SYNTHESIS, CHARACTERIZATION AND PROPERTIES OF COORDINATION- AND LOW BAND GAP POLYMERS FOR POTENTIAL CATALYTIC AND PHOTOVOLTAIC APPLICATIONS BY CHRISTOPHER M. MACNEILL A Dissertation Submitted to the Graduate Faculty of WAKE FOREST UNIVERSITY GRADUATE SCHOOL OF ARTS AND SCIENCES in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Chemistry May 2011 Winston-Salem, North Carolina Approved by: Ronald E. Noftle, Ph. D., Advisor David L. Carroll, Ph. D., Chair Christa L. Colyer, Ph.D. Stephen B. King, Ph. D. Abdessadek Lachgar, Ph. D. ACKNOWLEDGEMENTS I would first like to acknowledge and extend my warmest regards and thanks to my advisor, Dr. Ronald E. Noftle, who has supported and guided me through my research over the past five years. I would like to give a special thanks to Dr. Cynthia S. Day for her patience and kindness while collecting my crystal structure data for the coordination polymers project. I was not the best crystal grower, but with her skills and help, I didn’t have to be. I also want to thank my committee members Dr. David L. Carroll, Dr. Abdessadek Lachgar and Dr. S. Bruce King for excellent discussions in all phases of my research, especially Dr. David L. Carroll and Dr. Robert C. Coffin for their mentoring with the organic solar cell project. I’d like to thank my fellow group members at the Wake Forest Center for Nanotechnology and Molecular Materials, especially Eric Peterson, Wanyi Nie, Gregory Smith and Chanitpa Khantha. I would like to acknowledge my current and former group members, Melissa Donaldson, Amy Marts, Alex MacIntosh, Eric Tainsh and Kasha Patel. Dr. Jianjun Zhang, and Sergio A. Gamboa for help with the coordination polymers project. I would also like to thank my fellow graduate students in the department of chemistry for making the past five years fun and enjoyable. For my parents, Michael and Karen MacNeill, and my sisters, Kerri and Molly, for supporting me always in whatever I endeavor. Without them, I wouldn’t be the person I am today. The utmost thanks to my beautiful fiancée, Samantha Miller, who has stuck with me through thick and thin. She is the most generous and kind-hearted person I’ve had the chance to know and I love her with all my heart. ii TABLE OF CONTENTS Page Acknowledgements ii Table of Contents iii List of Figures ix List of Schemes xiii List of Equations xiii List of Tables xiv Abbreviations xv Abstract xvii Chapter 1. Introduction to 1 1.1. Coordination Polymers 1 1.1.1. Coordination Chemistry 1 1.1.2. Coordination Polymers 2 1.2. Tuning Pore Size and Functionality 3 1.3. Gas Adsorption Properties of Coordination Polymers 6 1.3.1. Carbon Dioxide Gas 6 1.3.2. Hydrogen Gas 7 1.4. Luminescent Properties of Coordination Polymers 8 1.4.1. Luminescence 8 1.4.2. Luminescence of Coordination Polymers 9 1.4.3. Luminescence of Lanthanide-based Coordination Polymers 9 iii 1.5. Catalytic Properties of Coordination Polymers 10 1.5.1. Zeolites vs. Coordination Polymers 10 1.5.2. Catalytic Sites in Coordination Polymers 11 1.5.3. Catalytic Reactions using Coordination Polymers 12 1.5.3.1. Cyanosilylation of Aldehydes 12 1.5.3.2. The Biginelli Reaction 14 1.5.3.3. Knoevenagel Condensation 15 1.6. Research Goal 17 2. Experimental 18 2.1. Materials 18 2.2. Methods 19 2.2.1. Analytical Methods 19 2.2.2. X-ray Diffraction Methods 19 2.3. Synthesis 20 2.3.1. Solvothermal Method 20 2.3.2. Reflux Method 22 2.3.3. Vapor Diffusion Method 23 2.3.4. Catalytic Experiments 25 2.3.4.1. Heterogeneous Catalysts 25 2.3.4.2. Homogeneous Catalysts 27 3. Synthesis, Crystal Structure and Properties of Coordination Polymers 1-4 28 3.1. Synthesis of Coordination Polymers 1-4 29 iv 3.2. Single Crystal X-ray Diffraction 29 3.2.1. Crystal structure of La2(2,5-TDC)3(DMF)2H2O . DMF (1) 29 3.2.2. Crystal structure of Gd2(2,5-TDC)3(DMF)2H2O (2) 32 3.2.3. Crystal structure of Eu4(C6H2O4S)6(H2O)2(DMF)3 (H2O/n-prOH) (3) 35 3.2.4. Crystal structure of Y(2,5-TDC)(DMF)2(NO3) (4) 37 3.3. Thermogravimetric Analysis 38 3.4. Infrared Spectroscopy 39 3.5. Solid State Photoluminescence 42 3.6. Catalytic Properties 43 3.7. Conclusion 46 4. Synthesis, Crystal Structure and Properties of Coordination Polymers 5-9 48 4.1. Synthesis of Coordination Polymers 5-9 49 4.2. Single Crystal X-ray Diffraction 50 4.2.1. Crystal Structure of Tb2(F4BDC)3(DEF)2EtOH2 . 2(DEF) (5) 50 4.2.2. Crystal Structure of Gd2(F4BDC)3(DEF)2EtOH2 . 2(DEF) (6), Eu2(F4BDC)3-(DEF)2EtOH2 . 2(DEF) (7), La2(F4BDC)3-(DEF)2EtOH2 . 2(DEF) (8) and Nd2(F4BDC)3-(DEF)2EtOH2 . 2(DEF) (9) 53 4.3. Thermogravimetric Analysis 53 4.4. Infrared Spectroscopy 54 v 4.5. Solid State Photoluminescence 55 4.6. Catalytic Properties 57 4.7. Conclusion 59 5. Introduction to 61 5.1. The Environment 61 5.2. History of Photovoltaics 62 5.2.1. The Photoelectric Effect 62 5.2.2. Inorganic Photovoltaics 62 5.2.3. Organic Photovoltaics 64 5.3. Theory and Device Physics of Organic Solar Cells 65 5.3.1. Open Circuit Voltage 66 5.3.2. Short Circuit Current 67 5.3.3. Fill Factor 67 5.4. Device Architectures of Organic Solar Cells 69 5.5. Critical Parameters of Organic Solar Cells 70 5.6. Research Goal 73 6. Experimental 75 6.1 Materials 75 6.2. Methods 75 6.2.1. Analytical Methods 75 6.2.2. Electrochemical Methods 76 6.2.3. X-ray Diffraction Methods 76 6.2.4. Photovoltaic Methods 77 vi 6.3. Synthesis 78 7. Synthesis, Characterization and Photovoltaic Properties of P1-P3 87 7.1. Synthesis of Polymers P1-P3 88 7.2. Thermogravimetric Analysis of P1-P3 91 7.3. UV-Visible Spectroscopy of P1-P3 92 7.4. Electrochemistry of P1-P3 92 7.5. X-ray Powder Diffraction of P1-P3 94 7.6. Photovoltaic Properties of P1-P3 95 7.7. Conclusion 97 8. Synthesis, Characterization and Photovoltaic Properties of P4-P11 99 8.1. Synthesis of Polymers P4-P11 100 8.2. Thermogravimetric Analysis of P7-P11 103 8.3. UV-Visible Spectroscopy of P7-P11 104 8.4. Electrochemistry of P7-P11 105 8.5. X-ray Powder Diffraction of P7-P11 106 8.6. Photovoltaic Properties of P7-P11 108 8.7. Solvent Additive Processing of Polymer P11 110 8.8. Conclusion 113 9. Synthesis, Characterization and Photovoltaic Properties of P12-P14 115 9.1. Synthesis of Polymers P12-P14 116 9.2. Thermogravimetric Analysis of P12-P14 117 9.3. UV-Visible Spectroscopy of P12-P14 118 vii 9.4. Electrochemistry of P12-P14 119 9.5. X-ray Powder Diffraction of P12-P14 120 9.6. Photovoltaic Properties of P12-P13 122 9.7. Conclusion 124 Conclusions 126 Future Work 129 References 131 Appendix A 154 Appendix B 221 Publishing Permission and License 231 Scholastic Vitae 256 viii List of Figures Page Figure 1: Examples of coordination polymers with different dimensionalities. 2 Figure 2: The molecular building block (MBB) approach to coordination polymers. Adapted from James.51 4 Figure 3: Organic linkers based on geometry for use in the synthesis of coordination polymers. 5 Figure 4: Coordination environment around (a) La3+(1) and (b) La3+(2) ion. 30 Figure 5: (a) The La(1)-La(2) dimer formed by four bridging TDC2- linkages. (b) A chain formed through linking of dimers from coordination polymer 1 shown down the a-axis. The La environment is shown as teal polyhedra, O (red), C (grey), S (yellow). 31 Figure 6: A perspective view of coordination polymer 1 along the a-axis with solvent molecules omitted for clarity. 32 Figure 7: The coordination environments around (a) Gd3+(1) and (b) Gd3+(2) ion. 33 Figure 8: (a) The Gd(1)-Gd(1) dimer formed by four bridging TDC2- linkages. b) The Gd(2)-Gd(2) dimer formed by four bridging TDC2- linkages. c) A chain formed through the linking of dimers 1 and 2 down the a-axis for coordination polymer 2. The Gd environment is shown as blue polyhedra. 34 Figure 9: The coordination environments around the (a) Eu3+(1) ion and (b) Eu3+(2) ion. 35 Figure 10: (a) The asymmetric unit of Eu(1) and Eu(2) (pink) linked by two TDC2- (bridging) linkages along with eight TDC2- linkages (all monodentate), two DMF molecules and one H2O molecule (bridging) forming Eu4(2,5-TDC)6(DMF)3(H2O)2(H2O/n-prOH) (3). (b) A chain formed through the linking of dimers in (a) of coordination polymer 3 down the a-axis. Carboxylates are shown in red. 36 ix Figure 11: (a) A representation of the environment around the yttrium ion in coordination polymer 4 along the crystallographic ab-plane. b) A view of coordination polymer 4 along the crystallographic a-axis. 37 Figure 12: The TGA curves of coordination polymers 1-4. 38 Figure 13: The infrared spectra of coordination polymer 1 at room temperature (RT) and after heating to 380oC (compound 1a). 40 Figure 14: X-ray powder diffraction spectra comparing the room temperature pattern to the patterns at 380oC and 900oC of coordination polymer 1. 41 Figure 15: (a) Excitation (inset) and emission spectra of coordination polymer 3 excited at 390 nm.