design and synthesis of crystalline and amorphous

Design and Synthesis of Crystalline and Amorphous

Coordination Materials

By

Shuangbing Han

B.S. Taiyuan University of Technology, 1992

M.S. Beijing University of Chemical Technology, 1999

A Dissertation Submitted in Partial Fulfillment of the

Requirements for the Degree of Doctor of Philosophy

in the Department of Chemistry at Brown University

Providence, Rhode Island

May 2009

ii

Copyright © 2009, by

Shuangbing Han

iii

This dissertation by Shuangbing Han is accepted in its present form by

the Department of Chemistry as satisfying the dissertation requirement

for the Degree of Doctor of Philosophy

Date___________ _____________________________

Brian Moulton, Director

Recommended to the Graduate Council by

Date___________ _____________________________

Dwight Sweigart, Reader

Date__________ _____________________________

Shouheng Sun, Reader

Approved by the Graduate Council

Date__________ _____________________________

Sheila Bonde Dean of the Graduate School

iv

Vita

Shuangbing Han was born on May 20, 1970 in Yichen, Linfen, Shanxi Province of

China. She started her undergraduate study in the Department of Chemical Engineering at

Taiyuan University of Technology in 1988. After getting her Bachelor’s degree in

chemical engineering in 1992, she worked in Taiyuan Chemical Industry Group

Company for four years as an assistant engineer. Shuangbing received her M.Sc. in

Materials Science from Beijing University of Chemical Technology in 1999. After

getting her Master’s degree, she worked in Chinese Academy of Medical Sciences &

Peking Union Medical College as research scientist. She has studied in the Ph.D. program

of the Chemistry Department of Brown University under the supervision of Professor

Brian Moulton since August 2003. Her research focused on design and synthesis of

coordination polymers. She is a member of the American Chemical Society.

Publications

1. Han, Shuangbing, Russell Hopson, Brian, S. Luisi, Zhenbo Ma, David Budil,

Stefano gulla', Brian Moultion, “A convergent strategy for the synthesis of

new coordination compounds: covalently linking(or modifying) pre-assembled

Secondary Building Units (SBUs) via organic coupling reaction” Submitted to

Crystal Growth and Design

2. Han, Shuangbing, Brian S. Luisi, Indrek Kulaots, Victor Ch. Kravtsov and

Brian Moulton, “Generating Free Volume in Crystalline Coordination

Polymers: Diagonal Interpenetration” Submitted to ChemCommon.

3. Han, Shuangbing, Brian Moulton, Zaworotko, M. J., “Pillared kagome and

nano-bowl networks” To be submitted to J. Am. Chem. Soc. In preparation

v

4. Han, Shuangbing, Luisi, Brian, Rowland, Kelvin, Jr., Moulton, Brian,

“Amorphous coordination polymers: sol-gels, xerogels and aerogels” Polymer

Preprints, 2007, 48(2) 617

5. Yang, Zhibin, Xu, Haiyan, Han, Shuangbing, Kong, Hua, Peng, Yi, “non-PVC

multi-layer film used for intravenous solution packaging” Faming Zhuanli

Shengqing Gongkai Shuomingshu (2002) CN 1371803 A 20021002, CAN

140:223381 AN 2003:612049.

6. Yuan, Huilin, Han, Shuangbing, Li, Xuming, “Study on the rheological property

of silane-crosslinkable polyethylene” Gongcheng Suliao he Yingyong, 2000, 8,

21-24.

7. Han, Shuangbing, Yuan, Huilin, “Technology for the crosslinking of

polyethylene” Huagong Jinzhan, 1999, 3, 66-64.

vi

Acknowledgments

Firstly, I would sincerely express my appreciations to my advisor, Dr. Brian Moulton,

for his aborative guidance to my research and for all the opportunities he has made

available for my professional growth and development. Dr. Brian Moulton is not only my

mentor but also my friend. I will forever benefit from his guidance, his encouragement,

his patience and his friendship.

I also would like to express my sincerest thanks the chair of chemistry department,

Professor Peter Weber, for everything he did to help me accomplish my research projects.

He is very supportive and responsible. I cannot finish my work here without the supports

from him and the department.

I would like to sincerely thank Russell Hopson for his help on my NMR and ESR

experiments, research projects and writing. He gave me so much help so that I cannot

even count them all. Besides his help on my NMR and ESR experiments, he also gave me

a lot of advice and help on my research projects and my thesis writing. I really appreciate

all the valuable time he spent on helping me.

I would like to express the deepest thanks to Amanda Figgins who help me with the

English language on my thesis writing. She is very nice, patient and helpful. Working

with her and Russell Hopson, my English writing skill was improved gradually. This is a

very valuable experience for me.

Many thanks to Professor William Risen for his valuable suggestions in my RP and

my TA job, to Professor Dwight Sweigart for his valuable time and suggestions in my

thesis, to Professor Shouheng Sun for his valuable suggestions and time on my RP and

vii

thesis, to Professor Matthew Zimmt for questions on organic synthesis and so many

conversations about the life here, and to Professor Amit Basu for his valuable time and

suggestions on my RP.

Special thanks to Gen Goditt, Lynn Rossi, Ginni McGee, Stacey Calis and Sheila

Quigley for their kind help in everything, to Dr. Tungli Shen for acquiring MS data for

my important compounds, to Eric Friedfeld, John Geleney and David Lans for ordering

and delivering chemicals. Actually a lot of people in the department also helped me

much. I would like to extend my deep appreciation to all of them.

I would also like to express my sincere gratitude to all my colleagues, Zhenbo Ma,

Brian Luisi and Kevin D. Rowland. Particular thanks to Dr. Victor Kravtsov for his

contributions to the crystallography and his friendship.

I would also want to acknowledge my friends at Brown University including

Xiaoliang Wei, Wenjun Tong, Deyu Li, Sa Wang, Lili Ma, Chengjie Xu, Jie Xie, Xin

Lin, Chao Wang, Shang Peng, Yanglong Hou, Xinyuan Liu, Aihui Yan for their kind

helps and discussions about science.

A very special thank you goes to my husband, Yanhu Wei, for his love, concern,

understanding and fully support.

Finally I would like to thank my parents and my sisters for their supports for all these

years.

viii

List of Tables

Table 1.1. Classification of pores---------------------------------------------------------------18

Table 2.1. Porosity and N2 adsorption capacity of 1 and 2----------------------------------52

Table 4.1. EPR parameters of calculated spectrum------------------------------------------106

Appendices

Table 2A.1. Crystallographic Table of 1-------------------------------------------------------56

Table 3A. 1 Crystal data and structure refinement for 3----------------------------------86


Table 4A. 1 Crystal data and structure refinement for SBU1·quinoline---------------130

Table 4A. 2 Crystal data and structure refinement for SBU·2CH3CN-----------------131

Table 4A. 3. Crystal data and structure refinement for SBU2--------------------------132

Table 4A. 4 Crystal data and structure refinement for I---------------------------------133

Table 4A. 5 Crystal data and structure refinement for II--------------------------------134

Table 4A. 6 Crystal data and structure refinement for 7---------------------------------135


ix

List of Figures

Chapter 1

Figure 1.1 Figure 1.1 A schematic representation of some of the simple 1D, 2D and 3D network topologies: (a) Zigzag chain; (b) Helix; (c) Ladder; (d) Brick wall; (e) Herringbone; (f) 2D bilayer; (g) 2D square grid; (h) 2D honeycomb; (i) Octahedral; (j) Cubic diamondoid; (k) Hexagonal diamondoid.-------------------------------------------9

Figure 1.2 Figure 1.2 (a) Formation of square grid (4,4) network by square planar metal nodes and 4,4’-bipyridine in 1:2 ratio;68 (b) Formation of diamondoid network by tetrahedral nodes and 4,4’-bipyridine in 1:2 ratio.---------------------------------10

Figure 1.3 Figure 1.3 Three commonly occurring inorganic SBUs in metal carboxylates: (a) Metal carboxylate paddle-wheel M2(OOC-)4 (M= Cu2+, Zn2+, Ni2+, Fe2+ and Co2+); (b) Octahedral zinc carboxylate Zn4O(OOC-)6; (c) Trigonal prismatic building units Fe3O(COO-)6---------------------------------------------------------------------------12

Figure 1.4 Examples of polytopic carboxylate organic SBUs -----------------------------------12

Figure 1.5 (a) Small rhombihexahedron based on square SBUs and 1,3-BDC;45 (b) Square grid network based on square SBUs and 1,4-BDC;77 (c) Primitive cubic network (MOF-5) based on octahedral SBUs and 1,4-BDC.47 (All the solvents are omitted for clarity)----------------------------------------------------------------------------------13

Figure 1.6 Primitive cubic network [Cu24(L)12(H2O)16(DMSO)8]n constructed by SBBs [Cu24(L)12] (L= 1,3-bis(5-methoxy-1,3-benzene dicarboxylic acid)benzene).-----15

Figure 1.7 A summary of design strategies for coordination polymers ----------------------------16

Figure 1.8 Classification of porous compounds as 1st, 2nd, and 3rd generation.------------------19

Figure 1.9 IUPAC classification of adsorption isotherms.---------------------------------------19

Figure 1.10 New MOFs have displayed impressive increases in their apparent surface areas since the measurement of the first low temperature isotherm for these materials.107-108 The nitrogen sorption isotherms were measured at 77 K and display Type I behaviour, as expected for compounds with uniform micropores.----------------------------------20

Figure 1.11 (a) Schematic representation of a single cell of a primitive cubic network with SBUs shown as cubes and linkers depicted as rods. The yellow sphere represents the large

x

pore defined within the framework; (b) 2-fold interpenetration of the same network reducing the dimensions of the pore. The smaller yellow sphere represents the divided pore.---------------------------------------------------------------------------22

Figure 1.12 (a) Structure of the Bethe lattice with f = 3; (b) Bond percolation at the gel point, pc = 0.5, in a square lattice.--------------------------------------------------------------24

Chapter 2

Figure 2.1 (a) Schematic representation of the contraction or expansion of the doubly interpenetrating (10,3)-b networks on the removal or addition of guest molecules, respectively; (b) Schematic representation of shifting of two-fold interpenetrating α-Po related networks when exchanged dicyanamide(yellow bent rods) with a linear ion N3

-(red rods).----------------------------------------------------------------------39

Figure 2.2 Schematic illustration of three modes of inclined interpenetrating 2D grid networks: (a) parallel/parallel, (b) diagonal/parallel, (c) diagonal/diagonal.-------------------41

Figure 2.3 (a) Crystal structures of IRMOF-10 and its catenane isomer 2-fold parallel interpenetrating cubic networks of IRMOF-9; (b) Crystal structures of IRMOF-16 and its catenane isomer 2-fold parallel interpenetrating cubic networks of IRMOF-15.----------------------------------------------------------------------------41

Figure 2.4 Synthesis of organic ligand H2L1. a. PdCl2(PPh3)2, CuI, THF, reflux, under Argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c. PdCl2(PPh3)2, CuI, I2, THF, room temperature, 24hours; d. (1) LiOH·H2O, THF, room temperature, 3days, (2) 3M HCl.----------------------------------------43

Figure 2.5 Synthesis of organic ligand H2L2. a. PdCl2(PPh3)2, CuI, THF, reflux, under argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c. PdCl2(PPh3)2, CuI, Methyl-4-iodobenzoate, THF, reflux, under argon, 24hours; d. (1) LiOH·H2O, THF, room temperature, 3days, (2) 3MHCl.--------------------------------------------------------------------------------43

Figure 2.6 (a) Crystal structure for usual μ4-oxo tetrazinc chromophore with all Zn atoms in tetrahedral geometry in network A; (b) Crystal structure for μ4-oxo tetrazinc chromophore with one zinc hold octahedral geometry due to two additional DMF molecules coordinated to it in network B; (c) A single cubic cavity in networks A and (d) A single cubic cavity in network.-------------------------------------------------48

Figure 2.7 (a) The parallel interpenetrating networks in 1; (b) The diagonally interpenetrating

xi

networks in 1; (c) The schematic representation of 4-fold mixed parallel/diagonal interpenetration in 1. The purple network parallelly interpenetrates the red network; the green blue network parallelly interpenetrates the deep blue network; and the purple and red networks diagonally interpenetrate the light and deep blue networks -----------------------------------------------------------------------------------------49

Figure 2.8 (a) Space-filled representations of 1 viewed along (001) showing 3 different size microporous 1D channels; (red, oxygen; blue, nitrogen; dark gray, carbon; light blue gray, zinc. ) (b) N2 sorption isotherm of 1 at 77 K (filled cirle, sorption; open cirle, desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po).------------------------------------------------------------------------------------51

Figure 2A.1 Powder X-Ray Diffraction Pattern of as synthesized 1 and chloroform exchanged 1.------------------------------------------------------------------------57


Figure 2A.3 The TGA diagram of as synthesized 1.-----------------------------------------58

Figure 2A.4 The TGA diagram of 1 after solvent was extracted.---------------------------58

Figure 2A.5 The TGA diagram of as synthesized 2------------------------------------------59

Figure 2A.6 The TGA diagram 2 after solvent was extracted.------------------------------59

Chapter 3

Figure 3.1 Space-filling diagram of the crystal structure of (a) one tetragonal 2D grid

layer and (b) one kagomé 2D layer.----------------------------------------------62

Figure 3.2 Schematic representation of the pillared-layer strategy -----------------------------63

Figure 3.3 Synthetic scheme for organic ligand L3-H4. a. PdCl2(PPh3)2, CuI, THF, reflux, under Argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c. PdCl2(PPh3)2, CuI, I2, THF, room temperature, 24hours; d. (1) LiOH·H2O, THF, room temperature, 3days. (2) 3M HCl.---------------------------64

Figure 3.4 Space-filled diagram of 3D pillared-layer structure of 3 viewed along (1,0,0) direction.------------------------------------------------------------------------------68

xii

Figure 3.5 (a) The schematic representation of 2D square grid lattices; (b) Space-filled diagram of the crystal structure of the tetragonal layers viewed along (0,0,1) direction.---69

Figure 3.6 (a) Schematic illustration of square SBU by linking centroids of the benzene rings; (b) How four square SBUs combine to form a bowl-shaped tetragonal nSBUs; (c) Schematic representation of one undulating tetragonal grid layer in 3---------- --69

Figure 3.7 (a) Schematic representations on how two adjacent undulating grid layers are covalently linked face to face by pillars L3; (b)The two cavities in pillared-layered structure of 3.--------------------------------------------------------------------------71

Figure 3.8 N2 sorption isotherm of 3 at 77 K (filled cirle: sorption; open cirle: desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po).--------------------------72

Figure 3.9 The two different sizes of windows in the tetragonal grid sheet, one is represented by yellow spheres and the other one is represented by blue spheres.----------------------72

Figure 3.10 The space-filled crystal structure of pillared kagomé network of 4-------------------75

Figure 3.11 (a) The schematic representation of 2D kagomé lattices; (b) The top view of space-filled diagram of the undulating 2D kagomé layer in 4 (In the green circles are triagonal and hexagonal cavities).----------------------------------------------------75

Figure 3.12 The illustrations of the two possible packing fashions for kagomé 2D lattices: (a) triangle face to face and (b) a triangle to a hexagon packing fashions -------------76

Figure 3.13 (a) The cone shape triangle (metalla[3]calix) and (b) 1,3,5-alternate conformational hexagon(metalla[6]calix).--------------------------------------------------------------77

Figure 3.14 The illustrations of how a triangle in one layer link to a hexagon in the neighboring layer: (a) viewed along (0,0,1) and (b) viewed along (1,0,0)------------------------77

Figure 3.15 (a) The triangle nanoscale nSBUs consisting of three square SBUs (b) Schematic representation of an undulating kagomé layer. (c) Schematic representation of an undulating kagomé layer viewed from top ------------------------------------------78

Figure 3.16 (a) The sphere cavity and (b) the long and narrow cavity in 4.--------------------79

Figure 3.17 N2 sorption isotherm of 4 at 77 K (filled cirle: sorption; open cirle: desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po).--------------------80

xiii

Figure 3.18 Two different sizes of windows in the kagomé 2D sheet, one is represented by yellow spheres and the other one is represented by blue spheres.------------------80

Chapter 4

Figure 4.1 (a) Single crystal X-ray structures of SBU1; (b) SBU1 viewed along axial direction; (c) SBU2. (Atom colors: gray: carbon; pink: copper; oxygen: red; nitrogen: blue; green: zinc)---------------------------------------------------------------------------98

Figure 4.2 1H spectra of methyl propiolate (top), SBU1·quinoline (middle), and 5 (bottom) in DMSO-d6---------------------------------------------------------------------------101

Figure 4.3 (a) 1H DOSY spectrum of 5 in DMSO-d6 and (b) 1H DOSY spectrum of mixture of 5 and free 1,4-regioisomer L in DMSO-d6-------------------------------------------102

Figure 4.4 (a) 1H spectra of methyl propiolate (top), SBU2 (middle), and 6 (bottom); (b) 13C spectrum of 6. -----------------------------------------------------------------------103

Figure 4.5 (a) 1H DOSY spectrum of 2 and (b) 1H DOSY spectrum of 2 in presence of free L-H ----------------------------------------------------------------------------------104

Figure 4.6(a) Crystal X-band spectrum of SBU1 recorded at 160 K (blue) and calculated spectrum (red). Insert: energy level diagram showing Δms = 1 transitions (red) and Δms = 2 transitions (gray) for the two canonical orientations B0||x,y (top) B0||z (bottom).---------------------------------------------------------------------------106

Figure 4.7 X-band ESR spectra of SBU1 and 1 in frozen DMSO at (a) 160K and (b) 200K. (red: SBU1; blue: 1) Inset shows simulated EPR spectrum of mononuclear Cu (II) plus dinuclear Cu (II) in a 1:10 ratio.---------------------------------------------------107

Figure 4.8 I: Recrystallized from mixture solution of THF and quinoline; II: recrystallized from methanol solution in presence of DMSO and quinoline (Atom colors: gray: carbon; blue: nitrogen; red: oxygen; gray blue: zinc; yellow: sulfur) ; III: mononuclear zinc complex 6. ------------------------------------------------------------------------109

Figure 4.9 Synthesis of copper coordination polymer gel via click reaction between SBU1 and 1, 3-diethynylbenzene and the picture of gel in an inverted vial.--------------------111

Figure 4.10 (a) A representation of two SBU1 linked by 1,3-diethynybenzene. (b) A model diagram of the 3D cross-linked gel network.---------------------------------------111

xiv

Figure 4.11 Frequency dependent of storage moduli (G’) and loss moduli (G’’) curves of copper coordination gels at two different SBU1 concentrations: 0.005M and 0.01M with the ratio of SBU1 to organic linker=1.--------------------------------------------------113

Figure 4.12 (a) Crystal structure of double zigzag chain in 7; (b) space filling representation of 7 viewed along (1,0,0). (Atom colors: gray-carbon; blue-nitrogen; red-oxygen; orange-Cu)---------------------------------------------------------------------------115

Figure 4.13 (a) Crystal structure of the 1D coordination polymer in 8; (b) Space filling representation of 8 viewed along (0, 0, 1). (Atom colors: gray-carbon; blue-nitrogen; red-oxygen; orange-Cu)---------------------------------------------116

Figure 4A.1 1H spectrum of SBU1 in DMSO-d6----------------------------------------------125

Figure 4A.2 1H spectra of quinoline, pyridine-d5 substituted SBU1 and SBU1 in DMSO-d6.--125

Figure 4A.3 COSY NMR (300.13 Mz ) of SUB1 in DMSO-d6.--------------------------------126

Figure 4A.4 HSQC(400.13 Mz) of SBU1 in DMSO-d6-----------------------------------------126

Figure 4A.5 1H NMR (400 Mz) spectrum of 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3 -triazole (L)-----------------------------------------------------------------------------------127

Figure 4A.6 13C NMR spectrum of 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3-triazole (L) -------------------------------------------------------------------------------------------------127

Figure 4A.7 1H spectra of 5 and 5 plus free 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3 -triazole (L). red: 5, blue: 5 plus free triazole ligand L.--------------------------------------128

Figure 4A.8 HSQC NMR spectra of 6 in DMSO-d6.-------------------------------------------128

Figure 4A.9 HMBC NMR spectrum of 6 in DMSO-d6-----------------------------------------129

Chapter 5

Figure 5.1 The nine uniform faceted polyhedra.----------------------------------------------138

Figure 5.2 The crystal structure of hydroxylated nanoball: (a) stick mode; (b) space-filled mod----------------------------------------------------------------------------------------139

Figure 5.3 (a) The schematic representation of the hydroxylated nanoball; (b) The alkylation of

xv

hydroxylated nanoball.------------------------------------------------------------142

Figure 5.4 The HRTEM image of hydroxylated nanoball; (b) The HRTEM image of alkylated nanoball 9.-------------------------------------------------------------------------143

Figure 5.5 Hydrodynamic size distribution of 9 dispersed in hexane -----------------------144

Figure 5.6 (a) MALDI-MS of 9; (b) MALDI-MS of 10.-----------------------------------144

xvi

Abstract

This dissertation is centered on two areas: (i) rational design and synthesis of robust

porous metal-organic frameworks using well-defined building blocks and (ii) synthesis of

crystalline and amorphous coordination polymers based upon traditional organic

chemistry. For the rational design and synthesis, we demonstrated how to achieve

maximum interpenetration by fine tuning the size of the organic spacer using the

Secondary Building Units (SBUs) approach, and how to avoid interpenetration using

almost the same size of organic spacer via a pillared-layer strategy. For synthesis based

on organic chemistry, we have developed a complementary and alternative

covalent-based synthetic strategy for the synthesis of new coordination compounds in an

effort to incorporate a wider range of compounds in the family of coordination materials.

We synthesized a 4-fold mixed parallel/diagonal interpenetrating cubic metal-organic

framework using octahedral zinc carboxylate Zn4O(OOC-)6 SBUs as nodes and a long

and narrow organic ligand, 1,4-(4-carboxylic-phenyl) butadiyne, as linkers. Despite the

maximum 4-fold interpenetration, it contains large void space and high specific surface

area. We synthesized two pillared-layer metal-organic frameworks using infinite 2D

tetragonal grid lattices and kagomé lattices as Supramolecular Building Blocks (SBBs),

respectively. The interpenetration was forbidden in these two frameworks by judicious

choice of impenetrable 2D SBBs. Both pillared-layered frameworks possess

unprecedented levels of porosity. The pillared-layer architecture paradigm we

demonstrated in this dissertation points to a design strategy for the synthesis of large

xvii

microporous, even mesoporous metal organic frameworks (MOFs).

We modified discrete SBUs, synthesized coordination polymer gels and crystalline

coordination polymers by using common organic coupling reactions including Huisgen 1,

3-dipolar cycloaddition and homo-alkyne coupling reactions. We modified coordination

nanospheres with long hydrocarbon chains by esterification reactions. The new covalent-

based synthetic method can provide a wider range of coordination materials.

xviii

Table of Contents

Index

Title page-------------------------------------------------------------------------------------------i

Copyright------------------------------------------------------------------------------------------ii

Signature page------------------------------------------------------------------------------------iii

Vita-------------------------------------------------------------------------------------------------v

Acknowledgements------------------------------------------------------------------------------vi

List of Tables------------------------------------------------------------------------------------viii

List of Figures------------------------------------------------------------------------------------ix

Abstract-----------------------------------------------------------------------------------------xvii

Table of contents------------------------------------------------------------------------------xviii

Chapter 1. Introduction------------------------------------------------------------------------1

1.1.Supramolecular Chemistry-----------------------------------------------------------1

1.2.Crystal Engineering-------------------------------------------------------------------2

1.3.Crystalline Coordination Polymer--------------------------------------------------4

1.3.1 General Introduction-----------------------------------------------------------4

1.3.2 Synthetic Methods-------------------------------------------------------------5

1.3.3 Supramolecular Isomerism---------------------------------------------------6

1.3.4 Design Strategies--------------------------------------------------------------8

1.3.4.1 Network Based on First Principles

xix

―Node and Spacer Approach---------------------------------------8

1.3.4.2 Reticular Synthesis―A Building Block Approach--------------11

1.3.5 Porosity and Applications---------------------------------------------------17

1.4 Amorphous Coordination Polymers-----------------------------------------------23

1.5 Thesis Overview---------------------------------------------------------------------26

References--------------------------------------------------------------------------------28

Chapter 2. Unprecedented Mixed Parallel and Diagonal Interpenetrating α-Po-Related Coordination Networks with Large Free Volume ------38

2.1 Introduction---------------------------------------------------------------------------38

2.2 Experimental Section----------------------------------------------------------------42

2.2.1 Materials and Synthesis-------------------------------------------------------42

2.2.2 Characterization ---------------------------------------------------------------46

2.3 Results and Discussion--------------------------------------------------------------47

2.4 Conclusion----------------------------------------------------------------------------53

References---------------------------------------------------------------------------------55

Appendixes--------------------------------------------------------------------------------57

Chapter 3. Highly Porous Pillared-Layer Tetragonal Grid and Kagome Networks ----------------------------------------------------------61

3.1 Introduction---------------------------------------------------------------------------61

3.1.1 The Evolution of the “Node and Spacer” Strategy -----------------------61

3.2.1 Infinite 2D Supramolecular Building Blocks -----------------------------62

3.2.1 The “Pillared-Layer” Strategy ----------------------------------------------64


xx

3.2.1 Materials and Synthesis-------------------------------------------------------65

3.2.2 Methods-------------------------------------------------------------------------68


3.3.1 Pillared-Layer Tetragonal Grid Networks ---------------------------------68

3.3.2 Pillared-Layer Kagomé Networks ------------------------------------------74

3.4 Conclusion----------------------------------------------------------------------------82

References---------------------------------------------------------------------------------83

Appendixes--------------------------------------------------------------------------------86

Chapter 4. Engineering Discrete Coordination Units via Click Reactions: a Convergent Strategy for the Synthesis of New Coordination Compounds-----------------------------------------------------------------------89

4.1 Introduction---------------------------------------------------------------------------89


4.2.1 Materials and Synthesis------------------------------------------------------92

4.2.2 Methods------------------------------------------------------------------------96


4.3.1 Click methyl propiolate on SBU1 and SBU2------------------------------98

4.3.2 Syntheses of Coordination Polymer Gels---------------------------------111

4.3.3 Syntheses of 1D coordination polymers via in situ alkyne-alkyne coupling reactions ------------------------------------------115

4.4 Conclusion---------------------------------------------------------------------------118

References--------------------------------------------------------------------------------120

Appendixes-------------------------------------------------------------------------------126

xxi

Chapter 5. Functionalization of Discrete Coordination Nanospheres via Organic Reactions ----------------------------------------------------------138

5.1 Introduction--------------------------------------------------------------------------138

5.2 Experimental Section---------------------------------------------------------------141

5.2.1 Materials and Synthesis------------------------------------------------------141

5.2.2Characterization----------------------------------------------------------------142


5.4 Conclusion----------------------------------------------------------------------------146

References---------------------------------------------------------------------------------147

Chapter 6. Conclusions and Future Prospects-------------------------------------------148

6.1 Introduction---------------------------------------------------------------------------148

6.1.1 Synthesis of Porous Metal-Organic Frameworks by Design -----------148

6.1.2 Synthesis of Coordination Polymers via Organic Coupling Approach-------------------------------------------149

6.2 Future Prospects---------------------------------------------------------------------150

6.2.1 Rational Design and Synthesis of

Amorphous Coordination Polymers----------------------------------------150

6.2.2 Exohedral Functionalization of Nanoscale

Coordination Architectures--------------------------------------------------151

References--------------------------------------------------------------------------------153

xxii

List of Tables

Table 1.1. Classification of pores---------------------------------------------------------------18

Table 2.1. Porosity and N2 adsorption capacity of 1 and 2----------------------------------52

Table 4.1. EPR parameters of calculated spectrum------------------------------------------107

Appendices

Table 2A.1. Crystallographic Table of 1-------------------------------------------------------57



Table 4A. 1 Crystal data and structure refinement for SBU1·quinoline---------------131

Table 4A. 2 Crystal data and structure refinement for SBU·2CH3CN-----------------132

Table 4A. 3. Crystal data and structure refinement for SBU2--------------------------133

Table 4A. 4 Crystal data and structure refinement for I---------------------------------134

Table 4A. 5 Crystal data and structure refinement for II--------------------------------135



xxiii

List of Figures

Chapter 1

Figure 1.1 Figure 1.1 A schematic representation of some of the simple 1D, 2D and 3D network topologies: (a) Zigzag chain; (b) Helix; (c) Ladder; (d) Brick wall; (e) Herringbone; (f) 2D bilayer; (g) 2D square grid; (h) 2D honeycomb; (i) Octahedral; (j) Cubic diamondoid; (k) Hexagonal diamondoid.-------------------------------------------9

Figure 1.2 Figure 1.2 (a) Formation of square grid (4,4) network by square planar metal nodes and 4,4’-bipyridine in 1:2 ratio;68 (b) Formation of diamondoid network by tetrahedral nodes and 4,4’-bipyridine in 1:2 ratio.---------------------------------10

Figure 1.3 Figure 1.3 Three commonly occurring inorganic SBUs in metal carboxylates: (a) Metal carboxylate paddle-wheel M2(OOC-)4 (M= Cu2+, Zn2+, Ni2+, Fe2+ and Co2+); (b) Octahedral zinc carboxylate Zn4O(OOC-)6; (c) Trigonal prismatic building units Fe3O(COO-)6---------------------------------------------------------------------------12

Figure 1.4 Examples of polytopic carboxylate organic SBUs -----------------------------------12

Figure 1.5 (a) Small rhombihexahedron based on square SBUs and 1,3-BDC;45 (b) Square grid network based on square SBUs and 1,4-BDC;77 (c) Primitive cubic network (MOF-5) based on octahedral SBUs and 1,4-BDC.47 (All the solvents are omitted for clarity)----------------------------------------------------------------------------------13

Figure 1.6 Primitive cubic network [Cu24(L)12(H2O)16(DMSO)8]n constructed by SBBs [Cu24(L)12] (L= 1,3-bis(5-methoxy-1,3-benzene dicarboxylic acid)benzene).-----15

Figure 1.7 A summary of design strategies for coordination polymers ----------------------------16

Figure 1.8 Classification of porous compounds as 1st, 2nd, and 3rd generation.------------------19

Figure 1.9 IUPAC classification of adsorption isotherms.---------------------------------------19

xxiv

Figure 1.10 New MOFs have displayed impressive increases in their apparent surface areas since the measurement of the first low temperature isotherm for these materials.107-108 The nitrogen sorption isotherms were measured at 77 K and display Type I behaviour, as expected for compounds with uniform micropores.----------------------------------20

Figure 1.11 (a) Schematic representation of a single cell of a primitive cubic network with SBUs shown as cubes and linkers depicted as rods. The yellow sphere represents the large pore defined within the framework; (b) 2-fold interpenetration of the same network reducing the dimensions of the pore. The smaller yellow sphere represents the divided pore.---------------------------------------------------------------------------22

Figure 1.12 (a) Structure of the Bethe lattice with f = 3; (b) Bond percolation at the gel point, pc = 0.5, in a square lattice.--------------------------------------------------------------24

Chapter 2

Figure 2.1 (a) Schematic representation of the contraction or expansion of the doubly interpenetrating (10,3)-b networks on the removal or addition of guest molecules, respectively; (b) Schematic representation of shifting of two-fold interpenetrating α-Po related networks when exchanged dicyanamide(yellow bent rods) with a linear ion N3

-(red rods).----------------------------------------------------------------------39

Figure 2.2 Schematic illustration of three modes of inclined interpenetrating 2D grid networks: (a) parallel/parallel, (b) diagonal/parallel, (c) diagonal/diagonal.-------------------41

Figure 2.3 (a) Crystal structures of IRMOF-10 and its catenane isomer 2-fold parallel interpenetrating cubic networks of IRMOF-9; (b) Crystal structures of IRMOF-16 and its catenane isomer 2-fold parallel interpenetrating cubic networks of IRMOF-15.----------------------------------------------------------------------------41

Figure 2.4 Synthesis of organic ligand H2L1. a. PdCl2(PPh3)2, CuI, THF, reflux, under Argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c. PdCl2(PPh3)2, CuI, I2, THF, room temperature, 24hours; d. (1) LiOH·H2O, THF, room temperature, 3days, (2) 3M HCl.----------------------------------------43

Figure 2.5 Synthesis of organic ligand H2L2. a. PdCl2(PPh3)2, CuI, THF, reflux, under argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c. PdCl2(PPh3)2, CuI, Methyl-4-iodobenzoate, THF, reflux, under argon, 24hours; d. (1) LiOH·H2O, THF, room temperature, 3days, (2) 3MHCl.--------------------------------------------------------------------------------43

xxv

Figure 2.6 (a) Crystal structure for usual μ4-oxo tetrazinc chromophore with all Zn atoms in tetrahedral geometry in network A; (b) Crystal structure for μ4-oxo tetrazinc chromophore with one zinc hold octahedral geometry due to two additional DMF molecules coordinated to it in network B; (c) A single cubic cavity in networks A and (d) A single cubic cavity in network.-------------------------------------------------48

Figure 2.7 (a) The parallel interpenetrating networks in 1; (b) The diagonally interpenetrating networks in 1; (c) The schematic representation of 4-fold mixed parallel/diagonal interpenetration in 1. The purple network parallelly interpenetrates the red network; the green blue network parallelly interpenetrates the deep blue network; and the purple and red networks diagonally interpenetrate the light and deep blue networks -----------------------------------------------------------------------------------------49

Figure 2.8 (a) Space-filled representations of 1 viewed along (001) showing 3 different size microporous 1D channels; (red, oxygen; blue, nitrogen; dark gray, carbon; light blue gray, zinc. ) (b) N2 sorption isotherm of 1 at 77 K (filled cirle, sorption; open cirle, desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po).------------------------------------------------------------------------------------51

Figure 2.9 (a) N2 sorption isotherm of 2 at 77 K (filled cirle, sorption; open cirle, desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po). (b) The proposed 2-fold parallel interpenetration in 2.------------------------------------------------------52



Figure 2A.3 The TGA diagram of as synthesized 1.------------------------------------------59

Figure 2A.4 The TGA diagram of 1 after solvent was extracted.---------------------------59

Figure 2A.5 The TGA diagram of as synthesized 2-------------------------------------------60

Figure 2A.6 The TGA diagram 2 after solvent was extracted.------------------------------60

Chapter 3

xxvi

Figure 3.1 Space-filling diagram of the crystal structure of (a) one tetragonal 2D grid

layer and (b) one kagomé 2D layer.-----------------------------------------------63

Figure 3.2 Schematic representation of the pillared-layer strategy ------------------------------64

Figure 3.3 Synthetic scheme for organic ligand L3-H4. a. PdCl2(PPh3)2, CuI, THF, reflux, under Argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c. PdCl2(PPh3)2, CuI, I2, THF, room temperature, 24hours; d. (1) LiOH·H2O, THF, room temperature, 3days. (2) 3M HCl.--------------------------65

Figure 3.4 Space-filled diagram of 3D pillared-layer structure of 3 viewed along (1,0,0) direction.------------------------------------------------------------------------------69

Figure 3.5 (a) The schematic representation of 2D square grid lattices; (b) Space-filled diagram of the crystal structure of the tetragonal layers viewed along (0,0,1) direction.---70

Figure 3.6 (a) Schematic illustration of square SBU by linking centroids of the benzene rings; (b) How four square SBUs combine to form a bowl-shaped tetragonal nSBUs; (c) Schematic representation of one undulating tetragonal grid layer in 3-------------70

Figure 3.7 (a) Schematic representations on how two adjacent undulating grid layers are covalently linked face to face by pillars L3; (b)The two cavities in pillared-layered structure of 3.--------------------------------------------------------------------------72

Figure 3.8 N2 sorption isotherm of 3 at 77 K (filled cirle: sorption; open cirle: desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po).--------------------------73

Figure 3.9 The two different sizes of windows in the tetragonal grid sheet, one is represented by yellow spheres and the other one is represented by blue spheres.----------------------73

Figure 3.10 The space-filled crystal structure of pillared kagomé network of 4-------------------76

Figure 3.11 (a) The schematic representation of 2D kagomé lattices; (b) The top view of space-filled diagram of the undulating 2D kagomé layer in 4 (In the green circles are triagonal and hexagonal cavities).----------------------------------------------------76

Figure 3.12 The illustrations of the two possible packing fashions for kagomé 2D lattices: (a) triangle face to face and (b) a triangle to a hexagon packing fashions -------------77

Figure 3.13 (a) The cone shape triangle (metalla[3]calix) and (b) 1,3,5-alternate conformational

xxvii

hexagon(metalla[6]calix).--------------------------------------------------------------78

Figure 3.14 The illustrations of how a triangle in one layer link to a hexagon in the neighboring layer: (a) viewed along (0,0,1) and (b) viewed along (1,0,0)------------------------78

Figure 3.15 (a) The triangle nanoscale nSBUs consisting of three square SBUs (b) Schematic representation of an undulating kagomé layer. (c) Schematic representation of an undulating kagomé layer viewed from top ------------------------------------------79

Figure 3.16 (a) The sphere cavity and (b) the long and narrow cavity in 4.--------------------80

Figure 3.17 N2 sorption isotherm of 4 at 77 K (filled cirle: sorption; open cirle: desorption ). P/Po is the ratio of gas pressure (P) to saturation pressure (Po).--------------------80

Figure 3.18 Two different sizes of windows in the kagomé 2D sheet, one is represented by yellow spheres and the other one is represented by blue spheres.------------------81

Figure 3B.1 TGA of pillared-layer tetragonal grid network 3---------------------------------------88

Chapter 4

Figure 4.1 (a) Single crystal X-ray structures of SBU1; (b) SBU1 viewed along axial direction; (c) SBU2. (Atom colors: gray: carbon; pink: copper; oxygen: red; nitrogen: blue; green: zinc)---------------------------------------------------------------------------99

Figure 4.2 1H spectra of methyl propiolate (top), SBU1·quinoline (middle), and 5 (bottom) in DMSO-d6----------------------------------------------------------------------------102

Figure 4.3 (a) 1H DOSY spectrum of 5 in DMSO-d6 and (b) 1H DOSY spectrum of mixture of 5 and free 1,4-regioisomer L in DMSO-d6-------------------------------------------103

Figure 4.4 (a) 1H spectra of methyl propiolate (top), SBU2 (middle), and 6 (bottom); (b) 13C spectrum of 6. -----------------------------------------------------------------------104

Figure 4.5 (a) 1H DOSY spectrum of 2 and (b) 1H DOSY spectrum of 2 in presence of free L-H ----------------------------------------------------------------------------------105

Figure 4.6(a) Crystal X-band spectrum of SBU1 recorded at 160 K (blue) and calculated spectrum (red). Insert: energy level diagram showing Δms = 1 transitions (red) and Δms = 2 transitions (gray) for the two canonical orientations B0||x,y (top) B0||z (bottom).----------------------------------------------------------------------------107

xxviii

Figure 4.7 X-band ESR spectra of SBU1 and 1 in frozen DMSO at (a) 160K and (b) 200K. (red: SBU1; blue: 1) Inset shows simulated EPR spectrum of mononuclear Cu (II) plus dinuclear Cu (II) in a 1:10 ratio.---------------------------------------------------108

Figure 4.8 I: Recrystallized from mixture solution of THF and quinoline; II: recrystallized from methanol solution in presence of DMSO and quinoline (Atom colors: gray: carbon; blue: nitrogen; red: oxygen; gray blue: zinc; yellow: sulfur) ; III: mononuclear zinc complex 6. ------------------------------------------------------------------------110

Figure 4.9 Synthesis of copper coordination polymer gel via click reaction between SBU1 and 1, 3-diethynylbenzene and the picture of gel in an inverted vial.--------------------112

Figure 4.10 (a) A representation of two SBU1 linked by 1,3-diethynybenzene. (b) A model diagram of the 3D cross-linked gel network.---------------------------------------112

Figure 4.11 Frequency dependent of storage moduli (G’) and loss moduli (G’’) curves of copper coordination gels at two different SBU1 concentrations: 0.005M and 0.01M with the ratio of SBU1 to organic linker=1.--------------------------------------------------114

Figure 4.12 (a) Crystal structure of double zigzag chain in 7; (b) space filling representation of 7 viewed along (1,0,0). (Atom colors: gray-carbon; blue-nitrogen; red-oxygen; orange-Cu)---------------------------------------------------------------------------116

Figure 4.13 (a) Crystal structure of the 1D coordination polymer in 8; (b) Space filling representation of 8 viewed along (0, 0, 1). (Atom colors: gray-carbon; blue-nitrogen; red-oxygen; orange-Cu)---------------------------------------------117

Figure 4A.1 1H spectrum of SBU1 in DMSO-d6----------------------------------------------126

Figure 4A.2 1H spectra of quinoline, pyridine-d5 substituted SBU1 and SBU1 in DMSO-d6.--126

Figure 4A.3 COSY NMR (300.13 Mz ) of SUB1 in DMSO-d6.---------------------------------127

Figure 4A.4 HSQC(400.13 Mz) of SBU1 in DMSO-d6-----------------------------------------127

Figure 4A.5 1H NMR (400 Mz) spectrum of 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3 -triazole (L)------------------------------------------------------------------------------------128

Figure 4A.6 13C NMR spectrum of 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3-triazole (L) --------------------------------------------------------------------------------------------------128

xxix

Figure 4A.7 1H spectra of 5 and 5 plus free 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3 -triazole (L). red: 5, blue: 5 plus free triazole ligand L.---------------------------------------129

Figure 4A.8 HSQC NMR spectra of 6 in DMSO-d6.--------------------------------------------129

Figure 4A.9 HMBC NMR spectrum of 6 in DMSO-d6------------------------------------------130

Chapter 5

Figure 5.1 The nine uniform faceted polyhedra.------------------------------------------------139

Figure 5.2 The crystal structure of hydroxylated nanoball: (a) stick mode; (b) space-filled mod------------------------------------------------------------------------------------------140

Figure 5.3 (a) The schematic representation of the hydroxylated nanoball; (b) The alkylation of hydroxylated nanoball.--------------------------------------------------------------143

Figure 5.4 The HRTEM image of hydroxylated nanoball; (b) The HRTEM image of alkylated nanoball 9.---------------------------------------------------------------------------144

Figure 5.5 Hydrodynamic size distribution of 9 dispersed in hexane -------------------------145

Figure 5.6 (a) MALDI-MS of 9; (b) MALDI-MS of 10.-------------------------------------145

1

Chapter 1

Introduction

1.1 Supramolecular Chemistry

Supramolecular chemistry, defined as “chemistry beyond the molecule” by

Jean-Marie Lehn, aims at constructing highly complex, functional chemical systems from

components held together by intermolecular interactions.1-2 In the past forty years, it has

developed into a highly interdisciplinary science and technology which has spanned from

chemistry to biology, physics, materials science and nanotechnology and benefited all

these fields.3-6 The Nobel Prize in chemistry was awarded to the pioneer of this field,

Donald J. Cram, Jean-Marie Lehn and Charles J. Pedersen, for their development on the

chemical foundation of molecular recognition. Supramolecular synthesis, the

construction of supramolecular architectures, is performed by breaking or making

intermolecular bonds under thermodynamic control. It has provided an alternative and

complementary synthetic strategy to covalent chemistry.7-9 Since intermolecular

interactions, such as metal ion coordination, electrostatic forces, hydrogen bonding, van

der Waals interactions, donor-acceptor interactions, etc. are in general weaker than

covalent bonds, the supramolecular entities are dynamic materials by nature allowing

error-checking and resulting in defect-free products.

The principle of molecular recognition, learned from biological systems,10-12 has

2

significantly advanced our understanding of biomolecular processes in living organisms

and often plays a pivotal role in drug discovery.4 Self-organization, a spontaneous but

information-directed generation of organized functional supramolecular architectures by

self-assembly from their components, has been the fundamental process in the generation

of complex matter.13-16 It provides the access to a generation of well-defined, functional

supramolecular architectures of nanometer dimensions which can not easily be achieved

using covalent bonds.17-19 Supramolecular chemistry is inherently related to another

well-developed field―crystal engineering, and its principle and concepts breed two

important classes of materials: organic solid materials and metal-organic coordination

polymers. When applied to crystalline solids, the paradigm shift leads directly from

supramolecular chemistry to crystal engineering.

1.2 Crystal Engineering

…the understanding of intermolecular interactions in the context of crystal packing

and in the utilisation of such understanding in the design of new solids with desired

physical and chemical properties.20

Gautam R. Desiraju

Crystal engineering, the rational design of functional solids using intermolecular

interactions, has emerged as an intense research area due to its wide application in

synthetic chemistry, materials science and pharmaceuticals.21-22 G. M. J. Schmidt’s work

in 1971 on topochemistry is considered by many as the formal beginnings of crystal

engineering.23 The crystal engineering has experienced rapid growth since then due to the

3

advent of automated diffractometers, powerful and inexpensive computers, advanced

crystallographic technologies, accessible Cambridge Structural Database (CSD) and more

importantly the understanding of intermolecular interactions.24-26 A crystal can actually

be viewed as a supramolecular entity as expressed by Dunitz―the crystal is a

supermolecule par excellene.27 The collective properties of the crystalline solids depend

on the arranged patterns of intermolecular interactions in the crystal lattice as well as the

properties of the individual components. Understanding and controlling intermolecular

interactions is critical to crystal synthesis and prediction. These interactions can be

non-covalent bonds between neutral molecules (hydrogen bonds, van de Waals, etc.),

coordination bonds between metal ions and ligands, as well as covalent bonds. The

strength and directional nature of these interactions allows us to make crystals by design.

The aim of the crystal engineering is to construct crystal structures from neutral or

ionic molecular building blocks. The design is usually based on a blueprint which has

been identified. The first step is to synthesize or identify suitable molecular building

blocks with predisposed geometries and functionalities, then assemble these molecular

building blocks into a desired architecture by engineering the intermolecular interactions

between these building blocks. To fully appreciate the recognition events during the

crystallization, in 1995 Guatam R. Desiraju defined a concept of supramolecular synthon

as “structural units within supermolecules which can be formed and/or assembled by

known or conceivable synthetic operation involving intermolecular interactions” and led

to hydrogen bonds being perhaps the most widely exploited of non-covalent interactions

4

in the context of crystal engineering.28

Polymorphism,29-31 having different crystal forms of the same chemical compound or

substance, is a complex phenomenon that is very significant in pharmaceutical

development.32 It often occurs when the compounds are conformationally flexible and

also contain groups that are able to form strong hydrogen bonds, like –OH, –NH2, –CO2H,

and –CONH2. The study of polymorphism is critical for us to understand the

crystallization mechanisms. According to the definition, all polymorphs can be regarded

as supramolecular isomers (another very important term that we will address later in this

chapter), but not necessarily vice versa.26

Though crystal engineering has its origins in organic chemistry, the ideas have found

an extraordinarily fertile soil in the fields of metal-organic coordination chemistry.33-35 A

main motivation for this field is the design and preparation of zeolite-type nanoporous

structures with voids and channels that can be used for sensing, trapping, and storing

small molecules. Coordination polymers exemplify how crystal engineering has become

a paradigm for the design of new supramolecular structures.

1.3 Crystalline Coordination Polymers

1.3.1 General Introduction

Coordination polymers, also known as metal-organic frameworks (MOFs), are

infinite one-, two-, three dimensional (1D, 2D, or 3D) structures constructed from metal

ions and organic ligands based on coordination bonds.36-42 A coordination bond is

basically a dative covalent bond which is formed when a donor atom on an organic ligand

5

(Lewis base) donates a pair of electrons to a metal ion (Lewis acid).43 It is generally

weaker than conventional covalent bonds, but stronger than non-covalent bonds, which

makes it kinetically stable, but thermodynamically labile.1 The formation of coordination

compounds is in principle a self-assembly process. That is why coordination polymers

can be viewed as supramolecular entities.

Coordination polymers contain two main components, connectors and linkers.

Transition metal ions, usually acting as connectors, offer several advantages over pure

organic assemblies. They provide a range of coordination numbers from 2 to 10 and a set

of coordination geometries including linear, T- or Y-shaped, tetrahedral, square-planar,

square-pyramidal, trigonal-bipyramidal, octahedral, trigonal-prismatic,

pentagonal-bipyramidal and corresponding distorted forms.36,44 Furthermore, the use of

ligand regulation can block unnecessary binding sites on a metal ion. Metal ions also

provide a range of binding strengths (10-30 kcal/mol) and a variety of photochemical,

electrochemical and reactional properties. Polyfunctional organic ligands, acting as

linkers, can offer a variety of binding sites depending on the number of donor atoms.

Particularly rigid organic linkers can provide directions and geometries which allow

certain control during the assembly process.

1.3.2 Synthetic Methods

Since the formation of coordination polymers is a self-assembly process, the

majority of coordination polymers are synthesized in one-step reactions. A variety of

techniques have been developed to synthesize highly crystalline coordination polymers,

6

especially single crystals. These generally included the slow introduction of the

molecular components. Methods included slow evaporation, layering of solution, and

slow diffusion of one component solution into another.45-46 A volatile base such as

pyridine or triethylamine which is used to deprotonate ligands can be added slowly via

vapor diffusion.47 Solvothermal techniques display obvious advantages when we

synthesize robust porous frameworks by using metal carboxylate building units.48-50 In

this technique, all the molecular components and solvent and template molecules are

heated in a sealed vessel, such as a Teflon-lined stainless steel bomb or a microwave vial,

under autogenous pressure. Recently micro-wave and ultrasonic methods were also

reported for synthesizing coordination polymers.51-52

Synthesis plays a key role in realizing new structures and materials. New synthetic

methods sometimes mean a wide range of new functional materials. In this thesis, we

propose a covalent based convergent synthetic strategy in which the pre-assembled

building units are linked by the common organic coupling reactions. The new method can

be applied to the construction of a wider range of coordination compounds from

amorphous to crystalline materials, and from discrete nanostructures to infinite networks.

1.3.3 Supramolecular Isomerism

The term of supramolecular isomerism was first introduced by Zaworotko et al. to

define the existence of more than one type of superstructure for the same molecular

components.37,53 In most cases, supramolecular isomers are the consequences of different

reaction conditions, such as temperature, template or solvent molecules, concentrations,

7

etc.,54-55 However, they may form under very similar or the same reaction conditions.56

Supramolecular isomerism represents the superstructural diversity for a given set of

molecular building blocks and can determine the properties of the crystal by influencing

the crystal structures. Supramolecular isomerism is closely related to the term

polymorphism in crystal engineering.37 They could be synonymous in some

instances,57-58 however when variation of guest or solvent occurs in the networks, it is

inappropriate to replace supramolecular isomerism with polymorphism.59-61

Supramolecular isomerism can be classified into the following categories.37,62 (1)

Frameworks having different topologies based the same molecular components, the same

interactions between the molecular components and the same localized connectivities.

This class of isomerism can be considered as polymorphism.57-58 (2) Frameworks having

different topologies based on the same molecular components, but different interactions

between the molecular components. This class of isomerism can be considered as

structural isomerism. (3) Frameworks having different topologies based on the same

molecular components but with different non-interacting guest molecules. This class of

isomerism can be considered as pseudo-polymorphism. (4) Different crystal structures

arising from the conformational changes in flexible ligands such as

1,2-bis(pyridyl)ethane lead to conformational isomerism. (5) Frameworks with different

manners and degrees of catenane (including interpenetration and interweavement) lead to

catenane isomerism. (6) Chiral frameworks in which at least two enantiomers can be

isolated lead to optical isomerism.

8

A great deal of effort has been focused on controlling supramolecular isomerism. It

is not only useful for understanding the crystal nucleation, growth and supramolecular

synthons from the fundamental point of view, but also provides novel functional

materials from the application point of view. In this thesis, we synthesize two

supramolecular isomers which display completely different porosity and magnetism by

controlling the reaction conditions.

1.3.4 Design Strategies

1.3.4.1 Network Based on First Principles―Node and Spacer Approach

The “node and spacer” approach was first delineated by Wells for characterization of

inorganic compounds in terms of their topology.43,63 He simplified the structures of

minerals by reducing them to a series of points (nodes) of certain geometry (octahedral,

tetrahedral, etc.) that are connected to a fixed number of other points. The resulting

structures can be either discrete (zero-dimensional) polyhedra or infinite (one-, two-, and

three-dimensional) periodic nets. In the early 1990s, Robson extended Wells’ work into

the field of metal-organic coordination networks.64-67 In this context, the “node” is

typically a transition metal and the “spacer” is typically an organic ligand that propagates

the node. Figure 1.1 illustrates some coordination polymer network topologies based

upon the node and spacer modes. The schematic representations of coordination networks

can be regarded as blueprints for constructing networks from a wide variety of transition

metal ions and polytopic organic ligands, and provide access to predictable networks.

9

Figure 1.1 A schematic representation of some of the simple 1D, 2D and 3D network topologies:

(a) Zigzag chain; (b) Helix; (c) Ladder; (d) Brick wall; (e) Herringbone; (f) 2D bilayer; (g) 2D

square grid; (h) 2D honeycomb; (i) Octahedral; (j) Cubic diamondoid; (k) Hexagonal

diamondoid.

Figure 1.2 (a) illustrates a prototypical example of 2D (4,4) square grid coordination

polymer [Ni(4,4’-bipyridine)2(NO3)2]n which was generated by using 4-connected nodes

(Ni2+) and linear bifunctional 4,4-bipy spacers.68 All the metal ions are in octahedral

coordination mode with two opposite sites terminated by nitrate anions. This square grid

network possesses inner cavities of ca. 8 × 8 Å2. Figure 1.2 (b) illustrates a 3D

diamondoid coordination polymer [Cu(4,4’-bipy)2](PF6)] which is generated by

tetrahedral nodes (Cu2+) and linear spacers, 4,4-bipy.69

(a) (b) (c) (d) (e)

(f) (g) (h)

(i) (j) (k)

10

Figure 1.2 (a) Formation of square grid (4,4) network by square planar metal nodes and

4,4’-bipyridine in 1:2 ratio;68 (b) Formation of diamondoid network by tetrahedral nodes and

4,4’-bipyridine in 1:2 ratio.69

Although constructing coordination networks based on the “node and spacer”

principle has been greatly successful at producing various coordination networks, we

should acknowledge that using simple metal ions as nodes to construct robust porous

coordination materials has its inherent limitations. Metal ions usually hold little

directional information which leads to a general lack of control on the overall structures.

Coordination frameworks based on M-N linkages, with a few exceptions, have a

tendency to collapse upon removal of solvent or guest molecules. Reticular synthesis, a

conceptual approach based on the use of secondary building units (SBUs), addresses

N N+

(a)

+ N N

(b)

11

these limitations and provides access to logical design and synthesis of robust porous

networks with predetermined topologies and properties.70-72

1.3.4.2 Reticular Synthesis―A Building Block Approach

Reticular synthesis, defined by Yaghi and his coworkers,70 is the process of

assembling judiciously designed rigid SBUs into predetermined ordered structures

(networks), which are held together by strong bonding. SBU is a concept which was first

used in zeolites to describe the conceptual subunits. In the context of coordination

networks, SBUs are rigid molecular complexes and cluster entities hold together by

strong bonding, such as metal-oxygen-carbon bonds, whose geometry and coordination

mode can be transformed into extended porous networks using polytopic linkers. The

geometry of a SBU is defined by those atoms representing points of extension to other

SBUs.73 Rigid SBUs with a variety of geometries have been identified and used in

metal-organic frameworks. Three examples of SBUs, metal carboxylate paddle wheel

(M2(OOC-)4),74-77 octahedral basic zinc-carboxylate, (Zn4O(OOC-)6)47,78-79 and

oxo-centered trinuclear iron clusters (Fe3O(COO-)6)80-81 which act as square planar,

octahedral and trigonal prismatic vertices, respectively, are illustrated in Figure 1.3.

These inorganic SBUs are generally not introduced directly, but formed in situ under

specific reaction conditions. Linking the inorganic SBUs with specific geometry via

simple organic linkers or rigid organic SBUs (see Figure 1.4), which are usually

pre-synthesized using the considerable sophistication of organic synthetic procedures,

will lead to the formation of predetermined networks.

12

Figure 1.3 Three commonly occurring inorganic SBUs in metal carboxylates: (a) Metal

carboxylate paddle-wheel M2(OOC-)4 (M= Cu2+, Zn2+, Ni2+, Fe2+ and Co2+); (b) Octahedral zinc

carboxylate Zn4O(OOC-)6; (c) Trigonal prismatic building units Fe3O(COO-)6.

Figure 1.4 Examples of polytopic carboxylate organic SBUs

C

C

O OH

OHO

CO OH

COHO

C

C

O OH

OHO

C

C

OHO

HO O

COHO

CHO O

1,4-BDC 2,6-NDC PBDC PDC TPDC

(a)

(b)

(c)

13

Figure 1.5 (a) Small rhombihexahedron based on square SBUs and 1,3-BDC;45 (b) Square grid

network based on square SBUs and 1,4-BDC;77 (c) Primitive cubic network (MOF-5) based on

octahedral SBUs and 1,4-BDC.47 (All the solvents are omitted for clarity)

Square paddle-wheel SBUs linked by different polytopic carboxylate spacers can

lead to various topologies including polyhedra and infinite networks.82 Figure 1.5 (a)

illustrates a discrete small rhombihexahedron [Cu24(bdc)24(MeOH)m(H2O)n] formed by

square SBUs and 1,3-BDC45 and Figure 1.5 (b) shows a decorated square grid

coordination network Zn2(BDC)2(2H2O)·(2DMF) (MOF-2) formed by square

paddle-wheel SBUs and 1,4-BDC.77 Compound Zn4O(BDC)3·(DMF)8·(C6H5Cl) (MOF-5)

showed in Figure 1.5 (c) is a primitive cubic network based on octahedral zinc

(b)

(c)

(a)

14

carboxylate SBUs and 1,4-BDC.47 Indeed, replacement of 1,4-BDC with other length

bi-carboxylate ligands results in a series of IRMOF-n (n=1-16).78

The secondary building units approach can be viewed as an evolutive version of the

“node and spacer” approach where SBUs replacing metal ions act as nodes. The

replacement of an N-connected metal ion node with an SBU which has N vertices is

called augmentation, and the replacement of a short ligand with a longer one to increase

the space between vertices is called expansion.73 Apparently, SBUs introduce several

important features into MOFs including (1) robustness, (2) predictability and

designability, (3) and larger porosity.

Infinite rod-shaped SBUs have been explored to construct rigid porous MOFs.83-86 It

has been demonstrated that rod-shaped SBUs can provide a means to accessing MOFs

without interpenetration due to the rod packing arrangement. Usually rods are aligned in

parallel and organic linkers are closely arranged along the rod direction, generating

organic walls that do not allow catenation. A typical example is infinite Zn-O-C SBUs in

MOF-69.86 Infinite Zn-O-C SBUs were linked by 4,4’-biphenyldicarboxylate (BPDC) or

2,6-naphthalenedicarboxylate (NDC) linkers which closely arrange in the [001] direction

and form an impenetrable wall in MOF-69. Thus the catenation is forbidden in the

structures. When using infinite one-dimensional SBUs, the node-spacer approach evolves

into the rod-linker approach.

More complicated building units, so-called tertiary building units (TBUs), or

supermolecular building blocks (SBBs), which are formed by using SBUs as subunits can

15

be utilized as high level building blocks to build up open MOFs.87-90 The geometry and

connectivity features of metal-organic polyhedra (MOP) make them ideal node

candidates. MOPs used as SBBs to construct hierarchical porous MOFs have been

reported by several research groups. A small rhombihexahedron ([Cu2(bdc)2L2]12), which

is formed by linking 12 square molecular building blocks ([Cu2(bdc)2L2]) via 1,3-BDC

linkers was utilized as an octahedral node to construct primitive cubic nets (Figure 1.6)87

and as an rhombicuboctahedral node to construct a (3,24)-connected MOF having rht-like

topology, respectively.89 An anionic cubohemioctahedron ([M6(bdc)12]12- (M = Ni, Co))

was used as a 12-connected fcu net to generate face-centered cubic networks.88 An

anionic truncated tetrahedron ([(Fe3O)4 (SO4)12(BPDC)6 (py)12]8–) was used as a

tetrahedral node to generate a 4-connected MOF with high-symmetry β-cristobalite (SiO2)

topology.90 The SBBs approach, which constructs highly rigid porous MOFs by using

larger SBBs (about several nanometers), will potentially provide large micropores, even

mesopores. It can build up high connectivity nets (n≥8) which are not easily reached by

the conventional SBUs approach.

Figure 1.6 Primitive cubic network [Cu24(L)12(H2O)16(DMSO)8]n constructed by SBBs

[Cu24(L)12] (L= 1,3-bis(5-methoxy-1,3-benzene dicarboxylic acid)benzene).

16

Figure 1.7 A summary of design strategies for coordination polymers.

Metal

ion n

odes

SB

Us n

odes

SB

Bs n

odes

In

finit

2D

SB

Bs

Node a

nd S

pacer A

pproach

Infi

nit

1D

SB

Us

Rod a

nd S

pacer A

pproach

Incr

easi

ng n

ode

size

, com

plex

ity a

nd d

imen

sion

Pil

lared-

Layer S

trategy

+

17

The “pillared-layer” strategy has been demonstrated to be effective in synthesizing

various porous frameworks, where well-defined 2D layers are connected by pillar

molecules such as pyrazine, 1,4-bipyridine, 1 2-di-(4-pyridyl)ethylene, dabco,

diphosphonate, disulfonate and etc.36,91-92 A more detailed introduction on this strategy

will be given in Chapter 3.

A diagram summary of the design strategies, as shown in Figure 1.7, illustrates the

ongoing evolution of this new field. Three things are clear from this diagram. (1)

Repeating the target frameworks at a larger scale can lead to larger pore sizes which are

impossible to achieve using smaller building blocks. (2) With increasing size, complexity

and dimension of the building blocks, more information can be encoded in the

predesigned subunit structures which are predisposed for forming the target frameworks.

Therefore we can reach a degree of predictability that is not present when using simpler

building blocks. (3) Infinite building blocks can provide an access to rational design of

MOFs without catenation.

1.3.5 Porosity and Applications

Porous coordination polymers (PCPs) have received considerable attention recently

due to their potential applications in gas storage, molecule separation, sensors, and

selective catalysis.93-98 They added a new category to the conventional porous materials.

Zeolite and active carbon-based materials were the two main types of porous materials

before the emergence of PCPs. Zeolites, as microporous materials, have regular channels

18

or cavities of 4-10Å, but a low porosity (the reported maximum BET specific surface

area are ca. 900 m2/g). Active carbon materials have a high porosity, but irregular pore

sizes and a wide pore size distribution. Compared with these two conventional porous

materials, PCPs possess pore regularity, high porosity, high surface area, and

designability. According to IUPAC recommendation, pores are classified as

ultramicropore, micropore, mesopore and macropore (see table 1). The pore sizes of most

PCPs fall into the range of micropore. PCPs were classified into the three categories, 1st,

2nd, and 3rd generation according to Kitagawa’s suggestion (see Figure1.8).36, The pores

in 1st generation PCPs cannot remain after removal of guest molecules due to the

framework collapse. The 2nd generation PCPs retain their frameworks upon solvent

exchange and evacuation leading to permanent porosity. The 3rd generation PCPs exhibit

flexible and dynamic frameworks, which respond to external stimuli, such as light and

guest molecules. The interests in PCPs are mainly focused on 2nd and 3rd generation

compounds.

Table 1: Classification of pores

Pore type Pore size (Å) Ultramicropore <5

Micropore 5-20

Mesopore 20-500

Macropore >500

19

Figure 1.8 Classification of porous compounds as 1st, 2nd, and 3rd generation.36

Figure 1.9 IUPAC classification of adsorption isotherms.

One of the most attractive and promising application of PCPs is gas storage. Over the

past few years, much attention and efforts have been paid to enhance the gas uptake,

especially for H2 and CH4.99-103 These two molecules are attractive candidates for the

replacement of fossil fuels. Therefore, an efficient storage technique is critical for their

wide applications. To test the gas uptake capability, the measurement of gas isotherms on

the evacuated samples is indispensable. According to IUPAC classifications, there are six

type of adsorption isotherms (see Figure 1.9) which represent the adsorption of different

20

types of porous structure. Type I represents the characteristic adsorption of micropores.

Type II, III and VI represent the adsorption of non-pore or macropores and type IV and V

represent for mesopores.

The measurement of N2 or Ar isotherm at low temperature is usually used to quantify

the pore volumes and apparent surface areas. Various strategies have been developed to

increase the porosity, such as using larger organic ligands and introduction of

coordinatively unsaturated metal centers (UMCs) into porous frameworks.104-106 MOFs

with progressively increasing surface areas were synthesized in a very short period of

time as show in Figure1.10.107-108

Figure 1.10 New MOFs have displayed impressive increases in their apparent surface areas since

the measurement of the first low temperature isotherm for these materials.107-108 The nitrogen

sorption isotherms were measured at 77 K and display Type I behaviour, as expected for

compounds with uniform micropores.

21

The hydrogen adsorption was first studied by Yaghi and Férey’s group on MOF-5

(IRMOF-1)102 and MIL-53109 in 2003, respectively. The hydrogen uptake in MOF-5

reached 1 wt% at room temperature, 20 kPa and 4.5 wt% at 77K, 0.8 kPa. These values

were later adjusted downward due to the adsorption of some impurity gases.110 In 2006,

even higher hydrogen uptake was observed in MIL and IRMOF series materials.

IRMOF-20 showed hydrogen uptake of 6.7 wt% at 77K, between 70 to 80 kPa.111

MIL-101 showed hydrogen uptake of 6.1 wt% at 77K, under 8 MPa.112 These hydrogen

adsorption values are the highest ever reported for porous materials.

Recent studies on the relationship between hydrogen uptake and pore volume and

apparent surface area indicate that smaller pores are more efficient for hydrogen uptake

than large ones and that maximum hydrogen uptake is linearly correlated to the apparent

surface area.103,113 The ideal pore size is 2.8-3.3Å (van der Waals dimension) which is

compatible with the ca. 2.89Å kinetic diameter of H2.107 However, the small pore size and

high surface area generally go in opposite directions. Small pores often lead to reduced

surface area. The key to success is to synthesize PCPs having both an optimum pore size

and a high specific surface area.

Interpenetration is the phenomenon in which two or more infinite networks are

physically entangled in one another and cannot be separated without breaking the

network connections.114-115 One direct result of interpenetration is a reduction of pore

dimension by subdividing large single pores into several smaller ones, at the same time

maximizing the exposed surface area (see Figure1.11).107 Therefore, it is potentially a

22

strategy to enhance hydrogen (or other molecules) uptake by optimizing the pore size and

surface area. Four-fold interpenetrating networks Zn4O(L1)3

(L1=6,6’-dichloro-2,2’-diethoxy-1,1’-binaphthyl-4,4’-dibenzoate) which possess open

channels of less than 5Å and a BET surface area of 502 m2/g adsorb 1.2 wt% hydrogen at

room temperature and 48 kPa,116 whereas non-interpenetrating MIL-101 which has BET

surface area of 5500 m2/g adsorbs only 0.43 wt% under the same condition.103, 112

Figure 1.11 (a) Schematic representation of a single cell of a primitive cubic network with SBUs

shown as cubes and linkers depicted as rods. The yellow sphere represents the large pore defined

within the framework; (b) 2-fold interpenetration of the same network reducing the dimensions of

the pore. The smaller yellow sphere represents the divided pore.107

Strategies for crystallizing networks with novel porosity have largely focused on

increasing topological metrics and affecting network interpenetration. When large pore

sizes are needed, such as adsorption of large biomolecules and controlled release agents,

strategies avoiding interpenetration are required. When high surface area or high gas

uptake are desired, strategies to optimize the interpenetration are important. In this thesis,

we will address the topic of interpenetration and focus on controlling the topology of

(a) (b)

23

interpenetration and identifying novel modes of interpenetration as targets for thermally

robust porous materials

1.4 Amorphous Coordination Polymers

Despite the huge progress and remarkable success that has been made in crystalline

coordination polymers, our knowledge of amorphous coordination polymers is very

limited. This is probably due to the lack of structural information on amorphous materials

which hinders our ability to truly design and control the structures and properties.

However, advances in characterization techniques indicate that the structures of

amorphous materials are much richer than is commonly acknowledged.117-118 Amorphous

materials can have ‘intermediate-range order’ which is larger than so-called short-range

order, but not enough to constitute long-range order. Understanding and controlling

structural features of intermediate-range order provides possible access to engineering

amorphous materials. Synthesizing amorphous coordination polymer via a building block

approach means that ordered subunits are pre-built into the resulting amorphous

structures, allowing prediction and rational design on the structures.

Recently, coordination polymer gels (CPGs), a form of amorphous coordination

polymers, have attracted immense interest due to their high potential for a wide range of

advanced applications and their high processability.119-123 Usually, the formation of CPGs

is a self-assembly process between organic ligands and metal ion. Incorporating unique

electronic, magnetic, optical, geometrical, or catalytic properties from metal ions into

CPGs will provide gel materials with interesting behaviors and functions.

24

In general, gels are viscoelastic solid-like materials comprised of two main

components. One of them is an elastic 3D cross-linked network and the other one is

liquid, present in substantial quantity, which is entrapped in the network.124-127 The process

leading to the formation of a gel, or in other words, the phase transition from a fluid state

(sol) to a gel state, is called gelation.128 During the gelation process, there exists a well

defined gel point once a critical number of intermolecular reactions has been reached. At

the gel point, an infinite network is just formed and the sample no longer flows like a

liquid. The critical gelation time, gelation temperature and gelation concentration depend

on the particular gelation conditions.

Figure 1.12 (a) Structure of the Bethe lattice with f = 3; (b) Bond percolation at the gel point, pc =

0.5, in a square lattice.133

Two most accepted theories, the branching theory and the percolation theory, are very

important for understanding the gelation process. In the branching theory model, the gelation

is a branching process of multifunctional monomers with specific functionality in the

(a) (b)

25

framework of a mean field theory. 124,129-130 One of the multifunctional molecules must have

at least three functional groups and the other must have at least two functional groups. A

tree-like structure, the Bethe lattice or Cayley tree, can depict the gelation process as shown

in Figure 1.12 (a). For a system with an average number of functional groups f, the critical

extent of reaction pc at which the molecular weight diverges , Mw→∞, was derived as

Percolation theory describes the random growth of molecular clusters on a d-dimensional

lattice.131-132 In random bond percolation, monomers occupy sites on a periodic lattice and

can form bonds, with a certain probability p, with the monomers on its neighbor lattice sites.

The main concept of percolation theory is the existence of a percolation threshold Pc, beyond

which the probability of finding a volume spanning cluster is non-zero. Figure 1.12 (b) shows

the resulting cluster at the gel point for a square lattice.133

The syntheses of CPGs based on metal-organic interactions aimed at different

applications such as catalysis, magnetism, sensor, separation, and reaction medium have

been reported by others,119,121-122,134-135 as well as our group.136 In this thesis, we will

focus on the synthesis of CPGs by covalently connecting well-defined SBUs which is

expected to provide a general approach for synthesizing a variety of CPGs by changing or

fine tuning SBUs.

pc1

f - 1=

26

1.5 Thesis Overview

The research described in the following chapters is centered on two areas: (i)

synthesis of crystalline coordination polymers based on crystal engineering approach and

(ii) synthesis of crystalline and amorphous coordination polymers based on traditional

organic chemistry. For synthesis based on the crystal engineering approach, we

demonstrated how to achieve maximum interpenetration by fine tuning the size of the

organic spacer using the SBUs approach, and how to avoid interpenetration using almost

the same size of organic spacer via a pillared-layer strategy in term of design. For

synthesis based on organic chemistry, we proposed an alternative convergent synthetical

strategy and demonstrated its feasibility.

In Chapter 2, we investigated the effect of geometry parameters of SBUs and ligands

on the interpenetration topology and demonstrated how to achieve maximum

interpenetration, especially diagonal interpenetration, by fine tuning the size of the

organic spacer. In Chapter 3, we demonstrated how to achieve non-interpenetrating

networks using infinite 2D supramolecular building blocks via a pillared-layer strategy.

Although the organic spacer we used in this Chapter has similar size with the one used in

Chapter 2 to achieve the maximum interpenetration, Interpenetration was avoided by

rational design. We shifted the synthetic approach from coordination to polymerization in

Chapter 4 and 5. In Chapter 4, we modified discrete SBUs, synthesized coordination

polymer gels and crystalline coordination polymers by using common organic coupling

reactions including Huisgen 1, 3-dipolar cycloaddition and homo-alkyne coupling

27

reactions. In chapter 5, we modified coordination nanospheres with long hydrocarbon

chains by esterification reactions. The new covalent based synthetic method can provide a

wider range of coordination materials. Finally, we summarize the results of each section

and discuss future directions for those projects in Chapter 6.

28

References

(1) J.-M. Lehn, Supramolecular Chemistry: Concepts and Perspectives, VCH: Weinheim,

1995.

(2) J. L. Atwood, J. E. D. Davies, D. D. MacNicol, F. Vögtle, J.-M. Lehn, Comprehensive

Supramolecular Chemistry, Pergamon: Oxford, 1996.

(3) J.-M. Lehn, Angew. Chem. Int. Ed. 1988, 27, 89-112.

(4) F. Diederich, Angew. Chem. Int. Ed. 2007, 46, 68-69.

(5) J. Steed and J. L. Atwood, Supramolecular Chemistry, Wiley: New York, 2000.

(6) J.-M. Lehn, Proc. Natl. Acad. Sci. U. S. A. 2002, 99, 4763-4768.

(7) Lehn, J. M. Science 2002, 295, 2400-2403.

(8) Braga, D. Chem. Commun. 2003, 2751-2754.

(9) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. Rev. 2000, 100, 853-907

(10) R. Jaenicke, Biochemistry 1991, 30, 3147-3161.

(11) W. Saenger, Principles of Nucleic Acid Structure; Springler-Verlag: New York,

1984.

(12) B. Alberts, D.Bray, J. Lewis, M. Raff , K. Roberts, J. D. Watson, Molecular

Biology of the Cell, 3rd ed. Garland Publishing: London, 1994.

(13) D. S. Lawrence, T. Jiang, M. Levett, Chem. Rev. 1995, 95, 2229-2260.

(14) S. Leinninger, B. Olenyuk, P. J. Stang, Chem. Rev. 2000, 100, 853-908.

(15) S. R. Seidel, P. J. Stang, Acc. Chem.Res. 2002, 35, 972-983.

(16) D. Philp, J. F. Stoddart, Angew.Chem. Int. Ed. 1996, 35, 1154-1196.

29

(17) L. R. MacGIllivray, J. L. Atwood, Angew.Chem. Int. Ed. 1999, 38, 1018-1033.

(18) B. J. Holliday, C. A. Mirkin, Angew.Chem. Int. Ed. 2001, 40, 2202-2243.

(19) G. F. Swiegers, T. J. Malefetse, Chem. Rev. 2000, 100, 3483-3537.

(20) G. R. Desiraju, Crystal Engineering. The Design of Organic Solids, Elsevier:

Amsterdam, 1989.

(21) G. R. Desiraju, Current Science 2001, 81, 1038-1042.

(22) G. R. Desiraju, Angew. Chem. Int. Ed. 2007, 46, 2 – 17.

(23) G. M. J. Schmidt, Pure Appl. Chem. 1971, 27, 647-678.

(24) D. Braga, L. Brammer, N. R. Champness, CrystEngComm 2005, 7, 1–19.

(25) D. Braga, Chem. Commun. 2003, 2751-2754.

(26) K. Biradha, CrystEngComm 2003, 5, 374–384

(27) J. D. Dunitz, Pure Appl. Chem. 1991, 63, 177-185.

(28) G. R. Desiraju, Angew. Chem. Int. Ed. 1995, 34, 2311-2327.

(29) G. R. Desiraju, Crystal Growth & Design, 2008, 3-5.

(30) J. Bernstein, Polymorphism in Molecular Crystals, Clarendon: Oxford, 2002.

(31) J. Bernstein, Chem. Commun. 2005, 5007-5012.

(32) R. Hilfiker, Polymorphism in the Pharmaecutical Industry, Wiley-VCH: Weinheim,

Germany, 2006.

(33) M. J. Zaworotko, K. R. Seddon, Crystal Engineering: the Design and

Application of Functional Solid, Kluwer: Dordrecht, 1999.

(34) M. C. Etter, Acc. Chem. Res. 1990, 23, 120-126.

30

(35) M. J. Zaworotko, Chem. Soc. Rev. 1994, 23, 283-288.

(36) S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed. 2004, 43, 2334-2375.

(37) B. Moulton, M. J. Zaworotko, Chem. Rev. 2001, 101, 1629-1658.

(38) O. M. Yaghi, H. Li, C. Davis, D. Richardson, T. L. Groy, Acc.Chem. Res. 1998, 31,

474-484.

(39) K. Kim, Chem. Soc. Rev. 2002, 31, 96-107.

(40) O. R. Evans, W. Lin, Acc. Chem. Res. 2002, 35, 511-522.

(41) S. Kitagawa, S. Kawata, Coord. Chem. Rev. 2002, 224, 11-34.

(42) S. L. James, Chem. Soc. Rev. 2003, 32, 276-288.

(43) A. F. Wells, Structural Inorganic Chemistry, 5th Edition, Oxford University

Press: Oxford, 1984.

(44) F. A. Cotton, G. Wilkinson, C. A. Murillo, M. Bochmann, Advaced Inorganic

Chemistry, 6th Edition, John Wiley and Sons, Inc: New York, 1999.

(45) Moulton, B.; Lu, J.; Mondol, A.; Zaworokto, M. J. Chem. Comm. 2001 (9), 863-864.

(46) D. L. Long, A. J. Blake, N. R. Champness, C. Wilson, M. Schroder, Chem, Eur. J. 2002,

8, 2026-2033.

(47) H.-L. Li, M. Eddaoudi, M. O’Keeffe, O. M. Yaghi, Nature, 1999, 402, 276-279.

(48) Janiak, C. Angew. Chem. Int. Ed. 1997, 36(13-14), 1431-1434.

(49) Paz, F. A. A.; Rocha, J.; Klinowski, J.; Trindade, T.; Shi, F. N.; Mafra, L. Prog. Solid

State Chem. 2005, 33(2-4), 113-125.

(50) Ferey, G.; Chem. Mater. 2001, 13(10), 3084-3098.

31

(51) Z. Ni, R. I. Masel, J. Am.Chem.Soc. 2006, 128, 12394 -12395.

(52) L.-G. Qiu, Z.-Q. Li, Y. Wu, W. Wang, T. Xu, X. Jiang, Chem.Commun. 2008, 3642–3644.

(53) T. L. Hennigar, D. C. MacQuarrie, P. Losier, R. D. Rogers, M. J. Zaworotko, Angew.

Chem. Int. Ed. 1997, 36, 972-973.

(54) K. N. Power, T. L. Hennigar, M. J. Zaworotko, New J. Chem. 1998, 22, 177-181.

(55) H.Gudbjartson, K. Biradha, K. M. Poirier, M. J. Zaworotko, J. Am. Chem. Soc 1999, 121,

2599-2600.

(56) B. S. Luisi, V. Ch. Kravtsov, B. Moulton, Crystal Growth & Design 2006, 6, 2207-2209.

(57) Z.-G. Li, G.-H. Wang, H.-Q. Jia, N.-H. Hu, J.-W. Xu, CrystEngComm 2007, 9, 882–887.

(58) L. Carlucci, G, Ciani, D. M. Proserpio, A. Sironi, J. Chem. Soc., Chem. Commun. 1994,

2755-2756.

(59) X.-C. Huang, J.-P. Zhang, X.-M. Chen, J. Am. Chem. Soc. 2004, 126, 13218-13219.

(60) A. Gale, M. E. Light, R. Quesada, Chem. Commun. 2005, 5864-5866.

(61) B. Moulton, H. Abourahma, M. W. Bradner, J. Lu, G. J. McManus, M. J. Zaworotko,

Chem. Commun. 2003, 1342-1343.

(62) J. L. Atwood, J. W. Steed, Encyclopedia of Supramolecular Chemistry, CRC Press, 2004.

(63) A. F. Wells, Three-dimensional Nets and Polyhedra; Wiley: New York, 1977.

(64) B. F. Abrahams, B. F. Hoskins, R. Robson, J. Am. Chem. Soc 1991, 113, 3606-3607.

(65) B. F. Abrahams, B. F. Hoskins, J. P. Liu, R. Robson, J. Am. Chem. Soc. 1991, 113,

3045-3051.

(66) S. R. Batten, B. F. Hoskins, R. Robson, Chem. Commun. 1991, 445-447.

32

(67) R. W. Gable, B. F. Hoskins, R. Robson, Chem. Commun. 1990, 762-763.

(68) K. Biradha, A. Mondal, B. Moulton, M. J. Zaworotko, Dalton Trans. 2000, 3837-3844.

(69) L. R. MacGillivray, S. Subramanian, M. J. Zaworotko, J. Chem. Soc., Chem.Commun.

1994, 1325-1326.

(70) O. M. Yaghi, M. O. Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi, J. Kim, Nature,

2003, 423, 705-712.

(71) N. W. Ockwig, O. Delgado-Friedrichs, M. O’Keeffe, O. M. Yaghi, Acc. Chem. Res.

2005, 38, 176-182.

(72) D. J. Tranchemontagne, J. David, Z. Ni, M. O’Keeffe, O. M. Yaghi, Angew. Chem. Int.

Ed. 2008, 47(28), 5136-5147.

(73) M. Eddaoudi, D. B. Moler, H.-L. Li, B.-L. Chen, T. M. Reineke, M. O’Keeffe, O. M.

Yaghi, Acc. Chem. Res. 2001, 34, 319-330.

(74) H. Abourahma, G. J. Bodwell, Lu, J. J. B. Moulton, I. R. Pottie, R. B. Walsh, M. J.

Zaworotko, Crystal Growth & Design, 2003, 3, 513-519.

(75) M. Eddaoudi, J. Kim, M. O’Keeffe, O. M.Yaghi, J. Am. Chem. Soc. 2002 124,

376–377.

(76) J. Lu, A. Mondal, B. Moulton, M. J. Zaworotko, Angew. Chem.Int. Ed. 2001, 40,

2113-2115.

(77) H. Li, M. Eddaoudi, T. L. Groy, O. M. Yaghi, J. Am. Chem. Soc.1998, 120, 8571

(78) M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O’Keeffe, O. M. Yaghi,

Science, 2002, 295, 469-472.

33

(79) H. K. Chae,; D. Y. Siberio-Perez, J. Kim, Y. Go, M. Eddaoudi, A. J. Matzger, M.

O'keeffe, O. M. Yaghi, Nature, 2004, 427, 253-257.

(80) A. C. Sudik, A. P. Côté, O. M. Yaghi, Inorganic Chemistry, 2005, 44, 2998-3000.

(81) A. C. Sudik, A. R. Millward, N. W. Ockwig, A. P. Côté, J. Kim, O. M. Yaghi, J. Am.

Chem. Soc. 2005, 127, 7110-7118.

(82) M. Eddaoudi, J. Kim, D. Vodak, A. Sudik, J. Wachter, M. O’Keeffe, O. M. Yaghi, PNAS,

2002, 99, 4900-4904.

(83) N. L. Rosi, J. Kim, M. Eddaoudi, B. Chen, M. O’Keeffe, O. M. Yaghi, J. Am. Chem. Soc.

2005, 127, 1504-1518.

(84) K. Barthelet, J. Marrot, G. Férey, D. Riou, Chem. Commun. 2004, 520-521.

(85) K. Barthelet, J. Marrot, D. Riou, G. Férey, Angew. Chem. Int. Ed. 2002, 41, 281-284.

(86) N. L. Rosi, M. Eddaoudi, J. Kim, M. O’Keeffe, O. M. Yaghi, Angew. Chem. Int. Ed.

2002, 41, 284-287.

(87) J. J. Perry IV, V. Ch. Kravtsov, G. J. McManus, M. J. Zaworotko, J. Am. Chem. Soc.

2007, 129, 10076-10077.

(88) A. J. Cairns, J. A. Perman, L. Wojtas, V. Ch. Kravtsov, M. H. Alkordi, M. Eddaoudi, M.

J. Zaworotko, J. Am. Chem. Soc. 2008, 130, 1560-1561.

(89) F. Nouar, J. F. Eubank, T. Bousquet, L. Wojtas, M. J. Zaworotko, M. Eddaoudi, J. Am.

Chem. Soc. 2008, 130, 1833-1835.

(90) A. C. Sudik, A. P. Côté, A. G. Wong-Foy, M. O’Keeffe, O. M. Yaghi. Angew. Chem. Int.

Ed. 2006, 45, 2528-2533.

34

(91) S. Kitagawa, R. Matsuda, Coord. Chem. Rev. 2007, 251, 2490-2509.

(92) M. Kondo, T. Okubo, A. Asami, S. Noro, T. Yoshitomi, S. Kitagawa, T. Ishii, H.

Matsuzaka, K. Seki, Angew. Chem. Int. Ed. 1999, 38, 140-143.

(93) D. Sun, S. Ma, Y. Ke, D. J. Collins, H.-C. Zhou, J. Am. Chem. Soc. 2006, 128,

3896-3897.

(94) T. K. Maji, S. Kitagawa, Pure Appl. Chem. 2007, 79(12), 2155-2177.

(95) J. L. C. Rowsell, O. M. Yaghi, J. Am. Chem. Soc. 2006, 128, 1304-1315.

(96) H. Frost, T. Dulren, R. Q. Snurr, J. Phys. Chem. B. 2006, 110, 9565-9570.

(97) J. L.C. Rowsell, E. C. Spencer, J. Eckert, J. A. K. Howard, O. M. Yaghi, Science, 2005,

309, 1350-1354.

(98) A. R. Millward, O. M. Yaghi, J. Am. Chem. Soc. 2005, 127, 17998-17999.

(99) W. Zhou, H. Wu, M. R. Hartman, T. Yildirim, J. Phys. Chem. C 2007, 111,

16131-16137.

(100) S. Bourrelly, P. L. Llewellyn, C. Serre, F. Millange, T. Loiseau, G. Férey, J. Am. Chem.

Soc. 2005, 127, 13519-13521.

(101) P. L. Llewellyn, S. Bourrelly, C. Serre, A. Vimont, M. Daturi, L. Hamon, G. D.

Weireld, J.-S. Chang, D.-Y. Hong, Y. K. Huang, S. H. Jhung, G. Férey, Langmuir 2008,

24, 7245-7250.

(102) N. L. Rosi, J. Eckert, M. Eddaoudi, D. T. Vodak, J. Kim, M. O’Keeffe, O. M. Yaghi,

Science, 2003, 1127-1129.

(103) D. J. Collins, H.-C. Zhou, J. Mater. Chem. 2007, 17, 3154–3160.

35

(104) B. Chen, N. W. Ockwig, A. R. Millward, D. S. Contreras, O. M. Yaghi, Angew. Chem.

Int. Ed. 2005, 44, 4745-4749.

(105) S. Noro, S. Kitagawa, M. Yamashita, T. Wada, Chem. Commun. 2002, 222 – 223.

(106) R. Kitaura, G. Onoyama, H. Sakamoto, R. Matsuda, S. Noro, S. Kitagawa, Angew.

Chem. Int. Ed. 2004, 43, 2684-2687.

(107) J. L. C. Rowsell, O. M. Yaghi, Angew. Chem. Int. Ed. 2005, 44, 4670-4679.

(108) J. L. C. Rowsell, O. M. Yaghi, Microporous and Mesoporous Materials 2004, 73,

3–14.

(109) G. Férey, M. Latroche, C. Serre, F. Millange, T. Loiseau, A. Percheron-Guégan, Chem.

Commun. 2003, 2976-2977.

(110) J. L. C. Rowsell, A. R. Millward, K. S. Park and O. M. Yaghi, J. Am. Chem. Soc. 2004,

126, 5666-5667.

(111) A. G. Wong-Foy, A. J. Matzger, O. M. Yaghi, J. Am. Chem. Soc. 2006, 128,

3494-3495.

(112) M. Latroche, S. Surblé , C. Serre, C. Mellot-Draznieks, P. L. Llewellyn, J.-H. Lee, J.-S.

Chang, S. H. Jhung and G. Férey, Angew. Chem. Int. Ed. 2006, 45, 8227-8231.

(113) M. Hirscher, B. Panella, Scripta Materialia 2007, 56, 809-812.

(114) S. R. Batten, R. Robson, Angew. Chem. Int. Ed. 1998, 37, 1460-1494.

(115) Batten, S. R. CrystEngComm 2001, 18, 1-7.

(116) B. Kesanli, Y. Cui, M. R. Smith, E. W. Bittner, B. C. Bockrath and W. Lin, Angew.

Chem. Int. Ed. 2005, 44, 72-75.

36

(117) T. D. Hufnagel, Nature Materials, 2004, 3, 666-667.

(118) J. D. Martin, S. J. Goettler, N. Fossé, L. Iton, Nature, 2002, 419, 381-383.

(119) F. Fages. Angew. Chem. Int. Ed. 2006, 45, 1680-1682.

(120) O. Roubeau, A. Colin, W. Schmitt, R. Clerac, Angewandte Chemie-International

Edition 2004, 43, 3283-3286.

(121) H. J. Kim, J. H. Lee, M. Lee, Angew. Chem. Int. Ed. 2005, 44, 5810-5814.

(122) B. G. Xing, M. F. Choi, B. Xu, Chem. Eur. J. 2002, 8, 5028-5032.

(123) S. J. Rowan, J. B. Beck, Faraday Discussions 2005, 128, 43-53.

(124) P. J. Flory, J. Am. Chem. Soc. 1941, 63, 3083-3090.

(125) P. J. Flory, Journal of Physical Chemistry 1942, 46, 132-140.

(126) K, D. J. Almdal, S, Hvidt, O. Kramer, Polymer Gels and Networks 1993, 1, 5-17.

(127) N. M. Sangeetha, U. Maitra, Chem. Sov. Rev. 2005, 34, 821-836.

(128) G. M. Kavanagh, S. B. Ross-Murphy, Progress in Polymer Science 1998, 23, 533-562.

(129) W. H. Stockmayer, Journal of Chemcial Physics 1943, 11, 45-55.

(130) W. H. Stockmayer, Journal of Chemcial Physics 1944, 12, 125-131.

(131) D.Stauffer, Introduction to Percolation Theory. Taylor & Francis: London, 1992.

(132) D. Stauffer, A. Coniglio, M. Adam, Advances in Polymer Science 1982, 44, 103-158.

(133) W. Weng, Gel formation of metallo-supramolecular polymers Ph.D Dissertation. Case

Western Reserve University, 2008.

(134) J. M. J. Paulusse, J. M. van Beek, R. P. Sijbesma, J. Am. Chem. Soc. 2007, 129,

2392-2397.

37

(135) A. Y. Y. Tam, K. M. C. Wong, G. X. Wang, V. Wing-Wah, Chem. Commun. 2007, 20,

2028-2030.

(136) B. S. Luisi, K. D. Rowland, B. Moulton, Chem Commun. 2007, 2802-2804.

38

Chapter 2

Unprecedented Mixed Parallel/Diagonal Interpenetrating

Cubic Coordination Networks with Large Free Volume

2.1 Introduction

Crystalline coordination polymers are currently the subject of research aimed at the

design and synthesis of ordered porous networks with a large surface area, permanent

porosity and high thermal stability.1 The occurrence of interpenetrating coordination

networks in which two or more independent infinite networks interpenetrate each other is

becoming increasingly common with the discovery of more coordination networks,

especially when larger organic linkers are used to generate the networks.2 According to

Batten and Robson, entanglement of interpenetrating polymeric networks, although there

is no direct connection between the networks, cannot be separated without requiring the

breaking of network connections.3 When the individual networks are sufficiently open,

interpenetration of two or more networks can occur. That is nature’s way of filling up

space. Interpenetration was initially considered as a drawback to porosity, however, a

number of recent studies identify it as a mixed blessing.2b,4 Coordination polymers

comprised of optimum interpenetrating networks may possess not only permanent

porosity and high thermal stability, but also flexible and dynamic property arising from

the slip and glide motion of independent networks.1c,5 Figure 2.1 shows two examples of

39

dynamic interpenetrating networks. A two-fold interpenetrating (10,3)-b network

reported by Makoto Fujita and his colleague, 5a as shown in Figure 2.1(a), contracts and

expands during the removal or addition of the guest network, respectively. The two-fold

interpenetrating α-polonium networks reported by Susumu Kitagawa and his

colleagues,5b as shown in Figure 2.1b, displayed the glide motion of the two independent

interpenetrating networks due to guest-exchange.

Figure 2.1 (a) Schematic representation of the contraction or expansion of the doubly

interpenetrating (10,3)-b networks on the removal or addition of guest molecules, respectively;

(b) Schematic representation of shifting of two-fold interpenetrating α-Po related networks when

exchanged dicyanamide(yellow bent rods) with a linear ion N3-(red rods).

The flexible and dynamic porous frameworks, which Susumu Kitagawa called

‘third-generation materials’,1c have potential applications in selective sorption, separation,

sensing and actuator. Furthermore, materials with interpenetrating networks are highly

expected to have useful optical, electrical, magnetic and catalytic properties.6

Interpenetration is becoming a basic functionality of micro- or mesoporous materials

which can tune the pore size/shape and overall porous activity through framework

(a) (b)

40

dynamics to achieve selectivity and increased binding of ions and gases. Strategies for

crystallizing networks with novel porosity have largely focused on increasing topological

metrics and affecting network interpenetration.

Characterization of structures with interpenetrating networks requires an

understanding not only of the individual network topologies but also the interpenetrated

network topology. The general classifications and definitions of the topology of

interpenetration have been elaborately described in literatures on coordination

polymers.3,7 Two of the most common kinds of interpenetration are inclined

interpenetration of 2D grid networks and parallel interpenetration of 3D α-polonium

networks.2d,2g,2h,8 Inclined interpenetration in 2D grid crystalline coordination polymers is

known to proceed in a parallel/parallel, parallel/diagonal, and diagonal/diagonal manner.9

As shown in Figure 2.2, in parallel mode, the spacer ligands of one grid pass through the

windows of another grid. In diagonal mode, the nodes of one network lie at the windows

of another network. However, to the best of our present knowledge, interpenetration in

α-Po-related 3D metal-organic crystalline coordination polymers proceeds in only a

purely parallel fashion. Figure 2.3 shows two doubly parallel interpenetrating cubic

networks of IRMOF structures synthesized by Yaghi and his colleagues.2d Obviously,

from the design and synthesis point of view, understanding the factors governing the

ability to generate diagonal interpenetration in 3D coordination polymers is worthy of

pursuit.

41

Figure 2.2 Schematic illustrations of three modes of inclined interpenetrating 2D grid networks:

(a) parallel/parallel, (b) diagonal/parallel, (c) diagonal/diagonal.

Figure 2.3 (a) Crystal structures of IRMOF-10 and its catenane isomer 2-fold parallel

interpenetrating cubic networks of IRMOF-9; (b) Crystal structures of IRMOF-16 and its

catenane isomer 2-fold parallel interpenetrating cubic networks of IRMOF-15.

The maximum number of networks which may interpenetrate for a given crystalline

coordination polymer is a question that has been visited previously by Yaghi and his

coworkers.4a By considering the spatial requirements necessary for an SBU and linker

of given sizes to interpenetrate, it is possible to calculate the maximum degree of

interpenetration and as a consequence estimate the resulting free volume of the cell,

according to Yaghi’s dlnv calculation for ideal cubic systems (d is the diameter of SBU, l

is the length of the linker, n is the number of interpenetrating frameworks, and v is

(c) (b) (a)

(a) (b)

42

percentage of free volume).4a However, this calculation assumes purely parallel

interpenetration.

Herein, we report on the first example of a diagonally interpenetrating 3D

metal-organic crystalline coordination polymer generated by tuning the length and the

diameter of the organic linkers. Despite the maximum 4-fold interpenetration, the final

structure is found to be highly microporous with an N2 Langmuir surface area of 1850

m2/g, as well as thermally robust with a decomposition temperature of 351°C.

2.2 Experimental Section

2.2.1 Materials and Synthesis

Fresh solvents were taken directly from the Solvent Dispensing System. All the

commercially available chemicals were used as received without further purification.

We designed and synthesized bi-acetylene organic ligands 1,4-bis

(4-carboxylphenyl)butydiyne (H2L1) and mono-acetylene organic ligands 1,2

bis(4-carboxylphenyl)ethyne (H2L2) to explore the effect of ligand size on the topology

of interpenetration of expanded MOF-5 structures and the effect of alkyne units in the

organic ligands on the N2 adsorption. Figure 2.4 and Figure 2.5 show the synthetic

schemes for generating H2L1 and H2L2. Solvothermal reactions of H2L1 and H2L2 with

zinc nitrate hexahydrate in DMF afforded single crystal 1 and 2, respectively.

43

Figure 2.4 Synthesis of organic ligand H2L1. a. PdCl2(PPh3)2, CuI, THF, reflux, under Argon,

24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c.

PdCl2(PPh3)2, CuI, I2, THF, room temperature, 24hours; d. (1) LiOH·H2O, THF, room

temperature, 3days, (2) 3M HCl.

Figure 2.5 Synthesis of organic ligand H2L2. a. PdCl2(PPh3)2, CuI, THF, reflux, under argon, 24

hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature, 1hour; c.

PdCl2(PPh3)2, CuI, Methyl-4-iodobenzoate, THF, reflux, under argon, 24hours; d. (1) LiOH·H2O,

THF, room temperature, 3days, (2) 3MHCl.

Methyl-4-ethynyl trimethylsilane benzoate (L1a): Methyl-4-iodobenzoate (5mmol,

1.31g), PdCl2(PPh3)2 (0.15mmol, 105mg), CuI (0.3mmol, 57mg) were added into a

flamed two-neck round flask under Argon. The flask was attached to a Schlenk line, then

evacuated and flushed with Argon three times. Fresh Et3N (9ml), THF (30ml) and

O

MeO

I TMS+

O

MeO

TMS

O

MeO

H

O

MeO

L1a L1b

L2-H2

OMe

OO

HO OH

O

L2a

a b

c

d

O

OMe

I TMS+

O

OMe

TMS

O

OMe

H

O

OMe

O

MeO

O

HO

O

OHH2L1

L1a L1b

L1c

a b

c

d

44

degassed ethyny trimethylsilane (6mmol, 831μL) were added to the flask. The reaction

mixture was evacuated and flushed with Argon twice. The reaction mixture was then

refluxed for 24 hours. The solvent was removed in vacuo, the residue was dissolved in

CH2Cl2 and purified by passing through a silica gel column to get 1a. The yield of 1a is

ca. 96%.

Methyl-4-ethyny benzoate (L1b): To a solution of L1a (4.5mmol,1.0g) in 90 ml THF

was added Tetrabutylammonium fluoride hydrate (TBAF) solution (7.5mmol TBAF in

30ml THF) dropwise with stirring. The reaction mixture was kept stirring at room

temperature for about 1 hour after TBAF addition. The solvent was removed in vacuo

and the residue was dissolved in CH2Cl2 and purified by passing through a silica gel

column to get L1b. The yield of L1b is ca. 90%.

1, 4-Bis(4-carbomethoxyphenyl)butadiyne (L1c): To a solution of L1b (4mmol, 0.64g)

in 40 ml diisopropylamine under Argon were added PdCl2(PPh3)2 (0.1mmol, 70mg), CuI

(0.25mmol, 95mg) and I2(3mmol, 0.76g) while stirring. The reaction mixture was

stirred at room temperature for 24 hours.The solvent was removed in vacuo and the

residue was dissolved in CH2Cl2 and purified by passage through a silica gel column to

get L1c. Yield of L1c is 85%

1,4-(4-carboxylic-phenyl) butadiyne (H2L1): To the solution of LiOH·H2O (16mmol,

0.67g ) in a small amount of water was added L1c (1.57 mmol, 0.5g) in 30ml THF while

stirring. The reaction mixture was stirring for 3 days. 3M HCl was added to adjust the PH

of the reaction mixture to 2 ~ 3 and a white precipitate formed in the solution. H2L1 was

45

obtained by filtration after washing with cool water and hexanes. The yield of L1-H2 is ca.

89%

1,2-Bis(methyl-4-carboxylic-phenyl)ethyne (L2a): Methyl-4-iodobenzoate (5mmol,

1.3g), methyl-4-ethylbenzoate (5mmol, 0.8g), PdCl2(PPh3)2(0.15mmol, 105mg) and CuI

(0.3mmol, 57mg) were added into a flamed two-neck round flask (100ml). The flask was

attached to a Schlenk line, then evacuated and flushed with Argon three times. Fresh

Et3N (9ml), THF (30ml) were added to the flask. The reaction mixture was evacuated and

flushed with Argon twice and then were refluxed for 24 hours. The solvent was removed

in vacuo, the residue was dissolved in CH2Cl2 and purified by passing through a silica gel

column to get L2a. The yield of L2a is ca. 92%

1,2-Bis(4-carboxylic-phenyl)ethyne (H2L2): To the solution of LiOH·H2O (30mmol,

1.26g ) in a little bit of water was added L2a (3.6mmol,1.15g) in 60ml THF while

stirring. The reaction mixtures was stirred for 3 days. 3M HCl was added to adjust the PH

of the reaction mixture to 2 ~ 3 and a white precipitate formed in the solution. H2L2 was

obtained by filtration after washing with cool water and hexanes. The yield of H2L2 is ca.

89%

[Zn4O(L1)3] [Zn4O(L1)3(DMF)2] (DMF)2 (H2O)16 (1): 1, 4-(4-carboxylic-benzene)

butydiyne (0.1mmol, 29mg) and Zn(NO3)2·6H2O (0.2mmol, 60mg) in 10ml fresh DMF

were added into a 23ml Teflon linear bomb. The reaction mixture was slowly heated up

to 100°C and held at this temperature for 48 hours. Upon cooling to down, pale yellow

46

crystal formed, which were collected by filtration, and washed with fresh DMF and

MeOH. The yield was ca. 85%.

[Zn4O(2)3].mDMF.nH2O (2): 1, 4-(4-carboxylpheny)butydiyne (0.1mmol, 29mg) and

Zn(NO3)2·6H2O (0.2mmol, 60mg) in 10ml fresh DMF were added into a 23ml Teflon

linear bomb. The reaction mixture was slowly heated up to 100°C and held at this

temperature for 48 hours. Upon cooling to room temperature, pale yellow crystals

formed, which were collected by filtration, and washed with fresh DMF and MeOH. The

yield was ca. 83%.

2.2.2 Characterization

Single-crystal X-ray diffraction data were collected on a BRUKER SMART-APEX

CCD diffractometer using Mo Kα radiation (λ= 0.71073 Å). The structure was solved by

direct methods and refined by full-matrix least-squares refinement with anisotropic

displacement parameters for all non-hydrogen atoms. The hydrogen atoms were

generated geometrically and included in the refinement with fixed position and thermal

parameters. Powder X-ray diffraction (PXRD) data were recorded on a Bruker AXS D8

diffractometer operated at 1600W power (40 kV, 40 mA) for Cu Kαmean (λ=1.5418Å)

with a step size 0.01 in 2θ at room temperature.

NMR experiments were recorded on either a Bruker DRX-300 with a z-gradient BBI

probe or Bruker DPX-400 with a z-gradient BBO probe operating at 300.13 MHz and

400.13 MHz for 1H observe respectively.

47

Thermal Gravimetric Analysis was performed with a TA instruments Q500 instrument

in air from room temperature to 650℃.

N2 adsorption isotherms were obtained with a Quantachrome Autosorb instrument

between 0 and 1 partial pressure of nitrogen. Samples were outgassed at 70℃ under

vacuum to remove any adsorbed solvent or moisture.

2.3 Results and discussion

The solvothermal reaction of Zn(NO3)2 · 6H2O and 1,4-(4-carboxylic-phenyl)

butydiyne (H2L1) in DMF at 100°C for 2 days afforded pale yellow crystals of 1. The

overall network formula of 1 is {[Zn4O(L1)3] [Zn4O(L1)3(DMF)2] (DMF)2 (H2O)16}

which was determined by single crystal X-ray diffraction. The disordered solvents DMF

and water occupied the cavities and their compositions were not completely solved.

The crystal structure of 1 revealed two types of symmetry independent metal-organic

3D networks A and B with composition [Zn4O(L1)3] and [Zn4O(L1)3(DMF)2],

respectively. The networks A and B slightly differ in their metrics. Network A has usual

μ4-oxo tetrazinc chromophore with all Zn atoms in tetrahedral surrounding (Figure 2.6

(a)),1b but in tetranuclear chromophore of network B one of Zn atoms has octahedral

surrounding due to additionally coordinated two DMF molecules(Fig. 2.6 (b)).2a In both

cases the octahedral carboxylato Zn4O(CO2)6 secondary building units (SBUs) locate at

the vertexes of a 3D octahedral framework and are linked by the exo-ligand L1 in the

48

similar manner, as shown in Fig. 2.6 (c) and (d), forming distorted cubic networks with

cage size of approximately a≈b≈c≈22Å and α≈β≈γ≈84o.

Figure 2.6 (a) Crystal structure for usual μ4-oxo tetrazinc chromophore with all Zn atoms in

tetrahedral geometry in network A; (b) Crystal structure for μ4-oxo tetrazinc chromophore with

one zinc hold octahedral geometry due to two additional DMF molecules coordinated to it in

network B; (c) A single cubic cavity in networks A and (d) A single cubic cavity in network.

1 crystallizes in trigonal space group P3112 and features 4-fold mixed interpenetration

consisting of two sets of two networks in parallel interpenetration undergoing diagonal

interpenetration with each other. For parallelly interpenetrating α-Po-like networks in 1,

the nodes of one network lie along the body diagonals of the cubes in another network

(Fig. 2.7 (a)). For diagonally interpenetrating networks in 1, the nodes of one network lie

along the face diagonals of the cubes in another network (Fig. 2.7 (b)). The 4-fold mixed

parallel/diagonal interpenetration, as shown in Fig. 2.7 (c), is formed by diagonally

(a) (b)

(c) (d)

49

interpenetrating the two sets of two-fold parallel interpenetrating networks, A1∥B1 (A1,

purple; B1, red ) and A2∥B2 (A2, blue; B2, light blue).

Figure 2.7 (a) The parallel interpenetrating networks in 1; (b) The diagonally interpenetrating

networks in 1; (c) The 4-fold mixed parallel/diagonal interpenetration in 1.

(a)

(b)

(c)

1

+

+

1

50

According to Yaghi’s dlnv calculation for ideal cubic systems, the expected maximum

interpenetration for 1 (consider Zn4O(CO2)6 as a sphere SBU, dSBU=10.5Å(van der Waals

dimension), l=15.1Å) in pure parallel fashion is 3 (n≤ 3.7) with about v≈72% free

volume. However, through a combination of parallel and diagonal entanglement 4-fold

interpenetration is achieved in 1. The long and narrow butadiyne bridging L1 leaves the

cubic windows enough space for diagonally interpenetrated networks to propagate past

one another resulting in acetylene-benzene π overlap (carbon-carbon distances of 3.5 Å

and 3.8 Å respectively) in addition to 2 types of edge to face π stacking between benzene

rings with average distances and dihedral angles of 3.34 Å, 62.81°, 3.21 Å and 87.05° as

calculated between the planes of each molecule. The implication of our results is that the

diagonal interpenetration might occur if there is still enough space for at least one more

network to penetrate after the maximally parallel interpenetration is achieved. Another

requirement is that the windows of each cube have to be open enough for the SBUs to

penetrate. Therefore, the shape and size of L1 is a key factor for generating the mixed

parallel and diagonal interpenetration.

Despite undergoing a 4-fold interpenetration, 1 contains a large free volume of 56%

and a high surface area. There are in fact 3 types of microporous 1D channels with

effective diameters of ca. 6.6 Å, 6 Å and 3 Å marked as yellow spheres as shown in

Figure 2.8 (a). Powder X-ray diffraction studies indicated that the frameworks of 1

persist upon guest-exchange or complete guest removal (See Appendix: Figure 2A.1).

The as-synthesized 1 was soaked in fresh chloroform for a week. The chloroform

51

exchanged 1 was outgassed at 70℃ for 12 hours and then the N2 adsorption

measurements was taken. Nitrogen adsorption at 77 K showed a reversible type I

isotherm, characteristic of a microporous material, which yields a Langmuir surface area

of 1850 m2/g and BET surface area of 1296 m2/g (Figure 2.8 (b)). Furthermore, the

individual porous channels are separated by walls with thicknesses of ca. 6 Å to 6.5 Å.

A coordination polymer must demonstrate network stability upon loss of guest if it is to

operate as a functional porous material. Separating channels with thick rigid walls may

prove to be a valuable tool in the design of mechanically and thermally robust

coordination polymers.10 TGA results indicated that 1 shows a high thermal stability with

network decomposition beginning at 351°C (See Appendix C: Figure 2A.3 ). The first

weight loss, of 25.9 % spanning 50°C to150°C, is attributed to solvent removal. The

second weight loss (ca. 22.93%) at 350~500℃ corresponds to the decomposition of the

framework.

Figure 2.8 (a) Space-filled representations of 1 viewed along (001) showing 3 different size

microporous 1D channels; (red, oxygen; blue, nitrogen; dark gray, carbon; light blue gray, zinc. )

Relative Pressure (P/Po)0.0 0.2 0.4 0.6 0.8 1.0 1.2

Vol

ume

(cc/

g)

0

100

200

300

400

500

600(a) (b)

52

(b) N2 sorption isotherm of 1 at 77 K (filled cirle, sorption; open cirle, desorption ). P/Po is the

ratio of gas pressure (P) to saturation pressure (Po).

Figure 2.9 (a) N2 sorption isotherm of 2 at 77 K (filled cirle, sorption; open cirle, desorption ).

P/Po is the ratio of gas pressure (P) to saturation pressure (Po). (b) The proposed 2-fold parallel

interpenetration in 2.

Table 2.1 Porosity and N2 adsorption capacity of 1 and 2

BET surface area (cc/g) Langmuire area (cc/g) Pore Volume

(cc/g)

1 1296 1852 0.7160

2 818 1127 0.464

The solvothermal reaction of Zn(NO3)2 · 6H2O and L2-H2 in DMF at 90°C for 2 days

afforded cubic white crystals of 2. The quality of the crystals was insufficient for single

crystal X-ray structure. Powder X-ray Diffraction studies on 2 proved the stability of 2

(a) (b)

53

upon solvent-exchange and complete guest removal (Appendix B: Figure 2A.2). The 77K

N2 adsorption measurement revealed the reversible type I isotherm, indicating the

permanent micropores in 2 with a Langmuir surface area of 1127 m2/g and BET surface

area of 818 m2/g (Figure 2.9 (a)). The surface area and pore volume of 1 and 2 derived

from the N2 isotherm via DFT analysis, as shown in Table 2.1, suggest that the surface

area and pore volume decrease from 1 to 2. Without the Single Crystal X-ray structure,

we can not tell the exact structure and interpenetration topology in 2. The dlnv

calculation on 2 shows that the expected maximum interpenetration for 2 in pure parallel

fashion is 3 (n≤ 3.04) with about 10% free volume implying almost no adsorption and no

surface area, the N2 adsorption isotherm suggests that most likely 2 contains 2-fold

parallel interpenetration as shown in Figure 2.9 (b).

2.4 Conclusion

We have synthesized 2 alkyne containing coordination polymers 1 and 2 by using a

butadiyne organic ligand H2L1 and ethyne organic ligand H2L2, respectively. 1 possesses

a 4-fold mixed parallel/diagonal interpenetrating network, which contains about 56% free

volume with a N2 Langmuir surface area of 1850 m2/g and BET surface area of 1296

m2/g. This is the first example of diagonal interpenetrating 3D cubic coordination

network. 2 also contains permanent porosity with a N2 Langmuir surface area of 1127

m2/g and BET surface area of 818 m2/g. Our results indicate that interpenetration itself

can become a useful tool in the production of porosity. This research underscores the

54

importance of identifying novel modes of interpenetration as targets for thermally robust

porous materials.

55

References

(1) (a) Chae, H. K.; Siberio-Pérez, D. Y.; Kim, J.; Go, Y. B.; Eddaoudi, M.; Matzger, A. J.; Yaghi,

O. M. Nature, 2004, 427, 523-527. (b) Li, H. L.; Eddaoudi, M.; Yaghi, O. M. Nature 1999,

402, 276-279. (c) Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem. Int. Ed. 2004, 43,

2334-2375. (d) Collins, D. J.; Zhou, H. C. J. Mater. Chem. 2007, 17, 3154-3160. (e) Zhou,

W.; Wu, H.; Hartman, M. R.; Yildirim, T.; J. Phys. Chem. C 2007, 111, 16131-16137.

(2) (a) Kesanli, B.; Cui, Y.; Smith, M. R.; Bittner, E. W.; Bockrath, B. C.; Lin, W. B. Angew.

Chem. Int. Ed. 2005, 44, 72-75. (b) Ma, S. Q.; Sun, D. F.; Ambrogio, M.; Fillinger, J. A.;

Parkin, S.; Zhou, H. C. J. Am. Chem. Soc. 2007, 129, 1858-1859. (c) Rowsell, J. L.; Yaghi, O.

M. J. Am. Chem. Soc. 2006, 128, 1304-1315. (d) Rowsell, J. L.; Yaghi, O. M. Microporous

and Mesoporous Materials 2004, 73, 3-14. (e) Blatov, V. A.; Carlucci, L.; Ciani, G.;

Proserpio, D. M. CrystEngComm 2004, 6(65), 377-395. (f) Baburin, I. A.; Blatov, V. A.;

Carlucci, L.; Ciani, G.; Proserpio, D. M. J. of Solid State Chemistry 2005, 178, 2452-2474. (g)

Abrahams, B. F.; Hoskins, B. F.; Robson, R.; Slizys, D. A. CrystEngComm 2002, 4(79),

478-482. (h) Jensen, P.; Batten, S. B.; Moubaraki, B.; Murray, K. S. J. Chem. Soc., Dalton

Trans. 2002, 3712-3722.

(3) (a) Batten, S. R.; Robson, R. Angew. Chem. Int. Ed. 1998, 37, 1460-1494. (b) Batten, S. R.

CrystEngComm 2001, 18, 1-7.

(4) (a) Reineke, T. M.; Eddaoudi, M.; Moler, D.; Yaghi, O. M. J. Am. Chem. Soc. 2000, 122,

4843-4844. (b) Chen, B.; Eddaoudi, M.; Hyde, S. T.; Yaghi, O. M. Science 2001, 291,

1021-1023. (c) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.; Yaghi, O. M.

56

Acc. Chem. Res. 2001, 34, 319-330.

(5) (a) Biradha, K.; Fujita, Makoto. Angew. Chem. Int. Ed. 2002, 41, 3392-3395. (b) Maji, T. K.;

Matsuda, R.; Kitagawa, S. Nature Materials 2007, 6, 142-148. (c) Kitaura, R.; Seki, K.;

Akiyama, G.; Kitagawa, S. Angew. Chem. Int. Ed. 2003, 42, 428-431. (d) Seki, K. Phys.

Chem. Chem. Phys. 2002, 4, 1968-1971. (d) Halder, G. J.; Kepert, C. J.; Moubaraki, B.;

Murray, K. S.; Cashion, J. D. Science, 2002, 298, 1762– 1765.

(6) (a) Miller, J. S. Adv. Mater. 2001, 13, 525-527. (b) Jensen, P.; Batten, S. R.; Fallon, G. D.;

Hockless, D. C. R.; Moubaraki, B.; Murray, K. S.; Robson, R. Journal of Solid State

Chemistry 1999, 145, 387-393.

(7) Carlucci, L.; Ciani, G.; Proserpio, D. M. Coord. Chem. Rev. 2003, 246, 247-289.

(8) Sun B. W.; Gao, S.; Ma, B. Q.; Wang, Z. M. New J. Chem. 2000, 24, 953-954.

(9) (a) Moulton, B.; Zaworotko, M. J. Chem. Rev. 2001, 101, 1629-1658. (b) Carlucci, L.; Ciani,

G.; Proserpio, D. M. New J. Chem. 1998, 22, 1319-1321. (c) Soma, T.; Iwamoto, T. Acta

Crystallogr. 1996, C52, 1200-1203. (d) Biradha, K.; Mondal, A.; Moulton, B.; Zaworotko, M.

J. DaltonTrans. 2000, 21, 3837-3844. (e) Gable, R. W.; Hoskins, B. F.; Robson, R. Chem.

Commun. 1990, 1677-1678.

(10) Moulton, B.; Zaworotko, M. Current Opinion in Solid State and Materials Science 2002, 6,

117-123.

57

Appendix 2A.

Table 2A.1 Crystallographic Table of 1

Identification code p3112_v3 Empirical formula C120 H108 N4 O46 Zn8 Formula weight 2865.06 Temperature 100(2) K Wavelength 0.71073 Ả Crystal system Trigonal Space group P3(1)12 Unit cell dimensions a = 29.536(2) Ả = 90°.　 b = 29.536(2) Ả = 90°.　 c = 41.760(6) Ả = 120°.　

Volume 31550(5) Ả 3

Z 6

Density (calculated) 0.905 Mg/m3

Absorption coefficient 0.949 mm-1

F(000) 8784

Crystal size 0.05 x 0.02 x 0.03 mm3

Theta range for data collection 2.11 to 24.00°. Index ranges -33<=h<=21, -33<=k<=33, -42<=l<=47 Reflections collected 128083 Independent reflections 33043 [R(int) = 0.2061] Completeness to theta = 24.00° 99.9 %

Refinement method Full-matrix least-squares on F2

Data / restraints / parameters 33043 / 1833 / 1318

Goodness-of-fit on F2 1.000

Final R indices [I>2sigma(I)] R1 = 0.0698, wR2 = 0.1640 R indices (all data) R1 = 0.1006, wR2 = 0.1717 Absolute structure parameter 0.008(19)

Largest diff. peak and hole 0.640 and -0.404 e. Ả -3

58

Appendix B. Powder X-Ray Diffraction of 1 and 2

Figure 2A.1 Powder X-Ray Diffraction Pattern of as synthesized 1 and chloroform exchanged 1.

Figure 2A.2 Powder X-Ray Diffraction Pattern of as synthesized 2 and chloroform exchanged 2.

59

Appendix C. Thermal Gravimetric Analysis Figure 2A.3 The TGA diagram of as synthesized 1. Figure 2A.4 The TGA diagram of 1 after solvent was extracted.

60

Figure 2A.5 The TGA diagram of as synthesized 2. Figure 2A.6 The TGA diagram 2 after solvent was extracted.

61

Chapter 3

Highly Porous Pillared-Layer Tetragonal Grid

and Kagome Networks

3.1 Introduction

3.1.1 The Evolution of the “Node and Spacer” Strategy

One fascinating feature of metal-organic frameworks is that a given topology can be

constructed from very different molecular building blocks and reproduced at different

scales.1 The “node and spacer” approach, which was first described by Wells2 for

inorganic network structures and then was introduced to the field of metal-organic

coordination chemistry by Robson3 in 1990, has witnessed with remarkable success.4

Elaborate application of this strategy at different scales and levels has resulted in many of

topology and property interesting coordination compounds. At the first level, metal ions,

which serve as nodes, are connected by simple linear organic molecules, which serve as

spacers, to generate infinite or discrete metal-organic frameworks.5 At the second level,

secondary building units (SBUs) are used as “nodes” replacing metal ions to build up

microporous structures.4c,6 The use of SBUs affords unprecedented breakthroughs in

predicting, designing and synthesizing porous MOFs with specific topology. The scale

shift of the “nodes and spacers” paradigm has proven to be a very useful strategy for

controlling and optimizing the porosity. 4c,6a,7

62

Zaworotko and his colleagues lifted the scale of the “node and spacer” to its third

level by using nanoscale supramolecular building blocks (SBBs) as nodes. In one of his

works,8 a small rhombihexahedron nanoball with a diameter of 2.73nm, comprised of 12

square dicopper tetacaboxylato SBUs, was used as an octahedral node to build up

primitive cubic nets. In another of his works,9 an anionic cubohemioctahedron

[M6(bdc)12]12- (M = Ni, Co) was used as a 12-connected fcu net to generate face-centered

cubic networks. The nanoscale SBBs nodes facilitate the synthesis of MOFs which

cannot be easily accessed through SBUs nodes.

The shift of the “nodes and spacers” paradigm can not only be processed at different

scales but also in different dimensions. Instead of using discrete SBUs, Yaghi and his

colleagues used an infinite 1D Zn-O-C rod SBU to establish large nanoporous nets

without catenation, which indicates a design strategy based on rod packing for the

synthesis of mesoporous MOFs.10

3.1.2 Infinite 2D Supramolecular Building Blocks

It has been illustrated by Zaworotko and his colleagues that a square nSBUs (a

cluster of four dicopper tetracarboxylato “paddlewheel” SBUs) or a triangular nSBUs (a

cluster of three dicopper tetracarboxylato “paddlewheel” SBUs) can be generated if the

molecular squares are linked by 1, 3-benzenedicarboxylate which subtends the 120o

angle.11 These nSBUs can self-assemble to form two supramolecular isomers: tetragonal

2D grid lattices and Kagomé 2D lattices (Figure 3.1). Although these two lattices have

exactly the same chemical composition, they displayed very different porosities and

63

magnetic properties due to their topology differences. The tetragonal 2D sheet is a layer

of bowl-shaped square nSBUs in which each bowl has an outer diameter of 9.4 nm and a

depth of 0.84 nm. This structure possesses paramagnetic properties. The kagomé 2D

sheet contains large hexagonal cavities with effective dimension of 0.91 nm in diameter

and small triangle cavities with an outer diameter of 8.9 nm and a depth of 0.84 nm. This

kagomé lattice possesses ferromagnetic properties due to disruption of the perfect

antiferromagnetic ordering by introducing spin frustration that leads to a canted

arrangement of spins.

Figure 3.1 Space-filling diagram of the crystal structure of (a) one tetragonal 2D

grid layer and (b) one kagomé 2D layer.

In Chapter 2, we described the synthesis of maximally interpenetrated crystalline

coordination polymers by using long and narrow bi-acetylene organic ligands H2L1.

The use of long spacers for constructing frameworks almost unexceptionally results in

catenated structures. Avoiding catenation when we build up large porous networks via

the crystal engineering approach is still a big challenge. The research in this chapter will

(b) (a)

64

demonstrate a new design strategy aimed at non-catenated MOFs with unprecedented

levels of porosity by using these two 2D lattices as SBBs via a pillared-layer approach.

3.1.3 The “Pillared-Layer” Strategy

The “pillared-layer” strategy is one of the most rational methods to construct

three-dimensional networks with large channels, in which well-defined 2D layers are

connected by pillar molecules (Figure 3.2).4b,12 The size and functionality of channels can

be easily controlled by tuning a pillar module.13 This strategy has been demonstrated to

be effective in synthesizing various porous frameworks, where bidentate spacer ligands,

such as 1, 4-bipyridine, dabco, diphosphonate and disulfonate, are generally used as pillar

molecules interconnecting layers through coordination or hydrogen bonds. A reasonable

strategy to generate non-interpenetrating pillared-layer structures is using impenetrable

2D layers or 2D layers whose windows are not open enough for another network to

penetrate. Herein, we cross-linked the tetragonal 2D grid layers and the Kagomé 2D

layers to generate non-interpenetrating pillared-layer microporous MOFs by covalent

linking 1, 3-bdc moieties through the 5-positions.

Figure 3.2 Schematic representation of the pillared-layer strategy

+

Layers Pillars Pillared-layer Structure

65



Fresh solvents were taken directly from the Solvent Dispensing System; Dimethyl

5-iodoisophthalate was purchased from Trans World Chemicals, Inc.; Deuterated

solvents were purchased from Cambridge Isotope Laboratory and

ethynyltrimethylsilane, PdCl2(PPh3)2, CuI were purchased from Sigma-Aldrich Co. All

commercially available chemicals were used as received without further purification.

We designed and synthesized 1, 4-bis(1,3-dicarboxyl phenyl )butydiyne (H2L3) as a

pillar molecule. Figure 3.3 illustrate the synthetic schemes for H4L3.

Figure 3.3 Synthetic scheme for organic ligand L3-H4. a. PdCl2(PPh3)2, CuI, THF, reflux, under

Argon, 24 hours; b. Tetrabutylammonium fluoride hydrate (TBAF), THF, room temperature,

1hour; c. PdCl2(PPh3)2, CuI, I2, THF, room temperature, 24hours; d. (1) LiOH·H2O, THF, room

temperature, 3days. (2) 3M HCl.

H3COOC COOCH3

I

+ TMS

H3COOC COOCH3

TMS

H3COOC COOCH3

H3COOC

H3COOC COOCH3

COOCH3HOOC

HOOC COOH

COOH

a b

c

d

b

L3aL3b

H4L3 L3c

66

Dimethyl-5-ethynyltrimethylsilane-isophthalate (L3a): Dimehtyl-5-iodoisophalate

(10mmol, 3.2g), PdCl2(PPh3)2 (0.3mmol, 210mg), CuI (0.6mmol, 114mg) were added

into a flamed two-neck round flask under Argon. The flask was attached to a Schlenk

line, then evacuated and flushed with Argon three times. Fresh Et3N (18ml), THF (60ml)

and degassed ethyny trimethylsilane (15mmol, 2mL) were added to the flask. The

reaction mixture was evacuated and flushed with Argon twice and then refluxed for 24

hours. The solvent was removed in vacuo and the residue was dissolved in CH2Cl2 and

purified by passing through a silica gel column to get L3a. The yield of L3a is ca. 92%.

Dimethyl-5-ethynylisophthalate (L3b): To a solution of L3a (9mmol, 2.6g) in 90 ml

THF was added Tetrabutylammonium fluoride hydrate (TBAF) solution (15mmol TBAF

in 30ml THF) dropwise with stirring. Stirring was maintained at room temperature for

about 1 hour after TBAF addition. Two raw products were observed by TLC. One is

dimethyl-5-ethynylisophthalate (L3b) and the second one is 1,4-bis-(dimethyl-5-

isophalate)butadiyne (L3c). The solvent was removed in vacuo and the residue was

dissolved in CH2Cl2 and purified by passing through a silica gel column to get L3b and

L3c, respectively. The yield of L3b is ca. 63% and the yield of L3c is ca. 22%.

1,4-bis-(dimethyl-5-isophalate) butadiyne (L3c): To a solution of L3b (5mmol,

950mg) in 100 ml diisopropylamine under Argon were added PdCl2(PPh3)2 (0.1mmol,

70mg), CuI (0.25mmol, 95mg) and I2(3mmol, 0.76g) while stirring. The reaction

mixture was stirred at room temperature under Argon for 24 hours. The solvent was

67

removed in vacuo and the residue was dissolved in CH2Cl2 and purified by passing

through a silica gel column to get L3c. Yield of L3c is ca. 87%

1,4-bis-isophthalic butadiyne (H4L3): To the solution of LiOH·H2O (50mmol, 2.1g ) in

a small amount of water was added L3c (4mmol,1.73g) in 50ml THF while stirring. The

reaction mixture was stirred for 3 days. 3M HCl was added to adjust the PH of the

reaction mixture to 2 ~ 3. The product was extracted with ethyl acetate (3×30mL) and

washed with water three times (3×20mL). The ethyl acetate fractions were rotavapped to

dryness. The pale white raw product was dissolved in CH2Cl2 and purified by passing

through a silica gel column to obtain pure bi-acetylene tetracarboxylic acid ligand H4L3.

The yield of H4L3 is ac. 82%.

Pillared-layer tetragonal grid network (3): 3 was prepared by the solvothermal

reaction of H4L3 (0.02mmol, 7.6mg) and copper nitrate hemipentahydrate (0.08mmol,

19mg) in 6mL mixture solution of DMF, 1,4-dioxane and H2O (v:v:v=2:1:1) at 80℃

under acidic condition for 2 days. Blue-green block crystals were obtained by filtration

after washing with fresh DMF and cool water.

Pillared-layer kagomé network (4): 4 was prepared by the solvothermal reaction of

H4L3 (0.02mmol, 7.6mg) and copper nitrate hemipentahydrate (0.08mmol, 19mg) in 6 ml

mixture solution of DMF/CH3CN/ethylene glycol (v:v:v = 4:1:1) at 80℃ under acidic

condition for 3 to 4 days. Blue-green crystal was obtained by filtration after washing with

fresh DMF and cool methanol.

68

3.2.2 Methods








with a step size 0.01° in 2θ at room temperature. IR spectra were recorded on an ATI

Mattson Infinity series FTIR instrument. NMR experiments were recorded on either a

Bruker DRX-300 with a z-gradient BBI probe or Bruker DPX-400 with a z-gradient BBO

probe operating at 300.13 MHz and 400.13 MHz for 1H observe, respectively.

Thermal Gravimetric Analysis was performed with a TA instruments Q500

instruments in air from room temperature to 650 .℃

N2 adsorption isotherms were obtained with a Quantachrome Autosorb instrument

between 0 and 1 partial pressure of nitrogen. Samples were outgassed at 60℃ under

vacuum to remove any adsorbed solvent or moisture.

3.3 Results and Discussion

3.3.1 Pillared-Layer Tetragonal Grid Networks

The solvothermal reaction of Cu(NO3)2·2.5H2O with H4L3 in a mixture of DMF,

1,4-dioxane and H2O at 80℃ for 2 days afforded prismatic blue-green crystals of 3.

69

Single crystal X-ray data revealed that 3 is a pillared-layer 3D metal-organic framework

in which the undulating 44 tetragonal 2D grid layers are covalently cross-linked by

organic ligand L3 (Figure 3.4). 3 crystallizes in tetragonal space group I4/mmm and

formulates as {[Cu2(L3)(H2O)2] · xDMF ·yH2O}n. The undulating grid sheet, as depicted

in Figure 3.5, can be described as a layer of bowl-shaped tetragonal nSBUs

([Cu2(bdc)2(H2O)2]4 ) self-assembling at the vertexes, with copper dimers sitting on the

lattice points of the tetragonal grid lattices. There is one crystallographically independent

copper ion having a square pyramidal geometry (dCu1-Cu1=2.665(4) Å). The basal plane is

defined by four oxygen atoms of the four μ2 bdc moieties (dCu-O= 1.952(10), 1.952(10),

1.952(9), 1.952(9) Å) and the apical position is occupied by a water molecule (dCu-O=

2.126(16) Å).

Figure 3.4 Space-filled diagram of 3D pillared-layer structure of 3 viewed along (1,0,0)

direction.

Square grid sheet

Mirror plan

70

(a) (b)

Figure 3.5 (a) The schematic representation of 2D square grid lattices; (b) Space-filled diagram

of the crystal structure of the tetragonal layers viewed along (0,0,1) direction.

Figure 3.6 (a) Schematic illustration of square SBU by linking centroids of the benzene rings; (b)

How four square SBUs combine to form a bowl-shaped tetragonal nSBUs; (c) Schematic

representation of one undulating tetragonal grid layer in 3

(c)

(a) (b)

71

If we take the centroids of the benzene rings as the extension points of the square

dicopper tetracarboxylato SBUs (Figure 3.6(a)), the schematic representation of a

tetragonal bowl-shaped nanometer-scale SBU (nSBUs) can be depicted as four square

SBUs combining via 120o angle at the vertices imparted by 1,3-bdc moieties (in Figure

3.6(b)). The tetragonal nSBUs self-assemble with other tetragonal nSBUs to form the

undulating tetragonal 2D grid layer (Figure 3.6(c)).

The undulating tetragonal 2D grid layers are covalently cross-linked face-to-face

through the 5-positions of 1,3-bdc moieties, implying top against top and bottom against

bottom of the bowl-shaped tetragonal nSBUs in adjacent layers (Figure 3.7). One layer is

the mirror image of its adjacent layers and the mirror plane passes through the midpoints

of the organic ligands L3 which link between them, generating an ABAB-type packing in

3. The distance between the adjacent layers is ca. 14.328Å (measured mean plane to

mean plane). The undulating feature of the layers requires angular or bended pillars. The

benzene rings of 1,3-bdc moieties are not perpendicular (incline at an angle of c.a. 69.1o)

to the mean plane of the undulating tetragonal sheet. L3 has to bend itself in order to link

the tetragonal sheets face-to-face, in which two benzene rings in the same L3 bend

toward each other by an angle φ= 138.3o. It is clear from Figure 3.7 that two different

sizes of cavities are generated in the pillared-layer framework of 3. The large cavity

forms by linking the tops of two tetragonal nSBUs through 8 pillars and the small cavity

forms by linking the bottoms of the tetragonal nSBUs through 4 pillars. The effective

72

dimensions of the large and small cavities are c.a. 15.1Å and c.a. 10Å in diameter,

respectively (Figure 3.7(b)). Since the pillars are very narrow bi-acetylene ligands, the

windows of these cavities are very open. We can consider the micropore between the

layers as a continuing phase. These cavities are occupied by disorder DMF and water

molecules. Thermal gravimetric analysis (TGA) performed on a sample of the

as-synthesized 3 showed that network decomposition begins at c.a. 250°C (Appendix B).

The first weight loss of 20.39 % spanning 25°C to160°C is attributed to solvent removal.

(a) (b)

Figure 3.7 (a) Schematic representations on how two adjacent undulating grid layers are

covalently linked face to face by pillars L3; (b)The two cavities in pillared-layered structure of 3.

The guest molecules in crystals of 3 can exchange with methanol. The samples

maintain their structural integrity and crystallinity during the solvent exchange process,

as determined by PXRD. The methanol-exchanged samples of 3 were dried under argon

and then outgassed at 60℃ under ca. 10-5 torr for 24 hours to give the fully desolvated

samples. Nitrogen adsorption at 77 K on the desolvated samples shows a reversible type I

73

isotherm, characteristic of a microporous material, which yields a Langmuir surface area

of 1793 m2/g and BET surface area of 1267 m2/g (Figure 3.8).

Figure 3.8 N2 sorption isotherm of 3 at 77 K (filled circle: sorption; open circle: desorption ).

P/Po is the ratio of gas pressure (P) to saturation pressure (Po).

Figure 3.9 The two different sizes of windows in the tetragonal grid sheet, one is

represented by yellow spheres and the other one is represented by blue spheres.

5Å

3.2Å

74

A closer inspection on the structure of the tetragonal grid sheets helps us to

understand why the pillared-layer structure in 3 can be a prototype for networks that will

not interpenetrate. There are two different windows in the sheet. When measured at their

narrowest opening, the effective dimensions are 3.2Å (depicted as the yellow sphere in

Figure 3.9) and 5Å (depicted as the blue sphere in Figure 3.9), respectively. To penetrate

the sheet, a molecule (spacer) has to be able to penetrate the narrowest part of the

windows. The windows represented by the yellow spheres are actually impenetrable and

each of the windows represented by the blue spheres allows only one L3 or one other

molecule whose diameter is no larger than 5Å to penetrate. Although the tetragonal grid

sheet is penetrable, the number of the spacers that can penetrate the sheet is not enough to

afford another network, thus resulting in a non-interpenetrating pillared-layer network.

The implication here is that longer spacers can be used in the identical synthesis to

produce the same pillared-layer network, but with correspondingly larger pores.

3.3.2 Pillared-Layer Kagomé Networks

The solvothermal reaction of Cu(NO3)2·2.5H2O with H4L3 in a mixture of DMF,

acetonitrile and ethylene glycol at 80 ℃ for 3 days afforded prismatic blue-green crystals

of 4. 4 crystallizes in space group R3m and features a 3D pillared kagomé network, in

which the 2D kagomé layers {[Cu2(bdc)2(H2O)2]3 }n are covalently linked by pillars L3

(Figure 3.10). 4 is a supramolecular isomer of 3. The 2D kagomé layer, as shown in

Figure 3.11, can be described as bowl-shaped triangular nSBUs ([Cu2(bdc)2(H2O)2]3)

self-assembled at the vertexes into a 2D Kagomé lattice. The copper dimers occupy the

75

lattice points and are bridged by 1,3-bdc moieties, which results in trigonal blocks and

hexagonal cavities within the layer. The dimensions of the trigonal blocks are c.a. 12.1Å

and the effective dimensions of the hexagonal cavities are ca. 9Å. There is one

crystallographically independent copper ion having a square pyramidal geometry

(dCu1-Cu1=2.641(4) Å). The basal plane is defined by four oxygen atoms of the four μ2 bdc

moieties (dCu-O= 1.927(10), 1.927(10), 1.915(10), 1.915(10) Å) and the apical position is

occupied by a water molecule (dCu-O= 2.119(14) Å).

According to the feature of the kagomé 2D layers, there are two possible ways to

covalently link the kagomé 2D layer via the 5-positions of the bdc moieties to form 3D

pillared structures. One is analogous to what happens in the tetragonal 2D layer, the

kagomé layers are linked in face-to-face fashion (Figure 3.12(a)), which means that a

triangle is linked to a triangle and a hexagon is linked to a hexagon. It requires the pillar

molecules to be bent to match the undulating feature of the kagomé layers. The second

method is interlinking a triangle and a hexagon (Figure 3.12(b)). In this case, the pillar

L3 does not have to bend to accommodate the geometry requirement. The tensions of the

bent ligands are minimized compared to the first case. It occurred to us that the kagomé

layers are covalently linked in the second fashion.

76

Figure 3.10 The space-filled crystal structure of pillared kagomé network of 4.

(a) (b)

Figure 3.11 (a) The schematic representation of 2D kagomé lattices; (b) The top view of

space-filled diagram of the undulating 2D kagomé layer in 4 (In the green circles are triagonal

and hexagonal cavities).

2D kagomé sheet

77

(a) (b)

Figure 3.12 The illustrations of the two possible packing fashions for kagomé 2D lattices: (a)

triangle face to face and (b) a triangle to a hexagon packing fashions.

The triangle and the hexagon in the kagomé lattices can be regarded as

metalla[3]calix and metalla[6]calix, respectively. The metalla[3]calix adopts a cone

conformation(Figure 3.13(a)), which arranges in the 2D kagomé layer upward and

downward alternately(Figure 3.11(b)). The metalla[6]calix adopts a 1,3,5-alternate

conformation indicating the 5-positions of 1,3-bdc moieties from the edge of a hexagonal

cavity pointing upward and downward alternately (Figure 3.13 (b)). As depicted in Figure

3.14, a downward triangle in the top layer cross-links to a hexagon in the second layer

which is right below the top layer through its three upward 1,3-bdc moieties via

covalently cross-linking the 5-positons of the1,3-bdc moieties, respectively (Figure 3.14).

The three downward 1,3-bdc moieties in the same hexagon cross-link to a upward

triangle in the third layer in the same manner. This is how the undulating 2D kagomé

layers are cross-linked by the pillar L3 to form the pillared-layer kagomé network in 4, in

which the interlayer separation (distance between the mean planes of the adjacent

78

kagomé layers) is ca. 13.78Å. L3 is straight in 4 and its two benzene rings lie in the same

plan.

(a) (b)

Figure 3.13 (a) The cone shape triangle (metalla[3]calix) and (b) 1,3,5-alternate

conformational hexagon(metalla[6]calix).

(a) (b)

Figure 3.14 The illustrations of how a triangle in one layer link to a hexagon in the neighboring

layer: (a) viewed along (0,0,1) and (b) viewed along (1,0,0).

Analogous to 3, we take the centroids of the benzene rings as the extension points of

the square SBU. The schematic representations of an undulating 2D kagomé layer and the

3D pillared-layer kagomé network are depicted in Figure 3.15. From the schematic

diagram, we can see that two different sizes of cavities are generated in 4. One is a large

79

sphere cavity whose effective dimension is c.a.1.2 nm as depicted in Figure 3.16 (a). The

other is a long and narrow cavity (highlighted by purple) with the long dimension of ca.

27.57Å, which passes through three layers.

(a)

(b)

(c)

Figure 3.15 (a) The triangle nanoscale nSBUs consisting of three square SBUs (b) Schematic

representation of an undulating kagomé layer. (c) Schematic representation of the 3D

pillared-layer kagomé network.

z

80

Figure 3.16 (a) The sphere cavity and (b) the long and narrow cavity in 4.

Nitrogen adsorption at 77 K shows a reversible type I isotherm, characteristic of a

microporous material, which yields a Langmuir surface area of 4139 m2/g and BET

surface area of 2909 m2/g.

Figure 3.17 N2 sorption isotherm of 4 at 77 K (filled cirle: sorption; open cirle: desorption ). P/Po

is the ratio of gas pressure (P) to saturation pressure (Po).

(a)

(b)

81

Figure 3.18 Two different sizes of windows in the kagomé 2D sheet, one is represented by

yellow spheres and the other one is represented by blue spheres.

The interpenetration is also forbidden in this pillared-layer kagomé network. The

effective sizes of the two different sized windows, as depicted in Figure 3.18, are ca.

3.6Å and 9Å, respectively. The triangular cavities are too small for any spacers to

penetrate. For aromatic spacers, the maximum number of spacers which can penetrate

one hexagonal cavity is 2. Even for the narrowest spacer L3, less than 4 spacers can

penetrate one hexagonal cavity. Analogous to what happens in the pillared-layer

tetragonal grid network, the number of the spacers that can penetrate the kagomé sheet is

not enough to afford another network, thus resulting in a non-interpenetrating

pillared-layer network. Using tetragonal grid 2D lattices or kagomé 2D lattices as SBBs

to construct pillared-layer networks can be developed to a strategy aimed at large

microporous, even mesoporous frameworks without interpenetration, which was

evidenced by other pillared kagomé networks reported by Lin et al.14 More generally, the

9Å

3.6Å

82

pillared-layer strategy can be used to synthesize non-interpenetrating frameworks by

choosing impenetrable 2D layers.

3.4 Conclusion

We have demonstrated a pillared-layer strategy aimed at non-interpenetrating

metal-organic frameworks with unprecedented levels of porosity as exemplified by 3 and

4. The successful use of infinite 2D SBBs is very important for the formation of the

pillared-layer networks. In this study, tetragonal grid lattices and kagomé lattices are used

as infinite 2D SBBs, which are linked by pillar molecules L3 to form two supramolecular

isomers―pillared-layer tetragonal grid network 3 and kagomé network 4, respectively.

Since the open windows in these two infinite 2D SBBs are not large enough for another

network to pass through them, interpenetration is forbidden in both 3 and 4 in spite of the

use of long and narrow ligands L3. N2 adsorption studies revealed reversible type I

sorption behave for both 3 and 4, characteristic of microporous materials. 3 exhibits a

Langmuir surface area of 1793 m2/g and BET surface area of 1267 m2/g and 4 exhibits a

Langmuir surface area of 4139 m2/g and BET surface area of 2909 m2/g.

The pillared-layer architecture paradigm we demonstrated in this chapter points to a

design strategy for the synthesis of large microporous, even mesoporous MOFs. Simply

exchanging the pillar molecule L3 with a longer ligand will lead to larger sizes of pores

in the pillared-layer networks. Furthermore, we can develop other plane nets as infinite

2D SBBs.

83

References

(1) (a) Kuc, A.; Enyashin, A.; Seifert, G. J. Phys. Chem. B 2007, 111, 8179-8186. (b) Rosi, N.

L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. CrystEngComm 2000, 4(68),

401-404. (c) Düren, T. D.; Yaghi, O. M.; Snurr, R. Q. Langmuir 2004, 20, 2683-2689. (d)

Vagin, S. I.; Ott, A. K.; Rieger, B. Chemie Ingenieur Technik 2007, 79(6) 767-780.

(2) (a) Wells, A. F.; Structural Inorganic Chemistry, 5th ed.; Oxford University Press:

Oxford, 1984. (b) Wells, A. F. Three-dimensional Nets and Polyhedra; Wiley: New York,

1977.

(3) (a) Abrahams, B. F.; Hoskins, B. F.; Robson, R. J. Am. Chem. Soc.1991, 113, 3606-3607.

(b) Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1990, 112 (4), 1546-1554. (c) Robson,

R. J. Chem. Soc., Dalton Trans. 2000, 21, 3735-3744. (d) Batten, S. R.; Hoskins, B. F.;

Robson, R. Chem. Commun. 1991, 445-447.

(4) (a) Moulton, B.; Zaworotko, M. Chem. Rev. 2001, 101, 1629-1658. (b) Kitagawa, S.,

Kitaura, R. & Noro, S. Angew. Chem. Int. Ed. 2004, 43, 2334–2375. (c) 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. (d) Lin, X.; Jia, J.; Hubberstey, P.; Schröder, M.; Champness, N.

R. CrystEngComm 2007, 9, 438–448.

(5) (a) Shimizu, G. K. H.; J. Solid State Chem. 2005, 178, 2519–2526. (b) Hoskins, B. F.;

Robson, R. J. Am. Chem. Soc. 1990, 112, 1546-1554. (c) Moulton, B.; Zaworotko, M. J.

Rational Design of Polar Solids. Crystal Engineering: From Molecules and Crystals to

Materials; Braga, D., Ed.; Kluwer: Dordrecht, 1999; pp 311-330. (d) Caulder, D. L.;

84

Raymond, K. N. Acc. Chem. Res. 1999, 32, 975-982. (e) Seidel, S. R.; Stang, P. J. Acc.

Chem. Res. 2002, 35, 972-983.

(6) (a) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J.

Nature, 2003, 423, 705-714. (b) Ferey, G. J. Solid State Chem. 2000, 152, 37-48. (c)

McManus, G. J.; Wang, Z.; Beauchamp, D. A.; Zaworotko, M. J. Chem. Commun. 2007,

5212-5213. (d) Lu, J.; Mondal, A.; Moulton, B.; Zaworotko, M. J. Angew. Chem. Int. Ed.

2001, 40, 2113-2116.

(7) Wong-Foy, A. G.; Matzger, A. J.; Yaghi, O. M. J. Am. Chem. Soc. 2006, 128, 3494-3495.

(8) Perry IV, J. J.; Kravtsov, V. Ch.; McManus, G. J.; Zaworotko, M. J. J. Am. Chem. Soc.

2007, 129, 10076-10077.

(9) Cairns, A. J.; Perman, J. A.; Wojtas, L.; Kravtsov, V. Ch.; Alkordi, M. H.; Eddaoudi, M.;

Zawworotko, M. J. J. Am. Chem. Soc. 2008, 130, 1560-1561.

(10) Rosi, M. L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Angew. Chem. Int. Ed.

2002, 41,284-287.

(11) Bourne, S. A.; Lu, J.; Mondal, A.; Moulton, B.; Zaworotko, M. J. Angew. Chem. Int. Ed.

2001, 40,2111-2113.

(12) (a) Pillared Layered Structures: Current Trends and Applications, ed. I. V. Mitchell,

Elsevier, London, 1990. (b) Kitagawa, S.; Matsuda, R. Coord. Chem. Rev. 2007, 251

2490–250. (c) Seki, K.; Mori, W. J. Phys. Chem. B. 2002, 106, 1380-1385. (d) Xue, M.;

Zhu, G.; Zhang, Y.; Fang, Q.; Hewitt, I. J.; Qiu, S. Crystal Growth & Design, 2008, 8(2),

427-434. (e) Kitaura, R.; Iwahori, F.; Matsuda, R.; Kitagawa, S.; Kubota, Y.; Takata, M.;

85

Kobayashio, T. C. Inorg. Chem. 2004, 43(21), 6522-6524. (f) Chun, H.; Moon, J. Inorg.

Chem. 2007, 46, 4371-4373. (g) Pan, L.; Finkel,B. S.; Huang,X.; Li,J. Chem. Commun.

2001, 105-106.

(13) (a) Russell, V. A.; Evans, C. C.; Li, W.; Ward, M. D. Science, 1997, 276(25), 575-579.

(b) Li, C-J.; Hu, S.; Li, Wei, Lam, C-K.; Zheng, Y-Z.; Tong, M-L. Eur. J. Inorg. Chem.

2006, 1931–1935. (c) Kondo, M.; Okubo, T.; Asami, A.; Noro, S.; Yoshitomi, T.;

Kitagawa, S.; Ishii, T.; Matsuzaka, H.; Seki, K. Angew. Chem. Int. Ed. 1999, 38, 140-143.

(d) Chun, H.; Dybtsev, D. N.; Kim, H.; Kim, K. Chem. Eur. J. 2005, 11, 3521 – 3529. (e)

Horike, S.; Matsuda, R.; Tanaka, D.; Matsubara, S.; Mizuno, M.; Endo, K.; Kitagawa, S.

Angew. Chem. Int. Ed. 2006, 45, 7226 –7230.

(14) Lin, X.; Jia, J.; Zhao, X.; Thomas, K. M.; Blake, A. J.; Walker, G. S.; Champness, N. R.;

Hubberstey, P.; Schröder, M. Angew. Chem. Int. Ed. 2006, 45, 7358-7364.

86

Appendix A. Crystallographic Tables

Table 3A. 1 Crystal data and structure refinement for 3.

Identification code sh06391 (3)

Empirical formula C20 H20 Cu N4 O4 S2

Formula weight 508.06

Temperature 293(2) K

Wavelength 0.71073 Å

Crystal system Tetragonal

Space group I4/mmm

Unit cell dimensions a = 18.477(13) Å α= 90°.

b = 18.477(13) Å β= 90°.

c = 28.83(2) Å γ = 90°.

Volume 9841(13) Å3

Z 16



F(000) 4176


Theta range for data collection 1.41 to 22.60°.

Index ranges -19<=h<=19, -19<=k<=8, -30<=l<=27

Reflections collected 9555

Independent reflections 1810 [R(int) = 0.2912]

Completeness to theta = 22.60° 96.0 %




Final R indices [I>2sigma(I)] R1 = 0.1629, wR2 = 0.3637

R indices (all data) R1 = 0.2601, wR2 = 0.4122

Largest diff. peak and hole 2.247 and -1.075 e.Å-3

87


Identification code sh06463 (4)

Empirical formula C20 H12 Cu2 O11


Temperature 100(2) K


Crystal system Trigonal

Space group R-3m

Unit cell dimensions a = 18.316(17) Å α= 90°.

b = 18.316(17) Å β= 90°.

c = 41.14(6) Å γ = 120°.

Volume 11952(23) Å 3

Z 9



F(000) 2502



Index ranges -19<=h<=18, -17<=k<=16, -17<=l<=42




Max. and min. transmission 0.9918 and 0.9837






Largest diff. peak and hole 0.392 and -0.514 e·Å -3

88

Appendix B. TGA of Pillared-Layer Tetragonal Grid Network 3

Figure 3B.1 TGA of pillared-layer tetragonal grid network 3

89

Chapter 4

Engineering Discrete Coordination Units via Click Reactions:

a Convergent Strategy for the Synthesis of New Coordination

Compounds

4.1 Introduction

Metal-organic coordination compounds have attracted a great deal of attention due to

their application in gas storage, catalysis, separation and molecule recognition.1 The

“node and spacer” based modular synthetic approaches for metal-organic coordination

polymers offer the ability to rationally design and control the overall topologies, which

results in the development of tunable, functional materials.2 Although versatile synthetic

techniques, such as diffusion,3 hydro(solvent)thermal,4 refluxing5 and direct mixing,6

have been developed to prepare coordination polymers, they are based on the same

synthetic principles that metal ions or metal clusters act as nodes and multifunctional

organic ligands act as spacers, nodes and spacers are linked together via coordination

bonds. Thus, we refer to this as a coordination-based divergent strategy.7 The advantage

of this strategy is obvious: simply interchanging spacer ligands with the one bearing the

same basic shape and functionality;8 or even interchanging transition metals with one

which will exhibit similar coordination behavior will lead to an almost limitless number

of new materials whose properties can be controlled, particularly with regard to porosity

90

and magnetism.1d,3,9 However, there remain several limitations that need to be addressed.

For example, it is a challenge to establish the ideal reaction conditions for the in situ

generation of the desired coordination chromophore,10 especially metal containing

coordination chromophores,11 as there are often several chromophores that are

possible.12 It also has less control on the heterometal synthesis and sometimes suffers

from poor solubility of larger ligands.

An alternative covalent based convergent synthetic strategy7 is proposed in this work

to address the limitations of the divergent synthetic strategy. In the new strategy,

coordination compounds are synthesized by linking pre-assembled SBUs via common

organic coupling reactions. The pre-assembled SBUs have well-defined geometries and

specific functional groups at their peripheral positions (e.g. azides, alkynes, and iodides,

etc.). The premise of the strategy is that the chosen organic reactions can successfully

occur at specific sites on the pre-assembled SBUs with retention of structural integrity

throughout the reaction process. This new strategy avoids the in situ generation of SBUs

and makes the SBUs true building blocks. Large ligands can be formed from smaller

ligands via organic coupling reactions and heterometal frameworks can be designed and

obtained by linking SBUs containing different metals. Recent work reported by Ren et al.

involving click reactions on organometallic diruthenium complexes containing alkynes

supports the concept of convergent strategy. 13

This work focuses on demonstrating the feasibility of a convergent approach for the

synthesis of coordination polymers. Initially, we targeted on two common chromphores

91

in the traditional synthetical approach as the starting SBUs: one is dicopper(II)

tetracarboxylate Cu2(OOC-C6H4-N3)4·(Quinoline)2 (SBU1) and the other is tetrahedral

zinc dicarboxylate Zn2(OOC-C6H4-N3)4·(Quinoline)2 (SBU2). Monofunctional small

organic molecule methyl propiolate was “clicked” on pre-assembled SBU1 and SBU2 to

produce discrete coordination compounds Cu2(OOC-C6H4-C2N3H-COO-

CH3)4·(quinoline)2 (5) and Zn(OOC-C6H4-C2N3H-COO -CH3)2 (6) via Huisgen

1,3-dipolar cycloaddition, respectively. The results of single-X-ray diffraction, diffusion

NMR and ESR confirmed that the click reactions successfully modified all available sites

in SBU1 and SBU2.

This convergent stategy was also employed to prepare coordination polymer gels

(CPGs). Recently, CPGs have attracted immense interest due to their high potential for a

wide range of advanced applications: catalyst screening,14 chemical sensing,15

actuating,15b, 16 separating and as a reaction medium. Compared to crystalline materials,

an important feature of CPGs is the highly processable property. A universal approach

toward control of the synthesis and physical properties of cluster based coordination

polymer gels has been reported by our group.17 Herein, we report the synthesis of CPGs

based on convergent strategy. Ditopic molecules 1, 3-diethynyl benzene were used to link

SBU1 to generate amorphous coordination polymer gels (CPGs). At the end, convergent

strategy was used to synthesize crystalline coordination polymers. Finally, the convergent

approach was used to synthesize crystalline coordination 1D polymers [Cu2 (C7H5N)4

92

(CH3COO)2 (2MeOH)]n (7) and [Cu(C8H4O2)2(C5H5N)2 (6H2O)]n (8) via in situ

homo-alkyne coupling reaction.



All the metal salts, solvents, 3-ethynylpridine, 1,3-diethynylbenzene and methyl

propiolate were purchased from Aldrich Chemical Co. Sodium 4-ethynylbenzote was

purchased from VWR International Inc. 4-azidobenzoic acid was purchased from TCI

America. Deuterated solvents were purchased from Cambridge Isotope Laboratory. All

the materials were used as received, without further purification.

Cu2(OOC-C6H4-N3)4(quinoline)2 (SBU1): 4-azidobenzoic acid (10 mmol, 1.631g)

was suspended in 40ml mixture solution of water and ethanol (volume ratio 1:1). Copper

carbonate basic (2.5 mmol, 552.7 mg) was added into the suspension portion-wise. The

suspension was stirred for several hours until a green precipitate formed. A green

powder was obtained by filtration. Green block crystals SBU1·(S/L) (S = acetonitrile, L=

quinoline) formed by recrystallization of the green powder from THF, acetone, or

acetonitrile in presence of quinoline in good yield (70%~85%). For

[Cu2(OOC-C6H4-N3)4(quinoline)2]·2CH3CN, crystal data: C25H18CuN8O4, M=558.01,

Triclinic, P-1, a = 10.852(8) Å, b = 9.292(6) Å, c = 13.409(9) Å, α= 77.048(13)°, β=

80.273(11)°,γ = 69.079(11)°, Z=2, V=1224.9(15) Å3, Rf = 0.1368, GOF= 1.085. For

[Cu2(OOC-C6H4-N3)4(quinoline)2]· quinoline, cystal data: C55H37Cu2N15O8, M=1163.09,

Triclinic, P-1, a = 9.667(3) Å, b = 11.073(3) Å , c = 13.635(4) Å , α= 71.266(5)°, β=

93

74.446(6)°, γ = 67.057(5)°, Z=1, V=1255.7(6) Å3, Rf = 0.064, GOF= 0.79. IR

(DMSO, 2500-1400 cm-1): 2122.5 cm-1, 1630.2 cm-1, 1569.4 cm-1, 1501.4 cm-1, 1461.4

cm-1. 1H NMR (DMSO-d6, 300MHz): δ 9.31(very broad), 8.43, 8.10, 7.79, 7.69, 7.60

ppm. 13C NMR (DMSO-d6): δ 135.3, 128.9, 128.09, 126.26, 39.4 ppm.

Zn2(OOC-C6H4-N3)4(quinoline)2 (SBU2): 4-azidobenzoic acid (1mmol, 163mg) and

zinc nitrate hexahydrate (0.5mmol, 297mg) were dissolved in 10 methanol, then 1 ml

quinoline was added into the solution. The solution was placed in a 20ml vial which was

loosely capped and allowed to stand for about a week. Colorless prismatic crystals SBU2

were obtained at the bottom of the vial. Crystal data: Zn2C46O8N14H30, M=1037.58,

Triclinic, P-1, a = 8.3381(17) Å, b = 9.4324(19) Å, c = 15.273(3) Å, α = 80.33(3), β =

87.11(3), γ = 69.63(3). Z=1, V=1110.0(4) Å3, Rf =0.095, GOF=0.902. IR (DMSO,

2500-1400 cm-1): 2122.72 cm-1, 1700.53 cm-1, 1618.15 cm-1, 1601.68 cm-1, 1568.50 cm-1,

1501.35 cm-1, 1460.39 cm-1. 1H NMR (DMSO-d6, 300MHz): δ 8.908 (d, J = 3.12 Hz),

8.37(d, J = 8.16 Hz), 8.04(s), 8.005 (d, J = 3.66 Hz), 7.96 (d, J = 8.04 Hz), 7.77 (t, J = 7.5

Hz), 7.61( t, J = 7.5 Hz), 7.54 (q, J = 4.1 Hz), 7.14 (d, J = 8.16 Hz).

Cu2(OOC-C6H4-C2HN3-COOCH3)4·(quinoline)2 (5): SBU1·CH3CN (0.25 mmol,

260mg) was added into a round flask. Then 4ml THF and 100 μl methyl propiolate (1.12

mmol) were added to the flask in order. The reaction mixtures were stirred at room

temperature for 9 days. Green solid product 5 was obtained by filtration (washed with

cool THF and hexane for several times). The product was first air dried and then dried

under vacuum for 4 ~ 6 hours. Yield: 82.7%. IR (DMSO, 2500-1400 cm-1): 1738.89cm-1,

94

1636.35cm-1, 1609.25cm-1(sh), 1581.26cm-1, 1545.79, 1461.52cm-1. 1H NMR (DMSO-d6,

400MHz): δ 9.29, 8.46, 8.18, 7.81, 7.60, 3.79 ppm. 13C NMR (DMSO-d6, 400MHz): δ

160.17, 139.37, 138.16, 129.09, 126.93, 126.54, 51.79 ppm.

Zn(OOC-C6H4-C2HN3-COOCH3)2·(H2O)2 (6): Method A: SBU2 (0.25mmol,

260mg) and 90 μl methyl propiolate (1 mmol) were suspended in 10ml mixture solution

of water and t-butanol (v:v=1:1) in a round flask. Sodium ascorbate (25mg, prepared 1M

solution in water) was added and copper (II) sulfate pentahydrate (0.1 mmol, 25mg,

prepared in water) was added sequentially with stirring. The mixture was stirred

vigorously overnight. Pale yellow solid product 6 was obtained by filtration (washed with

cool water and ether for several times) and then was dried under vacuum for several

hours. Yield: 93%. Method B: SBU2 (0.5mmol, 520mg) and 178 μl methyl propiolate

(2mmol) were suspended in 20 ml mixture solution of water and t-butanol (1:1) in a

round flask. 50 mg copper (II) sulfate pentahydrate (0.2 mmol, prepared in water) and

300mg copper wire were added into the flask. The mixture was stirred for about 4 days.

Light yellow solid product 6 was obtained by filtration (washed with cool water and ether

for several times). The product was dried in air first and then dried under vacuum

overnight. Yield: 91.6%. Method C: SBU2 (0.3mmol, 311mg) and 160μl methyl

propiolate (1.8 mmol) were dissolved in 6 ml CH2Cl2 in a round flask. The mixtures were

stirred at room temperature for about 3 weeks. Pale yellow precipitate was formed. The

pale yellow product 6 was obtained by filtration. Yield: 86.3% IR (DMSO,

2500~1400cm-1) 1659.7, 1437.3, 1314.6cm-1. 1H NMR (DMSO-d6, 400MHz): δ 9.59,

95

8.13, 8.07, 3.9 ppm. 13C NMR (DMSO-d6, 400MHz): δ 160.98, 140.11, 138.20, 131.45,

127.85, 120.46, 52.49 ppm.

Recrystallization of 6:

Zn(OOC-C6H4-C2HN3-COOCH3)2·(quinoline)2 (I): 20mg pale yellow zinc complexes

6 was partly dissolved in 11 ml mixture solution of THF, benzene and quinolline (volume

ratio 5:5:1). The mixture solution was heated to 80°C until all the solids were completely

dissolved. The solution was allowed to slowly cool to room temperature. Single crystal

did not form immediately after the solution was cooled down. Pale yellow single crystals

I · 3.5 quinoline formed in about one week. Crystal data: C143 H109N23O16Zn2, M

=2536.31, triclinic, P-1, a = 14.917(3) Å, b = 15.292(3) Å, c = 15.780(3) Å, α = 61.17(3),

β = 77.55(3), γ = 74.60(3). Z=1, V = 3023.9(11) Å3, Rf =0.0987, GOF=0.879.

Zn(OOC-C6H4-C2HN3-COOCH3)2·(quinoline)·DMSO (II): 20 mg pale yellow zinc

complexes 6 was added in 14 ml mixture solution of methanol, quinoline and DMSO

(volume ratio 9:3:2). The mixture was heated up to 90℃ until all the solid was dissolved.

The solution was allowed to slowly cool to room temperature. Single crystal did not form

immediately after the solution was cooled down. Pale yellow single crystals II formed in

about one week. Crystal data: ZnC33O9N7SH29, M =765.06, triclinic, P-1, a = 7.8535(16)

Å, b = 12.429(3) Å, c = 17.564(4) Å, α = 98.68(3), β = 100.40(3), γ = 91.27(3). Z=2, V =

1664.8(6) Å3, Rf =0.065, GOF=0.928.

96

Coordination Polymer gels (CPGs): In a typical reaction, CPGs were formed when

1×10-4 moles of SBU1 (116.3 mg) were mixed with 1×10-4 moles of

1,3-diethynylbenzene in 20 ml of THF for weeks.

[Cu2(C7H4N)4(CH3COO)4·(5H2O)]n (7): Copper acetate hydrate (0.5 mmol, 90.8 mg)

and 3-ethynypyridne(1 mmol,103mg) dissolved in 15ml MeOH in a 20 ml vial. Blue

crystal 7 formed at the bottom of the vial in weeks. Crystal data: C18H14CuN2O6.50, M =

425.85, Triclinic, P-1, a = 8.7262(16) Å, b = 10.1308(18) Å, c = 11.292(2) Å, α =

87.035(3), β = 87.300(3), γ =71.511(3). Z=2, V = 945.0(3) Å3 Rf =0.0655, GOF=0.932.

[Cu(C8H4O2)2(C5H5N)2·(6 H2O)]n (8): 10 mL methanolic solution of copper nitrate

pentahemihydrate (0.05M) was layered on 10 ml H2O solution of 4-ethynylbenzoic acid

sodium salt (1mmol, 168mg) by using 5ml benzene as buffer solution in a 11 dram vial.

Blue crystal 8 formed in a week. Cystal data: C33H23CuN3O9.50, M = 677.08, Monoclinic,

C2, a = 32.692(6) Å, b = 14.431(3) Å, c = 8.4580(15) Å, α = 90°, β = 94.972(3)°, γ =90°.

Z=4, V = 3975.3(12) Å3 Rf = 0.0803, GOF=1.008.

4.2.2 Methods







97


with a step size 0.01° in 2θ at room temperature. IR spectra were recorded on an ATI

Mattson Infinity series FTIR instrument. NMR experiments were recorded on either a

Bruker DRX-300 with a z-gradient BBI probe or Bruker DPX-400 with a z-gradient BBO

probe operating at 300.13 MHz and 400.13 MHz for 1H observe respectively. DOSY

spectra were acquired using the Bruker pulse programs, dstebpgp3s for 5 and ledbpgp2s

for 6, using sinusoidal gradients with durations between 1.25 and 3.5 ms. The gradient

strength was varied between 2% and 95% in 16-32 square spaced increments for 5, and

128 increments for 6. Diffusion times of 14 to 20 ms were used for 5, and 70 to 80 ms

for 6. DOSY spectra were processed using the Bruker Topspin software with

exponential line fitting. X-band EPR Spectra were recorded at X-band (9.5 GHz) using

a Bruker EMX EPR spectrometer equipped with a Bruker high sensitivity cylindrical

resonator. Variable temperature studies were performed using a Bruker variable

temperature unit (ER 4111VT) with liquid nitrogen reservoir and quartz dewar insert.

ESR spectra and energy level diagrams were simulated using the EasySpin18 set of

MATLAB program. The parameters used for the spectral simulation are summarized in

Table 1 (See Results and Discussion). Rheometric measurements were performed on a

Rheometrics Dynamic Stress Rheometer with parallel plate geometry(gap=0.5 mm) at a

temperature of 298 K. Frequency oscillation tests were performed at a constant strain of

2%; yield stress measurements were done at a constant frequency of 1 Hz while

98

increasing the elastic stress logarithmically and monitoring the strain. I would like to

thank Arkwright Incorporated of Coventry, R.I. for use of their rheometer.

4.3 Results and discussion

4.3.1 Click methyl propiolate on SBU1 and SBU2

To test the efficiency of this new convergent synthetic approach, we must determine

whether organic reactions can occur on the pre-assembled SBUs. Initially, to address this

question, we chose two discrete coordination units, one (SBU1) is considered robust and

the other (SBU2) is fragile. The Huisgen 1,3-dipolar cycloaddition of azides and alkynes

(click-reaction) 19 was chosen due to its mild reaction conditions. Click reactions can

occur at ambient temperature in a variety of solvents and have almost quantitative yield.

More specifically, using copper (I) catalyst leads to 1, 4-regioisomer which offers a 144o

angle.19b-19e (Scheme 4.1)

Scheme 4.1 Huisgen 1,3-dipolar cycloaddition of azides and alkynes

Click methyl propiolate on SBU1 and SBU2. Cu2(OOC-C6H4-N3)4(quinoline)2

(SBU1) is a dinuclear copper paddle-wheel structure with 4 azide groups at the peripheral

positions and two quinoline molecules at the axial positions (Figure 4.1(a)). SBU1 forms

a square when viewed along the axial direction (Figure 4.1(b)). The coordination

geometry of zinc in SBU2 is a distorted tetrahedron. As shown in Figure 4.1(c), SBU2

R1N

NN

+ -+

R2 NN

N

R1

R2wiht or without Cu+ N

N

N

R1 R2

+14 1

5

99

can be considered a weakly bound dimer, in which the carbonyl from an adjacent

complex binds to the zinc. The four azide groups at peripheral positions of SBU1 or

SBU2 provide potential for further modifying or extending the discrete building units to

infinite polymers.

Figure 4.1 (a) Single crystal X-ray structures of SBU1; (b) SBU1 viewed along axial direction;

(c) SBU2. (Atom colors: gray: carbon; pink: copper; oxygen: red; nitrogen: blue; green: zinc).

Green solid 5 was obtained by reacting 4 equivalents of methyl propiolate with 1

equivalent of SBU1 in THF solution and pale yellow solid 6 was obtained by reacting 4

equivalents of methyl propiolate with 1 equivalent SBU2 in a mixture solution of water

and tert-butyl alcohol (volume ratio=1:1) containing copper (II) sulfate pentahydrate and

sodium ascorbate. (Scheme 4.2) No catalyst was used in the click reaction of methyl

propiolate with SBU1 for fear that the sodium ascorbate might reduce the copper (II) of

SBU1 during the reaction, thereby destroying the integrity of the paddlewheel structure.

Consequently, the reaction required 9-10 days for completion and was monitored by IR

spectroscopy. Disappearance of the azide peak at ca. 2122cm-1 indicated completion of

the reaction. For the click reaction of methyl propiolate with SBU2, we used copper (II)

(a) (c) (b)

100

sulfate pentahydrate and sodium ascorbate to generate the copper (I) catalyst in situ.19

The reaction required ca. 12 hours for completion and was also monitored by IR

spectroscopy.

Scheme 4.2 Click reactions of methyl propiolate with SBU1 and SBU2

Chart 4.1 Triazole ligand L and proposed structure 5 and 6

1,4 regioisomer L-H 1,5 regioisomer L’-H

Proposed structure for 5* Proposed structure for 6

* Theoretically some L’ might present in 5, since we don’t know the proportion, we use L in the proposed structure

representing both L and L’.

If, as we expected, the two SBUs remain intact during the click reaction of the

4-azido-benzoate moiety in SBU1 and SBU2 with methyl propiolate, we should obtain

HO

ON N

N

H

OOCH3

O

HO

ON N

N

O

OOCH3H

Cu

Cu

NNN

H OCH3

OO

O

NNN

HOCH3

O

O

O

NN N

HH3CO

O O

O

NN N

HH3CO

O

O

ON

N

ZnO

ON

O

OZn

O

O

N

N

O

O

N

N

N

NN

NN

N N

N N

OOCH3

O

OCH3

H3CO

O

H3CO

O

H H

H

H

COOCH3Cu2(OOC-C6H4-N3)4( )2N

THF, RT

10 days+ 5 (1)4

COOCH3Zn2(OOC-C6H4-N3)4( )2

5%CuSO4 5H2O,10% Sodium ascorbate

H2O:t-butanol=1:1, overnight+ 6 (2)

N4

101

the products depicted in Chart 4.1. Various analytical techniques including 1H, 13C,

HSQC, HMBC and DOSY NMR, ESR, and single crystal X-ray diffraction were used to

confirm the structures.

NMR characterization. Based on the 1H, COSY and HSQC NMR spectra of SBU1

and 1H spectra of free quinoline and Cu2(OOC-C6H4-N3)4(pyridine-d5)2 in DMSO-d6

(Appendix A: Figure 2A. 2), the 5 broadened resonances between 7-10 ppm observed in

the 1H spectrum of SBU1 are assigned to quinoline (Figure 4.2). The 1H NMR spectrum

of 5 in DMSO-d6 confirmed that methyl propiolate was successfully clicked on

4-azidobenzoate in SBU1 to form 1-(4-carboxyphenyl)-4-methoxycarbonyl-

1,2,3-triazole (L, Simplified as 1,4-triazole ligand in this thesis). Comparison of the 1H

spectra of methyl propiolate, SBU1 and 5 clearly illustrates the disappearance of the

alkyne proton at 4.57ppm in 5, a downfield shift of the ester methyl protons from

3.72ppm to 3.79ppm, and the emergence of a new sharper peak at 9.3ppm which lies in

the expected range of triazole protons.19c,19f The integral ratio of this new peak to the

ester methyl peak is 1:3, consistent with the triazole structure. The integral ratio of the

new peak to the best resolved quinoline proton is 2: 1, which indicates that all four azides

groups on SBU1 reacted with methyl propiolate. Noteworthy in the 1H spectra of SBU1

and 5 is the absence of any resonances for the phenyl protons of the benzoate moiety.

This can be attributed to the significant line broadening experienced by these protons due

to fast relaxation caused by interactions of these nuclei with the unpaired electrons of

paramagnetic Cu (II) center.20 This effect is reduced as the distance from the

102

paramagnetic center is increased which is why the resonances for the triazole/methyl

ester groups could be observed. When free 1,4-triazole ligands were added to the NMR

sample 5, the phenyl peaks of the benzoate moiety from free 1,4-triazole ligand could be

observed. It seemed suspicious when first viewing the 1H spectrum of this molecule that

the quinoline ligands, which should be closer in proximity to the paramagnetic effects of

Cu (II) center displayed sharper resonances than those of the benzoate ligands. However,

when diffusion ordered spectroscopy (DOSY) experiments21 were conducted on 5, it

became clear that the quinoline ligands had undergone exchange with the solvent,

dimethyl sulfoxide, as evidenced by their faster diffusion than the triazole resonances in

the DOSY spectrum (Figure 4.3(a)). NMR experiments conducted on free 1,4-triazole

ligands, 5 and the mixture of 5 and 1,4 regioisomer triazole ligands confirmed that the

triazole moieties formed in 5 are 1,4 regioisomer, which suggests self-catalyzing.

Figure 4.2 1H spectra of methyl propiolate (top), SBU1·quinoline (middle), and 5 (bottom) in

DMSO-d6.

COOCHb3Hc

SBU1

5 Cu

Cu

NNN

HaOCHb

3

OO

O

4

quinoline

103

Figure 4.3 (a) 1H DOSY spectrum of 5 in DMSO-d6 and (b) 1H DOSY spectrum of mixture of 5

and free 1,4-regioisomer L in DMSO-d6.

In the 1H DOSY spectrum of 5 in DMSO-d6 (Figure 4.3(a)), the triazole proton Ha

(9.3ppm) and the ester methyl proton Hb (3.79ppm) exhibit the same diffusion coefficient

(LogD≈-8.45 m2/s), which indicates that they come from the same species. All the

signals corresponding to the quinoline protons were aligned and exhibited a faster

diffusion coefficient (Log D ≈-8.25 m2/s) due to exchange with the solvent, DMSO,

which had replaced them as the axial ligands on 5, essentially making them free ligands.

Free 1,4-triazole ligand was added to the NMR sample of 5 in an effort to see both the

free and coordinated triazole ligands. As shown in Figure 4.3(b), an additional set of

aligned triazole, methyl ester, and phenyl proton resonances appear upon addition of the

free 1,4-triazole ligands to 5. These aligned peaks which correspond to free 1,4-triazole

ligands exhibit a faster diffusion coefficient (LogD ≈-8.32 m2/s) than 5. This data

Coordinated triazole ligand L in 5

quinoline

quinoline Ha Hb (a)


quinoline

Free triazole ligand L added in solution of

Ha quinoline Hb

Phenyl protons (b)

104

highlights the excellent utility of diffusion ordered NMR spectroscopy for determining

solution structures of coordination compounds.

Figure 4.4 (a) 1H spectra of methyl propiolate (top), SBU2 (middle), and 6 (bottom); (b) 13C

spectrum of 6.

SBU2

methyl propiolate

6

Triazole Ha Phenyl proton

2 1

ester methyl H3

Phenyl

proton2

Phenyl

proton1

quinoline

(a)

O

O

NN

N

O

OCH3

Zn

ZnH

n

5

1 2

ab

4

3

67

7 4 b 5 6

1

a

2

3

(b)

105

The 1H and 13C NMR spectra of methyl propiolate, SBU2, and 6 are displayed in

Figure 4.4. Analogous to the result obtained for SBU1, methyl propiolate was

successfully “clicked” with all the 4-azidobenzoate moieties on SBU2 to form

1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3-triazole (L) as evidenced by the

disappearance of the acetylene proton at 4.57ppm, the persistence of the ester methyl

resonance at 3.9ppm and the emergence of the new triazole proton at ~9.7ppm. Also clear

from the spectrum of 6 is the loss of the axial quinoline ligands during the reaction or

work-up. All proton and carbon assignments were based on HSQC and HMBC

experiments (Appendix A: Figure 4A.8, Figure 4A.9 ).

Figure. 4.5 (a) 1H DOSY spectrum of 6 and (b) 1H DOSY spectrum of 6 in presence of free

L-H.

The DOSY spectra of 6, and 6 with added 1,4-triazole ligands are displayed in Figure

4.5. The aligned triazole proton, phenyl proton and ester methyl proton resonances


free triazole ligand L

Ha Phenyl proten

1and 2 H3

(b)


Ha Phenyl proten 1and 2 H3

(a)

106

observed for 6 (Figure 4.5(a)) indicate all these nuclei are from the same molecule.

Nevertheless, additional 1,4-triazole ligand L-H was added to the NMR sample of 6, and

as expected, the DOSY spectrum shows an additional set of aligned triazole, phenyl, and

methyl proton resonances corresponding to free L-H displaying a faster diffusion rate

than the Zn complex 6 (Figure 4.5(b)).

ESR characterization of SBU1 and 5. The experimental spectrum of crystalline

SBU1, as shown in Figure 4.6 (blue), exhibits feature characteristic of dinuclear Cu (II)

species22 with three peaks at 400 G (Hz1) (g║1 = 16.69), 4700G(H⊥2)(g⊥ = 1.41) and

6000G(Hz2)(g║2 = 1.10) due to the spin triplet state of the binuclear copper complex.

The spectrum can be simulated with reasonable agreement assuming a large negative

exchange energy (J). In this case, the spin state energy levels may be described as a

singlet ground state (S = 0) and an excited triplet state (S = 1) separated by an energy

difference of 2J.23 For large J, the EPR spectrum of the triplet state can be described

using an effective total spin S = 1 state. Figure 4.6 shows the calculated spectrum (red)

and the energy level diagram (insert) for the case of large zero field spitting (|D| > hν).

The parameters used to simulate the spectra are given in Table 4.1.18 A small peak at

3300 G can be attributed to mononuclear Cu (II). The seven hyperfine lines evident in the

z peaks at 400 G and 6000 G clearly show the interaction between two Cu(II) (I = 3/2)

nuclei in the paddle-wheel structure. The spectrum is consistent with two copper ions

occupying identical sites in an axially symmetric crystal field (E ≈ 0).

107

Figure 4.6 Crystal X-band spectrum of SBU1 recorded at 160 K (blue) and calculated spectrum

(red). Insert: energy level diagram showing Δms = 1 transitions (red) and Δms = 2 transitions

(gray) for the two canonical orientations B0||x,y (top) B0||z (bottom).

Table 4.1 EPR parameters of calculated spectrum

T(K) g|| g⊥ A||(cm-1) A⊥(cm-1) D(cm-1)

160 2.06 2.45 77 15 3670

Figure 4.7 compares the X-band ESR spectra of SBU1 and 5 in frozen DMSO at two

different temperatures. In addition to the peaks from the dinuclear Cu (II) noted above,

the spectra exhibit a somewhat more prominent mononuclear Cu (II) peak at 3300 Gauss.

The peaks in the dinuclear Cu spectra occur at nearly identical magnetic fields, indicating

retention of the dinuclear paddle-wheel chromophore of SBU1 after the click reaction

employed to form 5. The relative intensity of the mononuclear and dinuclear peaks is

108

unaffected by the click reaction. However, it is temperature dependent, with the dinuclear

Cu (II) exhibiting relatively less intensity at lower temperatures. This is consistent with a

large negative J value for the dinuclear Cu (II), so that the triplet state becomes

depopulated as the temperature is reduced below 200 K. Such temperature dependence

has previously been observed in similar dinuclear copper complexes.24

(a)

(b)

Figure 4.7 X-band ESR spectra of SBU1 and 5 in frozen DMSO at (a) 160K and (b) 200K. (red:

SBU1; blue: 5) Inset shows simulated EPR spectrum of mononuclear Cu (II) plus dinuclear Cu

(II) in a 1:10 ratio.

109

Because of this inverse temperature dependence, it is difficult to quantify the relative

amounts of mononuclear and dinuclear Cu from double integration of the spectrum. An

upper limit on the amount of mononuclear present may be estimated by simulating the

spectrum as a superposition of mononuclear and dinuclear spectra that have been

normalized to a doubly integrated intensity of 5. The inset of Figure 4.7 shows a

simulation of the spectrum assuming mononuclear to dinuclear ratio of 1:10. This

simulation exhibits relative intensities of the mononuclear peak at 3300 G and dinuclear

peak at 6000 G that are comparable to those of the 200 K experimental spectrum. Based

on the previously observed temperature dependence of a similar dinuclear Cu complex,24

the dinuclear intensity at 200 K is still below its maximum value, which places an upper

limit of about 10% on the relative amount of monomer present for both SBU1 and 5 in

DMSO. The major results from the comparisons in Figure 4.7 are that SBU1 maintained

its structural integrity throughout the click reaction process and the structures of SBU1

and 5 in DMSO are mainly dinuclear copper paddle-wheel with very small amount of

mononuclear impurity.

NMR and ESR data confirmed the proposed structure 5 as depicted in Chart 4.1. The

click reaction was successfully employed between the 4 azide groups of SBU1 and 4

methyl propiolate molecules. The dicopper (II) tetracarboxylate chromophore SBU1

proved stable enough to survive the ambient conditions of the click reaction. Although

displacement of the axial ligands can occur under certain conditions, there was no

evidence of any negative effect on the integrity of SBU1 structure.

110

Recrystallization was performed to further confirm the structure of 6. Crystal I and II

were recrystallized from THF solution in presence of quinoline and methanol solution in

presence of DMSO and quinoline respectively. As shown in Figure 8, the crystals

obtained were of mononuclear zinc complexes, in which zinc is tetrahedrally coordinated

to two 1,4-triazole ligands via oxygen and two quinolines via nitrogen (Figure 4.8 I) or

one quinoline via nitrogen and one DMSO via oxygen (Figure 4.8 II). This result

indicates that click reaction also successfully occurred on the two 4-azidebenzoate

ligands in the fragile tetrahedral zinc dicarboxylate SBU2 with dissociation of the loosely

bound dimer to monomer. The NMR result had already confirmed dissociation of

quinoline during the click reaction. Hence, the solid state structure of 6 is actually not

the one depicted in Chart 1, but the one in Figure 4.8 III.

Figure 4.8 I: Recrystallized from mixture solution of THF and quinoline; II: recrystallized from

methanol solution in presence of DMSO and quinoline (Atom colors: gray: carbon; blue:

nitrogen; red: oxygen; gray blue: zinc; yellow: sulfur) ; III: mononuclear zinc complex 6.

The stability and reactivity of both robust dicopper (II) tetracarboxylate chromophore

and fragile tetrahedral zinc dicarboxylate chromophore under the click reaction

conditions strongly support the concept that pre-assembled SBUs may be used as

III I II

ZnO

O

N

OO

N

O

HH

O

H

H

N N

NNO

OOCH3

O

H3COOC

111

building blocks for the generation of coordination polymers via organic coupling

reactions

4.3.2 Syntheses of Coordination Polymer Gels

When the monofunctional organic molecule methyl propiolate was used to modify

SBU1, it reacted with all the available sites on SBU1 and a more complicated discrete

molecule resulted. We expect an infinite polymer formation if polytopic organic linker

molecules are used to react with tetratopic SBU1s. An amorphous polymer or gel will

result if the four available binding sites on SBU1 randomly react with the polytopic linker

molecules. Herein, 1,3-diethynylbenzene was used as a ditopic organic linker molecule to

react with SBU1 via Huisgen 1,3-dipolar cycloaddition. Green gels formed when

1,3-diethynylbenzene reacted with SBU1 in THF as shown in Figure 4.9. Gels are

viscoelastic solid-like materials comprised of an elastic cross-linked network with

entrapped low molecular weight liquids or solvents. Generally, the liquids or solvents are

the major component in the gels. Figure 4.10 shows a model diagram of 3D cross-linked

network composed of randomly linked SBU1 and 1,3-diethynylbenzene. In comparison

to crystalline coordination polymers, the CPGs exhibit extraordinary porosity: ca 90%

THF by mass was entrapped into the pores of the network as determined by

thermogravimetric analysis (TGA).

112

Figure 4.9 Synthesis of copper coordination polymer gel via click reaction between SBU1 and 1,

3-diethynylbenzene and the picture of gel in an inverted vial.

Figure 4.10 (a) A representation of two SBU1 linked by 1,3-diethynybenzene. (b) A model

diagram of the 3D cross-linked gel network.

Since the organic linkers are ditopic, to obtain a 3D cross-linked network, the

average number of binding sites on each reacted SBU1 has to be more than 2. Stable gels

formed at the concentration of SBU1 above 5mM with the mole ratio of SBU1 to organic

Cu

Cu

N3

O

O

N3

O

O

N3

O

O

N3

O

O

N

N

1,3-diethynylbenzene, THF

r. t., a couple of weeks

Cu

Cu

N

O

O

N3

OO

N3

O

O

N3

O

O

NN

NN

N

Cu

Cu

N3O

O N3

O

OO

ON3

O

O

(a) (b)

113

linker molecule no less than 0.5. Oscillatory frequency shear tests and stress controlled

yield stress measurements were performed on the gels to investigate their rheological

properties. The results of the rheological measurement showed that both the

concentration and the ratio of SBU1 to organic linker molecule have a big effect on the

rheology properties of the gels. Higher concentration led to stronger gels. The ratio effect

is more complicated and is concentration related. Figure 4.11 shows the storage and loss

moduli vs shear frequency curves for the gel formed at two different SBU1 concentration

0.005M and 0.01M with the ratio of SBU1: organic linker=1:1. The curves indicate the

characteristic feature of a “strong” gel that the storage moduli G’ (ca. 1000 Pa) are higher

than the loss moduli G’’(less than 200 Pa) throughout the frequency range (from 0.1Hz to

10Hz), and G’ is almost independent of the frequency which imply the molecular

rearrangements within the network are very reduced over the time scales analyzed.25

Whereas, in weak gels, G’ is more dependent on frequency for the dynamic moduli,

suggesting the existence of relaxation processes occurring even at short time scales, and

the difference between G’ and G’’ is lower, indicating that a lower percentage of the

stored energy is recovered. Under the same conditions, a mixture of copper acetate and 1,

3-diethynylbenzene in THF did not form gels, which indicates that the formation of 3D

cross-linked networks is the result of the coupling between the organic linker molecules

and SBU1s.

114

Figure 4.11 Frequency dependent of storage moduli (G’) and loss moduli (G’’) curves of copper

coordination gels at two different SBU1 concentrations: 0.005M and 0.01M with the ratio of

SBU1 to organic linker=1.

Another distinct feature of the metallogels is their reversible formation. Fillip on the

gel vial caused liquefaction. Regellation occurred in a couple of days. The formation of

gels in this strategy is the result of the formation of covalent bonding. It is obvious that

the fillip will not cause the break of the new formed covalent bonds, the liquefaction is

most likely due to the break of the coordination bonds in SBU1.

The 3D cross-linked coordination polymer gels were prepared by using predefined

SBU1 and 1, 3-diethynylbenzene via Huisgen 1, 3-dipolar cycloaddition. Obviously, an

unlimited numbers of CPGs can form just by simply changing the SBUs and organic

115

R H + Br R' R R'CuI

Base

hetero-coupling (Cadiot-Chodkiewicz Coupling)

linkers. The convergent synthetic strategy is expected to find use as a general approach to

synthesize the coordination polymer gels.

4.3.3 Syntheses of 1D coordination polymers via in situ alkyne-alkyne coupling reactions

To extend the range of organic coupling reactions, which are compatible with

coordination complexes, is very important for the general application of this convergent

synthetical strategy, specifically, those that will result in linear connections so that a

wider range of network topologies can be targeted. The initial focus will be on homo- or

hetero- alkyne coupling reactions, and then probably Sonogashira reactions. Homo- or

hetero-alkyne coupling reactions can occur under very wide and mild reaction conditions

in which copper (copper (I), copper (II)) or palladium (Scheme 4.3) are typically used as

catalysts in various solvents (e.g. methanol, benzene, acetone, tetrahydrofuran, ethyl ester,

etc.).21 The rigid di- or oligo- acetylene moieties introduced will bring interesting

electronic and optical properties to the resulting products. Herein, we synthesize

coordination polymers containing 1,4-di-substituted-1,3-butadiyne moieties via in situ

alkyne-alkyne coupling reaction.

Scheme 4.3 Terminal alkyne-alkyne coupling reactions26

R H R RCu/Pd

2

homo-coupling (Eglinton Reaction, Glaser Coupling and Hay Coupling )

116

Figure 4.12 (a) Crystal structure of double zigzag chain in 7; (b) space filling representation of 7

viewed along (1,0,0). (Atom colors: gray-carbon; blue-nitrogen; red-oxygen; orange-Cu)

Reaction of copper acetate hydrate and 3-ethynylpyridine in methanol affords blue

crystal [Cu2(C7H4N)4(CH3COO)4·(5H2O)]n (7). In 7, as shown in Figure 4.12, two Cu

atoms bridged by two acetates formed Cu2O2 plane, in which each Cu atom has a square

pyramidal coordination with the basal plane consisting of two nitrogens from two

3-substituted pyridines and two oxygens from two acetates (one of them is bridging

acetate). The apical position is occupied by oxygen of another bridging acetate.

3-ethynylpyridines were homo-coupled to each other in situ by their terminal alkyne

groups during the metal organic self-assembly process which affords an infinite double

zigzag chain. (Figure 4.12(a)) The double zigzag chains parallelly aligned in the xz

plane to form layers which further parallelly packed along the y direction to form 7,

(a) (b)

117

which contains 1D channels along x axis with an effective dimension of 4Å (Figure 4.12

(b)). Water molecules (2.5 water molecules per copper) occupy the 1D channels.

Figure 4.13 (a) Crystal structure of the 1D coordination polymer in 8; (b) Space filling

representation of 8 viewed along (0, 0, 1). (Atom colors: gray-carbon; blue-nitrogen;

red-oxygen; orange-Cu)

Blue crystals [Cu(C8H4O2)2(C5H5N)2 (6H2O)]n (8) were formed by slowly diffusing

copper nitrate pentahemihydrate in methanol to an aqueous solution of 4-ethynylbenzoic

acid sodium salt in presence of pyridine. The single-crystal X-ray diffraction analysis

revealed, as shown in Figure 13 (a), the copper atom in 8 has trans-square-planner

coordination geometry in which two oxygens from two 4-ethynylbenzoic acids and two

nitrogens from two pyridines coordinated to copper. Analogous to formation of 7, the

terminal alkynes on the 4-ethynylbenzoate moiety coupled to each other in situ to form 1,

4-(4-carboxylic-benzene) butydiene creating an infinite 1D polymer chain. (Figure 4.13

(a) (b)

118

(a)) The 1D chains parallelly align to form layers which are alternately packed by an

ABAB pattern to form 8. The 1D chains in layer A and layer B have different

directions. The way these 1D chains packed together in 8 creates 1D channels along z

direction whose effective dimension is about 12Å and are filled by water molecules (6

water molecules per copper) (Figure 4.13 (b)).

The successful syntheses of these two di-acetylene 1D coordination polymers further

illustrate the feasibility of the convergent synthetical strategy. Organic coupling reactions

can not only be applied on pre-assembled SBUs but also occur in situ to link discrete

coordination units. When considering the discrete coordination units as monomers, these

syntheses fall into the traditional organic polymerizations. An additional benefit of

shifting from coordination to polymerization is that a lot of well-established concepts,

synthetic methods and experience in organic polymerizations can be directly applied to

the new convergent synthetic strategy for coordination polymers.

4.4 Conclusions

In this work, we have developed an alternative covalent-based convergent synthetic

strategy for the synthesis of new coordination compounds in which pre-assembled

coordination SBUs are coupled together via common organic coupling reactions. The

structural features and chemical or physical properties of these SBUs can be incorporated

into the resulting products. We demonstrated the feasibility of this new strategy by

applying it on the syntheses of discrete coordination compounds 5 and 6, amorphous

119

coordination polymer gels, and crystalline coordination polymers 7 and 8. We attached

methyl propiolate molecules on two discrete coordination units SBU1 and SBU2 via

Huisgen 1, 3-dipolar cycloaddition reactions to generate 5 and 6, respectively. We

prepared coordination polymer gels by linking SBU1 with 1,3-diethynylbenzene in THF

also via Huisgen 1, 3-dipolar cycloaddition reactions. We synthesized two 1D

coordination polymers 7 and 8 via homo-alkyne coupling reactions. Current studies focus

on synthesis of various discrete coordination units and polymerizing these discrete

coordination units into 1D, 2D and 3D coordination polymers. We expect that this new

strategy will generate new functional EMO (electronic, magnetic and optical) and porous

materials which can not be easily prepared by the established divergent methodology.

120

Referenes:

(1) (a) Yaghi, O. M.; Li, G.; Li, H. Nature 1995, 378, 703-706. (b) Moulton, B.;

Zaworotko, M. J. Curr. Opin. Solid state Mater. Sci. 2002, 6(2), 117-123. (c) Evans,

O. R.; Lin, W. B. Acc. Chem. Rev. 2002, 35(7), 511-522. (d) Rosseinsky, M. J.

Microporous and mesoporous mater. 2004, 73 (1-2), 15-30. (e) Batten, S. R. Curr.

Opin. Solid state Mater. Sci. 2001, 5(2-3), 107-114

(2) (a) Moulton, B.; Zaworokto, M. J. Chem. Rev. 2001, 101(6), 1629-1658. (b)

Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem., Int. Ed. Engl 2004, 43(18),

2334-2375.

(3) Moulton, B.; Lu, J.; Mondol, A.; Zaworokto, M. J. Chem. Comm. 2001 (9), 863-864

(4) (a) Paz, F. A. A.; Rocha, J.; Klinowski, J.; Trindade, T.; Shi, F. N.; Mafra, L. Prog.

Solid State Chem. 2005, 33(2-4), 113-125. (b) Ferey, G.; Chem. Mater. 2001,

13(10), 3084-3098. (c) Janiak, C. Angew. Chem. , Int. En. Engl 1997, 36(13-14),

1431-1434.

(5) Bourne, S. A.; Lu, J.; Mondal, A.; Moulton, B.; Zaworotko, M. J. Angew. Chem. , Int.

En. Engl 2001, 40 (11), 2111-2113.

(6) Huang, L. M.; Wang, H. T.; Chen, J. X.; Wang, Z. B.; Sun, J. Y.; Zhao, D. Y.; Yan,

Y. S. Microporous and mesoporous Mater. 2003, 58 (2), 105-114

121

(7) The concepts of divergent and convergent synthetic approaches originally come from

dendrimer chemistry : Divergent synthesis is the method where branches are

synthesized from the core outward in successive generations and convergent

synthesis is the method where branches are synthesized and then brought together to

make higher generations and finally attached to a core. In this work, we refer to the

traditional “node and spacer” approach for the synthesis of coordination polymers as

a divergent strategy, where each metal is considered a node that has an intrinsic

geometry; metals are linked together via organic spacer ligands capable of

coordination by at least two functional groups. Whereas, the convergent strategy is

the synthetic method where pre-assembled SBUs coupled together via organic

coupling reactions to generate higher dimensional coordination polymers.

(8) (a) Rowsell, J. L. C.; Yaghi, O. M.; J. Am. Chem. Soc. 2006, 128(4) 1304-1315. (b)

Yaghi, O. M.; O’ Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J.

Nature 2003, 423(6941), 705-714. (c) Yaghi, O. M.; O’ Keeffe, M.; Ockwig, N. W.;

Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003, 423(6941), 705-714. (d) Rosi, N.

L.; Eddaoudi, M.; Kim, J.; O’Keeffe, M.; Yaghi, O. M. Crystengcomm 2002,

401-404.

(9) (a) Pan, L.; Adams, K. M.; Hernandez, H. E.; Wang, X. T.; Zheng, C.; Hattori, Y.;

Kaneko, K. J Am. Chem. Soc. 2003, 125(10), 3062-3067. (b) Eddaoudi, M.; Moler,

D. B.; Li, H. L.; Chen, B. L.; Reineke, T. M.; O’Keeffe, M.; Yaghi, O. M. Acc.

122

Chem. Res. 2001, 34(4), 319-330. (c) Chui, S. S. Y.; Lo, S. M. F.; Charmant, J. P.

H.; Orpen, A. G.; Williams, I. D. Science 1999, 283(5405), 1148-1150. (d) Li, H.;

Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Nature 1999, 402(6759), 276-279. (e)

Gatteschi, D.; Curr. Opin. Solid state Mater. Sci. 1996, 1(2), 192-198. (f) Srikanth,

H.; Hajndl, R.; Moulton, B.; Zaworokto, M. J. J. Appl. Phys. 2003, 93(10),

7098-7091. (g) Moulton, B.; Lu, J. J.; Hajndl, R.; Hariharan, S.; Zaworokto, M. J.

Angew. Chem., Int. Ed. Engl. 2002, 41(15), 2821-2824.

(10) (a)Liu, Y. L.; Eubank, J. F.; Cairns, A. J.; Eckert, J.; Kravtsov, V. C.; Luebke, R.;

Eddaoudi, M. Angew. Chem., Int. Ed. Engl. 2007, 46(18), 3278-3283. (b) Biradha,

K. Curr. Sci. 2007, 92(5), 584-585.

(11) (a) Lu, J. J.; Mondal, A.; Moulton, B.; Zaworokto, M. J. Angew. Chem., Int. Ed.

Engl. 2001, 40(11), 2113-2116. (b) Chen, B. L.; Ockwig, N. W.; Millward, A. R.;

Contreras, D. S.; Yaghi, O. M.; Angew. Chem., Int. Ed. Engl. 2005, 44(30),

4745-4749. (c) Bauer, C. A.; Timofeeva, T. V.; Settersten, T. B.; Patterson, B. D.;

Liu, V. H.; Simmons, B. A.; Allendorf, M. D. J. Am. Chem. Soc. 2007, 129(22),

7136-7144. (d) Kesanli, B.; Cui, Y.; Smith, M. R.; Bittner, E. W.; Bockrath, B. C.;

Lin, W. B. Angew. Chem., Int. Ed. Engl. 2004, 44(1), 72-75.

(12) (a) Batten, S. R. J. Solid State Chem. 2005, 178, 2475-2479. (b) Erxleben, A. Coord.

Chem. Rev. 2003, 246, 203-228. (c) Wong-Foy, A. G.; Lebel, O.; Matzger, A. J. J.

Am. Chem. Soc. 2007, 129(51), 15740-15741.

123

(13) (a) Xu, G. L.; Ren, T. Organomethallics 2005, 24 (11), 2564-2566. (b) Chen, W. Z.;

Ren, T. Organomethallics 2005, 24 (11), 2660-2669. (c) Chen, W. Z.; Ren, T.

Organomethallics 2005, 23 (16), 3766-3768.

(14) (a) Xing, B. G.; Choi, M. F.; Xu, B. Chem. Eur. J. 2002, 8, 5028-5032. (b) Fages,

F. Angew. Chem. Int. Ed. 2006, 45, 1680-1682. (c) Paulusse, J. M. J.; van Beek, J.

M.; Sijbesma, R. P. J. Am. Chem. Soc. 2007, 129, 2392-2397. (d) Harris, R. F.;

Nation, A. J.; Copeland, G. T.; Miller, S. J. J. Am. Chem. Soc. 2000, 122,

11270-11271

(15) (a) Tam, A. Y. Y.; Wong, K. M. C.; Wang, G. X.; Wing-Wah, V. Chem. Commun.

2007, 20, 2028-2030. (b) Sangeetha, N. M.; Maitra, U. Chem. Soc. Rev. 2005, 34,

821-836. (c) Holtz, J. H.; Asher, S. A. Nature 1997, 389, 829-832. (d) Miyata, T.;

Asami, N.; Uragami, T. Nature 1999, 399, 766-769.

(16) Kim, H. J.; Lee, J. H.; Lee, M. Angew. Chem. Int. Ed. 2005, 44, 5810-5814

(17) Luisi, B. S.; Rowland, K. D.; Moulton, B. Chem Commun. 2007, 27, 2802-2804.

(18) Stoll, S.; Schweiger, A. J. Magn. Reson. 2006, 178(1), 42-55.

(19) (a) Huisgen, R. Helvetica Chimica Acta 1967, 50[8], 2421-2439. (b) Bock, V. D.;

Hiemstra, H.; Maarseveen, J. H. Eur. J. Org. Chem. 2006, (1), 51-68. (c) Rostovtsev,

V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. Angew. Chem., Int. Ed. Engl.

2002, 41(14), 2596-2599. (d) Chan, T. R.; Hilgraf, R.; Sharpless, K. B.; Fokin, V. V.

124

Org. Let. 2004, 6(17), 2853-1855. (e) Torno, C. W.; Christensen, C.; Meldal, M. J.

Org. Chem. 2002, 67(9), 3057-3064. (f) Zhou, Z.; Fahrni, C. J. J. Am. Chem. Soc.

2004, 126(29), 8862-8863.

(20) (a) Bertini, I.; Luchimat, C. NMR of Paramagnetic Molecules in Biological Systems;

Benjamin & Cummings: Menlo Park, CA, 1986. (b) La Mar, G. N.; de Ropp, J. S.

NMR Methodology for Paramagnetic Proteins; Plenum Press: New York, 1993, 12,

1-78. (c) Brink, J. M.; Rose, R. A.; Holz, R. C. Inorg. Chem. 1996, 35, 2878-2885.

(d) Arnesano, F.; Banci, L.; Bertini, I.; Felli, I. C.; Luchinat, C.; Thompsett, A. R. J.

Am. Chem. Soc. 2003, 125(24), 7200-7208. (e) Satcher, J. H.; Balch, A. L. Inorg.

Chem. 1995, 34(13), 3371-3373. (f) Murthy, N. N.; Karlin, K. D.; Bertini, I.;

Luchinat, C. J. Am. Chem. Soc. 1997, 119(9), 2156-2162.

(21) (a) Cohen, Y.; Avram, L.; Frish, L. Angew. Chem., Int. Ed. Engl. 2005, 44(4),

520-554. (b) Dehner, A.; Kessler, H. ChemBioChem. 2005, 5, 1550-1565. (c)

Allouche, L.; Marquis, A.; Lehn, J. M. Chem. Eur. J. 2006, 12(28), 7520-7525. (d)

Megyes, T.; Jude, H.; Grósz, T.; Bako, I.; Radnai, T.; Tárkányi, G.; Pálinkás, G.;

Stang, P. J. J. Am. Chem. Soc. 2005, 127(30), 10731-10738. (e) Hori, A.;

Yamashita, K.; Kusukawa, T.; Akasaka, A.; Biradha, K.; Fujita, M. Chem.Comm.

2004, (16), 1798-1799.

(22) (a) Melnink, M.; Coord. Chem. Rev. 1981, 36, 1-44. (b) Weder, J. E.; Hambley, T.

W.; Kennedy, B. J.; Lay, P. A.; MacLachlan, D.; Bramley, R.; Delfs, C. D.; Murray,

125

K. S.; Moubaraki, B.; Warwick, B.; Biffin, J. R.; Regtop, H. L. Inorg. Chem. 1999,

38, 1736-1744. (c) Bennett, B.; Antholine, W. E.; D’souza, V. M.; Chen, G. J.;

Ustinyuk, L.; Holz, R. C. J. Am. Chem. Soc. 2002, 124(44), 13025-13034. (d)

Casanova, J.; Alzuet, G.; Latorre, J.; Borrás, J. Inorg. Chem. 1997, 36, 2052-2058.

(e) Comarmond, J.; Plumeré, P.; Lehn, J. M.; Agnus, Y.; Louis, R.; Weiss, R.; Kahn,

O.; Morgenstern-Badarau, I. J. Am. Chem. Soc. 1982, 104(23), 6330-6340.

(23) (a) Atherton, N. M.; Principles of Electron Spin Resonance; Ellis Horwood PTR

Prentice Hall: New York, 1993. (b) Bersohn, M.; Baird, J. C. An Introduction to

Electron Paramagnetic Resonance; W. A. Benjamin, Inc.: New York, 1966.

(24) Kovala-Demertzi D.; Dkrzypek D.; Szymanska B.; Galani A.; Demertzis M.A.

Inorg. Chim. Acta 2005 358, 186-190.

(25) (a) Silva, J. A. L.; Rao, M. A. In Rheology of Fluid and Semisolid Foods; Rao, M.

A.; Springer 1999; Chapter 6. (b) Peyrelasse, J.; Lamarque, M.; Habas, J. P.; El

Bounia, N. Phys. Rev. E 1996, 53, 6126-6133.

(26) (a) Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem., Int. Ed. Engl. 2000,

39(15), 2632-2657. (b) Müller, T. J. J.; Blümel, J. J. Organomet. Chem. 2003, 683,

354-367. (c) Stiegman, A. E.; Graham, E.; Perry, K. J.; Khundkar, L. R.; Cheng, L.

T.; Perry, J. W. J. Am. Chem. Soc. 1991, 113(20), 7658-7666.

126

Appendix A. NMR spectra of SBU1, SBU2, 5 and 6

Figure. 4A.1 1H spectrum of SBU1 in DMSO-d6.

Figure 4A.2 1H spectra of quinoline, pyridine-d5 substituted SBU1 and SBU1 in DMSO-d6.

N1

2

3 4

5

6

7

Cu

Cu

N3

O

O

N3

O

O

N3

O

O

N3

O

O

N

N

DD D

D D

D

DD

D

D

Cu

Cu

N3

O

O

N3

O

O

N3

O

O

N3

O

O

N

N

[ppm] 10 9 8 7

[rel]

- 0.0

0.2

0.4

0.6

0.8

1.0

9.31

22

8.42

70

8.10

527.

8068

7.79

337.

6949

7.62

587.

6085

7.59

13

1.98

27

2.00

00

2.92

27

5.51

38

sh033812

sh033812 1 1 C:\Bruker\TOPSPIN guest

[ppm] 10 9 8 7

[rel]

- 0.0

0.2

0.4

0.6

0.8

1.0

9.31

22

8.42

70

8.10

527.

8068

7.79

337.

6949

7.62

587.

6085

7.59

13

1.98

27

2.00

00

2.92

27

5.51

38

sh033812

sh033812 1 1 C:\Bruker\TOPSPIN guest

127

Figure 4A.3 COSY NMR (300.13 Mz ) of SUB1 in DMSO-d6. Figure 4A.4 HSQC(400.13 Mz) of SBU1 in DMSO-d6.

128

Figure 4A.5 1H NMR (400 Mz) spectrum of 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3 -triazole (L). Figure 4A.6 13C NMR spectrum of 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3-triazole (L).

129

Figure 4A.7 1H spectra of 5 and 5 plus free 1-(4-carboxyphenyl)-4-methoxycarbonyl-1,2,3 -triazole (L). red: 5, blue: 5 plus free triazole ligand L. Figure 4A.8 HSQC NMR spectra of 6 in DMSO-d6.

130

Figure 4A.9 HMBC NMR spectrum of 6 in DMSO-d6.

131

Appendix A. Crystallographic Tables

Table 4A. 1 Crystal data and structure refinement for SBU1·quinoline.

Identification code sh03381m

Empirical formula C27 H18 Cu N8 O4 Formula weight 582.03

Temperature 90(2) K


Crystal system Triclinic Space group P-1

Unit cell dimensions a = 9.667(3) Å = 71.266(5)°.　

b = 11.073(3) Å = 74.446(6)°.　

c = 13.635(4) Å = 67.057(5)°.　

Volume 1255.7(6) Å3

Z 2



F(000) 594


Theta range for data collection 2.06 to 28.27°. Index ranges -11<=h<=12, -14<=k<=13, -18<=l<=16



Completeness to theta = 28.27° 92.4 % Absorption correction None







132

Table 4A. 2 Crystal data and structure refinement for SBU·2CH3CN.


Empirical formula C25 H18 Cu N8 O4


Temperature 90(2) K Wavelength 0.71073 Å

Crystal system Triclinic

Space group P-1

Unit cell dimensions a = 10.852(8) Å = 77.048(13)°. b = 9.292(6) Å = 80.273(11)°.

c = 13.409(9) Å = 69.079(11)°.

Volume 1224.9(15) Å3

Z 2



F(000) 570



Index ranges -8<=h<=14, -9<=k<=12, -16<=l<=17

Reflections collected 5907 Independent reflections 4808 [R(int) = 0.0690]


Absorption correction Empirical





Final R indices [I>2sigma(I)] R1 = 0.1368, wR2 = 0.3136 R indices (all data) R1 = 0.2132, wR2 = 0.3620


133

Table 4A.3. Crystal data and structure refinement for SBU2.

Identification code sh03773s

Empirical formula C46 H30 N14 O8 Zn2


Temperature 90(2) K

Wavelength 0.71073 A

Crystal system, space group Triclinic, P-1

Unit cell dimensions a = 8.3381(17) A alpha = 80.33(3) deg.

b = 9.4324(19) A beta = 87.11(3) deg.

c = 15.273(3) A gamma = 69.63(3) deg.

Volume 1110.0(4) A^3

Z, Calculated density 1, 1.552 Mg/m^3

Absorption coefficient 1.153 mm^-1

F(000) 528

Crystal size 0.28 x 0.18 x 0.05 mm

Theta range for data collection 2.33 to 25.00 deg.

Limiting indices -9<=h<=9, -5<=k<=11, -18<=l<=17

Reflections collected / unique 5108 / 3801 [R(int) = 0.1012]

Completeness to theta = 25.00 97.5 %

Absorption correction Sphere


Refinement method Full-matrix least-squares on F^2


Goodness-of-fit on F^2 0.902



Largest diff. peak and hole 1.106 and -1.239 e.A^-3

134

Table 4A. 4 Crystal data and structure refinement for I.


Empirical formula C143 H109 N23 O16 Zn2


Temperature 90(2) K




b = 15.292(3) A beta = 77.55(3) deg.

c = 15.780(3) A gamma = 74.60(3) deg.

Volume 3023.9(11) A^3



F(000) 1316














135

Table 4A. 5 Crystal data and structure refinement for II.


Empirical formula C33 H29 N7 O9 S Zn


Temperature 90(2) K




b = 12.429(3) A beta = 100.40(3) deg.

c = 17.564(4) A gamma = 91.27(3) deg.

Volume 1664.8(6) A^3



F(000) 788














136



Empirical formula C18 H14 Cu N2 O6.50



Crystal system Triclinic

Space group P-1

Unit cell dimensions a = 8.7262(16) Å = 87.035(3)°.　 b = 10.1308(18) Å = 87.300(3)°.　

c = 11.292(2) Å = 71.511(3)°.　

Volume 945.0(3) Å3

Z 2



F(000) 434



Index ranges -11<=h<=11, -13<=k<=13, -14<=l<=6



Absorption correction None







137



Empirical formula C33 H23 Cu N3 O9.50



Crystal system Monoclinic

Space group C2

Unit cell dimensions a = 32.692(6) Å = 90°.　 b = 14.431(3) Å = 94.972(3)°.　

c = 8.4580(15) Å = 90°.　

Volume 3975.3(12) Å3

Z 4



F(000) 1388



Index ranges -42<=h<=43, -19<=k<=15, -9<=l<=11



Absorption correction None





R indices (all data) R1 = 0.1264, wR2 = 0.2237 Absolute structure parameter 0.02(3)


138

Chapter 5

Functionalization of Discrete Coordination Nanospheres

via Organic Reactions

5.1 Introduction

The design and synthesis of discrete nanoscale coordination architectures with

desired shapes, geometries, and symmetries has been explored by several research

groups.1-6 These new classes of supermolecular species represent a new type of nanoscale

materials and offer many advantages over the conventional nanopariticles, which include

(1) identical in size, shape and symmetry, (2) precise control over the structure at atomic

level, (3) accessible cavities that can accommodate various guest molecules, (4) and large

versatility due to an unlimited number of building blocks, etc. Polygons and polyhedra,

which are based upon highly symmetric vertices and linkers, are the most common design

targets. Our interests are mainly focused on faceted polyhedra which are usually

generated by connecting polygons at their vertices.

The nine uniform faceted polyhedra which are closely related to the Platonic and

Archimedean solids are illustrated in Figure 5.1.7-8 The polyhedra represented by (a)-(c)

can be generated by connecting triangular building blocks via their vertices, the

polyhedra represented by (d)-(f) can be generated by connecting square building blocks

via their vertices, the polyhedra depicted by (g) are generated by connecting pentagonal

139

molecular building blocks via their vertices, and (h) and (i) can be generated by

connecting square with triangle and pentagon with triangle, respectively.

Figure 5.1 The nine uniform faceted polyhedra.

The two key geometric elements needed to be considered are the type of facets and

the dihedral angle between the facets. For example, connecting squares by a dihedral

angle of 90° can lead to a cubohemioctahedron (d), connecting squares by a dihedral

angle of 120° leads to a small rhombihexahedron (e), and connecting squares by a

dihedral angle of 144° leads to a small rhombidodecahedron (f).

Several versions of coordination nanospheres having approximate geometry of small

rhombihexahedron have been synthesized by Zaworotko et al and Yaghi et al.5,9-12 A

hydroxylated nanoball with a formula of [Cu2(5-OH-bdc)2L2]12,9 as shown in Figure 5.2,

140

consists of 12 square SBUs (Cu2(RCO2)4) which are linked by 1,3-bdc at an angle of 120°

via their vertices. This nanoball has an effective external diameter of ca. 2.99 nm

(measuring from opposite hydroxyl groups) and 24 hydroxyl groups decorating the

external surface.

Figure 5.2 The crystal structure of hydroxylated nanoball: (a) stick mode; (b) space-filled mode.9

These discrete coordination nanospheres can not only be used as building blocks to

construct even larger structures but also be used as nanoparticles, nanoscale containers,

drug carriers, etc. In many cases, functionalization of the nanospheres is very important.

In principle, there are two strategies used to functionalize the nanospheres: (1) using

pre-functionalized ligands to construct the nanospheres,12 (2) functionalization of

pre-assembled nanospheres via organic reactions. Although the first strategy is suitable

for a limited number of derivatives, it requires the determination of new synthetic

conditions for each ligand, and is therefore ineffective for the development of a broad

range of substituents. If the nanospheres bear external functional groups capable of

undergoing various organic reactions, the second strategy should prove very efficient for

141

decorating the nanosphere with a host of desired functionalities and chemical moieties.

Surprisingly, this strategy has been barely explored.13-14 In this chapter, we will

demonstrate the feasibility of the second strategy by postsynthetic functionalization of the

hydroxylated nanoball with long hydrocarbon chains via esterification reactions.



All the starting materials are commercially available and were used as received

without further purification. [Cu2 (5-OH-bdc)2 ·(DMSO)·(MeOH)]12, the hydroxylated

nanoball, (see Figure 5.3) was prepared by following a previously published procedure by

Zaworotko et al. A methanolic solution of Cu(NO3)2·2.5H2O (1 equivalent) and

5-OH-H2bdc (1equivalent) in the presence of 2 equivalents of 2,6-dimethylpyridine was

layered over several milliliter of DMSO in a 20ml vials. Blue-green crystals formed in

the vial in a several days.

Alkylated nanoball [Cu2(5-O2C12H23-bdc)2·(DMSO)·(MeOH)]12 (9): hydroxylated

nanoball (0.1mmol, 663mg), triethylamine Et3N (8ml), and dodecanoly chloride were

added into 40 ml fresh dichloromethane in a two-neck round bottom flask under Ar. The

reaction mixture was stirred at room temperature under Ar for ca. 48 hours. The solvent

was removed by Rotavap and a green solid was left. The green solid was washed with

methanol for several times and purified by using a snake skin dialysis tubing (3.5K

MWCO).

142

Alkylated nanoball [Cu2(5-O2C6H11-bdc)2·(DMSO)·(MeOH)]12 (10): Alkylated

nanoball 10 was prepared by following the same procedure used to synthesize alkylated

nanoball 9 except using hexanoyl chloride instead of dodecanoly chloride.

5.2.2 Characterization

NMR experiments were recorded on either a Bruker DRX-300 with a z-gradient BBI

probe or Bruker DPX-400 with a z-gradient BBO probe operating at 300.13 MHz and

400.13 MHz for 1H observe respectively. High-resolution TEM images were obtained on

a JEOL 2010 TEM instrument (200 kV). Hydrodynamic sizes of the alkylated nanoball

were measured by Malvern Zeta Sizer S90 dynamic light scattering instrument. Mass

analysis was performed on Voyager-DE PRO MALDI-MS and α-cyano-4-

hydroxycinnamic acid was used as matrix.

5. 3 Results and Discussion

The reaction of hydroxylated nanoballs with dodecanoly chloride in dichloromethane

in the presence of triethylamine affords an alkylated nanoball (9) as shown in Figure 5.3.

The first evidence for the successful attachment of dodecylcarboxylate on the

hydroxylated nanoball is the solubility change. The blue-green crystals of the

hydroxylated nanoball are very soluble in methanol, but insoluble in hexane and

dichloromethane, whereas 9 is insoluble in methanol, but soluble in hexane and

dichloromethane due to hydrophobic nature of the long hydrocarbon chains decorating

the external surface.

143

Figure 5.3 (a) The schematic representation of the hydroxylated nanoball; (b) The alkylation of

hydroxylated nanoball.

The main concern of using postsynthetic modification is whether the pre-assembled

coordination species can survive under various reaction conditions. In this specific case,

we need to test the stability of the hydroxylated nanoball under the esterification reaction

conditions. The high-resolution transmission electron microscopy (HRTEM) images of

the hydroxylated nanoball and alkylated nanoball 9 are illustrated in Figure 5.4. The

diameter of hydroxylated nanoball is ca. 2.2 nm (Figure 5.4 (a)) and the diameter of 9 is

ca. 2.2~2.5 nm (Figure 5.4 (b)). It is clear from the HRTEM images that the hydroxylated

nanoball did not fall apart during the reaction process and the size of the alkylated

nanoball 9 is similar to the original hydroxylated nanoball on HRTEM.

OH

OH

HO OH

OH

OHHO

HO

OH

OH

HO

HO

+ CH3(CH2)10COClEt3N

CH2Cl2 rt, 48 hrs

O

O

OO

O

O

O

O

O

O

OO

O

O

OO

OO

O OOO

O

O

OH

OH

HO OH

OH

OHHO

HO

OH

OH

HO

HO

(a)

(b) 9

hydroxylated nanoball

144

Figure 5.4 (a) The HRTEM image of hydroxylated nanoball; (b) The HRTEM image of alkylated

nanoball 9.

The size of the hydroxylated nanoball and alkylated nanoball 9 were also measured

by dynamic light scattering (DLS) in methanol and hexane, respectively. The

hydroxylated nanoball in methanol did not afford any peaks regardless of the

concentration. This is probably because hydroxylated nanoballs in methanol are

individual particles and their size is out of the measurement limit. A single size peak 11.3

±2.3 nm of 9 in hexane (ca. 0.05mM) indicates that tens of alkylated nanoballs

aggregate to form a cluster with an approximate size of 11 nm.(see Figure 5.5)

Measurements on more dilute solutions of 9, such as 0.01mM, did not give any size peaks

due to the dissolution of the clusters.

145

Figure 5.5 Hydrodynamic size distribution of 9 dispersed in hexane

Figure 5.6 (a) MALDI-MS of 9; (b) MALDI-MS of 10.

The matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS)

measurement on 9 shows M/Z peak 9970.8 (Figure 5.6 (a)) which confirms the successful

attachment of ca.18~19 dodecylcarboxylate on each hydroxylated nanoball. The reaction

of hydroxylated nanoball with hexanoyl chloride yields another alkylated nanoball 10. 10

is soluble in hexane and dichloromethane, but insoluble in methanol. MALDI-MS

146

measurement on 10 shows M/Z peak 7856.69 (Figure 5.6 (b)) that indicated ca.12-13

hexanoates are attached on each hydroxylated nanoball.

5. 4 Conclusions

We have demonstrated the feasibility of functionalization of pre-assembled discrete

coordination nanospheres via organic reactions. Dodecanoate and hexanoate were

successfully attached on the external surfaces of the hydroxylated nanoballs via

esterification reactions. The results indicate that postsynthetic functionalization of

nanospheres can dramatically change their stability, solubility, and etc. and bring these

classes of nanomaterials to a wider range of applications.

147

References

(1) P. J. Stang, B. Olenyuk, Acc. Chem. Res. 1997, 30, 502-518.

(2) L. R. MacGillivray, J. L. Atwood, Angew. Chem. Int. Ed. 1999, 38, 1018 –1033.

(3) M. Fujita, M. Tominaga, A. Hori, B. Therrien, Acc. Chem. Res. 2005, 38, 371-380.

(4) M.J. Rosseinsky, Microporous and Mesoporous Materials 2004, 73, 15–30.

(5) B. Moulton, J. Lu, A. Mondal, M. J. Zaworotko, Chem.Commun. 2001, 863-864.

(6) D. J. Tranchemontagne, Z. Ni, M. O’Keeffe, O. M. Yaghi, Angew. Chem. Int. Ed. 2008,

47, 5136 –5147.


(8) H. Abourahma, Structural Diversity in Metal-Organic Nanoscale Supramolecular

Architecture, Ph.D dissertation, University of South Florida, 2004.

(9) H. Abourahma, A. W. Coleman, B. Moulton, B. Rather, P. Shahgaldian, M. J.

Zaworotkto, Chem. Commun., 2001, 2380–2381.

(10) G. J. McManus, Z. Wang, M. J. Zaworotko, Crystal Growth & Design, 2004, 11-13.

(11) M. Eddaoudi, J. Kim, J. B. Wachter, H. K. Chae, M. O’Keeffe, O. M. Yaghi, J. Am.

Chem. Soc. 2001, 123, 4368-4369.

(12) H. Furukawa, J. Kim, K. E. Plass, O. M. Yaghi. J. Am. Chem. Soc. 2006, 128,

8398-8399.

(13) Z. Wang, S. M. Cohen, J. Am. Chem. Soc. 2007, 129, 12368-12369.

(14) Z. Wang, S. M. Cohen, Angew. Chem. Int. Ed. 2008, 47, 4699 –4702.

148

Chapter 6

Conclusions and Future Prospects

6.1 Conclusions

6.1.1 Synthesis of Porous Metal-Organic Frameworks by Design

The first aim of this dissertation was the rational design and synthesis of robust

porous metal-organic frameworks using well-defined building blocks. Self-assembly of

building blocks is directed by the information (structure and functionality) encoded in

them which is predisposed for forming the target frameworks. More information can be

encoded in the building blocks with increasing their size, complexity and dimension, and

therefore, a higher degree of control on the overall structures can be reached.

We synthesized a 4-fold mixed parallel/diagonal interpenetrating cubic metal-organic

framework 1 by using octahedral zinc carboxylate Zn4O(OOC-)6 SBUs as nodes and a

long and narrow organic ligand L1, as linkers. The implication of our results is that

diagonal interpenetration might occur if enough space remains for at least one more

network to penetrate after the maximally parallel interpenetration is achieved. Another

requirement is that the windows of each cube have to be open enough for the SBUs to

penetrate. Therefore, the shape and size of L1 is a key factor for generating the mixed

parallel and diagonal interpenetration. Despite the maximum 4-fold interpenetration, 1

contains large void space and high specific surface area. To the best of our knowledge,

this is the first time anyone has synthesized and observed mixed parallel/diagonal

149

interpenetrating α-Po coordination networks. The results indicate that interpenetration

itself can become a useful tool in the production of porosity.

We introduced a new concept of infinite 2D SBBs and synthesized pillared-layer

metal-organic frameworks 3 and 4 using infinite 2D tetragonal grid lattices and kagomé

lattices as SBBs, respectively. Although the organic spacer H4L3 which we used to

generate 3 and 4 is similar in size to H2L1 which was used to achieve the maximum

interpenetration, judicious choice of impenetrable 2D SBBs prevented interpenetration in

this case. Both 3 and 4 possess unprecedented levels of porosity. This result highlights the

higher degree of prediction and control achieved on the resulting structures using the

infinite 2D SBB approach. The pillared-layer architecture paradigm we demonstrated in

this dissertation points to a design strategy for the synthesis of large microporous, even

mesoporous MOFs.

6.1.2 Synthesis of Coordination Polymers via Organic Coupling Approach

We have developed a complementary and alternative covalent-based synthetic

strategy for the synthesis of new coordination compounds in which pre-assembled

coordination SBUs are modified or coupled together via common organic coupling

reactions. We modified discrete SBUs, synthesized coordination polymer gels and

crystalline coordination polymers by using common organic coupling reactions including

Huisgen 1, 3-dipolar cycloaddition and homo-alkyne coupling reactions. We modified

coordination nanospheres with long hydrocarbon chains by esterification reactions. The

SBUs and nanospheres were proved to maintain their structural integrity during the

150

organic reactions. The new covalent based synthetic method will lead to a wider range of

coordination materials.

6.2 Future Prospects

Design and synthesis of new crystalline coordination polymers with desired

structures and properties from molecular building blocks will still be the primary focus in

this field. Design and identification of new discrete or infinite building blocks targeting

optimal porosity and pore size, chiral networks, nondefault networks, and functional

networks with cooperative properties remains a challenge in the near future. Design and

synthesis of amorphous coordination polymers using the well-developed concepts and

principles in supramolecular chemistry and crystal engineering presents new prospects.

The latest advances and prospects of crystalline coordination polymers have been

addressed by a number of seminal papers, reviews and books and will not be enumerated

here.1-4 We will emphasize the future prospects and challenges of amorphous

coordination polymers and discrete nanoscale coordination architectures.

6.2.1 Rational Design and Synthesis of Amorphous Coordination Polymers

Modular synthesis based upon molecular building blocks can be applied to

synthesize an even wider range of coordination materials, such as amorphous

coordination polymers. When a more flexible ligand is involved or the geometry of

building blocks do not facilitate periodical propagation, a polycrystalline or amorphous

superstructure may form. These amorphous materials share a lot of featured properties

with their crystalline analogues and will likely possess unique properties that their

151

crystalline analogues do not have. For example, some coordination polymer gels exhibit

high processibility and have potential for use as stimuli-responsive materials.5-7 They can

be designed to have pore sizes ranging from microporous to mesoporous. A systematic

investigation on design and synthesis of amorphous materials, especially coordination

polymer gels, should be conducted. The characterization of amorphous coordination

polymers remains a huge challenge. A combination of advanced techniques, such as mass

spectrometry (MS), solid state NMR, solution NMR, X-ray powder diffraction,

transmission electron microscopy (TEM), scanning electron microscope (SEM), element

analysis, thermal gravity analysis (TGA), etc. will undoubtedly need to be explored, and

require development to characterize amorphous coordination polymers.

6.2.2 Exohedral Functionalization of Nanoscale Coordination Architectures

Discrete nanoscale metal-organic coordination architectures represent a new type of

nanoscale materials, which have tailorable size and properties, potential sites of

attachment and accessible cavities.8-10 Functionalization of these nanoscale coordination

architectures will lead them to a wider range of applications, such as nanoscale reactors,

dendrimers, drug delivery, etc. The results in Chapter 4 and 5 indicate that it is feasible to

functionalize pre-assembled discrete coordination architectures.

Further modification on hydroxylated nanoballs (small rhombihexahedron),

[Cu2(5-OH-bdc)2L2]12, with biomolecules, fluorophores, or drugs could be explored for

potential biological applications. It would also be interesting to synthesize the nanoball,

[Cu2(5-F-bdc)2L2]12,with other exterior functionalities, such as amines and azides. These

152

functional groups are easier for attaching biomolecules, fluorophores, or drugs. Synthesis

of new coordination polyhedra could also be targeted, specifically ones that are larger in

size than those previously reported. For example, a square SBUs based small

rhombidodecahedron nanoball. This nanoball can be generated by linking square SBUs at

an angle of 144o and will have a much larger size than the small rhombihexahedron

nanoball we used in Chapter 5.

153

References


(2) S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed. 2004, 43, 2334 –2375.

(3) O. M. Yaghi, M. O’Keffe, N. W. Ockwig, H. K. Chea, M. Eddaoudi, J. Kim, Nature, 2003,

423, 705-714.

(4) M.J. Rosseinsky, Microporous and Mesoporous Materials 2004, 73, 15–30.

(5) F. Fages. Angew. Chem. Int. Ed. 2006, 45, 1680-1682.

(6) H. J. Kim, J. H. Lee, M. Lee, Angew. Chem. Int. Ed. 2005, 44, 5810-5814.

(7) B. G. Xing, M. F. Choi, B. Xu, Chem. Eur. J. 2002, 8, 5028-5032.

(8) M. Fujita, M. Tominaga, A. Hori, B. Therrien, Acc. Chem. Res. 2005, 38, 371-380.

(9) B. Moulton, J. Lu, A. Mondal, M. J. Zaworotko, Chem. Commun. 2001, 863-864.

(10) B. Olenyuk, M. D. Levin, J. A.Whiteford, J. E. Shield, P. J. Stang, J. Am. Chem. Soc

1999, 121, 10434-10435.

design and synthesis of crystalline and amorphous

Documents