring several avenues has little limitations and valuable basic in formative aspects are aided by the comparative case study of the tunable system presented here. 0.000.250.500.751.00 0 1 2 3 4 5 6 7 8 9 Heats of adsorption, kJ/mol% Weight of H2 sorbed Insod -ZMOF, Li exchanged Ybsod -ZMOF, Li exchanged Ersod -ZMOF, Li exchanged

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208 Further on, gas sorption investig ations were conducted on compound 35 Cdrho ZMOF; the structural features of this neutra l material were largely described in Chapter 4, and herein its porosity is evaluated. Upon gue st removal, open channels are exploitable in all three directions; the diameter of the largest sphere that can be fit inside the -cage without interacting w ith the van der Waals atoms of the framework was approximated to 16.4 . The total solvent-accessible volume in 35 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework and was estimated to be 58% of the unit cell volume. Nitroge n and argon sorption studies were performed on the acetonitrile -exchanged, fully evacuated Cdrho -ZMOF, which confirmed its permanent microporosity (Figure 5.6.a). Th e apparent Langmuir surface area was estimated to be 1168 m2g-1, with a corresponding pore volume of 0.474 cm3g-1, calculated using the D-R equation. The hydrogen uptake m easurements conducted at 77K and 1 atm (Figure 5.6.b) revealed an approximate 1.16 wt% H2 stored, where the isosteric heat of adsorption reached a maximum value at lower loadings of 8.7 kJmol-1 (Figure 5.6.c).

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209 (a) (b) 0.00.20.40.60.81.0 0 50 100 150 200 250 300 350 400 Amount sorbed (cm3/g)P/P0 Argon adsorption @ 87K Nitrogen adsorption @ 77K0.00.20.40.60.8 0 1 2 3 4 5 6 7 8 9 Isosteric heat of adsorption (kJ/mol)% H2 sorbed rho -ZMOF0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 % Weight of H2 sorbedP/P0rho -ZMOF H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K (c) Figure 5.6. (a) Argon and Nitrogen adsorption is otherms measured at 77 and 87K, on compound 35 (b) Hydrogen sorption isotherms measured at 77 and 87K and (c) Isosteric heat of adsorption in compound 35 A direct comparison regardi ng the two distinct ZMOFs ( sod -ZMOF vs. rho -ZMOF), can highlight the effect of the pore size and of the charge effect. In the case of sod -ZMOFs, anionic frameworks, the hydrogen uptake at lowe r pressures is steepened as compared to the rho -ZMOF, neutral framework, as evidenced by the shape of the isotherm, which can

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210 be correlated with the polarization effect introduced by the extra-framework metal ions and by the narrower pore size. This factor is accounted also in their adsorption enthalpies, where it is observed that the is osteric heat of adsorption in rho -ZMOF decreases more rapidly as a function of the H2 loading, as expected, due to th e fact that the framework is neutral and encompasses extra-large cavities, allowing for a decrease in the overlap of potential energy fields of the pore walls. Continuing the series of investigations pertinent for hydrogen st orage purposes of the compounds thoroughly described in Chapter 4, next studies were directed towards the two ZMOFs derived from the d4R (metal-organ ic cube) approach. Following the in-depth analysis of structural features in 36 (MOC-2) and 37 (MOC-3), their porosity was evaluated. MOC-2 represents an open fr amework that resembles the zeolite ACO topology. The framework exhibits two types of infinite channels, having similar features and properties with a compound prev iously reported by us, with soc topology and high hydrogen storage.30 The first type of channels has small openings with an approximate diameter of 3.333 , while the second type of accessible channels can accommodate a sphere with the largest diam eter of 11.782, when considering the van der Waals radii of the nearest atoms. The total solvent-accessible volumes for 36 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework and this was estimated to be 56.1%. Gas sorption investigations were co nducted on the fully evacuated samples exchanged in acetonitrile for 24hours. Nitrogen and argon sorption studies on 36 (Figure 5.7.a) at 77K and 87K revealed fully reversib le type I isotherms, characteristic to

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211 microporous materials. The apparent estimated Langmuir surface area was determined to be 1420 m2g-1, with a corresponding pore volume of 0.535 cm3g-1, value obtained using the D-R equation. The structural features of 36 resembling the ones observed in soc -MOF, lead us to a detailed evaluati on of its hydrogen sorption propertie s. The sample was activated at 135 C, upon prior guest exchange in acetonitril e for 24 hours. It was evidenced that it stores up to 2.15 % weight H2 at 77K and atmospheric pressu res (Figure 5.7.b). In this context, 36 maintains its integrity upon solven t removal and thermal treatment under vacuum, as evidenced by the sorption isothe rms that show no hys teresis upon desorption. This material’s exceptional stability a nd gas sorption capabilities are remarkable, considering the fact that th e framework’s skeleton is en tirely sustained by hydrogen bonds. The isosteric heat of adsorptio n was calculated to be 6.5 kJmol-1 and found to be nearly constant at higher loadings, which points to a considerable averaging of the binding sites (Figure 5.7.c).

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212 Figure 5.7. (a) Argon and Nitrogen adsorption isot herms measured at 77 and 87K, (b) Hydrogen sorption isotherms measured at 77 and 87K, (c) Isosteric heat of adsorption and (d) INS spectra obtained at 15K on the quasielastic neutron spectrometer (QENS) at the intense pulsed neutron source (IPNS) at Argonne National Laboratory (ANL) for loadings of 1, 2 and 3 H2/In, in compound 36. (c) (d) (a) (b) 0.0020.4060.81.0 0.0 0.5 1.0 1.5 2.0 2.5 % Weight of H2 sorbed P/P0MOC-2 H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K 0.00.20.40.60.81.01.21.41.6 0 1 2 3 4 5 6 7 Heats of adsorption (kJ/mol)Amount adsorbed of H2 (% weight) MOC-2 outgassed @ 1350C0.00.20.40.60.81.0 0 100 200 300 400 Amount sorbed (cm3/g)P/P0MOC-2 Argon adsorption @ 87K Argon desorption @ 87K Nitrogen adsorption @ 78K Nitrogen desorption @ 78K

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213 Inelastic Neutron Scattering (INS) experiments were conducted on MOC-2 in order to gain a better understanding of the pr eferred sorption sites within this material. INS spectra were obtained from a sample of 2.52 g of 36 on the QENS spectrometer at the Intense Pulsed Neutron Source of Argonne National Laboratory, and were performed by Dr. Juergen Eckert, Dr. Jarrod Eubank, a nd by Mr. Farid Nouar. The sample was evacuated at temperatures up to 135C and tr ansferred under He atmosphere into the sample holder for the neutron scattering experi ments. Following collection of a data set of the “blank” sample at 25K, the sample was warmed to 77K, and an amount of hydrogen corresponding to one mol ecule per In adsorbed in-sit u. Subsequently data with two more loadings of hydrogen (2 and 3 pe r In) were obtained at 25 K. By close inspection of the adsorbed H2 molecules adsorbed at different loadings (Figure 5.6.d), many of the spectral features attributable to different bi nding sites show corresponding increases in intensity with loading. The identi fiable peaks in the otherwise rather broad INS spectra were assigned (Table 5.4.) on the basis of the same phenomenological model previously used by us, namely that of a hindered rotor with two angular degrees of freedom in a simple double-minimum potential.30 At the lowest loading of 1 H2/In the INS spectrum consists of strong peaks at 11 meV and 14 meV, where the former is accompanied by weaker shoulders at 10 meV and at 11.7 meV. Under the assumption that these transitions are between the two lowe st levels of the hindered rotor (“0-1”), we can assign both the 0-2 and 1-2 transitions from the experimental spectrum for four separate binding sites as listed in Table 5.4. We also note that there is a very broad “background” underlying the INS spectra, which increases in intensity as a function of

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214 hydrogen loading. This part of the spectrum is likely to arise from random, or nonspecific site adsorption of H2 on interior surfaces lined by oxygen atoms, as has been observed in many cases for H2 in zeolites.38 Table 5.4. Rotational transitions (meV) for hydrogen adsorbed on various sites in 36 Transition Frequency (meV) Barrier Height (V2/B) 0-1 0-2 1-2 11 17 6 2.0 10 17.8 (8) 2.6 11.7 16.5 (4.8) 1.6 14 15.1 (1.1) 0.4 13.2 15.6 (1.4) 0.8 In analogy with our previous work, we attribute the main peak at 11 meV along with the lowand high energy shoulders to binding sites around the octahedral indiumbased MBB. Not all of these faces are in fact accessible to a hydrogen molecule, as is indicated by the fact that the highest total loading in this material at 1 bar is far below (4.6 H2) the value of 8 H2/In that could in principle be pos sible. We may assume that the binding energies for the remaining availabl e sites on the octahedron are sufficiently similar for the transitions of hydrogen on all these can be assigned to this band between 10 and 12 meV. We note that these sites appear to bind hydrogen slig htly more strongly than those around the In carboxylat e trimer building block in soc -MOF (0-1 transition at 12.8 meV), except for the open binding site on the indium metal ion in the latter material. Peaks associated with hydrogen sorbed at su ch a site are indeed absent in MOC-2 as indium is fully coordinated in this case. Th e broad band at 14 meV falls into the energy

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215 range we have previously assigned to bi nding sites around organic linking groups. When the hydrogen loading is increased to 2 and 3 H2 per formula unit, we primarily observe increases in the intensity of existing bands, i.e. changes in the occupancy of the sites described above. This type of behavior is in dicative of a small va riation in the binding energies of the available sites. It is instructive to refer th e loading dependence of the INS spectra to the measured adsorption isothe rms and corresponding isosteric heat of adsorption. In the steep portion of the isothe rms more cluster sites are being filled up to the region between 1 or 2 H2/In where the slope of the isotherms decreases, at which point more sites on the link are becoming occupi ed with the result that the average value of isosteric heat for the syst em shows a slight decrease. In the case of 37 the discrete cubes generate a structure with the zeolite AST topology. The total solvent-accessible volum e for MOC-3 was obtained using PLATON software by summing voxels that are more th an 1.2 away from the framework and it represents approximately 31% of the total unit cell volume Nitrogen and argon adsorption studies were conducted on 37 (Figure 5.8.a and b) at 77K and 87K, and were used to determine the estimated Langmuir surface area and pore volume, which were found to be 456 m2g-1 and 0.1733 cm3g-1, respectively. The features associated with these two parameters (very small accessible volume) are reflected in the low amount of hydrogen sorbed at 77K and 1 atm, 0.73 wt% (Figure 5.8.c), correlate d also with enthalpy of adsorption that drops very quick to values of 2.77 kJ mol-1, at maximum loadings (Figure 5.8.d).

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216 Figure 5.8. (a) Argon adsorption isotherm measur ed at 87K, (b) Nitrogen adsorption isotherms measured at 77K, (c) Hydrogen sorption isotherms measured at 77 and 87K and (d) Isosteric heat of adsorption, in compound 37. 0.00.102030.40506 0 1 2 3 4 5 6 7 8 Heats of adsorption (kJ/mol)% Weight of H2 adsorbed00020.40.60.81.0 000 025 050 0.75 % Weight of H2 adsorbedP/P0MOC-3 Hydrogen adsorption @ 77K Hydrogen adsorption @ 87K0.00.20.40.60.81.0 20 40 60 80 100 120 140 Amount sorbed (cm3/g)P/P0MOC-3 Nitrogen adsorption @ 77K0.00.20.40.60.81.0 0 20 40 60 80 100 120 140 160 180 Amount sorbed (cm3/g)P/P0MOC-3 Argon adsorption @ 87K ( a ) ( b ) ( c ) ( d )

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217 0.00.20.40.60.81.0 50 100 150 200 250 300 350 400 450 Volume adsorbed (cc/g)P/P0me737 outgassed at 800C N2 adsorption @77K N2 desorption @77K (a) (b) 0.00.20.40.60.81.0 0 100 200 300 400 500 Amount sorbed (cc/g)P/P0me737 outgassed at 800C Ar adsorption @87K Ar desorption @87K Last of all materials investig ated for gas storage purposes is 38 compound constructed from extra-large cavities, holding pr omise to delineate high capacity in terms of gas storage, as a direct consequence of its mesoporosity. Accordingly, the total solvent-accessible volume for 38 was obtained using PLATON software by summing voxels that are more than 1.2 away from the framework, and it was found to correspond to approximately 62.7% of the unit cell volume. The diameter of the larges t sphere that can be fit inside the cage, c onsidering the van der Waals ra dii of the nearest atoms is 38, remarkably large value, qualifyi ng the compound amongst the largest MOMs reported to date. In order to assess the porosity in 38 the sample was exchanged in EtOH for 24 hours and was activated at room temp erature for 12 hours, followed by heating at 80C for 10 hours. Nitrogen and argon sorption studies on 38 (Figure 5.9.a. and b) at 77K and 87K revealed fully reversible pseudo-type I isotherms. Interestingly, correspondent to the structural features in 38 (narrow access apertures and extra-large cavities), a step in both N2 and Ar isotherms is observed in the pressure range up to 0.2 P/P0, equivalent to a secondary uptake. Figure 5.9. (a) Nitrogen sorption isotherms m easured at 77K, (b) Argon sorption isotherms measured at 87K in 38

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218 The apparent estimated Langmuir surface area was determined to be 1476 m2g-1, by using the data points from the adsorption points of the Ar isotherm, as shown in Figure 5.10.a.. Similarly, by applying the BET model, the calculated apparent surface area is 1018 m2g-1, Figure 5.10.b.. The corresponding pore volume is approximated to be 0.57 cm3g-1, value obtained using the D-R equation. Figure 5.10. (a) Langmuir equation fitting curve for Ar isotherm (adsorption branch data points, P/P0 = 0 1–0 14). Surface area 1476 m2 g 1, linearity 0.9997; (b) BET equation fitting curve for Ar isotherm (adsorption branch data points, P/P0 = 0 1–0 14). Surface area 1018 m2 g 1, linearity 0.99999. In order to calculate th e pore size distribution, the DFT/Monte-Carlo model was employed by using points from the Argon gas adsorption data at 87 K(zeolite/silica NLDFT eq.), Figure 5.11. As depicted in the pl ot, the value determined experimentally is in the 30 -38 range, which is in good agre ement with the expected value established from crystallographic analysis. 0.1100.1150.1200.1250.1300.1350.1400.145 0.250 0.275 0.300 0.325 (P/P0)/WP/P0Langmuir model ParameterValueError -----------------------------------------------------------A0.103719.81933E-4 B1.431380.0078 -----------------------------------------------------------RSDNP -----------------------------------------------------------0.999971.64104E-44<0.0001 ------------------------------------------------------------0.1100.1150.1200.1250.1300.1350.1400.145 0.28 0.29 0.30 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 1/(W((Po/P)-1))P/P0BET model ParameterValueError -----------------------------------------------------------A0.072537.79598E-4 B2.005530.00619 -----------------------------------------------------------RSDNP -----------------------------------------------------------0.999991.30289E-44<0.0001 -----------------------------------------------------------(a) (b)

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219 01020304050607080 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 Pore volume, cc g-1Pore width, Figure 5.11. Pore size distribution histogram calcu lated with a DFT/Monte-Carlo model using the Argon gas adsorption data at 87 K (zeolite/silica NLDFT eq). Fully reversible hydrogen sorption isot herms were measured at 77 and 87K, Figure 5.12.a.. The maximum uptake reaches 0.85 wt% of H2 sorbed under these conditions, while the high capacity associated with the mesoporosity in this material should be met at higher pressures. The isosteri c heat of adsorption fa lls within 6.8-5.2 kJ range, Figure 5.12.b., value commonly encountered in MOMs.

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220 Figure 5.12. (a) Hydrogen sorption isotherms measured at 77 and 87K, and (d) Isosteric heat of adsorption in compound 38. 5.2. Carbon Dioxide: Separation, Capture and Storage The awareness on global warming has been a subject of matter at all levels in recent years, especially in th e context of a predicted increas e in the energy demand in the next decades. Accordingly, the development of methodologies aimed to reduce the effects of the greenhouse gases is regard ed as highly necessary. Carbon dioxide represents the most signifi cant gas source of total an thropogenic greenhouse gases, namely, 77%.43 The most occurring source of CO2 is resulted from burning fossil fuels, process that is responsible for generati ng the primary energy source worldwide. An alarming 80% increase in the CO2 emissions has been recorded between 1970 and 2004, and therefore, intensive investigations ar e currently pursued for the development and implementation of CO2 capture technologies. While se veral methodologies are already (a) (b) 0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 Weight % of H2 sorbedP/P0 H2 adsorption @ 77K H2 desorption @ 77K H2 adsorption @ 87K H2 desorption @ 87K0102030405060 0 1 2 3 4 5 6 7 8 Heats of adsorption, kJ mol1Volume of H2 sorbed, cc g1

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221 proven effective in CO2 sequestration, major concerns are now associated with costs of production, and also with the abil ity of scaling up pilot plants to actual power plants. The Department of Energy Office of Fuel Energy has implemented a program that monitors efficient methods for CO2 sequestration. Similar to the hydrogen storage program, DOE has suggested targets that should be met by 2012; amongst these, an achievement of approximately 90% CO2 captured is preferred, corroborated with little increase of the production costs (between 10-20%).44 In this context, primary concerns are interrelated with managing low costs and a high efficiency of the separation, storag e/compression (sequestration in geological formations represents the most efficien t storage method) and transportation of CO2. Furthermore, its “recycling" would be rega rded advantageous fo r its utilization in chemical processes, enhancement of oil recovery, and enhancing coal bed methane production.45 Thus, various pathways for capturing CO2 were considered: postcombustion, pre-combustion and in oxy-co mbustion, whilst several advantages and disadvantages were correlated with each approach. Trapping emissions directly from the sour ce represents the main task that would allow for an efficient CO2 capture upon fuel combustion; whil e at this stage, its separation from the flue gas is deemed necessary, as CO2 is present in approximately only 15% in the mixture. To date, this process was carri ed out by utilizing liqui d methods (associated with high energy consumption) or solid adso rbents. Current technol ogies are focused on amine-based systems (the most used is monoethanolamine),46 carbonate-based systems,47 selective membranes-functionalized with mobile or fixed ammine carriers,48,49 zeolites

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222 (used primarily for separation from N2 at high temperatures),50 biological-based capture systems.51 Solid sorbents were less researched so far, and to some extent considered less desirable, due to small surface areas and lo w degree of amenability for modifications. Pre-combustion methods consider CO2 capture before the fuel is actually burned; several techniques are targeted for finding specific ways to capture CO2 without being intermediated by a chem ical reaction. The oxy-combustion process implies a m odification in the co mbustion protocol, limiting the amount of nitrogen, which would further enable a higher CO2 output. Even though the preand oxy-combustion methods represent promising alternative methodologies for future developments, the pos t-combustion approach receives so far the greatest attention due to its highest rele vance in the current industrial setting. In this general context, MOMs represen t a unique category of solid adsorbents, regarded as highly a ttractive due to their high apparent surface areas, modularity and tunability. An increased numb er of reports focus on CO2 storage in MOMs,52,53 with highest amount stored in MOF-177,54 33.5 mmol g-1 at 42 bar and 25C and 40 mmol g-1 at 50 bar and 25C,55 the record holders for highes t apparent surf ace area in MOMs. Additionally, an even more relevant aspect considers the abilit y offered by MOMs for CO2 separation from gas mixtures, along with a selective enhancement of the gas uptake. Its separation from binary mixtures of the type CO2 /N2 and CO2 /CH4 was successfully achieved with MOMs,52,53,56 showing therefore high pot ential in this area. In spite of possessing high adsorption capacity, this feature in MOMs is not readily transferable to complex systems, su ch as gas mixtures. Breakthrough experiments

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223 are now considered in order to exploit the highly modular nature of MOMs, which allows them to qualify as promising candidates in multi-component mixtures separations; we are mainly referring to all other harmful gases that are released in the atmosphere as a factor of various industrial processes. The breakthrough methodology is hence directly correlated to the affinity of the material towa rds a certain gas. Current industrial settings utilize filters that have metal-impre gnated activated carbon beds, but which find limitations especially due to lack of tunability of their pores (feature th at is transferable to their hydrogen storage disadva ntages, for example). Furthermore, functional groups, potential for metal sites and in general struct ure specificities in MOMs (large cages, small apertures), may play a decisive role in tuning specific applications and affinity for certain gases. A recent study by Yaghi et.al. shows the importance of functional groups in very similar materials; the ammonia dynamic capac ity was enhanced 18 folds in IRMOF-3 vs. MOF-5.57 5.2.1. Results and Discussion As highlighted in the succinct introdu ction concerning car bon dioxide and other harmful gases studies in MOMs, it became appare nt that structure specificities such as: pore size, pore volume, pore decoration with functional groups, chemical environment inside a cavity, the presence of local charge de nsities, play extremely important roles in the affinity and amounts of gas stored. Th e following experiments were conducted on all porous compounds that were tested for hydrogen storage in the previ ous section; in the same time, all structural details are deta iled in Chapter 4. The order in which the

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224 05000100001500020000 0 5 10 15 20 % Weight of CO2 sorbedPressure, TorrInsod -ZMOF, Li-exchanged, sample activated at 1150C CO2 adsorption measured at 00C CO2 desorption measured at 00C CO2 adsorption measured at 250C CO2 desorption measured at 250Ccompounds were characterized earlier will be maintained. Accordingly, investigations will assess the performance of structures that posses pores sizes around 1 nm, but different pore volumes, with or without the pr esence of local high local charge densities (sod-ZMOFs platform, compounds 27 28 29 versus MOC-2, 36 ), as well as large cavities in neutral materials (Cdrho -ZMOF, 35 ),and extra-large cavities in 38 A first series of experiments fo cused on pyrimidinedicarboxylate-based sod ZMOFs: In-, Yb-and Er-, all Li-exchanged. Figure 5.13. CO2 sorption isotherms measured at 0C and 25C, on compound 27 Figure 5.13. depicts the CO2 sorption isotherms, measured at 0C and 25C, respectively. The full reversibility of these isotherms additionally confirm the microporosity of the material, outlining the type I isotherm. Attributab le to rather narrow pore sizes and pore volume, the saturation capacity is reached at relati vely low pressures,

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225 05000100001500020000 0 5 10 15 20 % Weight of CO2 sorbedPressure, TorrYbsod -ZMOF, Li-exchanged, sample activated at 1150C CO2 adsorption measured at 00C CO2 desorption measured at 00C CO2 adsorption measured at 250C CO2 desorption measured at 250C05000100001500020000 0 5 10 15 % Weight of CO2 sorbedErsod -ZMOF, Li-exchanged, sample activated at 1150C CO2 adsorption measured at 00C CO2 desorption measured at 00C CO2 adsorption measured at 250C CO2 desorption measured at 250CPressure, Torraround 4 atm, recording a maximum amount stored of 18% wt CO2, results obtained at 0C, 25 atm and a correspondent 15.85% wt CO2 at 25C and 25 atm. At atmospheric conditions, 25C and 1atm, the Insod -ZMOF stores 10.43% wt CO2. Figure 5.14. CO2 sorption isotherms measured at 0C and 25C, on compound 28 Figure 5.15. CO2 sorption isotherms measured at 0C and 25C, on compound 29

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226 Sorption profiles measured on 28 and 29 outline similar behavior as in 27 where the saturation capacity is reached at relatively low pressures. The CO2 sorption isotherms on 28 regard a maximum 16% wt CO2, measured at 0C and 25 atm, Figure 5.14.. The run conducted at 25C does not perform to th e expected capacity, and possible reasons are related to technical errors in the experimental set up, therefore a new set of data would be suitable for collection to fully ev aluate its capabilitie s in those conditions. Figure 5.15. portrays the carbon dioxide sorption isotherms measured on 29 at 0C and 25C, and up to 25 atm, where the maximum uptake attains 13.7% wt CO2. In this context, 27 outperforms both 28 and 29 a reversed scenario upon direct comparison with the investigations pertinent to their hydr ogen storage capabilities. Up to now, there haven’t been conducted sufficient repetitive tests to fully confirm these preliminary findings, even though one possible reason for this behavior may be related to an incomplete activation/ion-exchange in this anionic sod -ZMOFs platform, or simply samples with a lesser degree of purity. Further on, the CO2 sorption studies were conducted on activated Cdrho -ZMOF, 35 A direct comparison with the sod -ZMOFs platform reveals a similar behavior to the one noted upon hydrogen sorption evaluation, also when carbon dioxide adsorption is concerned. The material’s la rge accessible space in the -cages allows for the saturation plateau to be reached at higher pr essures, as compared to smaller -cages in sod -ZMOFs where maximum uptake is reached at relatively low pressures. Th is effect is regarded also in the shape of the isothe rm, where a “step” is obser ved, as shown in Figure 5.16, corresponding to the gradual filling of the pores. The ma ximum amount stored reaches

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227 05000100001500020000 0 5 10 15 20 25 30 35 % Weight of CO2 sorbedPressure, TorrCdrho -ZMOF, sample activated at 800C CO2 adsorption measured at 00C CO2 desorption measured at 00C CO2 adsorption measured at 250C CO2 desorption measured at 250C33.94 wt % CO2 stored at 0C, 25 atm, and 28.13 % at 25C, 25 atm, respectively; at room temperatures and pressure the material stores 10.32 wt % CO2. Figure 5.16. CO2 sorption isotherms measured at 0C and 25C, on compound 35 The carbon dioxide sorption capabilities of MOC-2 were tested on the evacuated acetonitrile activated sample, heated to 135 C for 12 hours. The material’s permanent porosity was once again confirmed by the fully reversible carbon dioxide sorption isotherms, Figure 5.17., in addition to the ar gon, nitrogen and hydroge n ones, highlighted earlier on in this chapter. The relatively narrow pore size, in combination with averaged preferential adsorption sites ar e indicated by the steep rise of the isotherm, in the lower pressure region. MOC-2 stores up to 12.8 wt% CO2 at 25C and 1 atm.

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228 05000100001500020000 -5 0 5 10 15 20 25 30 35 40 45 % Weight of CO2 sorbedPressure, TorrMOC-2, sample activated at 1350C CO2 adsorption measured at 00C CO2 desorption measured at 00C CO2 adsorption measured at 250C CO2 desorption measured at 250C Figure 5.17. CO2 sorption isotherms measured at 0C and 25C, on compound 36 The overall capacity at 25 atm is 40 wt % CO2 (0C) and 36 wt % CO2 (25C), values which are exceeding the best performances of zeolite materials, 32.5 wt% CO2 at 25C and 30 bar.58 In the same time, it is important to point out that the material reaches amounts close to its saturation capacity, at relatively low pressures, 6 atm. Compound 37 was activated at room temperatur e, and revealed fully reversible type I isotherms, Figure 5.18.. MOC-3 stores up to 19 wt% CO2 at 0C and 25 atm, 16.7 wt% CO2 at 25C and 25 atm and 6.6 wt% CO2 at atmospheric conditions. The relative high capacity experimentally observed in this material is to so me extent unexpected, especially due to small pore volume and availa ble surface area. In this context, it may be hypothesized that this behavior is directly correlated with its structural features, that may allow for enhanced interac tions with the adsorbate.

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229 0 50001000015000 0 10 20 30 40 50 % Weight of CO2 sorbedPressure, Torrme737, sample activated at 750C CO2 adsorpion measured at 00C CO2 desorpion measured at 00C CO2 adsorpion measured at 250C CO2 desorpion measured at 250C05000100001500020000 0 5 10 15 20 % Weight of CO2 sorbedPressure, TorrMOC-3 sample activated at 250C CO2 adsorption measured at 00C CO2 desorption measured at 00C CO2 adsorption measured at 250C CO2 desorption measured at 250C Figure 5.18. CO2 sorption isotherms measured at 0C and 25C, on compound 37. Returning to monitoring the performances of materials with large and extra-large cavities, high surface area and high pore volume, the carbon dioxide capacity of 38 was measured at 0C and 25C, and 20 atm, Figure 5.19. Figure 5.19. CO2 sorption isotherms measured at 0C and 25C, on compound 38.

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230 The carbon dioxide sorption is otherm reveals a similar pr ofile as the one observed in Cdrho -ZMOF; that is, the amount of gas stor ed is progressively enhanced with increased pressure, correspondent of the gradua l pore filling. As exp ected, this material reaches high storage capacities at high pre ssures, in conjunction w ith its high specific surface area. Accordingly, 38 stores up to 48 wt% CO2 at 0C and 20 atm, and a correspondent 30 wt% CO2 at 25C and similar pressures. However, the shape of the isotherm does not outline a saturation plateau at around 20 atm, indicativ e of the fact that maximum capacity should be reached at highe r pressures. At atmo spheric temperatures and pressures the uptake is relatively modest, 5.6 wt% CO2. Since 38 is derived from an amine-based pyrimidinedicarboxylate, namely 2-amino-4,6-PmDC, it is deemed necessary to open the discussion that considers the possible influences introduced by these functional groups, primarily on the carbon dioxide sorption energetics. Amine grafted solid adsorbents such as zeolites, and membranes, are strongly considered as desi rable candidates for an enhanced/selective CO2 sorption.49 This behavior was investigated in MOMs as well, where increased adsorption enthalpies were recorded in the amine-functionalized materials, as compared to the non-functional isos tructural correspondents.57 In this instance, the capability was mainly attributed to the expect ed affinity occurring between CO2 and the functional groups. However, dependent on the reaction en vironment, the direct exposure between the two reactive species can l ead to the formation of carba mate species and carbonic acid, and hence, significantly increase th e carbon dioxide sele ctive adsorption;59 this phenomenon has not been yet observed in MOMs materials. In this context, upon close

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231 05000100001500020000 0 10 20 30 40 50 % Weight of CO2 sorbedPressure, Torrmeasurements at 00C CO2 adsorption in Insod -ZMOF, Li-exchanged CO2 desorption in Insod -ZMOF, Li-exchanged CO2 adsorption in Cdrho -ZMOF CO2 desorption in Cdrho -ZMOF CO2 adsorption in MOC-2 CO2 desorption in MOC-2 CO2 adsorption me737 CO2 desorption me737inspection, we were unable to distinguish enhanced adsorption car bon dioxide capacities at low coverage. One of the possible reasons that counteract the effect of the amine groups is related with their lo cation within the windows, whic h does not allow for a direct exposure. The carbon dioxide uptake at 0C on 27 35 36 and 38 is plotted in Figure 5.20. Upon close inspection, a similar adsorption profile for material s with small pore sizes, as compared to materials with large cavities is noted. That is, saturation is reached at lower pressures in compounds that have small pores ( 27 and 36 ), while materials with large cavities are reaching maximum cap acities at higher pressures ( 35 and 38 ). Interestingly, the shape of the isotherms and the maximum cap acities can be interand/or extrapolated when considering the pore volume, in good agreement with the measured data. Figure 5.20. CO2 sorption isotherms measured at 0C, on compounds 27 35 36 and 38

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232 In this context, it is informative to highlight the eventual relevance of all compounds included in this discussion. That is the advantageous attr ibutes of all these diverse materials, with different capacities, r eached at different pressure ranges, allow for their capabilities’ exploitation as function of intended applicat ions (more so, as there is not a set target for a prototype material to perform well under cer tain circumstances). Thus, materials that possess relatively na rrow pore sizes, but large pore volume are suitable for carbon dioxide storage at low pressu re, as satisfactory performances close to ambiental pressures are directly equivale nt with decreased en ergy consumption, and therefore, indicative of pract ical considerations. Altern atively, compounds with both large and extra-large cavities and high pore volumes, become essentially important for applications conducted at high pre ssures. Pressure swing adsorption60 studies become relevant in this context, in conjunction with the selectiveness capac ity of some of these compounds. Along these lines, Table 5.4. summari zes the most relevant hydrogen and carbon dioxide adsorption properties of th e compounds discussed in this chapter.

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233 Table 5.5. Hydrogen and CO2 uptake in compounds 27 28 29 35 36 37 38 n.m.= not measured Material Langmuir Surface area (m2 g-1) Pore vol. (cc g-1) Max. H2 uptake (% wt), 77K, 1 atm Max. CO2 uptake (% wt) Experimental conditions: T, P Insod -ZMOF, 27 616 0.245 0.95 18 15.85 10.43 0C, 25 atm 25C, 25 atm 25C, 1 atm Ybsod -ZMOF, 28 n.m. n.m. 1.12 16.12 8.56 4.95 0C, 25 atm 25C, 25 atm 25C, 1 atm Ersod -ZMOF, 29 n.m. n.m. 1.15 13.72 11.86 6.78 0C, 25 atm 25C, 25 atm 25C, 1 atm Cdrho -ZMOF, 35 1168 0.474 1.16 33.94 28.13 10.32 0C, 25 atm 25C, 25 atm 25C, 1 atm MOC-2, 36 1420 0.535 2.15 40 36 12.8 0C, 25 atm 25C, 25 atm 25C, 1 atm MOC-3, 37 456 0.1733 0.73 19.3 16.7 6.6 0C, 25 atm 25C, 25 atm 25C, 1 atm me737, 38 1429 0.6 0.86 48 30 5.6 0C, 25 atm 25C, 25 atm 25C, 1 atm

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234 5.3. Summary Cost effective methods to reach targets regarding the hydrogen storage for vehicular on-board applications and carbon dioxide separation, sequestration and storage represent prerequisites in order to attempt their implementation in the current industrial and economic setting. The work conducted in this dissertation and particularly, in this chapter, focused on measuring the hydrogen an d carbon dioxide capacities in a repertoire of diverse MOMs. The great majority of th e compounds studied and discussed herein are synthesized in water-based solvent systems, and hence, their stability in air is highly advantageous from a practicability viewpoint. With respect to the hydrogen sorption studies measured on these compounds, several remarks can be emphasized. Materials with high charge densities were proven to be suitable to increase the binding affini ties between dihydrogen and framework. The anionic series of sod -ZMOFs ( 27 28 29 ) revealed high values for the isosteric heat of adsorption, as compared to the adsorption enth alpy in the neutral, larger cavities in rho ZMOF ( 35 ), as a direct consequence of the higher electrostatic field in the cavities. These findings are promising and may be regarded as very useful information towards improving binding energies to values in the range of 1520 kJ mol-1, and consequently, towards gaining superior performances at moderate operational temperatures. ZMOFs qualify therefore as suitable candidates to inve stigate this aspect, especially by tuning the intraand/or extra-framework cations, wh ile considering introducing other chemical species that may increase the pol arizability in the interior of the cavities. INS studies on the 36 confirmed the overall high capacity of th e material originates from the large

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235 number of relatively strong binding sites about the metal cen ters, in combination with small pore size. Further work needs to be di rected towards the construction of ZMOFs, with emphasis on evaluating the effect of the pore size and charge density in the hydrogen uptake and isosteri c heat of adsorption. Studies concerning the carbon dioxide st orage capabilities in these materials showed potential for promising storage capac ities at ambient conditions, and increased capacities at high pressures. Along these lines, future directions are directed towards studies concerned with the adsorption of other harmful gases, their separation from mixtures and selective storage. The results of these inves tigations are in accordance w ith recent findings by other groups, which suggest that gas storage in porous MOMs is dependant not only on surface area, pore size and pore volume, but also on th e generation of favorable sites for the gas adsorption, while attempting to increase the binding affinities between the gas and material. Thus, good performances in terms of dynamic gas adsorption are to be most likely accomplished by structures that i) have potential for exploitable open metal sites, ii) are constructed from func tionalized organic ligands, and iii) possess the ability to allow fine tuning and tailoring of their pores. Highlighting th e structure-function relationship, the fundamental understanding of the sorption mechanism in porous MOMs needs to be pursued and detailed in conjuncti on with computational st udies, resulting in the advancement of the field by aiding the design of superior materials.

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236 5.4. References 1. Sherif, S.; Vezirglu,T.; Zeytinoglu, N. Int. J. Hydrogen Energy 1997 22 683-688. 2. U.S. Department of Energy, Ener gy Efficiency and Renewable Energy http://www1.eere.energy.gov/hydrogenandf uelcells/storage/pdfs/targetsonbo ard_hydro_storage.pdf 3. Graetz, J. Chem. Soc. Rev. 2009 38 73-82. 4. Brunauer, S.; Emmett, P. H.; Teller, E. J. Am. Chem. Soc. 1938 60, 309-319. 5. Langmuir, I. J. Am. Chem. Soc. 1918 40 1361-1402. 6. Dubinin, M.M. and Radushkevich, L.V. Dokl. Akad. Nauk. SSSR 1947 55 327-329. 7. Polanyi, M. Verh. Dtsch. Phys. Ges. 1914 16 1012-1016. 8. Zhao, D.; Yuan D. and Zhou, H.-C. Energy Environ. Sci 2008 1 222–235. 9. Spencer, E.; Howard, J.; McIntyre, G.; Rowsell, J.; Yaghi, O. Chem. Commun. 2006 278–280. 10. Panella, B.; Hirscher, M. and Roth, S. Carbon 2005 43 2209-2214. 11. Jorda-Beneyto, M.; Suarez-Garcia, F.; Lozano-Castello, D.; Cazorla-Amoros, D.; Linares-Solano, A. Carbon 2007 45 293-303. 12. Langmi, H. W.; Book, D.; Walton, A.; Johnson, S. R.; Al-Mamouri, M. M.; Speight, J. D.; Edwards, P. P.; Harris, I. R.; Anderson, P. A. J. Alloys Compd. 2005 637 404-406. 13. Rowsell, J. L. C.; Yaghi, O. M. Angew. Chem. Int. Ed. 2005 44 4670-4679. 14. Hirscher, M.; Panella, B. Scr. Mater. 2007 56 809-812. 15. Collins, D. J.; Zhou, H.-C. J. Mater. Chem. 2007 17 3154-3160. 16. Lin, X.; Jia, J.; Hubberstey, P.; Schroder, M.; Champness, N. R. Cryst.Eng.Comm. 2007 9 438-448.

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237 17. Dinc M.; Long, J. R. Angew. Chem. Int. Ed. 2008 47 6766-6779. 18. Murray, L.J.; Dinc M. and. Long J. R. Chem. Soc. Rev. 2009 38 1294– 1314. 19. Dren, T.; Bae, Youn-Sang; Snurr, Randall Q. Chem. Soc. Rev. 2009 38 1237-1247. 20. Han, S. S.; Mendoza-Cortes, J. L.; Goddard, W. A., III. Chem. Soc. Rev. 2009 38 1460-1476. 21. Furukawa, H.; Miller, M. A. and Yaghi, O. M. J. Mater.Chem 2007 17 31973204. 22. Kaye, S. S.; Dailly, A.; Yaghi, O. M. and Long, J. R. J. Am. Chem. Soc. 2007 129 14176-14177. 23. Latroche, M.; Suble, S.; Serre C.; Mellot-Draznieks, C.; Llewellyn, P. L.; Lee, J.-H.; Chang, J.-S.; Jhung, S. H.; Ferey, G. Angew. Chem. Int. Ed. 2006 45 8227-8231. 24. Nouar, F.; Eubank, J. F.; Bousquet, T.; Wojtas, L.; Zaworotko, M. J.; Eddaoudi, M. J. Am. Chem. Soc. 2008 130 1833–1835. 25. Wong-Foy, A. G.; Lebel, O. and Matzger, A. J. J. Am. Chem. Soc. 2007 129 15740-15741. 26. Lin, X.; Jia, J. H.; Zhao, X. B.; Thomas, K. M.; Blake, A. J. Walker, G. S.; Champness, N. R.; Hubberstey, P. and Schrder, M. Angew. Chem. Int. Ed. 2006 45 7358-7364. 27. Wang, X. S.; Ma, S. Q.; Rauch, K.; Simmons, J. M.; Yuan, D. Q.; Wang, X. P.; Yildirim, T.; Cole, W. C.; Lopez, J. J.; de Meijere, A. and Zhou, H. C. Chem. Mater. 2008 20 3145-3152. 28. Dinc M.; Dailly, A.; Liu, Y.; Brown, C. M.; Neumann, D. A. and Long, J. R. J. Am. Chem. Soc. 2006 128 16876-16883. 29. Chun, H.; Jung, H.; Koo, G.; Jeong, H. and Kim, D.-K. Inorg. Chem 2008 47 5355-5359. 30. Liu, Y.; Eubank, J. F.; Cairns, A. J. ; Eckert, J. ; Kravtsov, V. Ch.; Luebke, R.; Eddaoudi, M. Angew. Chem. Int. Ed. 2007 46 3278-3283.

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238 31. Xiao, B.; Wheatley, P. S.; Zhao, X. B.; Fletcher, A. J.; Fox, S.; Rossi, A. G.; Megson, I. L.; Bordiga, S.; Regli, L.; Thomas, K.M. and Morris, R. E. J. Am. Chem. Soc. 2007 129 1203-1209. 32. Latroche, M.; Suble, S.; Serre C.; Mellot-Draznieks, C.; Llewellyn, P. L.; Lee, J.-H.; Chang, J.-S.; Jhung, S. H.; Ferey, G. Angew. Chem. Int. Ed. 2006 45 8227-8231. 33. Koh, K; Wong-Foy, A.G.; Matzger, A.J. J. Am. Chem. Soc. 2009 131 4184-4185. 34. Daniels, F.; Williams, J. W.; Bender, P.; Alberty, R. A.; Cornwell, C. D. Experimental Physical Chemistry 1962 ; McGraw-Hill: New York. 35. Jaroniek, M.M.R. 1988 Physical Adsorption on Heterogeneous Solids, Elsevier, Amsterdam. 36. Czepirski, L.; Jagiello, J. Chem. Eng. Sci. 1989 44 797–801. 37. Bhatia, S. K.; Myers, A. L. Langmuir 2006 22 1688-1700. 38. Nouar, F.; Eckert, J.; Eubank, J. F.; Forster, P.; Eddaoudi, M. J. Am. Chem. Soc. 2009 131 2864-2870. 39. Trewin, A.; Darling, G. R. and Cooper, A. I. New J. Chem. 2008 32 17-20. 40. Li, Y. W. and Yang, R. T. Langmuir 2007 23 12937-12944. 41. Li, Y. W. and Yang, R. T. J. Am. Chem. Soc. 2006 128 8136-8137. 42. Belof, J. L.; Stern, A. C.; Eddaoudi, M.; Space, B. J. Am. Chem. Soc. 2007 129 15202-15210. 43. Yu, K. M. K.; Curcic, I. ; Gabriel, J.; Tsang, S. C. E. Chem.Sus.Chem. 2008 1 893-899. 44. http://fossil.energy.gov/progr ams/sequestration/index.html 45. Figueroa, J.D.; Fout, T.; Plasynski S.; McIlvried, H.; Srivastava, R.D. Int. J. Greenhouse Gas Control 2008 2 9-20. 46. Hakka, L., 2007 Cansolv Technologies Inc ., private communication.

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239 47. Rochelle, G., Chen, E., Dugas, R., Oyenakan, B., Seibert, F. 2005 Annual Conference on Capture and Sequestration, Alexandria, VA. 48. Huang, J.; Zou, J.; Winston H. W. S., Ind. Eng. Chem. Res. 2008 47 1261-1267. 49. Pederson, O. F.; Dannstrom, H.; Gronvold, M.; Stuksrud, D.; Ronning, O. 2000 Fifth International Conferen ce on Greenhouse Gas Control Technologies, Cairns, Australia. 50. Zhang, L.F. 2006. The southwest regional carbon sequestration partnership-development of CO2 capture technology. In: Second Annual Carbon Capture and Transportati on Working Group Workshop, Palo Alto, CA. 51. Yang, W.C.; Ciferno, J. 2006 DOE/NETL 401/072606. 52. Banerjee, R.; Phan, A.; Wang, B.; K nobler, C.; Furukawa, H.; O'Keeffe, M.; Yaghi, O.M. Science 2008 319 939-943. 53. Wang, B.; Cote, A. P.; Furukawa, H.; O'Keeffe, M. and Yaghi, O. M. Nature 2008 453 207-211. 54. Millward, A. R.; Yaghi, O. M. J. Am. Chem. Soc. 2005 127 17998-17999. 55. Llewellyn, P. L.; Bourrelly, S.; Serr e, C.; Vimont, A.; Daturi, M.; Hamon, L.; De Weireld, G.; Chang, J.S.; Hong, D.-Y.; Hwang, Y.K.; Jhung, S.H.; Ferey, G. Langmuir 2008 24 7245-7250. 56. Bastin, L.; Barcia, P. S.; Hurtado, E. J.; Silva, J. A. C.; Rodrigues, A. E.; Chen, B. J. Phys. Chem.C 2008 112 1575-1581. 57. Britt D.; Tranchemontagne D.; Yaghi O.M. Proc. Nat. Acad. Sci. 2008 105 11623-11627. 58. Cavenati, S.; Grande, C. A.; Rodrigues, A. E. J. Chem. Eng. Data 2004 49 1095-1101. 59. Arstad, B.; Fjellvaag, H.; Kongs haug, K. O.; Swang, O.; Blom, R. Adsorption 2008 14 755-762. 60. Ritter, J. A.; Mehrotra, A.; Ebne r, A.D.Proceedings -Annual International Pittsburgh Coal Conference 2008 25th 475/1-475/2.

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240 Chapter 6. Summary and Future Outlook 6.1. Summary The research findings comprised in this dissertation highlight a unique approach toward the design, synthesis and characterizatio n of a repertoire of MOMs. That is, the work demonstrates the reliability and vi ability of the single-metal-ion-based MBB strategy, as an appropriate route toward s the construction of functional MOMs. This novel route allowed for the forma tion of intended MBBs assembled from multifunctional heterocoordinating organic li nkers containing Nand Odonor atoms, and single metal ions, yielding a large set of rigid and directiona l MBBs. The periodic assembly of the MBBs resulted in the form ation of simple nets with high regularity, commonly accessed in crystal chemistry. In addition, novel materials with complex transitivities and rare or unprecedented topologies and features were obtained upon implementation of this approach, highlighting the significant effect of the SDA directed synthesis. Specifically, emphasis was put on the construction of MO Ms with zeolitelike topologies and properties, and it was probed that the single-metal-ion approach is suitable

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241 to convey rigid and directional TBUs, which utilized in combination with appropriate angular heterofunctional ditopic organic liga nds, are capable to l ead the assembly of targeted ZMOFs. Furthermore, a novel appro ach to construct ZMOFs was considered by introducing a superior level of built-in information prior to the assembly process; that is, metal-organic cubes generated in situ (equivalent to d4R, com posite building units in inorganic zeolite materials), were utilized as intended building blocks to result in materials with zeotype features and properties. In the same context, similar design tools, in conjunction with a mixed ligands approach resulted in a remarkable material with zeolitelike features and unprecedented cages in th e mesoporous regime. This pioneering work demonstrates that complex structures based on non-default nets, such as ZMOFs can be designed and assembled by rational choi ce of rigid and direc tional building blocks containing the required hi erarchal information. The structure-function relationship inves tigations in these materials placed the primary focus on attributes arising from thei r porosity, such as host-guest sensing, and indepth gas adsorption studies. The hydrogen capacities measured in select MOMs with diverse features (various apparent surface areas, pore volumes and pore sizes) indicate that materials with high char ge densities are preferred wi th respect to enhancing the binding affinities between the hydrogen a nd framework. These fi ndings are promising and further studies need to be devised in order to improve the adsorption enthalpies toward the targeted desire d range of 1520 kJ mol-1. In particular, the results highlighted by the isostructural series of anionic sod -ZMOFs demonstrate the fact that this platform is relevant to investigate this aspect, es pecially by tuning the chemical environment inside the porous cavities. Studies concerni ng the carbon dioxide stor age capabilities in

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242 these materials, showed potential for promis ing storage capacities at ambient conditions, with increased feasibility at high pressures. In this context, future directions are indicating the potential of th e porous materials characterized herein to be extended to other types of investigations, such as for th e adsorption of harmful gases, and selective separation from mixtures, catalysis, and luminescence related properties. In spite of the fact that trends can be established as to what structure will most likely occur from a certain type of MBB, one of the greatest challe nges facing the singlemetal-ion-based approach is related with fi nding the exact experi mental conditions to yield the targeted MBB in situ at all times. Also, the o ccurrence of supramolecular isomers from similar MBBs interferes to so me degree with the inte nded control over the predictability of the to-be materials. In summary, the work described in this dissertation significantl y contributes to the advancement of the field by demonstrating the capacity of the single-metal-ion-based MBB approach to be a reliable design tool for the discovery of nontrivial materials. The present strategy offers great potential to acce ss complex structures that are not readily constructed from the conventional assembly of simple building blocks, aiding the advancement in the design and synthesis of functional solid-state materials.

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243 6.2. Future Outlook Two decades later from first attempts to construct crystalline hybrid materials with infinite periodic stru ctures, MOMs are now recognized as an important class of functional solid-state materials, capable to m eet current societal a nd technological needs. The great majority of investigations are associated with their porous nature, and concerted efforts are directed toward gas so rption/separation studi es: hydrogen storage as a clean energy source for mobile applications, along with selective storage and separation of greenhouse gases (CO2 and CH4). In this context, the gene ral interest in the area has been reinforced by recent materials with record breaking attributes, es pecially in terms of apparent surface areas and gas storage capabilities. Novel applications are gearing their f unctions towards other sectors, as well: controlled release in dr ug delivery, sensing, thin films, membranes, imaging, and optical devices. Furthermore, MOMs have made the transition from academia to industry, and some materials are now commercially availa ble to be purchased under the name of Basolite, synthesized in 100-kg-per-day batches. While the capability to engineer func tional porous solid-sta te materials through rational design strategies was greatly improved, the actual synt hetic process still requires substantial efforts. On the long run, concerted efforts and systematic studies need to be employed in order to increase their applicability to everyda y life purposes. In spite of certain drawbacks, such as l ack of resistance in harsh media, these materials are highly tunable, outlining a very diverse chemistr y. Noteworthy, the ultimate goal is regarding the ability to precisely construct the de sired material for the intended purpose.

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244 Paraphrasing Feynman’s famous talk “there is plenty of room on the bottom”, we are still far from the groundbreaking point where we can make materials at will, with exact tailored properties at na noscale. Nonetheless, the propensity for vast advancements offered by this subset of functional materi als is truly indubitable and indeed holds promise for great discoveries. And finally, wi th the risk of favoring the occurrence of a clich by overstating their a ttractive features, the concludi ng remark is: at the dynamic rate at which they are developing, the greatest results are yet to come and without doubt, MOMs have a bright future ahead!

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245 Appendices

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246 Appendix A. Single-Crystal Structur al Analysis and Refinement Data Table A.1. Crystal data and structure refinement for Compound 1 Identification code 1 Empirical formula C17.50 H16.67 Cd N2 O8.83 S2 Formula weight 572.85 Temperature 100 (2) K Wavelength 0.71073 Crystal system, space group P213, cubic Unit cell dimensions a = 18.925(3) alpha = 90 b = 18.925(3) beta = 90 c = 18.925(3) gamma = 90 Volume 6778.6(17) 3 Z, Calculated density 12, 1.684 Mg/m3 Absorption coefficient 1.201 mm-1 F(000) 3436 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collec tion 2.41 to 23.25 Limiting indices -8<=h<=21, -3<=k<=21, -15<=l<=16 Reflections collected / unique 9075 / 3259 [R(int) = 0.0736] Completeness to theta = 23.25 99.7 % Max. and min. transmission 0.8894 and 0.8894 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3259 / 0 / 246 Goodness-of-fit on F2 1.080 Final R indices [I>2sigma(I)] R1 = 0.0749, wR2 = 0.1928 R indices (all data) R1 = 0.0892, wR2 = 0.2028 Absolute structure parameter 0.04(8) Largest diff. peak and hole 1.100 and -0.749 e. -3

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247 Appendix A (continued) Table A.2. Crystal data and structure refinement for Compound 2 Identification code 2 Empirical formula C25.50 H29.25 Cd2.25 N6 O12.38 S2.25 Formula weight 942.83 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group Trigonal, R-3c Unit cell dimensions a = 16.2447(7) alpha = 90 b = 16.2447(7) beta = 90 c = 60.342(5) gamma = 120 Volume 13790.4(14) 3 Z, Calculated density 16, 1.816 Mg/m3 Absorption coefficient 1.588 mm-1 F(000) 7476 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.70 to 20.81 Limiting indices -16<=h<=14, -16<=k<=15, -60<=l<=57 Reflections collected / unique 13112 / 1416 [R(int) = 0.0296] Completeness to theta = 20.81 87.6 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1416 / 3 / 206 Goodness-of-fit on F2 1.000 Final R indices [I>2sigma(I)] R1 = 0.0260, wR2 = 0.0715 R indices (all data) R1 = 0.0265, wR2 = 0.0719 Largest diff. peak and hole 0.879 and -0.401 e. -3

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248 Appendix A (continued) Table A.3. Crystal data and structure refinement for Compound 3 Identification code 3 Empirical formula C120 H96 Co3 N8 O32 S6 Formula weight 2627.26 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group Cubic, I -4 3 d Unit cell dimensions a = 29.293(2) alpha = 90 b = 29.293(2) beta = 90 c = 29.293(2) gamma = 90 Volume 25134(3) 3 Z, Calculated density 8, 1.389 Mg/m3 Absorption coefficient 0.568 mm-1 F(000) 10824 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.71 to 51.00 Limiting indices -28<=h<=7, -14<=k<=28, -11<=l<=28 Reflections collected / unique 7483/1200 [R(int) = 0.07] Refinement method least-squares on F2 Data / restraints / parameters 1800 / 0 / 140 Goodness-of-fit on F2 1.0123 Final R indices [I>2sigma(I)] R1 = 0.0856, wR2=0.1543 Largest diff. peak and hole 0.71 and -0.81 e.A-3

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249 Appendix A (continued) Table A.4. Crystal data and structure refinement for Compound 4 Identification code 4 Empirical formula C24 H22 Co N2 O4.50 S Formula weight 501.43 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space group tertragonal, I4(1)/a Unit cell dimensions a = 26.113(5) alpha = 90 b = 26.113(5) beta = 90 c = 16.799(4) gamma = 90 Volume 11455(4) 3 Z, Calculated density 16, 1.163 Mg/m3 Absorption coefficient 0.701 mm-1 F(000) 4144 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.12 to 20.81 Limiting indices -25<=h<=26, -26<=k<=26, -14<=l<=16 Reflections collected / unique 20273 / 2991 [R(int) = 0.1195] Completeness to theta = 20.81 99.8 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 2991 / 0 / 289 Goodness-of-fit on F2 1.024 Final R indices [I>2sigma(I)] R1 = 0.0984, wR2 = 0.2618 R indices (all data) R1 = 0.1557, wR2 = 0.3032 Extinction coefficient 0.0074(9) Largest diff. peak and hole 0.592 and -0.422 e. -3

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250 Appendix A (continued) Table A.5. Crystal data and structure refinement for Compound 5 Identification code 5 Empirical formula C69 H75 Cd2 N7 O18 S3 Formula weight 1611.34 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group Orthorhombic, P2(1)2(1)2(1) Unit cell dimensions a = 16.162(4) alpha = 90 b = 19.486(5) beta = 90 c = 22.253(5) gamma = 90 Volume 7008(3) 3 Z, Calculated density 4, 1.527 Mg/m3 Absorption coefficient 0.772 mm-1 F(000) 3304 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 1.83 to 23.00 Limiting indices -17<=h<=17, 0<=k<=21, 0<=l<=24 Reflections collected / unique 10075 / 9754 [R(int) = 0.0840] Completeness to theta = 23.00 99.9 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 9754 / 1026 / 833 Goodness-of-fit on F2 1.001 Final R indices [I>2sigma(I)] R1 = 0.0645, wR2 = 0.0996 R indices (all data) R1 = 0.1667, wR2 = 0.1275 Absolute structure parameter 0.55(5) Largest diff. peak and hole 1.237 and -1.294 e. -3

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251 Appendix A (continued) Table A.6. Crystal data and structure refinement for Compound 6 Identification code 6 Empirical formula C18 H18 Fe N4 O11 S0 Formula weight 522.21 Temperature 100(2) K Wavelength 0.71073 Crystal system, space grou p Monoclinic, P2(1)/c Unit cell dimensions a = 13.2232(16) alpha = 90 b = 11.9750(15) beta = 100.875(2) c = 13.5891(16) gamma = 90 Volume 2113.2(4) 3 Z, Calculated density 4, 1.641 Mg/m3 Absorption coefficient 0.784 mm-1 F(000) 1072 Crystal size 0.09 x 0.08 x 0.07 mm Theta range for data collection 1.57 to 25.11 Limiting indices -15<=h<=15, -14<=k<=9, -16<=l<=16 Reflections collected / unique 10889 / 3765 [R(int) = 0.0955] Completeness to theta = 25.11 99.7 % Max. and min. transmission 1.000000 and 0.410292 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3765 / 0 / 297 Goodness-of-fit on F2 1.055 Final R indices [I>2sigma(I)] R1 = 0.0693, wR2 = 0.1667 R indices (all data) R1 = 0.1150, wR2 = 0.1932 Largest diff. peak and hole 0.919 and -0.495 e. -3

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252 Appendix A (continued) Table A.7. Crystal data and structure refinement for Compound 7 Identification code 7 Empirical formula C14 H6 Fe N2 O14.52 Formula weight 490.32 Temperature 100(2) K Wavelength 1.54178 A Crystal system, space group Trigonal, R-3c Unit cell dimensions a = 15.014(15) alpha = 90 b = 15.014(15) beta = 90 c = 55.07(8) gamma = 120 Volume 10750(21) 3 Z, Calculated density 18, 1.363 Mg/m3 Absorption coefficient 5.696 mm-1 F(000) 4430 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 4.68 to 38.14 Limiting indices -11<=h<=7, -11<=k<=7, -39<=l<=42 Reflections collected / unique 1877 / 626 [R(int) = 0.1004] Completeness to theta = 38.14 96.5 % Max. and min. transmission 0.5997 and 0.5997 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 626 / 0 / 102 Goodness-of-fit on F2 1.154 Final R indices [I>2sigma(I)] R1 = 0.2097, wR2 = 0.3907 R indices (all data) R1 = 0.2471, wR2 = 0.3166 Largest diff. peak and hole 0.521 and -0.942 e.-3

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253 Appendix A (continued) Table A.8. Crystal data and structure refinement for Compound 8 Identification code 8 Empirical formula C10 H9.50 Fe0.50 N3 O5 Formula weight 279.63 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group orthorho mbic, P2(1)2(1)2(1) Unit cell dimensions a = 10.8571(11) alpha = 90 b = 12.4178(12) beta = 90 c = 18.0423(18) gamma = 90 Volume 2432.5(4) 3 Z, Calculated density 8, 1.527 Mg/m3 Absorption coefficient 0.686 mm-1 F(000) 1148 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.74 to 28.22 Limiting indices -11<=h<=14, -16<=k<=15, -23<=l<=19 Reflections collected / unique 15413 / 5570 [R(int) = 0.0971] Completeness to theta = 28.22 95.1 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 5570 / 0 / 323 Goodness-of-fit on F2 1.078 Final R indices [I>2sigma(I)] R1 = 0.0817, wR2 = 0.1896 R indices (all data) R1 = 0.1122, wR2 = 0.2062 Absolute structure parameter 0.02(4) Largest diff. peak and hole 1.144 and -0.575 e. -3

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254 Appendix A (continued) Table A.9. Crystal data and structure refinement for Compound 9 Identification code 9 Empirical formula C14 H6 Fe N2 O9 Formula weight 402.06 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group Tetragonal, I -42 d Unit cell dimensions a = 20.778(3) alpha = 90 b = 20.778(3) beta = 90 c = 17.238(4) gamma = 90 Volume 7442(2) 3 Z, Calculated density 8, 0.718 Mg/m3 Absorption coefficient 0.429 mm-1 F(000) 1616 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 4 to 25 Limiting indices -21<=h<=21, 0<=k<=21, 0<=l<=19 Reflections collected / unique 11075 / 10754 [R(int) = 0.0840] Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 10754 / 1126 / 933 Goodness-of-fit on F2 1.001 Final R indices [I>2sigma(I)] R1 = 0.1245, wR2 = 0.1696 R indices (all data) R1 = 0.2267, wR2 =0.1975 Absolute structure parameter 0.55(5) Largest diff. peak and hole 1.237 and -1.294 e.-3

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255 Appendix A (continued) Table A.10. Crystal data and structure refinement for Compound 10 Identification code 10 Empirical formula C6 H12 Cd N2 O9 Formula weight 368.58 Temperature 100(2) K Wavelength 0.71073 Crystal system, space grou p Monoclinic, P2(1)/n Unit cell dimensions a = 12.3080(11) alpha = 90 b = 7.0447(6) beta = 108.547(2) c = 13.3809(12) gamma = 90 Volume 1099.95(17) 3 Z, Calculated density 3, 1.669 Mg/m3 Absorption coefficient 1.524 mm-1 F(000) 546 Crystal size 0.21 x 0.19 x 0.15 mm Theta range for data collection 1.96 to 28.20 Limiting indices -15<=h<=12, -9<=k<=9, -17<=l<=17 Reflections collected / unique 6459 / 2518 [R(int) = 0.0309] Completeness to theta = 28.20 93.1 % Max. and min. transmission 1.000 and 0.748 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 2518 / 0 / 163 Goodness-of-fit on F2 0.842 Final R indices [I>2sigma(I)] R1 = 0.0297, wR2 = 0.0688 R indices (all data) R1 = 0.0348, wR2 = 0.0719 Largest diff. peak and hole 0.872 and -0.563 e.-3

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256 Appendix A (continued) Table A.11. Crystal data and structure refinement for Compound 11 Identification code 11 Empirical formula C14 H22 N6 O16 Yb2 Formula weight 876.46 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space grou p Monoclinic, P2(1)/n Unit cell dimensions a = 7.4861(7) alpha = 90 b = 11.9893(11) beta = 99.710(2) c = 12.2647(11) gamma = 90 Volume 1085.02(17) 3 Z, Calculated density 2, 2.683 Mg/m3 Absorption coefficient 8.666 mm-1 F(000) 832 Crystal size 0.05 x 0.02 x 0.02 mm Theta range for data collection 2.39 to 28.26 Limiting indices -9<=h<=9, -12<=k<=15, -13<=l<=16 Reflections collected / unique 5249 / 2381 [R(int) = 0.0266] Completeness to theta = 28.26 88.9 % Max. and min. transmission 1.000 and 0.666 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 2381 / 0 / 172 Goodness-of-fit on F2 1.015 Final R indices [I>2sigma(I)] R1 = 0.0297, wR2 = 0.0648 R indices (all data) R1 = 0.0354, wR2 = 0.0675 Largest diff. peak and hole 1.866 and -1.033 e.-3

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257 Appendix A (continued) Table A.12. Crystal data and structure refinement for Compound 12 Identification code 12 Empirical formula C18 H19 N6 O16 Y Formula weight 664.30 Temperature 100(2) K Wavelength 1.54178 A Crystal system, space group monoclinic, P2(1)/n Unit cell dimensions a = 14.186(14) alpha = 90 b = 12.829(12) beta = 101.46(2) c = 16.273(16) gamma = 90 Volume 2902(5) 3 Z, Calculated density 4, 1.520 Mg/m3 Absorption coefficient 3.560 mm-1 F(000) 1344 Crystal size 0.20 x 0.10 x 0.10 mm Theta range for data collection 3.78 to 38.16 Limiting indices -9<=h<=11, -9<=k<=3, -12<=l<=8 Reflections collected / unique 1780 / 1344 [R(int) = 0.0538] Completeness to theta = 38.16 85.8 % Max. and min. transmission 0.7172 and 0.5362 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1344 / 0 / 152 Goodness-of-fit on F2 1.118 Final R indices [I>2sigma(I)] R1 = 0.1315, wR2 = 0.2861 R indices (all data) R1 = 0.2001, wR2 = 0.3391 Largest diff. peak and hole 0.983 and -1.356 e.-3

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258 Appendix A (continued) Table A.13. Crystal data and structure refinement for Compound 13 Identification code 13 Empirical formula C6 H8 Cd0.50 K N2 O7 Formula weight 315.44 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space grou p Orthorhombic, Pbcn Unit cell dimensions a = 10.596(8) alpha = 90 b = 24.135(20) beta = 90 c = 7.985(7) gamma = 90 Volume 2042(3) 3 Z, Calculated density 8, 2.052 Mg/m3 Absorption coefficient 1.560 mm-1 F(000) 1256 Crystal size 0.20 x 0.15 x 0.03 mm Theta range for data collection 3.06 to 25.22 Limiting indices -12<=h<=9, -6<=k<=28, -9<=l<=8 Reflections collected / unique 4026 / 1772 [R(int) = 0.0461] Completeness to theta = 25.22 96.0 % Max. and min. transmission 0.9547 and 0.7456 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1772 / 6 / 150 Goodness-of-fit on F2 1.043 Final R indices [I>2sigma(I)] R1 = 0.0375, wR2 = 0.0845 R indices (all data) R1 = 0.0566, wR2 = 0.0919 Largest diff. peak and hole 0.614 and -0.531 e.A-3

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259 Appendix A (continued) Table A.14. Crystal data and structure refinement for Compound 14 Identification code 14 Empirical formula C32 H48 Cd4 N16 O22 Formula weight 1458.46 Temperature 293(2) K Wavelength 1.54178 A Crystal system, space grou p Monoclinic, P21/c Unit cell dimensions a = 9.7125(2) alpha = 90 b = 33.8825(8) beta = 93.1660(10) c = 7.4416(2) gamma = 90 Volume 2445.17(10) 3 Z, Calculated density 2, 1.981 Mg/m3 Absorption coefficient 14.589 mm-1 F(000) 1440 Crystal size 0.10 x 0.10 x 0.05 mm Theta range for data collection 4.56 to 63.67 Limiting indices -11<=h<=1 0, -38<=k<=39, -8<=l<=8 Reflections collected / unique 13206 / 3952 [R(int) = 0.0601] Completeness to theta = 63.67 98.1 % Max. and min. transmission 0.5291 and 0.3232 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3952 / 0 / 334 Goodness-of-fit on F2 1.138 Final R indices [I>2sigma(I)] R1 = 0.0439, wR2 = 0.1047 R indices (all data) R1 = 0.0516, wR2 = 0.1087 Largest diff. peak and hole 1.004 and -1.836 e. -3

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260 Appendix A (continued) Table A.15. Crystal data and structure refinement for Compound 15 Identification code 15 Empirical formula C6 H3 Mn N2 O5 Formula weight 238.04 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space grou p Orthorhombic, Pbca Unit cell dimensions a = 9.9565(14) alpha = 90 b = 12.2961(18) beta = 90 c = 13.7452(19) gamma = 90 Volume 1682.8(4) 3 Z, Calculated density 8, 1.879 Mg/m3 Absorption coefficient 1.565 mm-1 F(000) 944 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 3.25 to 30.5 Limiting indices -9<=h<=14, -17<=k<=17, -19<=l<=19 Reflections collected / unique 14647 / 2533 [R(int) = 0.0955] Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 2533 / 0 / 145 Goodness-of-fit on F2 1.078 Final R indices [I>2sigma(I)] R1 = 0.0321, wR2 = 0.0880 R indices (all data) R1 = 0.0825, wR2 =0.0935 Largest diff. peak and hole 0.919 and -0.495 e.-3

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261 Appendix A (continued) Table A.16. Crystal data and structure refinement for Compound 16 Identification code 16 Empirical formula C13.50 H12.50 In K N4.50 O10.50 Formula weight 559.70 Temperature 193(2) K Wavelength 0.71073 Crystal system, space gr oup Monoclinic, C2 Unit cell dimensions a = 12.642(4) alpha = 90 b = 13.482(4) beta = 117.996(4) c = 12.340(4) gamma = 90 Volume 1857.1(9) 3 Z, Calculated density 4, 2.002 Mg/m3 Absorption coefficient 1.566 mm-1 F(000) 1108 Crystal size 0.05 x 0.05 x 0.03 mm Theta range for data collection 4.42 to 27.50 Limiting indices -16<=h<=16, -17<=k<=17, -16<=l<=15 Reflections collected / unique 8209 / 4144 [R(int) = 0.0600] Completeness to theta = 27.50 99.3 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 4144 / 79 / 315 Goodness-of-fit on F2 1.004 Final R indices [I>2sigma(I)] R1 = 0.0482, wR2 = 0.0860 R indices (all data) R1 = 0.0691, wR2 = 0.0929 Absolute structure parameter 0.46(6) Largest diff. peak and hole 0.929 and -1.476 e.-3

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262 Appendix A (continued) Table A.17. Crystal data and structure refinement for Compound 17 Identification code 17 Empirical formula C27 H32 In2 N10 O25 Formula weight 1126.27 Temperature 298(2) K Wavelength 0.71073 A Crystal system, space grou p Monoclinic, P2(1)/n Unit cell dimensions a = 16.217(5) alpha = 90 b = 14.814(4) A beta = 94.149(6) c = 18.948(6) A gamma = 90 Volume 4540(2) 3 Z, Calculated density 4, 1.648 Mg/m3 Absorption coefficient 1.110 mm-1 F(000) 2248 Crystal size 0.20 x 0.15 x 0.15 mm Theta range for data collection 1.72 to 25.19 Limiting indices -19<=h<=16, -17<=k<=15, -20<=l<=22 Reflections collected / unique 23431 / 8120 [R(int) = 0.0663] Completeness to theta = 25.19 99.2 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 8120 / 6 / 554 Goodness-of-fit on F2 1.007 Final R indices [I>2sigma(I)] R1 = 0.0455, wR2 = 0.1181 R indices (all data) R1 = 0.0840, wR2 = 0.1231 Largest diff. peak and hole 0.881 and -0.620 e.-3

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263 Appendix A (continued) Table A.18. Crystal data and structure refinement for Compound 18 Identification code 18 Empirical formula C16 H18 Fe N8 O8 Formula weight 506.23 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space group monoclinic, P21/c Unit cell dimensions a = 6.782(3) alpha = 90 b = 11.157(4) beta = 98.28(2) c = 12.388(4) gamma = 90 Volume 927.6(6) 3 Z, Calculated density 2, 1.812 Mg/m3 Absorption coefficient 0.884 mm-1 F(000) 520 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 2.47 to 23.26 Limiting indices -6<=h<=7, -12<=k<=6, -13<=l<=8 Reflections collected / unique 2807 / 1335 [R(int) = 0.0834] Completeness to theta = 23.26 99.6 % Max. and min. transmission 0.9168 and 0.9168 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1335 / 0 / 153 Goodness-of-fit on F2 1.015 Final R indices [I>2sigma(I)] R1 = 0.0756, wR2 = 0.1880 R indices (all data) R1 = 0.1314, wR2 = 0.2218 Largest diff. peak and hole 0.499 and -1.041 e.-3

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264 Appendix A (continued) Table A.19. Crystal data and structure refinement for Compound 19 Identification code 19 Empirical formula C6 H1.50 N2 O7.27 Yb Formula weight 390.90 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space gr oup trigonal, R32 Unit cell dimensions a = 12.183(3) alpha = 90 b = 12.183(3) beta = 90 c = 19.567(12) gamma = 120 Volume 2515.3(18) 3 Z, Calculated density 9, 2.323 Mg/m3 Absorption coefficient 8.389 mm-1 F(000) 1617 Crystal size 0.05 x 0.05 x 0.05 mm Theta range for data collection 2.84 to 28.16 Limiting indices -13<=h<=15, -12<=k<=14, -25<=l<=12 Reflections collected / unique 3238 / 1266 [R(int) = 0.0550] Completeness to theta = 28.16 96.3 % Max. and min. transmission 0.6791 and 0.6791 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1266 / 6 / 79 Goodness-of-fit on F2 1.043 Final R indices [I>2sigma(I)] R1 = 0.0347, wR2 = 0.0755 R indices (all data) R1 = 0.0392, wR2 = 0.0781 Absolute structure parameter 0.01(3) Largest diff. peak and hole 1.114 and -1.069 e-3

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265 Appendix A (continued) Table A.20. Crystal data and structure refinement for Compound 20 Identification code 20 Empirical formula C12 H4 In1.33 K N5 O14.67 Formula weight 645.06 Temperature 163(2) K Wavelength 0.71073 A Crystal system, space gr oup trigonal, R-3 Unit cell dimensions a = 16.544(2) alpha = 90 b = 16.544(2) beta = 90 c = 38.736(9) gamma = 120 Volume 9181(3) 3 Z, Calculated density 18, 2.100 Mg/m3 Absorption coefficient 1.818 mm-1 F(000) 5628 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 1.77 to 25.51 Limiting indices -18<=h<=20, -14<=k<=19, -46<=l<=43 Reflections collected / unique 11156 / 3705 [R(int) = 0.0580] Completeness to theta = 25.51 97.2 % Max. and min. transmission 0.8391 and 0.8391 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3705 / 6 / 309 Goodness-of-fit on F2 0.940 Final R indices [I>2sigma(I)] R1 = 0.0500, wR2 = 0.1319 R indices (all data) R1 = 0.0777, wR2 = 0.1429 Largest diff. peak and hole 1.334 and -0.899 e.-3

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266 Appendix A (continued) Table A.21. Crystal data and structure refinement for Compound 21 Identification code 21 Empirical formula C10 H3 N3.50 O6 Tb0.50 Formula weight 347.62 Temperature 293(2) K Wavelength 0.71073 Crystal system, space group monoclinic, C2 Unit cell dimensions a = 15.792(9) alpha = 90 b = 10.893(9) beta = 91.743(18) c = 8.343(6) gamma = 90 Volume 1434.5(17) 3 Z, Calculated density 4, 1.610 Mg/m3 Absorption coefficient 2.532 mm-1 F(000) 672 Crystal size 0.1 x 0.15 x 0.2 mm Theta range for data collection 2.58 to 25.46 Limiting indices -14<=h<=15, -13<=k<=3, -10<=l<=9 Reflections collected / unique 1711 / 1155 [R(int) = 0.0607] Completeness to theta = 25.46 70.3 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1155 / 1 / 74 Goodness-of-fit on F2 0.616 Final R indices [I>2sigma(I)] R1 = 0.0568, wR2 = 0.1435 R indices (all data) R1 = 0.0577, wR2 = 0.1462 Absolute structure parameter 0.34(5) Largest diff. peak and hole 1.158 and -0.957 e.-3

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267 Appendix A (continued) Table A.22. Crystal data and structure refinement for Compound 22 Identification code 22 Empirical formula C14.20 H8.50 K0.15 N7.35 O9.10 Tb Formula weight 592.47 Temperature 293(2) K Wavelength 0.71073 Crystal system, space group orthorhombic, Pnnn Unit cell dimensions a = 11.767(3) alpha = 90 b = 12.437(4) beta = 90 c = 26.859(8) gamma = 90 Volume 3931(2) 3 Z, Calculated density 8, 2.002 Mg/m3 Absorption coefficient 3.697 mm-1 F(000) 2286 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.38 to 28.20 Limiting indices -5<=h<=15, -10<=k<=16, -33<=l<=31 Reflections collected / unique 11912 / 4292 [R(int) = 0.0413] Completeness to theta = 28.20 88.3 % Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 4292 / 0 / 287 Goodness-of-fit on F2 1.050 Final R indices [I>2sigma(I)] R1 = 0.0426, wR2 = 0.1131 R indices (all data) R1 = 0.0789, wR2 = 0.1303 Largest diff. peak and hole 1.441 and -0.794 e.-3

PAGE 293

268 Appendix A (continued) Table A.23. Crystal data and structure refinement for Compound 23 Identification code 23 Empirical formula C18 H9 N9 O36.44 Y2 Formula weight 1112.28 Temperature 100(2) K Wavelength 1.54178 A Crystal system, space grou p orthorhombic, Pnma Unit cell dimensions a = 13.9934(4) alpha = 90 b = 23.3932(7) beta = 90 c = 13.3315(4) gamma = 90 Volume 4364.1(2) 3 Z, Calculated density 4, 1.693 Mg/m3 Absorption coefficient 4.662 mm-1 F(000) 2198 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 3.78 to 65.13 Limiting indices -15<=h<=15, -26<=k<=26, -15<=l<=10 Reflections collected / unique 22895 / 3727 [R(int) = 0.0742] Completeness to theta = 65.13 97.3 % Max. and min. transmission 0.6528 and 0.6528 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3727 / 0 / 322 Goodness-of-fit on F2 1.045 Final R indices [I>2sigma(I)] R1 = 0.0635, wR2 = 0.1603 R indices (all data) R1 = 0.0946, wR2 = 0.1766 Largest diff. peak and hole 1.055 and -0.903 e.-3

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269 Appendix A (continued) Table A.24. Crystal data and structure refinement for Compound 24 Identification code 24 Empirical formula C69 H27 N29 O65 Y9 Formula weight 3102.39 Temperature 100(2) K Wavelength 0.71073 A Crystal system, space group tetragonal, P-42(1)c Unit cell dimensions a = 37.623(13) alpha = 90 b = 37.623(13) beta = 90 c = 22.456(12) gamma = 90 Volume 31786(23) 3 Z, Calculated density 8, 1.297 Mg/m3 Absorption coefficient 3.327 mm-1 F(000) 12120 Crystal size 0.07 x 0.07 x 0.07 mm Theta range for data collection 1.71 to 20.81 Limiting indices -28<=h<=33, -37<=k<=35, -22<=l<=8 Reflections collected / unique 51325 / 16568 [R(int) = 0.1607] Completeness to theta = 20.81 99.9 % Max. and min. transmission 0.8005 and 0.8005 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 16568 / 0 / 662 Goodness-of-fit on F2 1.010 Final R indices [I>2sigma(I)] R1 = 0.1192, wR2 = 0.2971 R indices (all data) R1 = 0.1767, wR2 = 0.3192 Largest diff. peak and hole 1.423 and -0.961 e.-3

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270 Appendix A (continued) Table A.25. Crystal data and structure refinement for Compound 25 Identification code 25 Empirical formula C66 H33 Er6 N33 O59.20 Formula weight 3239.01 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group cubic, I-43m Unit cell dimensions a = 37.267(12) alpha = 90 b = 37.267(12) beta = 90 c = 37.267(12) gamma = 90 Volume 51755(29) ^3 Z, Calculated density 12, 1.247 Mg/m3 Absorption coefficient 2.957 mm-1 F(000) 18499 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 1.09 to 15.85 Limiting indices -28<=h<=5, -27<=k<=18, -7<=l<=27 Reflections collected / unique 7915 / 2219 [R(int) = 0.1694] Completeness to theta = 15.85 97.2 % Max. and min. transmission 0.7564 and 0.7564 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 2219 / 7 / 179 Goodness-of-fit on F2 1.194 Final R indices [I>2sigma(I)] R1 = 0.0989, wR2 = 0.2255 R indices (all data) R1 = 0.1302, wR2 = 0.2433 Absolute structure parameter 0.09(7) Largest diff. peak and hole 1.017 and -0.845 e.-3

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271 Appendix A (continued) Table A.26. Crystal data and structure refinement for Compound 26 Identification code 26 Empirical formula C66 H33 N33 O52.17 Yb6.34 Formula weight 3219.99 Temperature 90(2) K Wavelength 0.71073 Crystal system, space group cubic, I-43m Unit cell dimensions a = 37.0038(18) alpha = 90 b = 37.0038(18) beta = 90 c = 37.0038(18) gamma = 90 Volume 50669(4) 3 Z, Calculated density 12, 1.266 Mg/m3 Absorption coefficient 3.542 mm-1 F(000) 18254 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 2.06 to 20.81 Limiting indices -36<=h<=-1, -25<=k<=28, -13<=l<=32 Reflections collected / unique 15863 / 4759 [R(int) = 0.0896] Completeness to theta = 20.81 99.0 % Max. and min. transmission 0.7183 and 0.7183 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 4759 / 0 / 174 Goodness-of-fit on F2 1.047 Final R indices [I>2sigma(I)] R1 = 0.0878, wR2 = 0.2330 R indices (all data) R1 = 0.1243, wR2 = 0.2616 Absolute structure parameter 0.00(4) Largest diff. peak and hole 1.180 and -0.651 e.-3

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272 Appendix A (continued) Table A.27. Crystal data and structure refinement for Compound 27 Identification code 27 Empirical formula C1.50 H0.50 In0.125 K0.16 N0.58 Na0.045 O1.36 Formula weight 70.05 Temperature 298(2) K Wavelength 0.71073 Crystal system, space group Cubic, Im-3m Unit cell dimensions a = 18.761(4) alpha = 90 b = 18.761(4) beta = 90 c = 18.761(4) gamma = 90 Volume 6603(2) 3 Z, Calculated density 96, 1.691 Mg/m3 Absorption coefficient 1.381 mm-1 F(000) 3274 Crystal size 0.15 x 0.15 x 0.15 mm Theta range for data collection 2.66 to 20.75 Limiting indices -17<=h<=18, -13<=k<=18, -18<=l<=18 Reflections collected / unique 10664 / 373 [R(int) = 0.0675] Completeness to theta = 20.75 98.4 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.8196 and 0.8196 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 373 / 0 / 60 Goodness-of-fit on F2 1.173 Final R indices [I>2sigma(I)] R1 = 0.0436, wR2 = 0.1252 R indices (all data) R1 = 0.0462, wR2 = 0.1277 Largest diff. peak and hole 0.594 and -0.768 e.-3

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273 Appendix A (continued) Table A.28. Crystal data and structure refinement for Compound 28 Identification code 28 Empirical formula C12 H4 K N4 O15.73 Yb Formula weight 668.51 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group Cubic, Im-3m Unit cell dimensions a = 19.063(2) alpha = 90 b = 19.063(2) beta = 90 c = 19.063(2) gamma = 90 Volume 6927.6(13) 3 Z, Calculated density 12, 1.923 Mg/m3 Absorption coefficient 4.310 mm-1 F(000) 3829 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 3.02 to 25.21 Limiting indices -19<=h<=19, -22<=k<=13, -17<=l<=22 Reflections collected / unique 8379 / 650 [R(int) = 0.0991] Completeness to theta = 25.21 99.2 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.6725 and 0.6725 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 650 / 0 / 67 Goodness-of-fit on F2 1.109 Final R indices [I>2sigma(I)] R1 = 0.0564, wR2 = 0.1284 R indices (all data) R1 = 0.0622, wR2 = 0.1314 Largest diff. peak and hole 1.876 and -1.787 e.-3

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274 Appendix A (continued) Table A.29. Crystal data and structure refinement for Compound 29 Identification code 29 Empirical formula C12 H4 Er K N4 O8 Formula weight 538.55 Temperature 100(2) K Wavelength 1.54178 Crystal system, space group cubic, Im-3m Unit cell dimensions a = 19.311(13) alpha = 90 b = 19.311(13) beta = 90 c = 19.311(13) gamma = 90 Volume 7202(8) 3 Z, Calculated density 12, 1.490 Mg/m3 Absorption coefficient 8.382 mm-1 F(000) 3060 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 5.61 to 38.39 Limiting indices -11<=h<=15, -15<=k<=9, -15<=l<=4 Reflections collected / unique 1605 / 225 [R(int) = 0.0724] Completeness to theta = 38.39 98.3 % Max. and min. transmission 0.4878 and 0.4878 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 225 / 0 / 29 Goodness-of-fit on F2 1.066 Final R indices [I>2sigma(I)] R1 = 0.0891, wR2 = 0.2359 R indices (all data) R1 = 0.1006, wR2 = 0.2495 Largest diff. peak and hole 0.846 and -0.449 e.-3

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275 Appendix A (continued) Table A.30. Crystal data and structure refinement for Compound 30 Identification code 30 Empirical formula C9 H3 K0.75 N3 O10.26 Y0.75 Formula weight 413.39 Temperature 100(2) K Wavelength 1.54178 Crystal system, space group cubic, Im-3m Unit cell dimensions a = 19.36(2) alpha = 90 b = 19.36(2) beta = 90 c = 19.36(2) gamma = 90 Volume 7254(16) 3 Z, Calculated density 16, 1.514 Mg/m3 Absorption coefficient 5.564 mm-1 F(000) 3258 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 5.60 to 30.66 Limiting indices -11<=h<=3, -6<=k<=12, -12<=l<=11 Reflections collected / unique 644 / 131 [R(int) = 0.0983] Completeness to theta = 30.66 95.6 % Max. and min. transmission 0.6061 and 0.6061 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 131 / 0 / 45 Goodness-of-fit on F2 1.185 Final R indices [I>2sigma(I)] R1 = 0.0807, wR2 = 0.2201 R indices (all data) R1 = 0.1036, wR2 = 0.2480 Largest diff. peak and hole 0.909 and -0.316 e.-3

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276 Appendix A (continued) Table A.31. Crystal data and structure refinement for Compound 31 Identification code 31 Empirical formula C12 H4 Cd2 N4 O12.42 Formula weight 627.66 Temperature 100(2) K Wavelength 1.54178 Crystal system, space group cubic, Im-3m Unit cell dimensions a = 18.9166(2) alpha = 90 b = 18.9166(2) beta = 90 c = 18.9166(2) gamma = 90 Volume 6769.08(12) 3 Z, Calculated density 12, 1.848 Mg/m3 Absorption coefficient 15.698 mm-1 F(000) 3592 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 4.68 to 64.93 Limiting indices -21<=h<=20, -20<=k<=17, -19<=l<=17 Reflections collected / unique 4419 / 568 [R(int) = 0.0515] Completeness to theta = 64.93 93.0 % Max. and min. transmission 0.3028 and 0.3028 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 568 / 0 / 66 Goodness-of-fit on F2 1.093 Final R indices [I>2sigma(I)] R1 = 0.0509, wR2 = 0.1438 R indices (all data) R1 = 0.0559, wR2 = 0.1499 Largest diff. peak and hole 0.943 and -0.732 e.-3

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277 Appendix A (continued) Table A.32. Crystal data and structure refinement for Compound 32 Identification code 32 Empirical formula C15 H13 In N7 O13.10 Formula weight 615.74 Temperature 100(2) K Wavelength 0.71073 Crystal system, space gr oup trigonal, R-3 Unit cell dimensions a = 32.937(6) alpha = 90 b = 32.937(6) beta = 90 c = 20.133(7) gamma = 120 Volume 18915(8) 3 Z, Calculated density 18, 0.973 Mg/m3 Absorption coefficient 0.607 mm-1 F(000) 5504 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 2.14 to 18.49 Limiting indices -29<=h<=28, -29<=k<=27, -17<=l<=13 Reflections collected / unique 10635 / 3074 [R(int) = 0.0821] Completeness to theta = 18.49 98.2 % Max. and min. transmission 0.9418 and 0.9418 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 3074 / 0 / 190 Goodness-of-fit on F2 1.212 Final R indices [I>2sigma(I)] R1 = 0.1404, wR2 = 0.3350 R indices (all data) R1 = 0.1793, wR2 = 0.3550 Largest diff. peak and hole 0.896 and -0.730 e.-3

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278 Appendix A (continued) Table A.33. Crystal data and structure refinement for Compound 35 Identification code 35 Empirical formula C5.70 H3 Cd0.50 N2.35 O4.68 Formula weight 235.53 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group Cubic, Im-3m Unit cell dimensions a = 30.070(7) alpha = 90 b = 30.070(7) beta = 90 c = 30.070(7) gamma = 90 Volume 27189(11) 3 Z, Calculated density 96, 1.381 Mg/m3 Absorption coefficient 1.008 mm-1 F(000) 11051 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 2.53 to 19.96 Limiting indices -28<=h<=7, -14<=k<=28, -11<=l<=28 Reflections collected / unique 7483 / 1203 [R(int) = 0.0983] Completeness to theta = 19.96 95.5 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.9059 and 0.9059 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 1203 / 3 / 159 Goodness-of-fit on F2 1.123 Final R indices [I>2sigma(I)] R1 = 0.0771, wR2 = 0.1900 R indices (all data) R1 = 0.1024, wR2 = 0.2053 Largest diff. peak and hole 0.384 and -0.562 e.-3

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279 Appendix A (continued) Table A.34. Crystal data and structure refinement for Compound 36 Identification code 36 Empirical formula C65 H24 In8 N36 O50 Formula weight 3027.76 Temperature 293(2) K Wavelength 0.71073 Crystal system, space group Cubic, Pm-3n Unit cell dimensions a = 20.195(3) alpha = 90 b = 20.195(3) beta = 90 c = 20.195(3) gamma = 90 Volume 8235.8(18) 3 Z, Calculated density 2, 1.221 Mg/m3 Absorption coefficient 1.169 mm-1 F(000) 2916 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.02 to 21.97 Limiting indices 0<=h<=21, 0<=k<=21, 0<=l<=21 Reflections collected / unique 5196 / 936 [R(int) = 0.1354] Completeness to theta = 21.97 99.6 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.8921 and 0.8921 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 936 / 2 / 70 Goodness-of-fit on F2 1.001 Final R indices [I>2sigma(I)] R1 = 0.0442, wR2 = 0.0779 R indices (all data) R1 = 0.1274, wR2 = 0.0868 Largest diff. peak and hole 0.713 and -0.360 e.-3

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280 Appendix A (continued) Table A.35. Crystal data and structure refinement for Compound 37 Identification code 37 Empirical formula C60 H50 In8 N45 O48 Formula weight 3088.01 Temperature 298(2) K Wavelength 0.71073 Crystal system, space group Cubic, Fm-3 Unit cell dimensions a = 22.418(6) alpha = 90 b = 22.418(6) beta = 90 c = 22.418(6) gamma = 90 Volume 11266(5) 3 Z, Calculated density 4, 1.821 Mg/m3 Absorption coefficient 1.711 mm-1 F(000) 6004 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 2.57 to 20.76 Limiting indices -14<=h<=22, -16<=k<=22, -22<=l<=22 Reflections collected / unique 7884 / 548 [R(int) = 0.1372] Completeness to theta = 20.76 99.3 % Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.8475 and 0.8475 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 548 / 0 / 72 Goodness-of-fit on F2 1.000 Final R indices [I>2sigma(I)] R1 = 0.0611, wR2 = 0.1503 R indices (all data) R1 = 0.1054, wR2 = 0.1665 Largest diff. peak and hole 0.304 and -0.568 e.-3

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281 Appendix A (continued) Table A.36. Crystal data and structure refinement for Compound 38 Identification code 38 Empirical formula C1152 H624 N456 O1644.38 Y168 Formula weight 62100.03 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group cubic, Im-3m Unit cell dimensions a = 49.295(6) alpha = 90 b = 49.295(6) beta = 90 c = 49.295(6) gamma = 90 Volume 119787(24) 3 Z, Calculated density 1, 0.861 Mg/m3 Absorption coefficient 2.069 mm-1 F(000) 30435 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 2.11 to 20.82 Limiting indices -26<=h<=42, -2<=k<=49, -48<=l<=17 Reflections collected / unique 48074 / 5811 [R(int) = 0.2044] Completeness to theta = 20.82 99.6 % Max. and min. transmission 0.8198 and 0.8198 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 5811 / 18 / 384 Goodness-of-fit on F2 1.061 Final R indices [I>2sigma(I)] R1 = 0.0869, wR2 = 0.2475 R indices (all data) R1 = 0.1464, wR2 = 0.2865 Largest diff. peak and hole 0.850 and -0.510 e.-3

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282 510152025303540 0 100 200 300 400 500 600 700 ExperimentalIntensity2-theta/0 Calculated510152025303540 0 200 400 600 800 1000 Experimental Intensity2-theta/0 CalculatedAppendix B. X-ray Powder Diffraction Spectra Figure B.1. XRPD spectra of 1 ; red = calculated, blue = experimental. Figure B.2. XRPD spectra of 2 ; red = calculated, blue = experimental.

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283 Appendix B (continued) Figure B.3. XRPD spectra of 3 ; red = calculated, blue = experimental. Figure B.4. XRPD spectra of 4 ; red = calculated, blue = experimental. 510152025303540 0 50 100 150 200 250 300 CalculatedIntensity2-theta/0 Experimental510152025303540 0 50 100 150 200 250 300 CalculatedIntensity2-theta/0 Experimental

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284 Appendix B (continued) Figure B.5. XRPD spectra of 5; red = calculated, blue = experimental. Figure B.6. XRPD spectra of 6; red = calculated, blue = experimental. 510152025303540 0 20 40 60 80 100 120 Experimental Calculated Intensity2-theta/0510152025303540 0 200 400 600 800 1000 CalculatedIntensity2-theta/0 Experimenta

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285 Appendix B (continued) Figure B.7. XRPD spectra of 7 ; red = calculated, blue = experimental. Figure B.8. XRPD spectra of 8 ; red = calculated, blue = experimental. 510152025303540 0 50 100 150 200 250 300 350 ExperimentalIntensity2-theta/0 Calculated510152025303540 0 50 100 150 200 250 300 350 Experimental Intensity2-theta/0 Calculated

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286 Appendix B (continued) Figure B.9. XRPD spectra of 9 ; red = calculated, blue = experimental. Figure B.10. XRPD spectra of 11 ; red = calculated, blue = experimental. 510152025303540 0 100 200 300 400 500 600 Calculated ExperimentalIntensity2-theta/0510152025303540 0 200 400 600 800 1000 Calculated Intensity2-theta/0 Experimental

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287 Appendix B (continued) Figure B.11. XRPD spectra of 13 ; red = calculated, blue = experimental. Figure B.12. XRPD spectra of 14 ; red = calculated, blue = experimental. 510152025303540 0 100 200 300 400 500 ExperimentalIntensity2-theta/0 Calculated510152025303540 0 100 200 300 400 500 600 700 CalculatedIntensity2-theta/0 Experimental

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288 Appendix B (continued) Figure B.12. XRPD spectra of 15 ; red = calculated, blue = experimental. Figure B.13. XRPD spectra of 16 ; red = calculated, blue = experimental. 510152025303540 0 200 400 600 800 1000 Experimental Intensity2-theta/0 Calculated510152025303540 0 50 100 150 200 250 300 350 ExperimentalIntensity2-theta/0 Calculated

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289 Appendix B (continued) Figure B.14. XRPD spectra of 17 ; red = calculated, blue = experimental. Figure B.15. XRPD spectra of 18 ; red = calculated, blue = experimental. 510152025303540 0 100 200 300 400 500 ExperimentalIntensity2-theta/0 Calculated510152025303540 0 50 100 150 200 250 ExperimentalIntensity2-theta/0 Calculated

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290 Appendix B (continued) Figure B.16. XRPD spectra of 19 ; red = calculated, blue = experimental. Figure B.16. XRPD spectra of 20 ; red = calculated, blue = experimental. 510152025303540 0 100 200 300 400 500 600 700 800 ExperimentalIntensity2-theta/0 Calculated510152025303540 0 50 100 150 200 250 300 350 400 450 ExperimentalIntensity2-theta/0 Calculated

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291 Appendix B (continued) Figure B.17. XRPD spectra of 21 ; red = calculated, blue = experimental. Figure B.18. XRPD spectra of 22 ; red = calculated, blue = experimental. 510152025303540 0 100 200 300 400 500 600 700 800 900 ExperimentalIntensity2-theta/0 Calculated510152025303540 0 50 100 150 200 250 ExperimentalIntensity2-theta/0 Calculated

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292 Appendix B (continued) Figure B.19. XRPD spectra of 23 ; red = calculated, blue = experimental. Figure B.20. XRPD spectra of 24 ; red = calculated, blue = experimental. 510152025303540 0 200 400 600 800 1000 1200 1400 CalculatedIntensity2-theta/0 Experimental510152025303540 0 50 100 150 200 250 Experimental Intensity2-theta/0 Calculated

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293 Appendix B (continued) Figure B.21. XRPD spectra of 25 ; red = calculated, blue = experimental. Figure B.22. XRPD spectra of 26 ; red = calculated, blue = experimental. 510152025303540 0 50 100 150 200 250 300 350 400 CalculatedIntensity2-theta/0 Experimental510152025303540 0 200 400 600 800 1000 1200 1400 Experimental Intensity2-theta/0 Calculated

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294 Appendix B (continued) Figure B.23. XRPD spectra of 27 ; red = calculated, blue = experimental Figure B.24. XRPD spectra of 28 ; red = calculated, blue = experimental. 510152025303540 0 1000 2000 3000 4000 5000 6000 7000 8000 Calculated Intensity2-theta/0 Experimental510152025303540 0 100 200 300 400 500 600 Intensity2-theta/0 Calculated Experimental

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295 Appendix B (continued) Figure B.25. XRPD spectra of 29 ; red = calculated, blue = experimental. Figure B.26. XRPD spectra of 31 ; red = calculated, blue = experimental. 510152025303540 0 200 400 600 800 1000 1200 1400 1600 1800 CalculatedIntensity2-theta/0 Experimental510152025303540 0 100 200 300 400 500 600 700 CalculatedIntensity2-theta/0 Experimental

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296 Appendix B (continued) Figure B.27. XRPD spectra of 32 ; red = calculated, blue = experimental. Figure B.28. XRPD spectra of 35 ; red = calculated, blue = experimental. 510152025303540 0 50 100 150 200 250 300 Experimental Intensity2-theta/0 Calculated510152025303540 0 200 400 600 800 CalculatedIntensity2-theta/0 Experimental

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297 Appendix B (continued) Figure B.29. XRPD spectra of 36 ; red = calculated, blue = experimental. Figure B.30. XRPD spectra of 37 ; red = calculated, blue = experimental. 510152025303540 0 200 400 600 800 1000 1200 1400 Experimental Calculated Relative Intensity2-theta/0510152025303540 0 50 100 150 200 Calculated Experimental Relative Intensity2-theta/ 0

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298 Appendix B (continued) Figure B.31. XRPD spectra of 38 ; red = calculated, blue = experimental. 510152025303540 0 200 400 600 800 1000 1200 1400 1600 1800 2000 ExperimentalIntensity2-theta/0 Calculated

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About the Author Dorina F. Sava received her B.Sc. de gree in Materials Science and Engineering from Politehnica University of Bucharest, Romania in 2003. She then decided to pursue her doctoral degree in Materials Chemistry at University of South Florida (USF), program started in Spring 2004. Her research interests are relate d to the design and synthesis of functional metal-organic material s, and their relevan ce for gas storage and separation related purposes. As a result of the work conducted in Dr Eddaoudi’s research laboratory at USF, she authored several articles in peer-reviewed journals, and also presented her research findings at local, regional, a nd national ACS meetings. She ha s also been awarded several recognitions for her overall graduate performa nces, amongst which the most recent were the Theodore and Venette Askounes Ashford Doct oral Fellowship in Chemistry in 2008, and, the Alexiou Award in Environmental Chemistry in 2009.


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Quest towards the design and synthesis of functional metal-organic materials
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Dissertation (Ph.D.)--University of South Florida, 2009.
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ABSTRACT: The design of functional materials for specific applications has been an ongoing challenge for scientists aiming to resolve present and future societal needs. A burgeoning interest was awarded to developing methods for the design and synthesis of hybrid materials, which encompass superior functionality via their multi-component system. In this context, Metal-Organic Materials (MOMs) are nominated as a new generation of crystalline solid-state materials, proven to provide attractive features in terms of tunability and versatility in the synthesis process. In strong correlation with their structure, their functions are related to numerous attractive features, with emphasis on gas storage related applications. Throughout the past decade, several design approaches have been systematically developed for the synthesis of MOMs.Their construction from building blocks has facilitated the process of rational design and has set necessary conditions for the assembly of intended networks. Herein, the focus is on utilizing the single-metal-ion based Molecular Building Block (MBB) approach to construct frameworks assembled from predetermined MBBs of the type MNx(CO2)y. These MBBs are derived from multifunctional organic ligands that have at least one N- and O- heterochelate function and which possess the capability to fully saturate the coordination sphere of a single-metal-ion (of 6- or higher coordination number), ensuring rigidity and directionality in the resulting MBBs. Ultimately, the target is on deriving rigid and directional MBBs that can be regarded as Tetrahedral Building Units (TBUs), which in conjunction with appropriate heterofunctional angular ligands are capable to facilitate the construction of Zeolite-like Metal-Organic Frameworks (ZMOFs).ZMOFs represent a unique subset of MOMs, particularly attractive due to their potential for numerous applications, arising from their fully exploitable large and extra-large cavities. The research studies highlighted in this dissertation will probe the validity and versatility of the single-metal-ion-based MBB approach to generate a repertoire of intended MOMs, ZMOFs, as well as novel functional materials constructed from heterochelating bridging ligands. Emphasis will be put on investigating the structure-function relationship in MOMs synthesized via this approach; hydrogen and CO2 sorption studies, ion exchange, guest sensing, encapsulation of molecules, and magnetic measurements will be evaluated.
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