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Synthesis and characterization of late transition metal oligothiophene complexes for light harvesting… Moore, Stephanie Amber 2012

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SYNTHESIS AND CHARACTERIZATION OF LATE TRANSITION METAL OLIGOTHIOPHENE COMPLEXES FOR LIGHT HARVESTING APPLICATIONS  by  Stephanie Amber Moore  B.Sc. (Hons.), St. Francis Xavier University, 2006  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY in  The Faculty of Graduate Studies (CHEMISTRY)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  June 2012 © Stephanie Amber Moore, 2012.  ABSTRACT The synthesis and characterization of late transition metal complexes combined with the β-substituted 3ʹ-(diphenylphosphino)-2,2ʹ:5ʹ,2ʺ-terthiophene (PT3) to yield metal-oligothiophene hybrid complexes are reported. These new complexes (shown on the following page) were studied with absorption, emission, and transient absorption spectroscopies, electrochemistry and X-ray crystallography. Ru(II) and Os(II) bis(diimine) complexes (52-53 and 54-55, respectively) containing PT3 in two different coordination modes (PS and PC bound) are reported. The binding mode is shown to affect the structural, photophysical and electronic properties of the complexes. Transient absorption spectra and lifetimes were obtained for all the complexes, and support a PT3 ligand-based lowest excited state in the case of the PS bound complexes, and a charge separated lowest excited state in the PC bound complexes. The DFT calculations and experimental results agree well. Cyclometalated iridium (III) complexes (58-63) were synthesized using microwave irradiation. In addition to the PS and PC coordination modes observed in the group 8 complexes, a third, monodentate, coordination mode was observed (P). The lowest energy absorption band and emission band shift based on the PT3 coordination mode. The nature of the excited state lifetimes did not change with coordination mode; all were assigned as a PT3 ligand-based excited state, however, the excited state lifetimes are influenced by the coordination mode. Heteroleptic Cu(I) complexes (75-76) were synthesized and yielded three and four coordinate complexes. The electrochemical and photophysical properties of these complexes vary with solvent. Minor changes are observed in the absorption spectra when obtained in different solvents, but interesting differences are observed in the electrochemical reversibility, excited state lifetimes, and profiles of the emission and transient absorption spectra.  ii  iii  PREFACE Material in Chapter 2 has been previously published as a full paper: Moore, S.A., Nagle, J.K., Wolf, M.O., Patrick, B.O. Inorg. Chem., 2011, 50, 5113-5122. I am the primary author under the supervision of Professor Michael O. Wolf. Dr. Brian O. Patrick determined the X-ray crystal structures of 52, 54 and 55. Dr. Jeffrey Nagle of Bowdoin College in Brunswick, Maine carried out the DFT calculations on 48, 49, 54 and 55, and analyzed the results. Material in Chapter 3 will be published in the future with authors Moore, S.A., Wolf, M.O., Patrick, B.O. I am the primary author under the supervision of Professor Michael O. Wolf. Dr. Brian O. Patrick determined the X-ray crystal structures of 58, 59, 60 and 61. Material in Chapter 4 will be published in the future with authors Moore, S.A., Wolf, M.O., Patrick, B.O. I am the primary author under the supervision of Professor Michael O. Wolf. Dr. Brian O. Patrick determined the X-ray crystal structures of 75 and 76.  iv  TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii PREFACE .......................................................................................................................... iv TABLE OF CONTENTS .................................................................................................... v LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ........................................................................................................... ix LIST OF CHARTS ........................................................................................................... xv LIST OF SCHEMES........................................................................................................ xvi LIST OF SYMBOLS AND ABBREVIATIONS ........................................................... xvii ACKNOWLEDGEMENTS ........................................................................................... xxiii DEDICATION ............................................................................................................... xxiv CHAPTER 1 - INTRODUCTION ...................................................................................... 1 Section 1.1 – Overview ................................................................................................... 1 Section 1.2 ‒ π – Conjugated Materials .......................................................................... 2 Section 1.3 ‒ Oligo- and Polythiophenes ........................................................................ 3 Section 1.4 ‒ Metal Organic Hybrid Materials ............................................................... 7 Section 1.4.1 – General ............................................................................................... 7 Section 1.4.2 – Group 8 Metal Oligo- and Polythiophene Hybrids ............................ 8 Section 1.4.3 – Group 9 Metal Oligo- and Polythiophene Hybrids .......................... 14 Section 1.4.4 – Group 10 Metal Oligo- and Polythiophene Hybrids ........................ 16 Section 1.4.5 – Group 11 Metal Oligo- and Polythiophene Hybrids ........................ 20 Section 1.4.6 – Group 12 Metal Oligo- and Polythiophene Hybrids ........................ 24 Section 1.5 – Dye Sensitized Solar Cells ...................................................................... 26 Section 1.6 – Goals and Scope ...................................................................................... 29 CHAPTER 2 – GROUP 8 DIPHENYLPHOSPHINO(TERTHIOPHENE) COMPLEXES ................................................................................................................... 31 Section 2.1 ‒ Introduction ............................................................................................. 31 Section 2.2 ‒ Experimental .......................................................................................... 33 Section 2.2.1 ‒ General ............................................................................................ 33 Section 2.2.2 ‒ Procedures ........................................................................................ 34 v  Section 2.2.3 ‒ X-Ray Crystallography .................................................................... 37 Section 2.2.4 – DFT Calculations ............................................................................. 39 Section 2.3 ‒ Results and Discussion ........................................................................... 39 Section 2.3.1 ‒ Synthesis .......................................................................................... 39 Section 2.3.2 ‒ Solid-State Molecular Structures ..................................................... 41 Section 2.3.3 – DFT Calculations ............................................................................. 45 Section 2.3.4 ‒ Cyclic Voltammetry ......................................................................... 52 Section 2.3.5 ‒ Electronic Absorption Spectra ......................................................... 55 Section 2.3.6 ‒ Emission Spectra .............................................................................. 61 Section 2.3.7 ‒ Transient Absorption Spectra .......................................................... 65 Section 2.4 ‒ Conclusions ............................................................................................. 72 CHAPTER 3 – CYCLOMETALATED IRIDIUM(III) PHOSPHINO(TERTHIOPHENE) COMPLEXES ................................................................................................................... 74 Section 3.1 ‒ Introduction ............................................................................................. 74 Section 3.2 ‒ Experimental .......................................................................................... 78 Section 3.2.1 ‒ General ............................................................................................ 78 Section 3.2.2 ‒ Procedures ........................................................................................ 79 Section 3.2.3 ‒ X-Ray Crystallography .................................................................... 82 Section 3.3 ‒ Results and Discussion ........................................................................... 85 Section 3.3.1 ‒ Synthesis .......................................................................................... 85 Section 3.3.2 ‒ Solid-State Molecular Structures ..................................................... 88 Section 3.3.3 ‒ Cyclic Voltammetry ......................................................................... 95 Section 3.3.4 ‒ Electronic Absorption Spectra ....................................................... 100 Section 3.3.5 ‒ Emission Spectra ............................................................................ 103 Section 3.3.6 ‒ Transient Absorption Spectra ........................................................ 106 Section 3.4 ‒ Conclusions ........................................................................................... 109 CHAPTER 4 – COPPER(I) MIXED-LIGAND COMPLEXES CONTAINING A PHOSPHINO(TERTHIOPHENE) LIGAND ................................................................. 111 Section 4.1 ‒ Introduction ........................................................................................... 111 Section 4.2 ‒ Experimental ........................................................................................ 115 Section 4.2.1 ‒ General .......................................................................................... 115 vi  Section 4.2.2 ‒ Procedures ...................................................................................... 116 Section 4.2.3 ‒ X-Ray Crystallography .................................................................. 117 Section 4.3 ‒ Results and Discussion ......................................................................... 119 Section 4.3.1 ‒ Synthesis ........................................................................................ 119 Section 4.3.2 ‒ Solid-State Molecular Structures ................................................... 121 Section 4.3.3 ‒ Cyclic Voltammetry ....................................................................... 125 Section 4.3.4 ‒ Electronic Absorption Spectra ....................................................... 128 Section 4.3.5 – Emission Spectra ............................................................................ 131 Section 4.3.6 – Transient Absorption Spectra ........................................................ 134 Section 4.4 – Conclusions ........................................................................................... 137 CHAPTER 5 – CONCLUSIONS AND PERSPECTIVES ............................................ 139 REFERENCES ............................................................................................................... 142 APPENDIX ..................................................................................................................... 159  vii  LIST OF TABLES Table 2-1 Selected bond lengths and angles for [Ru(phen)2PT3-PS](PF6)2, (52). ........... 42 Table 2-2 Selected bond lengths and angles for [Os(bpy)2PT3-PS](PF6)2, (54) .............. 44 Table 2-3 Selected bond lengths and angles for [Os(bpy)2PT3-PC](PF6) , (55) .............. 45 Table 2-4 Total metal bond orders from ADF scalar relativistic calculations (G-J: Gophinatan-Jug; N-M: Nalejawski-Mrozek). ................................................................... 51 Table 2-5 Metal atom atomic charges Q/e from ADF relativistic calculations according to six different methods: Hirshfeld, Voronoi deformation density (VDD), Bader atoms in molecule (AIM), Weinhold natural population analysis (NPA), Mulliken, and multipolederived quadrupole (MDC-q). Spin-orbit effects were included in all but the NPA charges. ............................................................................................................................. 52 Table 2-6 Absorption spectroscopy data for [Ru(phen)2PT3-PS](PF6)2, (52), [Ru(phen)2PT3-PC](PF6), (53), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3PC](PF6) ,(55). .................................................................................................................. 58 Table 2-7 Photophysical data for PT3 and complexes [Ru(bpy)2PT3-PS](PF6)2, (48), [Ru(bpy)2PT3-PC](PF6), (49), [Ru(phen)2PT3-PS](PF6)2, (52), [Ru(phen)2PT3-PC](PF6), (53), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3-PC](PF6), (55). .......................... 64 Table 3-1 Selected bond lengths and angles for Ir(ppz)2PT3Cl-P, (58) ........................... 89 Table 3-2 Selected bond lengths and angles for [Ir(ppz)2PT3-PS](BF4), (59) ................. 91 Table 3-3 Selected bond lengths and angles for Ir(ppz)2PT3-PC, (60) ............................ 93 Table 3-4 Selected bond lengths and angles for Ir(ppy)2PT3Cl-P, (61). .......................... 95 Table 3-5 Cyclic voltammetry data of [Ir(ppz)2PT3-PS](PF6), (59), Ir(ppz)2PT3-PC, (60), [Ir(ppz)2PT3-PS](PF6), (62), and Ir(ppz)2PT3-PC, (63).a .................................................. 97 Table 3-6 Photophysical data for cyclometalated Ir(III) - PT3 complexesa ................... 105 Table 4-1 Selected bond lengths and angles for [Cu(dmp)(MeCN)PT3-P](PF6), (75). . 122 Table 4-2 Selected bond lengths and angles for [Cu(phen)PT3-P](PF6), (76). .............. 125 Table 4-3 Cyclic voltammetry data of [Cu(phen)PT3-P](PF6), (76).a ............................ 126 Table 4-4 Photophysical data for [Cu(dmp)(MeCN)PT3-P](PF6), (75), and [Cu(phen)PT3-P](PF6), (76), in various solvents. ........................................................... 134 Table A-1 Selected crystallographic data for [Ru(phen)2PT3-PS](PF6)2, (52), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3-PC](PF6), (55) .................................. 159 Table A-2 Selected crystallographic data for Ir(ppz)2PT3Cl-P, (58), [Ir(ppz)2PT3PS](BF4), (59), and Ir(ppz)2PT3-PC, (60) ....................................................................... 164 Table A-3 Selected crystallographic data for Ir(ppy)2PT3Cl-P, (61) ............................. 165 Table A-4 Selected crystallographic data for [Cu(dmp)(MeCN)PT3-P](PF6), (75) and [Cu(phen)PT3-P](PF6), (76) ............................................................................................ 169 viii  LIST OF FIGURES Figure 1-1 Energy level diagram for conjugated oligomers from ethylene to polyacetylene. ..................................................................................................................... 3 Figure 1-2 Schematic of different types of metal-containing polymer systems. ............... 8 Figure 1-3 Schematic of a DSSC showing the flow of electrons, adapted from Ref.84 ... 27 Figure 2-1 Solid-state structure of [Ru(phen)2PT3-PS](PF6)2, (52). Hydrogen atoms, counterions, and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability. ................................................................................................................ 42 Figure 2-2 Solid-state structure of [Os(bpy)2PT3-PS](PF6)2, (54). Hydrogen atoms, counterions, and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability. ................................................................................................................ 43 Figure 2-3 Solid-state structure of [Os(bpy)2PT3-PC](PF6), (55). Hydrogen atoms and counterions removed for clarity. Thermal ellipsoids drawn at 50% probability. ............. 45 Figure 2-4 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Ru(bpy)2PT3-PS](PF6)2, (48), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. ..................... 47 Figure 2-5 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Ru(bpy)2PT3-PC](PF6), (49), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. ..................... 48 Figure 2-6 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Os(bpy)2PT3-PS](PF6)2, (54), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. ..................... 49 Figure 2-7 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Os(bpy)2PT3-PC](PF6), (55), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. ..................... 50 Figure 2-8 Cyclic voltammograms of (a) [Os(bpy)2PT3-PS](PF6)2, (54), and (b) [Os(bpy)2PT3-PC](PF6), (55), in CH3CN, 0.1 M TBAPF6, 100mV/s scan rate, Pt disc working electrode, Pt mesh counter electrode and silver wire reference electrode. ......... 54 ix  Figure 2-9 Cyclic voltammograms of (a) [Ru(phen)2PT3-PS](PF6)2, (52), and (b) [Ru(phen)2PT3-PC](PF6), (53), in CH3CN, 0.1 M TBAPF6, 50mV/s scan rate, Pt disc working electrode, Pt mesh counter electrode and silver wire reference electrode. ......... 55 Figure 2-10 UV-vis absorption spectra of (a) [Ru(bpy)2PT3-PS](PF6)2, (48), [Ru(phen)2PT3-PS](PF6)2, (52), [Os(bpy)2PT3-PS](PF6)2, (54), and (b) [Ru(bpy)2PT3PC](PF6), (49), [Ru(phen)2PT3-PC](PF6), (53), and [Os(bpy)2PT3-PC](PF6), (55), in CH3CN. ............................................................................................................................. 57 Figure 2-11 UV-vis spectra of (a) PT3, (b) [Ru(bpy)2PT3-PS](PF6)2, (48), (c) [Os(bpy)2PT3-PS](PF6)2, (54), (d) [Ru(bpy)2PT3-PC](PF6), (49), and (e) [Os(bpy)2PT3PC](PF6), (55), in CH3CN after 0, 2, 5, 15, 30, 60, 90, and 120 minutes of irradiation at 366 nm. ............................................................................................................................. 60 Figure 2-12 Emission spectra of [Ru(phen)2PT3-PS](PF6)2, (52), and [Ru(phen)2PT3PC](PF6), (53), in nitrogen-sparged CH3CN. The emission of [Ru(phen)2PT3-PC](PF6) excited at 456 nm has been expanded by a factor of 5. .................................................... 62 Figure 2-13 Emission spectra of [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3PC](PF6), (55), in nitrogen-sparged CH3CN. ................................................................... 62 Figure 2-14 Time-resolved transient absorption spectra of (a) PT3 and (b) T3 in CH3CN. ex = 355 nm. .................................................................................................................... 66 Figure 2-15 Time-resolved transient absorption spectra of (a) [Ru(bpy)2PT3-PS](PF6)2 (48), (b) [Ru(phen)2PT3-PS](PF6)2, (52), and (c) [Os(bpy)2PT3-PS](PF6)2, (54), in CH3CN. ex = 355 nm. ..................................................................................................... 68 Figure 2-16 Time-resolved transient absorption spectra of (a) [Ru(bpy)2PT3-PC](PF6) (49), (b) [Ru(phen)2PT3-PC](PF6), (53), and (c) [Os(bpy)2PT3-PC](PF6), (55), in CH3CN. ex = 355 nm. ..................................................................................................... 71 Figure 2-17 Qualitative energy diagram for [Ru(bpy)2PT3-PS](PF6)2, (48), [Ru(bpy)2PT3PC](PF6), (49), [Ru(phen)2PT3-PS](PF6)2, (52), [Ru(phen)2PT3-PC](PF6), (53), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3-PC](PF6), (55). Abbreviations used indicate metal center and binding mode of the complexes. .............................................. 72 Figure 3-1 31P{1H} NMR spectra showing switching between [Ir(ppz)2PT3-PS](PF6), (59), ((a) and (c)) and Ir(ppz)2PT3-PC, (60), ((b) and (d)). Heating the PS bound complex (a) to reflux with base produced the PC bound complex (b). Addition of trifluoroacetic acid resulted in the sample switching back to the PS bound complex (c) instantly. Once again, heating to reflux with base yielded the PC complex (d). ....................................... 87 Figure 3-2 Solid-state structure of Ir(ppz)2PT3Cl-P, (58). Hydrogen atoms and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability. ................ 89 Figure 3-3 Solid-state structure of [Ir(ppz)2PT3-PS](BF4), (59). Hydrogen atoms, counterions, and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability. ................................................................................................................ 91 Figure 3-4 Solid-state structure of Ir(ppz)2PT3-PC, (60). Hydrogen atoms removed for clarity. Thermal ellipsoids drawn at 50% probability. ...................................................... 93  x  Figure 3-5 Solid-state structure of Ir(ppy)2PT3Cl-P, (61). Hydrogen atoms and solvent in lattice are removed for clarity. Thermal ellipsoids drawn at 50% probability. ................ 94 Figure 3-6 Cyclic voltammetry of (a) [Ir(ppz)2PT3-PS](PF6), (59), and (b) Ir(ppz)2PT3PC, (60), on a Pt disk electrode (scan rate 100 mv/s), electrolyte = 0.1 M [n-Bu4N](PF6), solvent = CH3CN. ............................................................................................................. 98 Figure 3-7 Cyclic voltammetry of (a) [Ir(ppy)2PT3-PS](PF6), (62), and (b) Ir(ppy)2PT3PC, (63), on a Pt disk electrode (scan rate 100 mv/s), electrolyte = 0.1 M [n-Bu4N](PF6), solvent = CH3CN. ............................................................................................................. 99 Figure 3-8 Solution absorption spectra of PT3, Ir(ppz)2PT3Cl-P, (58), [Ir(ppz)2PT3PS](PF6), (59), Ir(ppz)2PT3-PC, (60), in CH3CN........................................................... 101 Figure 3-9 Solution absorption spectra of PT3, Ir(ppy)2PT3Cl-P, (61), [Ir(ppy)2PT3PS](PF6), (62), Ir(ppy)2PT3-PC, (63), in CH3CN .......................................................... 102 Figure 3-10 Emission spectra of PT3, Ir(ppz)2PT3Cl-P, (58), [Ir(ppz)2PT3-PS](PF6), (59), Ir(ppz)2PT3-PC, (60), in CH3CN. ................................................................................... 104 Figure 3-11 Emission spectra of PT3, Ir(ppz)2PT3Cl-P, (61), [Ir(ppz)2PT3-PS](PF6), (62), Ir(ppz)2PT3-PC, (63), in CH3CN. ................................................................................... 105 Figure 3-12 Transient absorption spectra of (a) Ir(ppz)2PT3Cl-P,(58), (b) Ir(ppz)2PT3-PC, (60), and (c) [Ir(ppz)2PT3-PS](PF6), (59), in argon-sparged CH3CN. ............................ 107 Figure 3-13 Transient absorption spectra of (a) Ir(ppy)2PT3Cl-P, (61), (b) Ir(ppy)2PT3PC, (63), and (c) [Ir(ppy)2PT3-PS](PF6), (62), in argon-sparged CH3CN. ..................... 109 Figure 4-1 Solid-state structure of [Cu(dmp)(MeCN)PT3-P](PF6), (75). Hydrogen atoms and counterions were removed for clarity. Thermal ellipsoids are drawn at 50% probability. ...................................................................................................................... 122 Figure 4-2 Solid-state structure of [Cu(phen)PT3-P](PF6), (76), showing (a) the major disorder fragment and (b) the minor fragment. Hydrogen atoms and counterions were removed for clarity. Thermal ellipsoids are drawn at 50% probability. ......................... 124 Figure 4-3 Cyclic voltammogram of [Cu(phen)PT3-P](PF6), (76), in CH3CN, 0.1 M TBAPF6, 100mV/s scan rate, PT disc working electrode, Pt mesh counter electrode and silver wire reference electrode. ....................................................................................... 127 Figure 4-4 Cyclic voltammogram of [Cu(phen)PT3-P](PF6), (76), in CH2Cl2, 0.1 M TBAPF6, 100mV/s scan rate, PT disc working electrode, Pt mesh counter electrode and silver wire reference electrode. ....................................................................................... 128 Figure 4-5 Solution absorption spectrum of [Cu(dmp)(MeCN)PT3-P](PF6), (75), in CH3CN (black) and CH2Cl2 (red).................................................................................... 129 Figure 4-6 Solution absorption spectra of [Cu(phen)PT3-P](PF6), (76), in CH3CN (black) and CH2Cl2 (red). ............................................................................................................ 130 Figure 4-7 Emission spectra of [Cu(dmp)(MeCN)PT3-P](PF6), (75), in CH3CN (black) and CH2Cl2 (red). ............................................................................................................ 132 Figure 4-8 Emission spectra of [Cu(phen)PT3-P](PF6), (76), in CH3CN (black) and CH2Cl2 (red). ................................................................................................................... 133 xi  Figure 4-9 Transient absorption spectra of [Cu(dmp)(MeCN)PT3-P](PF6), (75), in (a) argon-sparged CH3CN and (b) argon-sparged CH2Cl2. .................................................. 135 Figure 4-10 Transient absorption spectra of [Cu(phen)PT3-P](PF6), (76), in (a) argonsparged CH3CN and (b) argon-sparged CH2Cl2. ............................................................ 136 Figure A-1 Decay of transient signal averaged over the 450 - 525 nm wavelength region for PT3 (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red). .............................................................................................. 160 Figure A-2 Decay of transient signal averaged over the 425 - 475 nm wavelength region for T3 (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red). ........................................................................................................................... 160 Figure A-3 Decay of transient signal averaged over the 575 - 625 nm wavelength region for [Ru(bpy)2PT3-PS](PF6)2, (48), (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red). ................................................................... 161 Figure A-4 Decay of transient signal averaged over the 560 - 590 nm wavelength region for [Ru(phen)2PT3-PS](PF6)2, (52), (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red). ................................................................... 161 Figure A-5 Decay of transient signal averaged over the 550 - 575 nm (black) and 375400 nm (green) wavelength regions for [Os(bpy)2PT3-PS](PF6)2, (54), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red and blue, respectively). ......................................................................................................................................... 162 Figure A-6 Decay of transient signal averaged over the 500 - 525 nm (black) and 425475 nm (green) wavelength regions for [Ru(bpy)2PT3-PC](PF6), (49), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red and blue, respectively). ......................................................................................................................................... 162 Figure A-7 Decay of transient signal averaged over the 500 - 525 nm (black) and 425475 nm (green) wavelength regions for [Ru(phen)2PT3-PC](PF6), (53), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red and blue, respectively). ......................................................................................................................................... 163 Figure A-8 Decay of transient signal averaged over the 465-485 nm (black), 550 - 575 nm (green) and 650-675 nm (orange) wavelength regions for [Os(bpy)2PT3-PC](PF6), (55), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red, blue, and purple, respectively). ....................................................................................... 163 Figure A-9 Decay of the transient signal averaged over the 450 - 475 nm wavelength region for Ir(ppz)2PT3Cl-P, (58), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). ................................................................... 166 Figure A-10 Decay of the transient signal averaged over the 450 -500 nm wavelength region for Ir(ppz)2PT3-PC, (60), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). ................................................................... 166 Figure A-11 Decay of the transient signal averaged over the 450 -500 nm wavelength region for [Ir(ppz)2PT3-PS](PF6), (59), (black) upon excitation at 355 nm in argonsparged CH3CN, and the monoexponential fit (red). ...................................................... 167 xii  Figure A-12 Decay of the transient signal averaged over the 460 -485 nm wavelength region for Ir(ppy)2PT3Cl-P, (61), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). ................................................................... 167 Figure A-13 Decay of the transient signal averaged over the 475 -525 nm wavelength region for Ir(ppy)2PT3-PC, (63), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). ................................................................... 168 Figure A-14 Decay of the transient signal averaged over the 475-525 nm wavelength region for [Ir(ppz)2PT3-PS](PF6), (62), (black) upon excitation at 355 nm in argonsparged CH3CN, and the monoexponential fit (red). ...................................................... 168 Figure A-15 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(dmp)(MeCN)PT3-P](PF6), (75), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). ........................................... 170 Figure A-16 Decay of the transient signal averaged over the 475-525 nm wavelength region for [Cu(dmp)(MeCN)PT3-P](PF6), (75), (black) upon excitation at 355 nm in argon-sparged CH2Cl2, and the monoexponential fit (red). ............................................ 170 Figure A-17 Decay of the transient signal averaged over the 550-600 nm wavelength region for [Cu(dmp)(MeCN)PT3-P](PF6), (75), (black) upon excitation at 355 nm in argon-sparged CH2Cl2, and the monoexponential fit (red). ............................................ 171 Figure A-18 Transient absorption spectra of PT3 in argon-sparged CH3CN. ................ 171 Figure A-19 Decay of the transient signal averaged over the 475-525 nm wavelength region for PT3 (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). .............................................................................................. 172 Figure A-20 Transient absorption spectra of PT3 in argon-sparged CH2Cl2. ................ 172 Figure A-21 Decay of the transient signal averaged over the 475-525 nm wavelength region for PT3 (black) upon excitation at 355 nm in argon-sparged CH2Cl2, and the monoexponential fit (red). .............................................................................................. 173 Figure A-22 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH3CN, and the monoexponential fit (red). ...................................................... 173 Figure A-23 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH2Cl2, and the monoexponential fit (red). ...................................................... 174 Figure A-24 Decay of the transient signal averaged over the 575-600 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH2Cl2, and the monoexponential fit (red). ...................................................... 174 Figure A-25 Transient absorption spectra of [Cu(phen)PT3-P](PF6), (76), in argonsparged CH3OH. ............................................................................................................. 175 Figure A-26 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH3OH, and the monoexponential fit (red). ...................................................... 175 xiii  Figure A-27 Transient absorption spectra of [Cu(phen)PT3-P](PF6), (76), in argonsparged pyridine. ............................................................................................................. 176 Figure A-28 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged pyridine, and the monoexponential fit (red). ..................................................... 176  xiv  LIST OF CHARTS Chart 1-1 ............................................................................................................................ 2 Chart 1-2 ............................................................................................................................ 4 Chart 1-3 ............................................................................................................................ 4 Chart 1-4 Ref.35-37 ............................................................................................................ 10 Chart 1-5 Ref.7, 39, 41 ......................................................................................................... 11 Chart 1-6 Ref.42-44 ............................................................................................................ 12 Chart 1-7 Ref.46, 47............................................................................................................ 13 Chart 1-8 Ref.9, 48-52 ......................................................................................................... 14 Chart 1-9 Ref.53, 54............................................................................................................ 17 Chart 1-10 Ref.55-57 .......................................................................................................... 18 Chart 1-11 Ref.58, 60, 61...................................................................................................... 20 Chart 1-12 Ref.63, 65-67 ...................................................................................................... 21 Chart 1-13 Ref.69-73 .......................................................................................................... 23 Chart 1-14 Ref.74-77 .......................................................................................................... 25 Chart 1-15 Ref.80, 81.......................................................................................................... 28 Chart 2-1 Ref.102-104 ......................................................................................................... 32 Chart 2-2 .......................................................................................................................... 33 Chart 3-1 Ref.93................................................................................................................ 75 Chart 3-2 .......................................................................................................................... 76 Chart 3-3 .......................................................................................................................... 76 Chart 3-4 .......................................................................................................................... 77 Chart 4-1 Ref.238, 239, 248.................................................................................................. 113 Chart 4-2 Ref.240 ............................................................................................................ 114 Chart 4-3 ........................................................................................................................ 114 Chart 5-1 Ref.274 ............................................................................................................ 140  xv  LIST OF SCHEMES Scheme 1-1 ......................................................................................................................... 6 Scheme 1-2 ......................................................................................................................... 7 Scheme 2-1 ....................................................................................................................... 40 Scheme 2-2 ....................................................................................................................... 40 Scheme 3-1 ....................................................................................................................... 76 Scheme 3-2 ....................................................................................................................... 85 Scheme 3-3 ....................................................................................................................... 87 Scheme 4-1 Ref.243 ......................................................................................................... 112 Scheme 4-2 ..................................................................................................................... 119 Scheme 4-3 ..................................................................................................................... 121  xvi  LIST OF SYMBOLS AND ABBREVIATIONS Abbreviation  Description  A  amperes  Å  Ångstrom  ADF  Amsterdam density functional  ADF-DFT  Amsterdam density functional - density functional theory  AIM  atoms in molecule  Anal.  Analysis  AO  atomic orbital  A2T3  3,3ʺ-bis(acetylene)-2,2ʹ-5ʹ,2ʺ-terthiophene  a.u.  arbitrary units  bdpp  1,2- bis(diphenylphosphino)benzene  bpy  2,2'-bipyridine  br.  broad  Calcd  calculated  CB  conduction band  cm  centimeter  C^N  cyclometalating ligand  CS  charge-separated  CT  charge transfer  CV  cyclic voltammogram/ voltammetry    chemical shift (ppm)  °  degrees  °C  degrees Celsius    heat    difference  E  energy difference between redox couples (mV)  D  dye  d  doublet  DCM  dichloromethane  dd  doublet of doublets xvii  ddd  doublet of doublets of doublets  DFT  density functional theory  DMF  dimethylformamide  dmp  2,9-dimethyl-1,10-phenanthroline  dppe  1,2- bis(diphenylphosphino)ethane  dppf  1,1ʹ- bis(diphenylphosphino)ferrocene  dppm  bis(diphenylphosphinomethane)  dppp  1,3- bis(diphenylphosphino)propane  DSSC  dye-sensitized solar cell    molar absorptivity (M-1cm-1)  x  hapticity  e-  electron  E1/2  half wave redox potential (V)  EA  elemental analysis  EDOT  3,4-ethylenedioxythiophene  Eg  band gap  Ep  peak potential, irreversible wave (V)  EPR  electron paramagnetic resonance  esd  estimated standard deviation  ESI  electrospray ionization  Et2O  diethylether  EtOH  ethanol  eq.  equivalents  eV  electron volts  F  X-ray scattering factor  Fc  ferrocene  g  gram  GGA  generalized gradient approximation  GHz  gigahertz  G-J  Gophinatan-Jug  HH  Head-to-Head  HOMO  highest occupied molecular orbital  xviii  hr  hour  HRMS  electron high-resolution mass spectrometry  HT  Head-to-Tail  Hz  Hertz  I  intensity of the X-ray reflection  IPCE  incident photon to current efficiency  IR  infrared  ITO  indium doped tin oxide  J  magnetic coupling constant  K  Kelvin  knr  non-radiative decay constant  kr  radiative decay constant  em  emission wavelength  ex  excitation wavelength (nm)  max  wavelength at band maximum (nm)  L  ligand  LC  ligand centered  LDA  lithium diisopropylamide  LEC  light-emitting electrochemical cell  LLʹCT  ligand to ligand charge transfer  LMCT  ligand to metal charge transfer  LUMO  lowest unoccupied molecular orbital    X-ray linear absorption coefficient    micro  A  microamperes  s  microseconds  M  molarity (mol/L), molecule (MS), metal  m  multiplet (NMR), milli  MALDI-TOF  matrix-assisted laser desorption ionization time of flight  MC  metal centered  MDC-q  multipole-derived quadrupole  MeOH  methanol xix  MeCN  acetonitrile  mg  milligram  MHz  Megahertz  min  minute  mL  millilter  MLCT  metal to ligand charge transfer  MLLʹCT  mixed metal-ligand to ligand charge transfer  mm  millimeter  mmol  millimole  MO  molecular orbital  mol  mole  MS  mass spectra  mV  millivolts  m/z  mass-to-charge ratio  n  number of units (ligands, oligomer, polymer), nano  Nd:YAG  neodymium-doped yttrium aluminium garnet  NHC  N-heterocyclic carbene  NIR  near infrared  nm  nanometer  N-M(1)  Nalejawski-Mrozek method1  N-M(2)  Nalejawski-Mrozek method2  N-M(3)  Nalejawski-Mrozek method3  NMR  nuclear magnetic resonance  N^N  diimine ligand  NPA  natural population analysis  ns  nanosecond    angle the X-ray source makes with the crystal  OLED  organic light emitting diode  ORTEP  Oak Ridge Thermal Ellipsoid Plot  OsPC  osmium complex with PC coordination of PT3  OsPS  osmium complex with PS coordination of PT3  Φem  emission quantum yield  xx    X-ray rotation axis  P  phosphine coordination  PAT  polyalkylthiophene  PEDOT  poly(3,4-ethylenedioxythiophene)  PC  phosphine, thienyl carbon coordination  Ph  phenyl (C6H5)  phen  1,10-phenanthroline  POP  bis(2-(diphenylphosphanyl)phenyl)ether  P^P  diphosphine ligand  ppm  parts per million  ppy  2-phenylpyridine  ppz  1-phenylpyrazole  PS  phosphine, thienyl sulphur coordination  PT  polythiophene  PT3  3´-(diphenylphosphino)-2,2ʹ:5ʹ,2ʺ-terthiophene  P2T3  3,3ʺ-bis(diphenylphosphino)-2,2ʹ:5ʹ,2ʺ-terthiophene  py  pyridine  q  quartet    density (g cm-1)  R  linear regression goodness of fit  Ref.  reference  RuPC  ruthenium complex with PC coordination of PT3  RuPS  ruthenium complex with PS coordination of PT3  ∑  the sum of    standard deviation of the X-ray intensity  s  singlet (NMR), second  SCE  standard calomel electrode  SEM  scanning electron microscopy  sh  shoulder  SOMO  singly occupied molecular orbital    lifetime    angle xxi    angle of diffraction  t  triplet  T3  terthiophene  TA  transient absorption  TBAPF6  tetrabutylammonium hexafluorophosphate  terpy  2,2';6',2"-terpyridine  TGA  thermogravimetric analysis  THF  tetrahydrofuran  tht  tetrahydrothiophene  TOF  time of flight  TT  Tail-to-Tail  UBC  University of British Columbia  UV  ultraviolet  V  volt, volume  VB  valence band  VDD  Voronoi deformation density  vis  visible  XY  bidentate ligand  δc  one electron spin-orbit coupling constant  Z  number of molecules in a crystallographic unit cell  ZORA  zeroth-order relativestic approximation  xxii  ACKNOWLEDGEMENTS Throughout this process there have been many people who have helped me achieve my goals. First and foremost, I would like to thank my supervisor, Dr. Mike Wolf, for his support, guidance, and helpful advice. Many thanks to my fellow Wolf group members, both past and present. I enjoyed the atmosphere, friendship, and support. It was a pleasure to work with each of you and to benefit from your knowledge, whether it was in the lab, at a pub or out in the wilderness. I am especially grateful to Tim Kelly for teaching me the ropes, and Glen Bremner for all his help with the potentiostat. Thanks to my friends outside of the Wolf group as well. You have made this journey much easier. Although I don‟t have room to mention everyone by name, I hope you know who you are! Yasmin, you are a wonderful and generous friend, and I admire your positive outlook despite some tough situations. CT, you are a fabulous friend. Your smile and support has been greatly appreciated. Thanks for everything.  I wish to thank all the shops, services, technicians and staff for keeping everything running smoothly. Special thanks are extended to the staff at the UBC Mass Spectrometry Centre, for collecting elemental analysis and mass spectrometry data on my complexes, Dr. Brian Patrick, for solving my crystal structures, and Saeid Kamal, for his vast knowledge and assistance with the TA instrument. Something that was once only considered future work is now a big part of my thesis. My thanks also go to Dr. Jeff Nagle (Bowdoin College) for calculations on the group 8 complexes, and Dr. Dai Davies (University of Leicester) for his helpful chats and suggestions related to the iridium work. Thanks to the Orvig group for the use of their microwave reactor. I am also thankful for funding from NSERC, UBC and the Walter C. Sumner Foundation. Of course no acknowledgments would be complete without giving thanks to my family. My parents have always expressed how proud they are of me and how much they love me. I too am proud of them and love them very much. I am grateful for them both and for the „smart genes‟ they passed on to me. I am also extremely grateful for my brother, Greg. In addition to knowing how to drive me crazy, he can always make me smile. Thanks for all your support, and for dragging me out of the house on more than one occasion.  xxiii  DEDICATION  To Mom and Dad  xxiv  CHAPTER 1 INTRODUCTION  Section 1.1 – Overview The development and use of sustainable energy sources in a society that is overly reliant on petroleum based fuels is essential. Alternative energy sources, such as solar, wind and hydrogen are all being actively investigated for replacements to fossil fuels. 1, 2 The sun gives us our most abundant energy source, and there is a need to acquire new methods to capture, transfer, store and use solar energy effectively. Photovoltaic cells based on inorganic semiconductors (silicon) have long been commercially available, but have a high production cost (compared to electrical energy generated using coal or oil).3 Semiconducting organic π-conjugated materials, such as polythiophene, are attractive for application in solar cells, sensors, optical devices and electrical conductors.4 They have good thermal stability, and can be functionalized to alter their optical and electronic properties, as well as lead to increased solubility.4 Conjugated polymer or oligomer materials may be easily spray or spin coated, reducing production costs significantly. When metal complexes are coordinated to conjugated polymers, interactions occur which modify the physical, chemical and electronic properties of both species.5 Metals can be incorporated into oligothiophene or polythiophene chains by direct insertion into the chain,6 direct bonding to the backbone through a thiophene,7 bypyridyl8 or other group, or as pendant groups attached directly through a ligand.9 Numerous analogues and derivatives can be made, resulting in a wide variety of materials. For example, oligo- and polythiophenes have been incorporated into organic light-emitting diodes (OLEDs), photovoltaics, transistors and other devices.10 This thesis focuses on the synthesis and characterization of metal-terthiophene complexes. The photophysical properties are investigated, along with the electrochemical properties of the complexes, to determine if there is promise for use of these, or similar, complexes as solar energy harvesters, such as dyes in dye-sensitized solar cells (DSSCs). 1  In this Chapter, π – conjugated materials, with emphasis on oligo- and polythiophenes, are discussed, followed by a section on metal organic hybrid materials. The effects of the incorporation of metal centers into conjugated materials are examined. Examples of some late transition metal oligo – and polythiophenes hybrids are given. Finally, a brief discussion on DSSCs and useful dye properties is included.  Section 1.2‒ π – Conjugated Materials π – Conjugated materials have alternating single and double bonds resulting in a backbone of sp2 hybridized carbon centers and/or heteroatoms with an extended π conjugated system. Common examples of conjugated polymers are shown in Chart 1-1. Heeger, MacDiarmid and Shirakawa discovered high conductivity in oxidized iodinedoped polyacetylene in 1977.11 Their discovery showing doped polyacetylene has up to 12 orders of magnitude greater conductivity than undoped polyacetylene launched research in the area of conducting polymers.12-15 The Nobel prize in Chemistry was awarded to these researchers in 200016 for “the discovery and development of conducting polymers.” Chart 1-1  Polyacetylene, and shorter oligomers, are composed of repeating ethylene units. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of polyacetylene oligomers are π and π* orbitals, respectively. With each additive ethylene unit in the chain, there is an increase in the number of π and π* MOs. This increase in conjugation causes a decrease in the HOMO-LUMO gap. In a polymer of infinite length, the π-orbitals overlap and form a valence band (VB), while the overlapping π*-orbitals form a conduction band (CB), similar to the bands found in 2  conventional (inorganic) semiconductors. The energy difference between the two bands is known as the band gap, or Eg. (Figure 1-1) If this value is small, as is the case for most conjugated polymers, the polymer behaves as an organic semiconductor. Conductivity of conjugated polymers varies greatly between different types of polymers, and is affected by a number of different factors. More background information on π – conjugated systems can be found in the Handbook of Conducting Polymers.17  Figure 1-1 Energy level diagram for conjugated oligomers from ethylene to polyacetylene.  Section 1.3‒ Oligo- and Polythiophenes Polythiophenes (PTs) are one of the most extensively studied classes of conducting polymers as they have interesting optical and electronic properties.4 Thiophenes are relatively stable and can be functionalized fairly easily, allowing for increased solubility and processability. PTs can be polymerized through the α or β positions of the thiophene ring (Chart 1-2). In terms of conductivity, it is most ideal to 3  have α,α linkages because other types of linkages (α,β or β,β) can lead to defects in the chain, such as twisting, which reduces the effective conjugation length. Therefore, although further functionalization can be carried out at either the α or β positions, it is more common for substituents to be incorporated at the β position(s). Chart 1-2  The  discovery  of  polyalkylthiophenes  (PATs),18,19  such  as  poly(3-  hexylthiophene), has resulted in materials with greatly increased solubility and allows for drop casting and spin coating of these materials. The introduction of a new functional group in the β position also leads to the possibility of more regioisomers being produced (Chart 1-3). Regioregular Head-to-Tail (HT) PATs have improved properties over nonregioregular analogues.20 As PATs have a β position functionalized, Head to Head (HH) coupling produces steric hindrance which can cause the thiophene rings to twist out of the plane,21 reducing the π-orbital overlap, and thus, conjugation of the chain.  Chart 1-3  There are numerous methods reported for the synthesis of polythiophenes. For a complete review, the Handbook of Oligo-and Polythiophenes4 is recommended. The main methods for synthesis include metal catalyzed cross coupling reactions, chemical oxidation or electrochemical polymerization. There are advantages and disadvantages to each method. 4  During electrochemical polymerization, a potential is applied across a solution containing a thiophene monomer. Oxidation of the monomer results in a radical cation, which can then couple with a second radical cation to form a dication dimer. Loss of two protons gives bithiophene, which can then react with another radical cation to form terthiophene. This process continues until a polymer is formed. As the chain gets longer, the oxidation potential decreases, driving formation of polymer. While electrochemical polymerization is convenient, since the polymer does not need to be isolated and purified (it is deposited directly on a substrate), it can produce polymers with undesirable α – β linkages and varying degrees of regioregularity. Additionally, the oxidation potential of the thiophene monomers is typically higher than the oxidation potential of the resulting polymer. Therefore, the polymer can be irreversibly oxidized and decompose at a rate comparable to the polymerization of the corresponding monomer. This phenomenon is referred to as the “polythiophene paradox”.22 Polymerization via chemical oxidation is similar, except the source of oxidant is different. In this case, FeCl3 is typically used as the oxidant. Chemical polymerization results in defects in the chain, and it has been reported that adding the oxidant very slowly may help to achieve better control of regioregularity.23 The oxidative polymerization of thiophenes can be performed at room temperature under less demanding conditions than required for the chemical crosscouplings described later in this chapter.  5  Scheme 1-1  Chemical synthesis allows for the use of a more diverse selection of monomers, and, with the appropriate catalysts, the ability to synthesize highly regioregular substituted PTs. Yamamoto et al. reported one of the first procedures for PT,24 based on the Kumada coupling25 of Grignard reagents (Scheme 1-2). Lin and Dudek26 published a similar route in the same year. The synthesis generally produces low molecular weight polymers caused by poor solubility of the unsubstituted thiophene. McCullough et al. developed the first synthesis of regioregular PATs27 (Scheme 1-2). Selective bromination forms 2-bromo-3-alkylthiophene, followed by a lithiation step, transmetallation and then Kumada cross-coupling with a nickel catalyst. This method produces nearly 100% HT– HT couplings.28 Rieke et al. observed selection of catalyst is important. When 2,5dibromo-3-alkylthiophene is treated with highly reactive “Rieke zinc," addition of Pd(PPh3)4 produces a regiorandom polymer.29 Using Ni(dppe)Cl2 instead yields regioregular PAT.29 Both McCullough and Rieke‟s methods produce fairly high molecular weight regioregular polymers, but also require low temperatures, and the careful exclusion of water and oxygen.  6  Scheme 1-2  Oligo- and polythiophenes have the capability to bind to metals. They can do so through the lone pair of the S atom, or via the ring in an ε2, ε4, or ε5 fashion. The metal can possibly back-bond into the π* orbital as well.  Section 1.4‒ Metal Organic Hybrid Materials Section 1.4.1 – General The incorporation of transition metals into conjugated materials can alter the chemical and electronic properties of the organic polymer. The metal groups can be incorporated in various ways, but can generally be classified as Type I, Type II or Type III (Figure 1-2).30, 31 In Type I hybrid materials, the metal is attached to the backbone, typically through a saturated linker, such as an alkyl chain. The metal and conjugated polymer are separated enough that there is no electronic communication between the components. The properties of the metal complex are similar to the untethered analogues. In Type II materials, the metal and polymer backbone are electronically coupled. This occurs when the metal is closely or directly tethered to the backbone of the polymer. This causes the properties of the material to be influenced by each component. In Type III materials, the metal center is directly inserted into the polymer backbone. Here, the 7  polymer is very strongly coupled to the metal, leading to electronic interactions between the two components and perturbation of both the polymer and metal system can occur.  Type I  Type II  n  metal group  n  conjugated backbone  Type III  n  Figure 1-2 Schematic of different types of metal-containing polymer systems. The use of monomer or oligomer units when probing interactions between metal and polymer components are advantageous. Shorter chained systems are easier to synthesize and isolate, and their properties are usually characteristic of their extended structures. There are several examples of oligo- and polythiophene complexes that fall into each hybrid classification, along with various metal groups that have been appended to or inserted into the polymer chain. As this thesis focuses on late transition metal complexes, selected examples of oligo- and polythiophene with metals from groups 8-12 of the periodic table will be discussed. For the interested reader, there are several reviews of metal containing polymers and oligomers of thiophene,30,31,  32  as well as book  chapters33, 34 that cover the field thoroughly.  Section 1.4.2 – Group 8 Metal Oligo- and Polythiophene Hybrids Ferrocene is stable, easy to functionalize and has a reversible FeII/III redox couple. For these reasons, ferrocene has been incorporated into a number of conjugated oligomers and polymers. Chart 1-4 shows examples where ferrocene has been  8  incorporated into a polythiophene backbone, or attached to the backbone by a linker group. Higgins and co-workers polymerized oligothiophenes where ferrocene was directly inserted into the backbone (1). When only one thiophene unit was attached to the ferrocene, electropolymerization was not observed.35 When bithiophene or terthiophene was used, the peak current for ferrocene oxidation shifted to a more positive potential and diminished with repeated scans, while the ferrocenium couple moved to a more negative potential and eventually disappeared. A new redox wave appeared at 0.89-0.92 V while this occurred, and was assigned as the reversible oxidation of quaterthiophene or sexithiophene, respectively. Curtis used polythiophene with a pendant ferrocene moiety to make regiorandom polymers (2). Fluorescence quenching of the polymer shows charge transfer between the pendant ferrocene groups and main chain of the polymer.36 Organic p/n photocells were created which demonstrated improved photoconductivities over the polymer without the ferrocene unit. This may be from efficient hole-hopping between the ferrocenes, provided the number of ferrocene groups is above the critical concentration. Swager used azaferrocene with polythiophene dervivatives (3, 4, and 5) to investigate the nature of metal – polymer interactions.37 The π-bound metal is inserted into a fully conjugated chain. The PEDOT analogue (4) shows larger separation between oxidation and reduction peaks than the others polymers. Desired properties could be improved upon with redox matching.  9  Chart 1-4 Ref.35-37  Mirkin‟s group has synthesized Ru(II) complexes from redox switchable hemilabile ligands (6 and 7, Chart 1-5).7, 38 The complexes show that tunable ligands can be used to electrochemically vary the metal center properties.7 The ligand allowed for a direct probe of the oxidation state of the metal center. Changes in the CO stretching band were observed upon oxidation of the monomer, as well as with polymerization. Guillerez and coworkers have created d6 transition metal polypyridine complexes interspersed within a poly(3-octylthiophene) π conjugated network (8, Chart 1-5).39,  40  These soluble polymers exhibited long-lived MLCT luminescence, although the emission was quite weak. In order for the materials to display efficient MLCT emission, it was determined the 3π – π* state of conjugated system must be kept above the MLCT energy state. These systems may be useful for applications that require photoconductivity. Ogawa and Araki describe complexes which show an intense broad band in the visible region (9, Chart 1-5).41 Electrochemistry of the complex shows four reversible reduction waves. In dimethylformamide (DMF), film formation was not observed. However, when using acetonitrile (CH3CN), electropolymerization occurs. In the film, two reversible reductions were observed at -1.12 and -1.34 V when scanned out to -1.6 V. 10  Irreversible and reversible oxidations were observed at 1.08 and 1.38 V, respectively. The films could be deposited onto several different substrates.  Chart 1-5 Ref.7, 39, 41  Swager showed electrochemical behavior of complexes is dependent on the amount and position of bithienyl substituents (10 and 11, Chart 1-6).8, 42 The bithienyl moieties cause reduction at more positive potential than the parent (Ru(bpy)32+ ) species. Changing the position of the thienyl groups from the 5, 5ʹ to the 4, 4ʹ positions decreases conductivity from 1 × 10-3 to 3 × 10-4 S cm-1.42  The Ru centers are in direct  communication via a conjugated bridge, and it was noted self-exchange between Ru centers is more favourable than through space. Wu and coworkers replaced one of the anchoring 2,2ʹ-bipyridyl-4,4ʹ-dicarboxylate ligands of N343 (12, Chart 1-6) with a highly conjugated ancillary ligand to give 13. (Chart 1-6).44 There are three absorption bands observed: 533 nm (MLCT transition), 400 nm (π – π* transition of the alkyl bithiophene substituted bipyridine and MLCT transitions), and 312 nm (π – π* transition of the dicarboxylatebipyridine).44 Complex 13 11  demonstrated a broad IPCE curve, covering almost the entire visible spectrum, from 350700 nm. Additionally, the alkyl groups can prevent complexes from water induced desorption of dye molecules from TiO2 surfaces, when used in DSSCs. Recent work in our group indicates the introduction of an amide linker between the diimine and oligothiophene group may be beneficial for use in photoactive devices due to long lifetimes.45  Chart 1-6 Ref.42-44  12  Constable and co-workers electropolymerized Ru(II) and Os(II) terpyridine complexes with thiophene (14, Chart 1-7).46 Upon electropolymerization, a red shift in the MLCT transition, due to increased conjugation, was observed. The terthienyl radical cation was the least stable, and rigorous exclusion of H2O and nucleophiles was required to achieve polymerization. The bithiophene complexes easily electropolymerized to give quaterthienyl bridged polymers, with conductivity of 1.6 (±0.3) × 10-3 S cm-1 regardless of the specific metal center (Ru or Os) used. The polymer displayed distinct metal and thienyl-bridged based redox waves.46 Charge transport rates were enhanced by matching the redox potential of the metal center and bridge states using different conjugated bridges.  Chart 1-7 Ref.46, 47  Holliday‟s group synthesized a tridentate system incorporating poly(3,4ethylenedioxythiophene) (PEDOT) (15, Chart 1-7).47 The monomer shows π-π* transitions and an MLCT transition, whereas the polymer exhibits a broad absorption of overlapping bands between 300 and 700 nm, suggesting potential for application in photovoltaic devices. With oxidation, a new band around 900 nm was observed. Most likely this band is caused by a localized EDOT based radical cation or polaron. The electropolymerized polymer shows two oxidation waves, similar to the monomer, attributed to the RuII/III and PEDOT0/I oxidations.  13  Section 1.4.3– Group 9 Metal Oligo- and Polythiophene Hybrids Endo and coworkers demonstrated reaction of organocobalt polymers with S8 to give substituted thiophenes (16, Chart 1-8).48 Cyclic voltammetry showed two oxidation peaks at high potentials, possibly because of the sterically hindered thiophene, and irregularities in the chain. The UV-vis spectra showed the main chain is partially conjugated, and thermogravimetric analyses (TGA) revealed the material displayed fairly high thermal stabilities. Chart 1-8 Ref.9, 48-52  Shin produced the first example of a conducting polymer appended by an organometallic cluster unit (17, Chart 1-8).49 When electropolymerized, a large anodic 14  shift with large peak separation was observed, possibly due to high resistivity from the strongly electron withdrawing Co(CO)3 groups. The UV-vis spectrum of the polymer exhibited a red shift in the π – π* transition of the thiophene compared to the monomer. Shin also investigated other Co clusters with thiophene.50 Complex 18 shows two highly irreversible oxidations due to the oligothiophene, and one reductive process from the metal cluster between 0 and -1.6 V. As only one irreversible reduction process was observed, it was suggested the redox centers of the clusters do not interact with each other. If there was mixing between the metal orbitals and π orbitals of the spacer, two redox waves would be observed in the CV due to the electronic communication between the metal centers. In the UV-vis spectrum, the high energy bands are assigned to π – π* transitions of thiophene, while medium to low energy bands are assigned as MLCT transitions. Swager and co-workers synthesized a cobalt salen-containing polymer with EDOT (19, Chart 1-8).51 It was observed that there was chemical degradation in acidic media via hydrolysis of the imine functionality. In pH 7 buffer, a featureless trace was observed in the absence of O2. However, in the presence of oxygen, a large enhancement of the reduction wave was observed. This wave is assigned as a four electron reduction of O2 to H2O, and no H2O2 is formed. It was found the reduction current was related to the rate of O2 arriving at electrode surface. Cowley used N-heterocyclic carbenes (NHCs) to bind metals to a polymer chain (20, Chart 1-8).52 The polymers were formed by electrochemical oxidation. These were robust complexes with a high degree of electrochromic reversibility. The UV-vis spectrum is red shifted compared to monomer, and showed a feature at 700 nm attributed to polaron induced π – π* transition. In 20 when the metal group (M) is Ir(CO)2Cl, a band attributed to a bipolaron was observed also. It is believe the CO ligands help to stabilize the formation of polarons and bipolarons. Mirkin electrochemically polymerized 21 (Chart 1-8) and saw terthiophene based redox processes.9 Oxidation of Rh(I) does not significantly interfere with the terthiophene polymerization, but it does for the corresponding monothiophene monomer.  15  Hydrogenation of the polymer results in the removal of C7H8 to give a crosslinked polymer with dimerized Rh centers.  Section 1.4.4– Group 10 Metal Oligo- and Polythiophene Hybrids Pickup has investigated polymerizable Ni-dithiolene complexes where Ni atoms form links in the polymer chain or peripheral to the polymer chain (22 and 23, Chart 1-9).53 No reduction was observed for 23, but one is observed in 22, likely because the electron donating strength of the phosphine ligand shifts the reduction. The oxidation potential was similar for both complexes. The monomer of complex 22 has intense absorptions at low energy transitions (visible/NIR) over delocalized orbitals of the NiS4C4 core. The monomer of complex 23 does not exhibit the low energy transitions. The electrochemistry studies show insight into the structurally different polymers and their conductivities. Skabara cross-linked polythiophene with nickel bis(dithiolene) units fused to main chain (24, Chart 1-9).54 Performing cyclic voltammetery resulted in the observation of three waves, which is different from what was observed for the bisdithienyl-dithiolene complexes of the Pickup group. One wave at -0.13 V is described as the oxidation of metal dithiolene, the one at 0.46 V is the second oxidation of the dithiolene, and the reduction at -1.16 V is thiophene based. The UV-vis spectra of the polymer is bathochromically shifted compared to the monomer, indicating increased conjugation. The polymer has a very broad absorption range, from 300 to 1000 nm, and therefore could be a useful light-harvesting component.  16  Chart 1-9 Ref.53, 54  Kim found that metals, such as Pd, could be attached to a polymer backbone via the pyridine N and β carbon of thiophene ring (25, Chart 1-10).55 Alternatively, it was observed the binding could be forced to only occur through β carbon, if Pd had strongly coordinating ligands (26). This results in rod shaped dinuclear complexes. Thus, Kim and coworkers demonstrate a hemilability of pyridyl thiophene ligands. Similar hemilability was previously observed with Pd complexes where a thienyl ring bound through the S was displaced.56 Our group showed metal centers could act as crosslinkers between conjugated chains. One thiophene ring was bound ε1 through the sulfur, while the other is bound through the β carbon (27, Chart 1-10).56 Cyclic voltammetry showed complexes could be polymerized if methyl groups do not block the α positions of the polymer. The complexes had absorption bands red shifted from the parent complex and terthiophene ligands, while polymerization caused a red shift and broadening of the bands, indicative of formation of longer oligomers. Small changes in the UV-vis spectra occur when the complex is reacted with isocyanide ligands, suggesting non-optimal electronic interactions between the metal and polymer backbone.  17  Chart 1-10 Ref.55-57  Seeber found that addition of Pd(II) to polymer or oligomer of 28 (Chart 1-10) caused a decrease of absorbance, due to conformational changes of the backbone when Pd is bound.57 However, a new band with a broad tail in the UV-vis spectrum was observed at 400 nm. The presence of the metal increases the oxidation potential of the ligand (due to the electron withdrawing nature). There was no evidence of polymer formation when starting with the bithenyl Pd complex. This is believed to be caused by dissociation to form free ligand, which then polymerizes. Bäuerle and co-workers demonstrated Pt-oligothiophene rings containing up to 35 thiophene units (29, Chart 1-11).58 The rings, where PtII centers act as templates before undergoing reductive elimination, are easily oxidized and aggregate. The method of formation allows for odd number of repeat units. It is believed some of the complexes exhibit a monomeric-dimeric equilibrium, probably due to π – π* interactions.58,59 Earlier 18  work showed the Pt could directly bind to oligothiophenes, and oxidants, such as silver triflate, removed the Pt. Homocoupling occurred to produce sexithiophene at room temperature, with comparable yields to other homocoupling methods to produce oligothiophene. Their results showed a red-shift in the UV-vis absorption band with increasing conjugation, and evidence of a Pt(II) to Pt(IV) oxidation. Potentiostatic electrolysis also yielded sexithiophene.59 Holliday used a pincer NCN ligand to incorporate Pt to an oliothiophene (30, Chart 1-11).60 With Pt incorporation, the π – π* transition of bithiophene red shifts and a new LMCT band is observed. With polymerization, the π – π* transition shifts out to about 400 nm. Doping was monitored, and changes in the LMCT transition could directly examine changes in electron density at the metal center. Wong and coworkers varied the number of thiophene rings in the backbone with Pt directly inserted (31, Chart 1-11).61, 62 It was observed that increasing the number of thiophene rings decreased the band gap. Also, as the number of thiophene units increased, the overall effect on the band gap decreased, therefore the investigators thought there would be little benefit in incorporating more than a terthienyl unit. The introduction of a Pt group also lowers the energy of the transitions, suggesting that π conjugation extends through the metal center.  19  Chart 1-11 Ref.58, 60, 61  Section 1.4.5– Group 11 Metal Oligo- and Polythiophene Hybrids Sauvage and co-workers made a conjugated polyrotaxane with a linear conjugated backbone63 (32) for better π orbital overlap, compared to the u-shaped backbones64,  65  (33) they previously used (Chart 1-12). In the methylated species (32, R=CH3), a reversible wave at 0.52 V was assigned as Cu redox wave, while the non-methylated analogue (32, R=H), showed an irreversible couple at 0.28 V.63 When polymerized, the waves assigned as thiophene-based shift to higher potentials, which suggests enhanced electron delocalization in the linear backbone. Complex 32 could be reversibly metallated and demetallated, either using Li+ as a template or without a template. In previous investigations with the u-shaped backbone, Li+ had to be present or the complex would collapse on itself.64, 65 Additionally, 32 could remetalate with a different metal.63 In those cases, a different value for the metal redox wave was observed but the polymer showed very similar values. This suggests there is weak electronic interaction between the metal  20  complex and thiophene backbone. Interestingly, there is a more pronounced interaction in the u-shaped complexes.63, 65 Similar to motifs employed by Sauvage and co-workers, Bäuerle made several different sized catenanes with thienyl groups appended to the phenanthroline units (34, Chart 1-12).66 In this case, the system is fully conjugated. Bäuerle and co-workers employed a similar template approach to one they used previously, where cis[Pt(dppp)Cl2] is incorporated into the ring structure, and then is eliminated along with CC bond formation to produce a macrocycle. It was observed that smaller catenanes cannot be demetalated, but the larger ones can.  Chart 1-12 Ref.63, 65-67  Reynolds has made species with multiple polymerization sites; polymerization could occur through the phenylene or thiophene groups, or mixture of the two sites (35 and 36, Chart 1-12).67 The polymerization of the thiophene resulted in the presence of a 21  low potential feature and a broad sloping onset. The phenylene systems showed a very sharp onset. Reynolds also synthesized Ni complexes in order to demonstrate that the type of metal dictates the electrochromic properties of these systems.67 Swager made complex 19 (Chart 1-8) using Cu as well.68 The polymer had two overlapping redox waves, and a well-defined wave at higher potentials in MeCN. The appearance of the CV was found to be dependent on the solvent. Only two waves were displayed in the CV when the films were grown in CH2Cl2 (versus three in MeCN). Perturbations of the interchain distance greatly alter the polymer conductivity profile, and increasing the steric bulk of the diamine bridge results in a drop in conductivity. The UVvis spectrum shows a sharp band at 430 nm, suggesting conjugation in the system is limited. Binding metal groups via chelating phosphines to thiophene showed significant effects on the electronic properties of the conjugated system. Our group has investigated several gold-phosphino-oligothiophene species (37, 38, 39, Chart 1-13).69-71 Complex 37 shows a blue shift in the π – π* transition band and an increase in oxidation potential compared to the ligands.70 Increasing the number of thienyl units decreases the oxidation potential and red shifts the absorption bands. When the complex has two Au atoms attached (37, R = PPh2-AuCl), the complex crystallizes as a dimer that displays gold-gold interactions.70 Dual emission is observed, attributed to monomer and dimer emission. The solution absorbance spectra of 38 show a bathochromic shift with increased conjugation length, but a hypsochromic shift relative to the unbound thienyl ligands. 69 Increasing the conjugation led to a decrease in the oxidation potentials of 38. Gold-acetyleneterthiophene complexes have also been investigated in our group. When the linear A2T3 ligand is reacted with gold, a digold complex is formed (39, Chart 1-13).71 The coordination of the metal results in a small red shift of the absorption bands. The dppm complex exhibits Au-Au interactions. The complexes are emissive at room temperature, except for the dppm complex. All complexes could be electropolymerized. The PPh3 complex shows an irreversible oxidation wave which shifts to higher potential with repeated scanning. This suggests a poorly conducting film is being formed, or the conjugation is decreased compared to the monomer. The dppm complex shows two oxidation waves, and still exhibits Au-Au interactions when polymerized. 22  Chart 1-13 Ref.69-73  Phospholes substituted for a thiophene unit in oligo- and polythiophene systems cause a red shift in the UV-vis absorption spectrum and lower the HOMO-LUMO gap.73 These factors indicate systems like these may be useful in applications where band gap optimization is important. Complex 40 (Chart 1-13) and similar species are not air or moisture sensitive.72 40 could be demetalated with PPh3 and remetalated with (tht)AuCl. The investigators found that gold was intimately connected to the extended π conjugated system of the polythiophene. Reau demonstrated post-functionalization could be performed on polymeric material of this type. The gold complexes showed promising optoelectronic properties and some complexes have been incorporated into OLEDs.73 Fused cyclic thienyl phospholes force rings to adopt coplanar geometry, maximizing π orbital overlap.73 Studies have included incorporation of various metals, but the system seemed relatively insensitive to the type of metal, except with gold. For complex 41 (Chart 1-13), two absorption bands were observed. Depending on the R group, either broad bands (R = SiMe3) or narrow bands (R = SiMe2tBu) were observed, likely due to reduced intermolecular interactions from steric bulk.  No gold-gold 23  interactions were observed. The emission in both solution and solid-state suggest little or no aggregation is occurring. It is believed these complexes are well suited for functional materials and devices.  Section 1.4.6 – Group 12 Metal Oligo- and Polythiophene Hybrids Li and coworkers synthesized and electropolymerized thiophene and EDOT substituted porphyrins and their zinc complexes (42, Chart 1-14).74 They used linear units allowing the metal centers to be in direct communication with the backbone. However, due to minimal π overlap between aryl rings and porphyrin, the polymer showed two isolated redox systems. The EDOT substituted porphyrin complex, 42, polymerized well on a number of different electrodes. When films formed, there was peak broadening and a red-shift, likely due to aggregation and stacking of porphyrins in solution. Overall, the spectra looked very similar to the spectra of the monomer, but with broader features. The metal containing species demonstrated a higher electrochemical stability than similar previously reported complexes. After 1000 scans, there was only a 5% decrease in the intensity of the peak currents were observed. This may be due to improved thermal and electrochemical stability, and higher conductivity of PEDOT compared to other polymers.  24  Chart 1-14 Ref.74-77  Shimidzu showed Zn porphyrins with terthiophene units were able to be polymerized (43, Chart 1-14).75,  78  A decrease in the IR band for α-CH out of plane  vibrations was noted, suggesting α-α coupling, and a quasi-two dimensional species. SEM confirmed this, although some disorder was observed. The thickness of the single scan suggested the porphyrin rings are in a planar orientation. With polymerization, absorption of the film is considerably broadened, suggesting strong π-π interaction. The authors suggest this and related materials offer the opportunity for 3-D materials, which may be used in organic electronic devices.75 Officer and co-workers made similar compounds, but some had the terthiophenes attached via the β positions of the thiophene76 (44, Chart 1-14) rather than the α positions. They attempted to make porphyrin/thiophene hybrids where porphyrins are attached via a conjugated linker, directly in the chain, or act as a crosslinker between two chains. There was difficulty making the pure compounds, as atropisomers were possibly formed. Metallation with zinc was successful (44) but required the use of excess zinc acetate at  25  high temperatures to obtain the desired product.75,  78  Slower metallation of specific  atropisomers, along with sterically hindered terthiophenes was used to explain the difficulty of complexation. Officer also synthesized 45 (Chart 1-14), via Wittig reactions and poryphrin condensation reactions, under the belief they would be useful for DSSCs.77 The longer thiophene chains exhibited more donor-acceptor character, red shifted the absorption bands, and decreased the band gap. However, the longer chains also had a lower solar cell efficiency. Further work is needed to rationalize the DSSC efficiency and the electronic properties for complexes of this type.  Section 1.5 – Dye Sensitized Solar Cells Dye sensitized solar cells have received much attention over the past few decades as they are promising alternatives to conventional silicon based photovoltaic devices due to their low production cost, good conversion efficiencies, and ability to tune their absorption range. In the dye-sensitized solar cell (DSSC) pioneered by Grätzel,79 electron injection into a wide bandgap semiconductor from dyes is central to absorption of solar light and charge separation. Typically in DSSCs, the sensitizer, or dye, is excited by absorbing a photon. The dye injects an electron into the conduction band of the TiO2, which travels through the TiO2 layer to the anode (often ITO or SnO coated glass). For dye regeneration, an electron is donated from the electrolyte, usually the iodide/triiodide redox couple. The iodide is regenerated by the reduction of triiodide at the cathode with the circuit being complete when connected to an external load (Figure 1-3). The most efficient DSSCs to date have ~10 – 13% efficiency, and are obtained using Ru-based dyes, such as Black dye80 and N71981 (Chart 1-15, 46 and 47, respectively), with an I-/I3- donor. Other “champion dyes” (dyes with more than 10 % efficiency) have been produced, and are typically a modification of these known dyes. Replacement of one of the anchoring 4,4ʹ-dicarboxylic acid-2,2ʹ-bipyridine (dcbpy) ligands with a highly conjugated ancillary ligand has led to an increase in the absorption coefficient, and therefore, photocurrent of the sensitizers.44, 82, 83 For example, replacing a 26  dcbpy ligand with a bipyridine substituted with alkyl bithiophene units led to a very high molar absorption coefficient, in addition to a high current density and conversion efficiency. The thiophene moieties allow for relatively easy functionalization, which can aid with solubility, polarity, and band-gap tuning.44 Substituting the alkyl chain for thioalkyl moieties on the bithiophene substituted bipyridines have also improved efficiencies.82  Anode  Cathode e-  e  -  D*/D+  e-  eee-  e  -  eI -/I3-  +  Electrolyte  D/D  e-  TiO2  e-  Load e-  Figure 1-3 Schematic of a DSSC showing the flow of electrons, adapted from Ref.84  27  Chart 1-15 Ref.80, 81  It is believed that the NCS- groups can cause problems and lead to degradation over time. Recently, a bis-tridentate dye (without any NCS- groups) was reported which avoids isomerization issues and is believed to improve upon the long term stability of dyes.85 Also, it has been noted that modification by replacing NCS- groups with cyclometalating groups allows for retention of the light-harvesting properties of these complexes.86-88 Another method which has recently yielded high efficiency DSSCs uses a porphyrin complex with a cobalt (II/III) based redox electrolye.89 While this redox couple often demonstrates faster charge recombination than iodide/triiodide, the introduction of long alkoxy groups can slow the charge recombination process. Grätzel and coworkers established that using a substituted zinc-porphyrin, which itself consists of a donor-π bridge-acceptor structure and absorbs across the visible spectrum, gives high conversion efficiencies using various electrolytes. Research focusing on the various components of a solar cell is still quite important, as each component influences the overall efficiency. The structures of the dyes themselves are central to a highly efficient device. In addition to requiring a broad absorption range and high photostability, the electronic ground and excited states are an important aspect to investigate as well. Several reviews have been published focusing on the synthesis and design of photosensitizers for this type of device.90-92  28  Section 1.6 – Goals and Scope The primary goal of this thesis is the synthesis and characterization of transitionmetal complexes appended to a phosphino(terthiophene) for use in light-harvesting applications. A terthiophene ligand with a diphenylphosphine linker was employed to study Type I and Type II materials. The diphenylphosphine group, situated at the β position of an oligothiophene chain is used to anchor the metal group, creating a Type I metal-terthiophene hybrid material. When the terthiophene moiety is in close proximity to the metal center, the S or C of a thiophene ring adjacent to the diphenylphosphine group may also coordinate to the metal center, creating Type II materials. Both classes of materials are investigated in this thesis. When considering complexes and materials for use as energy harvesters, such as dyes in DSSCs, certain criteria must be kept in mind. Ideal dyes will absorb all light below 920 nm, contain ligands that are functionalized or can be functionalized (with carboxylate, for example) for attachment to TiO2, or another semiconductor, and should be stable to photoinduced ligand loss.84 A relativity long-lived charge-separated excited state, with an energy well matched to the lower limit of the conduction band of the oxide material (to minimize loss during electron transfer) are desirable, as are appropriate redox potentials to allow for regeneration. Ruthenium polypyridyl complexes have been widely studied and produced the most promising complexes to date. Therefore, group 8 polypyridyl phosphino(terthiophene) complexes were explored. Chapter 2 investigates the ground and excited state behavior of Ru(II) and Os(II) diimine complexes containing 3ʹ-diphenylphosphinoterthiophene (PT3) in different coordination modes. The effect the coordination mode has on the complexes stability, absorption, transient absorption, emission and electrochemical properties are evaluated. Cyclometallated iridium (III) complexes have also shown promise in this field.93 Cyclometalated iridium (III) complexes may be isoelectronic to Ru(II) diimine complexes, and exhibit similar spectroscopic properties. Enhanced absorption across the UV-vis spectrum may be observed due to enhanced spin-orbit coupling of the Ir. In Chapter 3, cyclometalated Ir(III) complexes with phenylpyrazole or phenylpyridine 29  ligands and a PT3 ligand are explored. In this case, three different coordination modes of the PT3 ligand are observed, yielding Type I and Type II complexes. The photophysical and electrochemical properties are investigated, and comparisons to the Os(II) complexes are made. Cu(I) complexes with substituted 1,10-phenantroline (phen) ligands possess similar photophysical properties as [Ru(bpy)3]2+ salts. Incorporation of ligands containing phosphines or with chelating phosphines have produced complexes with long lifetimes, attributed to charge transfer states.94 Coupled with the distinct cost advantage of Cu over Ru, it is beneficial to consider these types of complexes as dyes. Chapter 4 discusses diimine Cu(I) complexes with phosphino-terthiophene ligands. Their synthesis and their photophysical and electrochemical properties are evaluated.  30  CHAPTER 2 GROUP 8 DIPHENYLPHOSPHINO(TERTHIOPHENE) COMPLEXES*1  Section 2.1‒ Introduction Group 8 polypyridyl complexes, particularly Ru(II) complexes, have been widely studied as photosensitizing dyes for solar energy harvesting because of their chemical stability, absorbance and emission properties, and their ability to participate in electron and energy transfer processes.95, 96 Conjugated oligomers and polymers are another class of materials that are being investigated for application as light absorbers in organic solar cells.97, 98 The efficiency of cells based on these materials is typically limited by exciton recombination on the conjugated chains.99 Another approach involves coupling a light absorbing metal dye to a conjugated backbone, with the goal of exciting an electron from the conjugated group to a peripheral ligand on the metal complex generating a chargeseparated excited state. This approach offers the possibility of hole transport over longer distances via the -conjugated backbone. However, energy transfer to competing, lowlying states can present complications.100, 101 Previous studies in our group have shown that the ground and excited state behavior of the Ru(II) bis(bipyridyl) complexes102, 103 48 and 49, where an oligothiophene is tethered to the metal through a diphenylphosphine ligand (Chart 2-1) either via PS or PC coordination, differ significantly from each other. Visible light excitation of an analogue  of  [Ru(bpy)2PT3-PC](PF6),  in  which  the  conjugation  in  the  phosphino(oligothiophene) ligand is extended to five thiophene rings (51), resulted in a transient species assigned as a charge-separated excited state.104 As mentioned above, others have recently explored the utility of cyclometallated complexes as dyes in DSSCs,86-88, 93 raising the possiblity that cyclometallated complexes such as these may find application in these types of cells.  1  *Part of this chapter has been published. Reproduced with permission from Moore, S.A., Nagle, J.K., Wolf, M.O., Patrick, B.O. (2011) Coordination Mode Dependent Excited State Behavior in Group 8 Phosphino(terthiophene) Complexes. Inorg. Chem., 50, 5113-5122.  31  Chart 2-1 Ref.102-104  The possible presence of low-lying metal-centered (MC) excited states101 or lowlying ligand-based triplet states100 which can be populated from the metal-to-ligand charge transfer (MLCT) state may lead to alternate routes for deactivation of the excited state in these Ru complexes. Os(II) has a larger ligand field splitting energy (by about ~30%) than Ru(II) which results in an increased energy gap between MLCT and MC states,101 thus Os(II) analogs of the Ru(II) complexes may have longer charge-separated lifetimes. On the other hand, some Os(II) polypyridyl complexes have been shown to have shorter excited state lifetimes than the analogous Ru(II) complexes due to enhanced spin-orbit coupling,105 and in cases where ligands with a triplet state close in energy to the 3MLCT state are present, energy transfer between the two states may occur.106 Os(II) polypyridyl complexes also typically have lower energy MLCT states, leading to broader absorption of light over more of the visible spectrum. This is an advantage for solar energy harvesting where low energy photons must also be captured for maximum efficiency. Additionally, the bipyridyl ligands on the Ru complexes were replaced with phenanthroline (phen) ligands. With their extended ring system, the phen complexes are known to result in increased emission lifetimes with respect to the analogous bpy complexes,107 and may exhibit other beneficial characteristics over the bpy analogues. In this chapter, four new complexes with a conjugated terthiophene based ligand are  described:  [Ru(phen)2PT3-PS](PF6)2,  [Ru(phen)2PT3-PC](PF6),  [Os(bpy)2PT3-  PS](PF6)2, and [Os(bpy)2PT3-PC](PF6). Their electrochemical, photophysical and excited 32  state electronic properties are compared to the [Ru(bpy)2PT3-PS](PF6)2 and [Ru(bpy)2PT3-PC](PF6) analogues and their usefulness as dyes are discussed. Chart 2-2  Section 2.2 ‒ Experimental Section 2.2.1 ‒ General All reactions were performed under N2 (99.0%). The compounds cisOs(bpy)2Cl2,108  and  3ʹ-(diphenylphosphino)-2,2ʹ:5ʹ,2ʺ-terthiophene  (PT3)109  were  synthesized according to literature procedures. The compound cis-Ru(phen)2Cl2 was synthesized according to literature procedure for cis-Ru(bpy)2Cl2,110 but bipyridine (bpy) was replaced with phenanthroline (phen). All other reagents were purchased from Aldrich, Alfa Aesar and Strem and used as received. 1H and 31P{1H} NMR spectra were collected on either a Bruker AV-300 or AV-400 spectrometer. 1H NMR spectra were referenced to residual solvent, and H3PO4.  31  P{1H} NMR spectra referenced to external 85%  ESI mass spectra were recorded on Bruker Esquire-LC ion trap mass  33  spectrometer equipped with an electrospray ion source. The solvent for the ESI-MS experiments was either methanol or dichloromethane/methanol and the concentration of the compound was ~10 M. High resolution mass spectra were recorded on a Waters Micromass LCT time-of-flight mass spectrometer equipped with an electrospray ion source. CHN elemental analyses were performed using an EA1108 elemental analyzer, using calibration factors. The calibration factor was determined by analyzing a suitable certified organic standard (OAS) of a known elemental composition. All mass spectrometry and microanalysis results were obtained by the staff at the UBC Mass Spectrometry Centre. Cyclic voltammetry experiments were carried out on an Autolab PG STAT 12 potentiostat or Pinechem potentiostat using a Pt working electrode, Pt mesh counter electrode and a silver wire reference electrode with 0.1 M [(n-Bu)4N]PF6 supporting electrolyte which was re-crystallized 3 times from ethanol and dried under vacuum at 100 °C for 3 days. Decamethylferrocene (-0.125 V vs SCE in acetonitrile)111 was used as an internal reference to correct the measured potentials with respect to the saturated calomel electrode (SCE).  UV-vis spectra were obtained on a Cary 5000  spectrometer in HPLC grade solvent. Emission spectra were obtained on a PTI Quantamaster spectrometer. Transient absorption measurements and fluorescence lifetimes were carried out on a Princeton Instruments Spectra Pro 2300i Imaging Triple Grating Monochrometer/Spectrograph with a Hamamatsu Dynamic Range Streak Camera (excitation source: EKSPLA Nd:YAG laser, 35 ps pulse duration,  = 355 nm). Solutions of the complexes in CH3CN having an optical density of 1 at 355 nm were prepared. The UV-vis spectra were obtained before and after each TA experiment to ensure the bulk of the sample did not change, due to degradation or another process. Section 2.2.2 ‒ Procedures [Ru(phen)2PT3-PS](PF6)2, (52). This compound was prepared based on the literature procedure for the preparation of the analogous bipyridine complex,102 but using Ru(phen)2Cl2·2H2O in place of Ru(bpy)2Cl2·2H2O. AgBF4 (0.068 g) was added to a nitrogen-sparged acetone solution (15 mL) of Ru(phen)2Cl2·2H2O (0.100 g), stirred for 12 hours and filtered. 3ʹ(diphenylphosphino)-2,2ʹ:5ʹ,2ʺ-terthiophene (0.092 g) was added to the filtrate and the 34  mixture was heated at reflux for 24 hours. The resulting solution was reduced in volume, added dropwise to a solution of ammonium hexafluorophosphate (0.284 g) in H2O (17 mL) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and diethyl ether to yield 64 mg (62%) of a yellow or orange-yellow solid. 1H NMR (300 MHz, CO(CD3)2): δ 6.52-6.66 (m, 3H), 6.67-6.73 (m, 1H), 7.06 (d, J = 3.0 Hz, 3H), 7.12 (dd, J = 5.0, 3.9 Hz, 1H), 7.30 (d, J = 3.0, 2H), 7.35-7.45 (m, 3H), 7.46-7.63 (m, 5H), 7.64-7.73 (m, 1H), 7.86 (dd, J = 8.1, 5.4 Hz, 1H), 7.92-8.01 (m, 1H), 8.05 (dd, J = 8.1, 5.4 Hz, 1H) 8.23-8.41 (m, 5H), 8.68 (d, J = 7.8 Hz, 1H), 8.74-8.84 (m, 1H), 8.89 (dd, J = 7.9, 2.9 Hz, 2H), 9.36 (d, J = 5.0 Hz, 1H), 9.48 (d, J = 5.3 Hz, 1H). 31P{1H} NMR (121 MHz, CO(CD3)2): δ 28.3 (s), -143.6 (septet, JPF = 708 Hz, PF6). m/z [M-PF6]+ 1039. HRMS (ESI) Calcd for C48H33F6N4PS3Ru (m/z [M-PF6]+): 1036.0306; Found: 1036.0327. Anal. C48H33F12N4S3P3Ru requires C, 48.69; H, 2.81; N, 4.73. Found C, 48.45; H, 2.91; N, 4.64 %.  [Ru(phen)2PT3-PC](PF6), (53). This compound was prepared based on the literature procedure for the preparation of the analogous bipyridine complex,102 with slight modification. Complex 52 (45 mg) was added to a solution of NaOH (0.20 g) dissolved in degassed methanol (5 mL) and heated to reflux under nitrogen, with stirring, for 18 hours. The solution was cooled to room temperature, and the MeOH was removed in vacuo. The precipitate was redissolved in 2 mL MeOH. The resulting dark solution was added dropwise to a solution of ammonium hexafluorophosphate (0.284 g) in H2O (17 mL) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and diethyl ether to yield 26 mg (66%) of a reddish-brown solid. 1H NMR (300 MHz, CO(CD3)2): δ 6.52-6.66 (m, 3H), 6.67-6.73 (m, 1H), 7.06 (d, J = 3.0 Hz, 3H), 7.12 (dd, J = 5.0, 3.9 Hz, 1H), 7.30 (d, J = 3.0, 2H), 7.35-7.45 (m, 3H), 7.467.63 (m, 5H), 7.64-7.73 (m, 1H), 7.86 (dd, J = 8.1, 5.4 Hz, 1H), 7.92-8.01 (m, 1H), 8.05 (dd, J = 8.1, 5.4 Hz, 1H) 8.23-8.41 (m, 5H), 8.68 (d, J = 7.8 Hz, 1H), 8.74-8.84 (m, 1H), 8.89 (dd, J = 7.9, 2.9 Hz, 2H), 9.36 (d, J = 5.0 Hz, 1H), 9.48 (d, J = 5.3 Hz, 1H). 31P{1H} NMR (121 MHz, CO(CD3)2): δ 46.1 (s), -143.6 (septet, JPF = 708 Hz, PF6). m/z [M-PF6]+ 893. HRMS (ESI) Calcd for C48H32N4S3Ru (m/z [M-PF6]+): 887.0603; Found: 887.0593. 35  Anal. C48H32F6N4S3P2Ru requires C, 55.54; H, 3.11; N, 5.40. Found C, 55.19; H, 3.29; N, 5.05%. [Os(bpy)2PT3-PS](PF6)2, (54). PT3 (0.164 g) was added to a degassed 2:1 EtOH-H2O mixture containing Os(bpy)2Cl2 (0.200 g). The reaction mixture was heated to reflux under nitrogen with stirring for 48 hours. The EtOH was removed in vacuo, and the remaining solution was added to aqueous ammonium hexafluorophosphate (1.136 g in 70 mL H2O) and stirred at room temperature for 30 minutes. The precipitate was filtered, washed with copious amounts of water and diethyl ether, and then dissolved in DCM and purified over neutral alumina. Once the brown band was eluted with DCM, acetone was used to elute the reddish-orange product band. The volume was reduced in vacuo, and the remaining solution was added to aqueous ammonium hexafluorophosphate (0.568 g in 30 mL H2O) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and diethyl ether to yield 0.1810 g (42%) of red solid. 1H NMR (300 MHz, CO(CD3)2): δ 9.16 (d, J = 5.9 Hz, 1H), 8.96 (d, J = 5.7 Hz, 1H), 8.71 (d, J = 8.2 Hz, 1H), 8.67-8.60 (m, 3H), 8.23-8.02 (m, 5H), 7.70 (d, J = 5.7 Hz, 1H), 7.647.47 (m, 7H), 7.43-7.29(m, 6H), 7.23-7.16 (m, 3H), 7.11-7.05(m, 2H), 6.97 (d, J = 3.3 Hz, 1H), 6.87-6.81(m, 2H).  31  P{1H} NMR (121 MHz, CO(CD3)2): δ -14.2 (s), -143.6  (septet, JPF = 708 Hz, PF6). C44H33N4F6OsP2S3  (m/z  m/z [M-PF6]+ 1080. HRMS (ESI) Calcd for  [M-PF6]+):  1081.0845;  Found:  1081.0862.  Anal.  C44H33N4S3OsP3F12 requires C, 43.14; H, 2.72; N, 4.57. Found C, 42.88; H, 2.99; N, 4.40%. [Os(bpy)2PT3-PC](PF6), (55). Complex 54 (50 mg) was added to a solution of NaOH (0.20 g) dissolved in degassed methanol (5 mL) and heated to reflux under nitrogen, with stirring, for 36 hours. The solution was cooled to room temperature, and the MeOH was removed in vacuo. The precipitate was redissolved in 2 mL MeOH. The resulting dark solution was added dropwise to a solution of ammonium hexafluorophosphate (0.284 g) in H2O (17 mL) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and diethyl ether to yield 27 mg (61%) of a dark 36  brown solid. 1H NMR (300 MHz, CO(CD3)2): δ 8.94 (d, J = 5.8 Hz, 1H), 8.57 (d, J = 8.2 Hz, 1H), 8.51-8.37 (m, 4H), 7.97(t, J = 7.8 Hz, 1H), 7.88-7.62 (m, 6H), 7.58-7.53(m, 1H), 7.43-7.35 (m, 6H), 7.18-7.02 (m, 4H), 6.95-6.81 (m, 4H), 6.65 (d, J = 2.7 Hz, 1H), 6.43 (t, J = 8.7 Hz, 2H), 6.20 (d, J = 4.9 Hz, 1H)  31  P{1H} NMR (121 MHz, CO(CD3)2): δ  -2.4 (s), -143.6 (septet, JPF = 708 Hz, PF6) m/z [M-PF6]+ 935. HRMS (ESI) Calcd for C44H32N4OsPS3  (m/z  [M-PF6]+):  935.1142;  Found:  935.1155.  Anal.  C44H32F6N4OsP2S3·2H2O requires C, 47.38 ; H, 3.26; N, 5.03. Found C, 47.59; H, 3.11; N, 4.89%.  Section 2.2.3 ‒ X-Ray Crystallography Suitable crystals of [Ru(phen)2PT3-PS](PF6)2, (52), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3-PC](PF6), (55), were grown from solution. The X-ray data were collected and solved by Dr. B.O. Patrick. In all cases, the crystals were mounted on a glass fiber and a Bruker X8 APEX II diffractometer with graphite monochromated MoΚα radiation was used for all measurements. Data were collected and integrated using the Bruker SAINT112-114software package. Data were corrected for absorption effects using the multi-scan technique (SADABS).115-117 The data were corrected for Lorentz and polarization effects. The structures were solved by direct methods.118 Solid-state diagrams were visualized using Mercury.119  [Ru(phen)2PT3-PS](PF6)2, (52). Data were collected in a series of ϕ and ω scans in 0.50° oscillations using 20.0 second exposures. The crystal to detector distance was 36.00 mm. The data were collected to a maximum 2ζ value of 55.9°. Of the 51075 reflections that were collected, 12063 were unique (Rint = 0.040); equivalent reflections were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),117 with minimum and maximum transmission coefficients of 0.825 and 0.970, respectively. The material crystallizes with one molecule of acetone in the asymmetric unit. One thiophene ring (S3 → C12) is disordered by a two-fold rotation about the C8 – C9 bond. The two ring fragments were modeled in both orientations using restraints to maintain reasonable 37  ring geometries. Additionally, the fluorines of one PF6- anion were disordered, again in two orientations. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions but were not refined. The final cycle of full2  matrix least-squares refinement120 on F was based on 12063 reflections and 734 variable parameters and converged (largest parameter shift was 0.00 times its esd).  [Os(bpy)2PT3-PS](PF6)2, (54). Data were collected in a series of ϕ and ω scans in 0.50° oscillations using 10.0 second exposures. The crystal to detector distance was 36.00 mm. The data were collected to a maximum 2ζ value of 56.2°. Of the 82845 reflections that were collected, 12304 were unique (Rint = 0.039); equivalent reflections were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),115 with minimum and maximum transmission coefficients of 0.613 and 0.861, respectively. The terminal thiophene ring of the material is disordered as was modeled in two orientations with roughly equal populations. Mild restraints were used to maintain reasonable geometries for the two fragments. Additionally, the material crystallizes with two molecules of CH2Cl2 solvent in the asymmetric unit. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions but were not refined. The final cycle of full-matrix least-squares refinement120 on F2 was based on 12304 reflections and 695 variable parameters and converged (largest parameter shift was 0.00 times its esd).  [Os(bpy)2PT3-PC](PF6), (55). Data were collected in a series of ϕ and ω scans in 0.50° oscillations using 5.0 second exposures. The crystal to detector distance was 40.00 mm. The data were collected to a maximum 2ζ value of 56.0°. Of the 56287 reflections that were collected, 9648 were unique (Rint = 0.050); equivalent reflections were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),116 with minimum and maximum transmission coefficients of 0.499 and 0.900, respectively. The terminal thiophene ring is disordered in two orientations. Mild restraints were employed to  38  maintain similar bond lengths and angles in the minor disordered fragment. All nonhydrogen atoms were refined anisotropically. All C-H hydrogen atoms were placed in calculated positions but were not refined. The final cycle of full-matrix least-squares refinement120 on F2 was based on 9648 reflections and 573 variable parameters and converged (largest parameter shift was 0.00 times its esd). Section 2.2.4 – DFT Calculations All calculations were performed by Dr. J. K. Nagle (Bowdoin College) using the 2009.01 version of the Amsterdam Density Functional (ADF) program.121-135 Experimental X-ray crystallographic cation geometries (C1 point group) were used for all four complexes.  All calculations included scalar and spin-orbit relativistic effects  through the zeroth-order relativistic approximation (ZORA),136-138 except for bond orders and natural population analysis (NPA) atomic charges139 which included only scalar relativistic effects. The generalized gradient approximation (GGA) of density functional theory (DFT) at the BP86 level was used in all cases.131-133 and all-electron (i. e., no frozen core approximation was applied) TZ2P basis sets from the ADF basis sets ZORA library were used for all atoms. Atomic charges on all atoms were calculated within ADF using the Voronoi (VDD),140 Hirshfeld,141-144 Bader atoms in molecule (AIM),145,  146  NPA, Mulliken, and multipole-derived quadrupole (MDC-q) methods. Bond orders were calculated within ADF using the Mayer, Gophinatan-Jug, and three Nalejawski-Mrozek methods N-M (1), N-M (2), and N-M (3) provided with the ADF program.147  Section 2.3‒ Results and Discussion Section 2.3.1 ‒ Synthesis The [Ru(phen)2PT3-PS](PF6)2 and [Ru(phen)2PT3-PC](PF6) complexes were prepared analogously to the previously synthesized Ru(II) bipyridine complexes.102 Dechlorination of Ru(phen)2Cl2 with silver tetrafluoroborate followed by addition of PT3 and precipitation with a hexafluorophosphate salt gave [Ru(phen)2PT3-PS](PF6)2. The reddish-brown [Ru(phen)2PT3-PC](PF6) complex (53) was obtained by reaction of 52 with base. 39  Scheme 2-1  Preparation of the corresponding Os(II) complexes were initially attempted using the same route, but the poor solubility of the (NH4)2OsCl6 starting material prevented successful isolation of [Os(bpy)2PT3-PS](PF6)2. Variation of the volume of solvent used, the time at reflux, and deletion of the filtering step did not help, and in all cases isolation of the desired Os analog of 48 was unsuccessful. Meyer and co-workers have previously reported that the use of Ag salts for dechlorination of Os complexes does not work well, and recommended heating the metal precursor and ligand together in high boiling solvents such as glycerol or ethylene glycol.148 When attempted here, this method yielded only a small amount of the desired product along with multiple other products, including the monochloro species according to mass spectroscopic analysis. Longer heating at reflux (up to 5 days) did not improve the yield. Further modifications to the conditions established that using a solvent mixture of ethanol and water, in a two-to-one ratio, with extended (36-48 hours) heating at reflux, gave the desired [Os(bpy)2PT3-PS](PF6)2 (54) in 42% yield (Scheme 2-2). The product was purified by column chromatography on neutral alumina. A similar procedure to that used to obtain [Ru(bpy)2PT3-PC](PF6) was employed to obtain the brown cyclometallated species [Os(bpy)2PT3-P,C](PF6), 55, in 61% yield. Scheme 2-2  40  Section 2.3.2‒ Solid-State Molecular Structures Crystals suitable for X-ray diffraction of three of the complexes were grown from appropriate solvents. The structures demonstrate the effects of the metal – diimine group and binding mode of the terthiophene ligand on the torsion angles and tilt angle of the metal bound thiophene ring. In all the solid-state structures, the metal center is in a slightly distorted octahedral environment. Single crystals of [Ru(phen)2PT3-PS](PF6)2 were grown from a CH2Cl2 – acetone – hexanes solution, and the solid-state structure is shown in Figure 2-1. Disorder was present in the thiophene ring containing S3. The Ru – N bond lengths are similar to those in [Ru(phen)3](PF6)2.149 There is very little difference between the bond lengths and angles between the previously synthesized bpy complex102 and the phen complex here. The torsion angles between the S1 and S2 rings as well as S2 to S3 rings are slightly more co-planar in the [Ru(phen)2PT3-PS](PF6)2 complex than the analogous Ru(bpy)2 complex. The thiophene ring coordinated to the metal through the sulfur is tilted out of the equatorial plane because of its sp3 hybridization. The tilt angle of the thiophene away from the Ru – S bond is 58.9 ° in the [Ru(phen)2PT3-PS](PF6)2 complex, whereas this ring is tilted 58.3 ° in [Ru(bpy)2PT3-PS](PF6)2. This tilting reorients the lone pair of electrons on the sulfur, allowing for a reduction in the unfavorable π antibonding interactions.150, 151  41  Figure 2-1 Solid-state structure of [Ru(phen)2PT3-PS](PF6)2, (52). Hydrogen atoms, counterions, and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability.  Table 2-1 Selected bond lengths and angles for [Ru(phen)2PT3-PS](PF6)2, (52). Bond Lengths (Å) Ru1 – S1  2.3579(7)  S1 – C1  1.742(3)  Ru1 – P1  2.3181(7)  C1 – C2  1.339(5)  Ru1 – N1  2.097(2)  C2 – C3  1.428(5)  Ru1 – N2  2.118(2)  C3 – C4  1.352(4)  Ru1 – N3  2.063(2)  C4 – S1  1.753(3)  Ru1 – N4  2.086(2)  C4 – C5  1.450(4)  148.48(16)  S2 – C8 – C9 – S3  148.4(2)  Torsion Angles (°) S1 – C4 – C5 – S2  42  Single crystals of [Os(bpy)2PT3-PS](PF6)2 were grown from a CH2Cl2 – hexanes solution (Figure 2-2). The metal – nitrogen bonds are slightly longer in [Os(bpy)2PT3PS](PF6)2 than in [Os(bpy)3](PF6)2.152 The bonding arrangement in this new structure is identical to the Ru analogue, and some differences in bond lengths and angles are observed between the two structures (Table 2-2). The S1 – C36 – C37 – S2 torsion angle of 154.9(3)° in [Os(bpy)2PT3-PS](PF6)2 is somewhat larger than in [Ru(bpy)2PT3-PS](PF6)2. The larger torsion angle indicates increased co-planarity, resulting in increased π-orbital overlap between adjacent thienyl rings. In the Os complex, the bound thiophene ring is tilted away from the the Os – S bond at an angle of 59.7°, slightly larger than the tilt angle in [Ru(bpy)2PT3-PS](PF6)2 (58.3°). The thiophene tilts away from the metal-sulfur bonds in these compounds in order to reduce unfavorable *-antibonding interactions between the thiophene and metal.150 The Os center may result in a greater degree of antibonding interaction, and consequently a larger tilt angle.  Figure 2-2 Solid-state structure of [Os(bpy)2PT3-PS](PF6)2, (54). Hydrogen atoms, counterions, and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability.  43  Table 2-2 Selected bond lengths and angles for [Os(bpy)2PT3-PS](PF6)2, (54). Bond Lengths (Å) Os1 – S1  2.3543(11)  S1 – C33  1.742(5)  Os1 – P1  2.3101(11)  C33 – C34  1.353(8)  Os1 – N1  2.105(4)  C34 – C35  1.421(8)  Os1 – N2  2.100(4)  C35 – C36  1.351(7)  Os1 – N3  2.072(4)  C36 – S1  1.751(5)  Os1 – N4  2.075(3)  C36 – C37  1.444(7)  154.9(3)  S2 – C40 – C41 – S3  33(3)  Torsion Angles (°) S1 – C36 – C37 – S2  Single crystals of [Os(bpy)2PT3-PC](PF6) were grown from a CH2Cl2 – hexanes solution, and the solid-state structure is shown in Figure 2-3. In the [Os(bpy)2PT3PC](PF6) complex, the Os – P bond was found to be 2.2892(9) Å, which is comparable to the metal carbon bond length in the Ru analogue, as are the other bond lengths. The S1 – C36 – C37 – S2 torsion angle indicates the two locked thiophene rings in [Os(bpy)2PT3PC](PF6) are more coplanar than in [Ru(bpy)2PT3-PC](PF6). The thiophene ring is almost coplanar with the vector of the Os – C bond (tilted 5.9°), a smaller tilt angle relative to the Ru analogue (7.3°). Here, the bound carbon is sp2 hybridized, and the tilt angle suggests antibonding interactions may also play a role in these complexes.  44  Figure 2-3 Solid-state structure of [Os(bpy)2PT3-PC](PF6), (55). Hydrogen atoms and counterions removed for clarity. Thermal ellipsoids drawn at 50% probability.  Table 2-3 Selected bond lengths and angles for [Os(bpy)2PT3-PC](PF6) , (55). Bond Lengths (Å) Os1 – C35  2.095(3)  C35 – C36  1.396(5)  Os1 – P1  2.2892(9)  C36 – C37  1.445(5)  Os1 – N1  2.060(3)  C36 – S1  1.753(3)  Os1 – N2  2.105(3)  S1 – C33  1.698(4)  Os1 – N3  2.124(3)  C33 – C34  1.362(5)  Os1 – N4  2.077(3)  C34 – C35  1.435(5)  5.0(4)  S2 – C40 – C41 – S3  153.0(2)  Torsion Angles (°) S1 – C36 – C37 – S2  Section 2.3.3– DFT Calculations Orbital plots for complexes [Ru(bpy)2PT3-PS](PF6)2, [Ru(bpy)2PT3-PC](PF6), [Os(bpy)2PT3-PS](PF6)2, and [Os(bpy)2PT3-PC](PF6) together with their energies, electron populations, and calculated metal contributions are shown in Figure 2-4 to 45  Figure 2-7. Spin-orbit effects were included in the calculations so that all orbitals are listed as a1/2 pairs. The results reveal many similarities in bonding between the corresponding Ru and Os complexes. In comparing the corresponding PS bound and PC bound complexes, it is found that for the [Ru(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3PS](PF6)2 complexes both the HOMO and HOMO-1 have no metal contributions while the [Ru(bpy)2PT3-PC](PF6) and [Os(bpy)2PT3-PC](PF6) complexes have minor metal character for the HOMO (3% Ru for [Ru(bpy)2PT3-PC](PF6) and 10% Os for [Os(bpy)2PT3-PC](PF6)2) and nearly equal metal and PT3 contributions for the HOMO-1 (56% Ru for [Ru(bpy)2PT3-PC](PF6) and 43% Os for [Os(bpy)2PT3-PC](PF6)). DFT calculations on all four complexes indicate that the total metal bond order calculated by five different methods (Mayer, Gophinatan-Jug, and three NalejawskiMrozek definitions) is greater by about 0.6 for [Os(bpy)2PT3-PS](PF6)2 vs. [Ru(bpy)2PT3PS](PF6)2 and [Os(bpy)2PT3-PC](PF6) vs. [Ru(bpy)2PT3-PC](PF6), indicating stronger overall M – L bonding in the Os complexes compared to the corresponding Ru complexes. The increase in the total metal bond orders of 0.3 for both the PC bound complexes over their respective PS bound complexes indicates stronger overall M – L bonding in the PC coordination mode where the PT3 ligand is formally deprotonated, compared to the PS mode where the ligand is formally uncharged. This is not surprising given the lower positive charge in [Ru(bpy)2PT3-PC](PF6) and [Os(bpy)2PT3-PC](PF6), which arises due to a negative formal charge on the coordinated C atom in the deprotonated PT3 ligand. The significantly larger M – C bond orders for [Ru(bpy)2PT3PC](PF6) and [Os(bpy)2PT3-PC](PF6) compared to [Ru(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PS](PF6)2 are consistent with this conclusion. There is little difference in the calculated M – P and M – N (N trans to P) bond orders between the Ru complexes and between the Os complexes. The values of the total metal bond orders are provided in Table 2-4 and range from 4.2 ± 0.4 for [Ru(bpy)2PT3-PS](PF6)2  to 5.0 ± 0.5 for  [Os(bpy)2PT3-PC](PF6) depending on the method used to calculate them.  46  Figure 2-4 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Ru(bpy)2PT3-PS](PF6)2, (48), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453 a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. 47  Figure 2-5 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Ru(bpy)2PT3-PC](PF6), (49), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453 a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. 48  Figure 2-6 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Os(bpy)2PT3-PS](PF6)2, (54), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453 a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. 49  Figure 2-7 ADF-calculated plots of some frontier molecular orbitals (one of each spinorbit pair shown, all a1/2 in C1 symmetry) for [Os(bpy)2PT3-PC](PF6), (55), together with calculated energies (eV) for selected orbitals, electron occupations, and Mulliken metal atomic orbital percentages. The lowest energy orbital (453 a1/2 for both complexes) plot is lower left in each case, alternating from one side to another with increasing energy so that the HOMO plot is on the left side and the LUMO plot is on the right side. 50  Table 2-4 Total metal bond orders from ADF scalar relativistic calculations (G-J: Gophinatan-Jug; N-M: Nalejawski-Mrozek). Compound  Mayer  G-J  N-M (1)  N-M (2)  N-M (3)  [Ru(bpy)2PT3-PS](PF6)2  4.18  3.82  4.62  3.93  4.41  [Ru(bpy)2PT3-PC](PF6)  4.10  4.09  4.77  4.37  4.57  [Os(bpy)2PT3-PS](PF6)2  4.86  4.20  5.27  4.37  5.01  [Os(bpy)2PT3-PC](PF6)  4.97  4.51  5.44  4.95  5.17  The Hirshfeld, VDD, Mulliken, and MDC-q methods of calculating atomic charges on the metals all result in higher positive charges by 0.1-0.2 for [Ru(bpy)2PT3PS](PF6)2 vs. [Os(bpy)2PT3-PS](PF6)2 and [Ru(bpy)2PT3-PC](PF6) vs. [Os(bpy)2PT3PS](PF6), while the opposite is found with the AIM and NPA methods (Table 2-5). The higher metal atomic charges for the Ru complexes compared to the corresponding Os complexes calculated by all but the AIM and NPA methods are consistent with a slightly higher electronegativity for Os compared to Ru,153 and in fact the electronegativity equalized charges154 calculated for the Ru complexes are higher by 0.1 than those for the corresponding Os complexes. All six ADF methods of calculating atomic charges on the metals show an increase in positive charge for the PC vs. the PS complexes. The unexpectedly larger charges for the complexes with the PC coordination mode suggest greater M – bpy π back-bonding and/or less bpy – M  donation compared to those with the PS mode. The more negative charges on the N atom trans to the coordinated C atom in [Ru(bpy)2PT3-PC](PF6) and [Os(bpy)2PT3-PC](PF6) compared to those for the N atom trans to the coordinated S atom in [Ru(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PS](PF6)2 are consistent with this conclusion. The longer M – N bond distances for the N atom trans to C in the [Ru(bpy)2PT3-PC](PF6) and [Os(bpy)2PT3-PS](PF6) complexes (2.15 and 2.12 Å, respectively) compared to the M – N bond distances for the N atom trans to S in [Ru(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PS](PF6)2 (2.07 Å for both complexes) suggests less N – M  donation in the PC bound complexes compared to the PS bound complexes.  51  Table 2-5 Metal atom atomic charges Q/e from ADF relativistic calculations according to six different methods: Hirshfeld, Voronoi deformation density (VDD), Bader atoms in molecule (AIM), Weinhold natural population analysis (NPA), Mulliken, and multipolederived quadrupole (MDC-q). Spin-orbit effects were included in all but the NPA charges. Compound  Hirshfeld  VDD  AIM  NPA  Mulliken  MDC-q  [Ru(bpy)2PT3-PS](PF6)2  0.17  0.11  0.81  0.23  0.43  0.87  [Ru(bpy)2PT3-PC](PF6)  0.18  0.15  0.88  0.29  0.73  0.88  [Os(bpy)2PT3-PS](PF6)2  0.06  -0.03  0.93  0.30  0.37  0.69  [Os(bpy)2PT3-PC](PF6)  0.09  0.01  1.03  0.44  0.62  0.71  Section 2.3.4‒ Cyclic Voltammetry The cyclic voltammogram of [Os(bpy)2PT3-PS](PF6)2 (Figure 2-8(a)) shows a quasi-reversible oxidation peak at 1.23 V vs SCE, ~ 0.25 V lower than the first oxidation peak of [Ru(bpy)2PT3-PS](PF6)2. ADF-calculated Mulliken AO contributions indicate that both the HOMO and HOMO-1 orbitals of [Ru(bpy)2PT3-PS](PF6)2  and  [Os(bpy)2PT3-PS](PF6)2 are completely localized on the PT3 ligand. The first reduction peak of [Os(bpy)2PT3-PS](PF6)2 occurs at -1.36 V vs SCE and is irreversible. This reduction is presumably localized on the bpy ligands, consistent with ADF calculations that reveal neither the LUMO nor LUMO+1 have more than a 5% Os AO contribution. The cyclic voltammogram of [Os(bpy)2PT3-PC](PF6) (Figure 2-8(b)) shows two reversible waves, at 0.28 and 0.95 V vs. SCE. Some small features are observed in the voltammogram and are attributed to products resulting from scanning over the full potential range. For [Os(bpy)2PT3-PC](PF6), the ADF-calculated HOMO is about 90% PT3 localized while the HOMO-1 (0.48 eV lower in energy) is nearly equally distributed between the Os and PT3 units, suggesting the oxidation wave at 0.28 V to be PT3localized and the 0.95 V oxidation wave to be due to removal of an electron from a mixed Os-PT3 orbital. These assignments differ from those previously reported for the Ru analogs.103 These earlier assignments were based only on the observation of small shifts in potential with methyl substitution on the PT3. The oxidation potential of 0.95 V for [Os(bpy)2PT3-PC](PF6) is 0.16 V lower than the corresponding value for [Ru(bpy)2PT3PC](PF6) and is consistent with the smaller calculated atomic charge for the metal in the 52  Os complex relative to the Ru complex. In addition, [Os(bpy)2PT3-PC](PF6) has reduction waves at -1.45 and -1.75 V vs SCE, both presumably corresponding to bpybased processes as indicated by the ADF-calculated AO parentages for the LUMO and LUMO+1. These values are 0.08 V and 0.03 V less negative, respectively, than the corresponding values for [Ru(bpy)2PT3-PC](PF6) and are consistent with the 0.06 V lower calculated LUMO energy for [Os(bpy)2PT3-PC](PF6) versus [Ru(bpy)2PT3PC](PF6). The cyclic voltammogram of [Ru(phen)2PT3-PS](PF6)2 (Figure 2-9) shows a quasi-reversible oxidation peak at 1.39 V vs SCE. The first reduction peak of [Ru(phen)2PT3-PS](PF6)2 occurs at -1.19 V vs SCE and is irreversible. This reduction is presumably localized on the phen ligands, as the first reduction for [Ru(bpy)2PT3PS](PF6)2 is assigned as a bpy based reduction. The less negative reduction here than for the bpy analogue (-1.28 V)103 may be due to the phenanthroline being a slightly better π acceptor than bipyridine. In the [Ru(phen)2PT3-PC](PF6) complex, two reversible oxidation waves are observed at 0.51 V and 1.04 V vs SCE. These oxidation waves occur at a potential slightly less positive than the [Ru(bpy)2PT3-PC](PF6) analogue (0.57 V and 1.11 V vs SCE).103 Using the information obtained from the calculations, the oxidation and reduction waves in [Os(bpy)2PT3-PC](PF6) were assigned (see above). Based on these assignments, the oxidation at 0.51 V in [Ru(phen)2PT3-PC](PF6) was determined to be PT3-localized while the wave at 1.04 V was assigned as an oxidation of a mixed metal-PT3 state. Three reduction waves were observed in the [Ru(phen)2PT3-PC](PF6) complex. These waves, occurring at -1.33 V, -1.66 V and -1.87 V vs. SCE, are assigned as phenanthroline based. These values are slightly more negative than the redox potentials observed for [Ru(phen)3](PF6)2.155  53  4  (a)  Current (A)  2 0 -2 -4 -6 -8 -1.5  -1.0  -0.5  0.0  0.5  1.0  1.5  Volts (V) vs SCE 8  (b)  Current (A)  6 4 2 0 -2 -4 -6 -8 -10 -3  -2  -1  0  1  2  Volts (V) vs SCE  Figure 2-8 Cyclic voltammograms of (a) [Os(bpy)2PT3-PS](PF6)2, (54), and (b) [Os(bpy)2PT3-PC](PF6), (55), in CH3CN, 0.1 M TBAPF6, 100mV/s scan rate, Pt disc working electrode, Pt mesh counter electrode and silver wire reference electrode. The substantial decrease in the Os2+/3+ oxidation potential between [Os(bpy)2PT3PS](PF6)2 and [Os(bpy)2PT3-PC](PF6) is consistent with the lower energy of the mixed metal-ligand to ligand charge transfer transition (MLL'CT) transition (see below). A similar reduction in the Ru2+/3+ oxidation potential was also observed between the PS and PC bound Ru bipyridine  103  and phenanthroline complexes, and can be accounted for at  least in part by the reduction in overall charge from +2 for [Ru(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PS](PF6)2 to +1 for [Ru(bpy)2PT3-PC](PF6) and [Os(bpy)2PT3-PC](PF6).  54  6  (a)  4  Current (A)  2 0 -2 -4 -6 -8 -2.0  -1.5  -1.0  -0.5  0.0  0.5  1.0  1.5  2.0  0.5  1.0  1.5  Volts (V) vs SCE 6 4 2 0 -2 -4 -6 -8 -10 -12 -14  Current (A)  (b)  -2.5  -2.0  -1.5  -1.0  -0.5  0.0  Volts (V) vs SCE  Figure 2-9 Cyclic voltammograms of (a) [Ru(phen)2PT3-PS](PF6)2, (52), and (b) [Ru(phen)2PT3-PC](PF6), (53), in CH3CN, 0.1 M TBAPF6, 50mV/s scan rate, Pt disc working electrode, Pt mesh counter electrode and silver wire reference electrode. Section 2.3.5‒ Electronic Absorption Spectra The UV-vis absorption spectra of [Ru(phen)2PT3-PS](PF6)2, [Ru(phen)2PT3PC](PF6), [Os(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PC](PF6) in CH3CN are shown in Figure 2-10, along with the spectra of the Ru(II) bipyridine analogues for comparison. The absorption spectrum of complex [Ru(phen)2PT3-PS](PF6)2 contains two major bands, a band at 261 nm assigned to the π → π* transition of the phenanthroline group, and a lower energy band with max = 382 nm. The low energy band is slightly blue shifted from the corresponding band in the spectrum of [Ru(bpy)2PT3-PS](PF6), similar to observations of the spectra of tris(bipyridine) metal complexes, where the 1MLCT band 55  in [Ru(bpy)3]2+ has max = 451 nm156 and max = 446 nm155 in [Ru(phen)3]2+. Changing the diimine ligands from bpy to phen caused the π → π* transition of the diimine ligands in the PS coordinated complexes to blue shift. A similar shift is observed when comparing the diimine π → π* transition of [Ru(bpy)3]2+ (286 nm) to [Ru(phen)3]2+ (262 nm).157 In [Ru(bpy)2PT3-PS](PF6)2, the shoulder at 320 nm was assigned to the terthienyl π → π* transition. This band is observed at 295 nm in [Ru(phen)2PT3-PS](PF6)2. The absorption spectrum of [Os(bpy)2PT3-PS](PF6)2 contains two major bands, a band at 286 nm assigned to the π → π* transition of the bipyridine group, and a lower energy band with max = 394 nm. The low energy band is shifted only very slightly from the corresponding band in the spectrum of [Ru(bpy)2PT3-PS](PF6)2, similar to observations of the spectra of tris(bipyridine) metal complexes, where the 1MLCT band in [Ru(bpy)3]2+ has max = 451 nm156 and max = 450 nm in [Os(bpy)3]2+ with the 3MLCT band observed between 520-700 nm.158 This lower energy band in [Ru(bpy)2PT3PS](PF6)2 was assigned to a charge transfer transition involving a mixed metal/terthiophene HOMO and bipyridyl based LUMO (a 1MLL'CT transition).103,  104  ADF calculations for the PS bound complexes indicate that the HOMO and HOMO-1 have no metal atomic orbital contributions, whereas the HOMO-2, -3, and -4 orbitals all contain substantial metal contributions and all lie within about 1 eV of the HOMO in energy. Therefore, for these complexes, the broad, overlapping absorption bands above 350 nm are likely to contain orbital contributions from both PT3-localized and M-PT3 delocalized orbitals and are best considered as 1MLL'CT bands. Similarly, the broad band between 450-575 nm in the spectrum of [Os(bpy)2PT3-PS](PF6)2 is assigned as a 3  MLL'CT transition based on the ADF calculations, increased in intensity relative to the  Ru analogue due to the larger spin-orbit coupling in Os. In [Ru(bpy)2PT3-PS](PF6)2, the shoulder at 320 nm was assigned to the terthienyl π → π* transition. This blue-shifts in [Os(bpy)2PT3-PS](PF6)2, and is almost completely hidden under the bpy transition, and a small shoulder can be seen at ~300 nm.  56  (a)  50 40  [Ru(bpy)2PT3-PS](PF6)2 (48) [Os(bpy)2PT3-PS](PF6)2 (54)  20  3  -1  -1  molar absorptivity x 10 (M cm )  [Ru(phen)2PT3-PS](PF6)2 (52) 30  10 70 0  (b) 60 50 [Ru(bpy)2PT3-PC](PF6) (49) 40  [Ru(phen)2PT3-PC](PF6) (53) [Os(bpy)2PT3-PC](PF6) (55)  30 20 10 0 300  400  500  600  700  800  wavelength (nm)  Figure 2-10 UV-vis absorption spectra of (a) [Ru(bpy)2PT3-PS](PF6)2, (48), [Ru(phen)2PT3-PS](PF6)2, (52), [Os(bpy)2PT3-PS](PF6)2, (54) and (b) [Ru(bpy)2PT3PC](PF6), (49), [Ru(phen)2PT3-PC](PF6), (53), and [Os(bpy)2PT3-PC](PF6), (55), in CH3CN. The absorption spectra of the PC complexes contain more peaks than their corresponding PS complexes. The π → π* transition of the phenanthroline group in [Ru(bpy)2PT3-PC](PF6) (268 nm) is blue shifted from that in [Ru(bpy)2PT3-PC](PF6) (294 nm). Otherwise, the spectra are very similar. The high energy peaks ( < 375 nm, assigned to bpy and terthienyl based * transitions do not shift much between [Ru(bpy)2PT3-PS](PF6) and [Os(bpy)2PT3-PS](PF6). A band at 400 nm is observed in the spectrum of the [Os(bpy)2PT3-PS](PF6) which is not present in the spectrum of [Ru(bpy)2PT3-PC](PF6) or [Ru(phen)2PT3-PC](PF6), it is not clear what the origin of this 57  new peak is. The charge transfer transition in [Os(bpy)2PT3-PC](PF6) is red-shifted relative to the corresponding band in the Ru complexes (Table 2-6). The 3MLL'CT transition, that ADF calculations suggest corresponds to a HOMO and/or HOMO-1 to LUMO transition, red shifts to 650 nm, with the addition of a new shoulder at 560 nm. This red shift is consistent with the lower calculated atomic charge on the metal in [Os(bpy)2PT3-PC](PF6) relative to that in [Os(bpy)2PT3-PS](PF6)2. There is a significant red-shift of the terthienyl band between the PS and PC complexes due to either the increased planarity of the thiophene rings in the PC bound complexes or the change in the charge of the PT3 ligand accompanying the orthometallation to form the PC derivatives.  Table 2-6 Absorption spectroscopy data for [Ru(phen)2PT3-PS](PF6)2, (52), [Ru(phen)2PT3-PC](PF6) , (53), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3PC](PF6) , (55). Compound  a  Abs max (nm) [ɛ (M-1cm-1)]a  [Ru(phen)2PT3-PS](PF6)2  260 (50.0 × 103), 293 (sh) (25.6 × 103), 383 (18.5 × 103)  [Ru(phen)2PT3-PC](PF6)  267 (65.0 × 103), 350 (15.4 × 103), 455 (17.3 × 103), 568 (sh) (2.96 × 103)  [Os(bpy)2PT3-PS](PF6)2  285 (40.6 × 103), 313 (sh) (20.6 × 103), 386 (17.8 × 103), 492 (sh) (1.75 × 103)  [Os(bpy)2PT3-PC](PF6)  285 (40.6 × 103), 313 (sh) (20.6 × 103), 386 (17.8 × 103), 492 (sh) (1.75 × 103)  Measurements carried out in CH3CN solution. Photostability studies of PT3 and the bipyridine complexes in CH3CN were  carried out by extended irradiation with 366 nm light, using UV-vis spectroscopy as a tool to probe stability. Irradiation of PT3 resulted in a decrease in the main absorption bands, and the growth of a low energy shoulder at ~450 nm (Figure 2-11 (a)). Previous studies have shown that irradiation of 2,2′:5′2″-terthiophene (T3) with UV light results in polymerization to give longer oligomers.159 The low energy absorption band observed upon irradiation of PT3 is consistent with oligomerization of the terthiophene, resulting in a red shift in the absorption band. Irradiation of complexes [Ru(bpy) 2PT3-PC](PF6), 58  [Os(bpy)2PT3-PS](PF6)2, and [Os(bpy)2PT3-PC](PF6) under the same conditions resulted in only very small changes to the UV-vis spectra (Figure 2-11 (c)-(e)), indicating that these complexes are all photostable under the irradiation conditions. On the contrary, irradiation of [Ru(bpy)2PT3-PS](PF6)2 results in substantial changes in the UV-vis spectrum (Figure 2-11 (b)), demonstrating that this complex is not photostable under these conditions in solution. Although a small low energy shoulder also appears in this experiment, the higher energy region shows different changes than observed when PT3 is irradiated, suggesting that different products are formed in the case of the [Ru(bpy)2PT3-PS](PF6)2 complex. Mass spectrometric analysis of a solution of photoirradiated [Ru(bpy)2PT3-PS](PF6)2 suggests that a bipyridyl group is being lost during the irradiation process. This has been observed before in other photoactive metal bipyridyl complexes.160 It is believed that excited state ligand dissociation proceeds via population of a low-lying ligand state.161 The photostability of the complexes did not change when irradiated under nitrogen or oxygen. Decomposition reactions of other metal bipyridyl complexes have been observed when MC states are accessible.162 The increased photostability of the PC bound species may be due to the reactive MC state lying higher in energy due to the coordination of the formally anionic ligand. The higher photostability of the [Os(bpy)2PT3-PS](PF6)2 complex may also be due to a higher barrier to the MC state, since the lowest energy CT excited state in this complex is lower in energy than in complex [Ru(bpy)2PT3-PS](PF6)2.  59  (a)  20 15  0 min 2 min 5 min 15 min 30 min 60 min 90 min 120 min  10 5 50 30  -1  20  (b)  10  3  -1  molar absorptivity x10 (M cm )  40  50 40 30 20 10  (c)  40  (d)  30 20 10  (e)  40 30 20 10 0 300  400  500  600  700  800  Wavelength (nm) Figure 2-11 UV-vis spectra of (a) PT3, (b) [Ru(bpy)2PT3-PS](PF6)2, (48), (c) [Os(bpy)2PT3-PS](PF6)2, (54), (d) [Ru(bpy)2PT3-PC](PF6), (49), and (e) [Os(bpy)2PT3PC](PF6), (55), in CH3CN after 0, 2, 5, 15, 30, 60, 90, and 120 minutes of irradiation at 366 nm.  60  Section 2.3.6‒ Emission Spectra PT3 has a short-lived emission centered at 435 nm (Table 1), attributed to radiative decay of the singlet  state.  The [Ru(bpy)2PT3-PS](PF6)2 and  [Ru(bpy)2PT3-PC](PF6) complexes were previously reported to be either non-emissive or very weakly emissive upon excitation with visible light.103 However, when excited at 355 nm, [Ru(bpy)2PT3-PS](PF6)2 exhibited short-lived emission at 430 nm.163 [Ru(phen)2PT3PS](PF6)2 exhibited a weak short-lived emission at 450 nm when excited at 355 nm (Figure 2-12). The Os-bipyridine analogue showed dual emission, with bands at 447 and 640 nm (Figure 2-13). Dual emission from metal complexes is unusual, but has been previously observed in some cases.164-168 In all the PS bound complexes, the lifetime of the species giving rise to the higher energy band is not sensitive to the presence of oxygen.  The lifetime of the species giving rise to the lower energy band in  [Os(bpy)2PT3-PS](PF6)2 is significantly shorter in oxygen sparged solution. Based on these observations, the higher energy band in the complexes is assigned to emission from a terthiophene-localized singlet state. In [Os(bpy)2PT3-PS](PF6)2, enhanced intersystem crossing due to the heavier Os center also populates either a 3MLL'CT or 3LL'CT state which emits at lower energy, and has a longer lifetime. The Ru PC bound complexes also emit when excited at 355 nm. In addition, upon excitation into the lowest energy absorption band of these complexes, [Ru(bpy)2PT3-PC](PF6) and [Ru(phen)2PT3PC](PF6) emit at 730 nm and 790 nm, respectively (spectra of [Ru(phen)2PT3-PC](PF6) shown in Figure 2-12). The [Os(bpy)2PT3-PC](PF6) also shows two emission bands (Figure 2-13). In the presence of O2 the lower energy band becomes very weak in these complexes, and in [Os(bpy)2PT3-PC](PF6) the lifetime is shorter in the presence of oxygen, supporting the assignment of this band to a triplet emission.  61  100000  [Ru(phen) PT -PS](PF ) (52)  = 355 nm 2 3 62 exc  -1  Emission Counts (s )  80000  [Ru(phen) PT -PC](PF ) 2 3 6  (53) exc = 355 nm  [Ru(phen) PT -PC](PF ) 2 3 6  (53)    exc = 456 nm  60000  40000  20000  x5 0 350  400  450  500  550  600  650  700  750  800  850  900  Wavelength (nm)  Figure 2-12 Emission spectra of [Ru(phen)2PT3-PS](PF6)2, (52), and [Ru(phen)2PT3PC](PF6) , (53), in nitrogen-sparged CH3CN. The emission of [Ru(phen)2PT3-PC](PF6) excited at 456 nm has been expanded by a factor of 5.  180000 [Os(bpy)2PT3-PS](PF6)2 (54)  exc=355 nm  -1  Emission Counts (s )  160000  [Os(bpy)2PT3-PC](PF6) (55)  exc=355 nm  140000 120000 100000 80000 60000 40000 20000 0 350  400  450  500  550  600  650  700  750  800  850  900  Wavelength (nm)  Figure 2-13 Emission spectra of [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3PC](PF6), (55) in nitrogen-sparged CH3CN.  62  Despite careful efforts to purify the complexes, the possibility of the higher energy emission band arising from free ligand cannot be entirely ruled out. However, emission of PT3 occurs with max = 435 nm, and the higher energy emission band observed in all the complexes is shifted from this maximum. Quantum yields were obtained for the lower energy emission band of the bipyridine complexes, and are comparable to those reported for related Os and Ru complexes.169,  169, 170  Values were  calculated for the radiative (kr) and non-radiative (knr) decay constants and show the nonradiative decay dominates.  63  Table 2-7 Photophysical data for PT3 and complexes [Ru(bpy)2PT3-PS](PF6)2, (48), [Ru(bpy)2PT3-PC](PF6), (49), [Ru(phen)2PT3PS](PF6)2, (52), [Ru(phen)2PT3-PC](PF6), (53), [Os(bpy)2PT3-PS](PF6)2, (54), and [Os(bpy)2PT3-PC](PF6) (55). Compound  ema  ema,b ±5%  ±2nm  TAa,b ±5%  N2 Sparged  O2 sparged  N2 sparged  O2 sparged  Φema,c ±10%  kr × 10-4 (s-1)d ±10%  knr × 10-4 (s-1)e ±10%  E1/2 ox ±0.01V vs SCE  E1/2 red ±0.01V vs SCE  PT3  435 nm  < 0.05 ns  < 0.05 ns  9 s  -  -  -  -  1.30f,g  48  430 nm  0.2 ns  0.1 ns  100 ns  35 ns  -  -  -  1.48f  -1.28d  423 nm  2 ns  1.5 ns  -  -  0.57  -1.53  8 ns  7 ns  10 ns  -  730 nm  20 ns  0.0001  1.9  58.6  1.11  -1.78  52  439 nm  -  -  100 ns  -  -  -  -  1.39f  -1.19d  53  445 nm  -  -  -  -  0.51  -1.33  -  -  -  -  790 nm  60 ns  -  -  -  1.04  -1.66  49  -1.87 54  55  447 nm  < 0.05 ns  < 0.05 ns  640 nm  170 ns  30 ns  419 nm  1.8 ns  1.5 ns  640 nm  25 ns  10 ns  800 ns  70 ns  2 ns  2 ns  -  -  -  0.003  1.1  399  -  -  0.0002  1.5  1.23  -1.36  -  0.28  -1.45  1249  0.95  -1.75  ex = 355 nm, CH3CN, btime for intensity to decay to 1/e of the initial intensity cΦem = # photons emitted/# photons absorbed, d calculated using kr= Φemem-1, ecalculated using knr = em-1 - kr using N2 sparged emission lifetimes, firreversible wave, Ep reported, g reference56 a  64  Section 2.3.7‒ Transient Absorption Spectra Transient absorption (TA) spectroscopy uses an excitation pulse to promote a fraction of molecules into the excited state and measures the difference in absorption between the ground state and excited state. The bands in a TA spectrum indicate an excited state absorption, while bleaches are due to stronger ground state absorptions than that of the excited state. The TA spectrum of PT3 is shown in Figure 2-14 (a). This spectrum shows a transient species absorbing between 400-600 nm, with a lifetime of about 9-10 s under N2 (Table 2-7, Appendix Figure A-1), that is quenched under O2. Excitation of unsubstituted terthiophene, T3, (Figure 2-14 (b)) also results in a species with a similar, but sharper, absorbance from 400-600 nm with a 2.8 s lifetime (Appendix Figure A-2). Under oxygen, the TA spectrum of T3 is also quenched. These data are consistent with the TA of both T3 and PT3 being due to a triplet-triplet excitation localized on the  system.  65  0.04  (a)  1 s 3 s 5 s 7 s 10 s 15 s 20 s  0.03 0.02 0.01   Abs.  0.00 -0.01 0.08  1 s 2 s 3 s 5 s 7 s 10 s 15 s 20 s  (b)  0.06  0.04  0.02  0.00 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure 2-14 Time-resolved transient absorption spectra of (a) PT3 and (b) T3 in CH3CN. ex = 355 nm. Excitation of [Ru(bpy)2PT3-PS](PF6)2 resulted in a broad TA spectrum with two overlapping bands between 400-700 nm (Figure 2-15 (a)). The species decays with a lifetime of 100 ns in nitrogen-sparged acetonitrile (Appendix Figure A-3), which is significantly reduced with oxygen sparging (Table 1). A similar broad TA spectrum is observed for [Ru(phen)2PT3-PS](PF6)2 (Figure 2-15 (b)), but the relative ratio of the overlapping bands is different. Both bands decay with a lifetime of approximately 100 ns, and the presence of oxygen decreased this value (Appendix Figure A-4). The [Os(bpy)2PT3-PS](PF6)2 complex also shows an intense, broad TA with two bands between 450-625 nm (Figure 2-15(c)). In addition, there is a bleach centered at 400 nm. 66  Both the absorptions and bleach decay with a lifetime of 800 ns (Appendix Figure A-5), which decreases in the presence of oxygen.  The TA spectra of these PS bound  complexes resemble the TA spectrum of PT3, although slightly red-shifted. In addition, no absorption due to a bipyridyl or phenanthroline anion is seen at ~375 nm,171 suggesting that the excited state observed in the TA spectra does not have metal-todiimine or thiophene-to-diimine charge transfer character. Even at short times following excitation, the TA spectra do not show features associated with an MLL'CT state. The dependence of the lifetime and intensity of these bands on the presence of oxygen supports the conclusion that these are due to a triplet state, and the similarity of the TA spectra to that of PT3 suggests that a PT3 ligand-centered triplet state (3LC) is being observed. The lack of observable emission in [Ru(bpy)2PT3-PS](PF6)2 suggests that in this complex triplet energy transfer to the 3LC state is very efficient. In the Os complex, [Os(bpy)2PT3-PS](PF6)2, weak emission attributed to decay of the 3MLL'CT or 3LL'CT is observed, and the 3LC state is still relatively efficiently populated and is the major species observed in the TA spectrum. The longer TA lifetime in [Os(bpy)2PT3-PS](PF6)2 indicates that the 3LC state must lie substantially lower in energy than the 3MLL'CT and 3  LL'CT states, and these states are not in thermal equilibrium as has been observed  previously in pyrene functionalized Ru diimine complexes.172,  173  In these cases the  pyrene 3LC state and Ru 3MLCT states have the same lifetimes due to the equilibrium between them. The longer TA lifetime for [Os(bpy)2PT3-PS](PF6)2 relative to [Ru(bpy)2PT3-PS](PF6)2 and [Ru(phen)2PT3-PS](PF6)2 is attributed to the higher energy barrier to the MC state (see above), consequently this deactivation pathway is less prevalent in the Os complex than in the Ru complexes.  67  0.05  (a)  50 ns 100 ns 150 ns 250 ns 500 ns  0.04 0.03 0.02 0.01 0.00   Abs.  0.03  (b)  50 ns 100 ns 150 ns 200 ns 250 ns 300 ns  (c)  0.25 s 0.50 s 0.75 s 1.00 s 1.50 s 2.00 s 2.50 s 3.00 s 4.00 s 5.00 s  0.02 0.01 0.00 0.4 0.3 0.2 0.1 0.0 -0.1 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure 2-15 Time-resolved transient absorption spectra of (a) [Ru(bpy)2PT3-PS](PF6)2, (48), (b) [Ru(phen)2PT3-PS](PF6)2, (52), and (c) [Os(bpy)2PT3-PS](PF6)2, (54), in CH3CN. ex = 355 nm. Interestingly, the TA spectra of the PC bound complexes (Figure 2-16) are very different from the corresponding PS-coordinated complexes. Each of the PC bound complexes shows an absorption at ~375 nm, and a bleach at ~450-475 nm. The TA spectra of [Ru(bpy)2PT3-PC](PF6) and [Ru(phen)2PT3-PC](PF6) also contain broad, tailing absorptions above 500 nm, while [Os(bpy)2PT3-PC](PF6) shows a weak, broad bleach in this region. The TA of [Ru(bpy)2PT3-PC](PF6) decays monoexponentially with 68  a lifetime of 20 ns under nitrogen (Appendix Figure A-6), which decreases under O2. The [Ru(phen)2PT3-PC](PF6) complex decays monoexponentially with a lifetime of about 60 ns under nitrogen (Appendix Figure A-7). The absorption at ~375 nm in the TA spectrum of these complexes is assigned as a transition of the bpy- or phen- anion based on comparison to related compounds.171 The presence of this band indicates the observed excited state has charge transfer character. The lower energy absorption bands (>500 nm) in [Ru(bpy)2PT3-PC](PF6) and [Ru(phen)2PT3-PC](PF6) are assigned to transitions of a cationic species having mixedmetal and ligand (PT3) character. This assignment is based on several comparisons. The TA spectrum of T3+ shows an absorbance band between 530 and 545 nm,174,  175  and  spectroelectrochemical studies on oxidized [Ru(bpy)2PT3-PC](PF6) have shown that this species has bands with absorption maxima at 558 and 632 nm.176 Both these species have similar absorptions to the band observed in the TA spectrum of [Ru(bpy)2PT3-PC](PF6) at ~515 nm, suggesting a similar origin. An EPR study of oxidized [Ru(bpy)2PT3PC](PF6) showed that there is a significant metal contribution to the singly occupied molecular orbital (SOMO) in this oxidized complex.104 This is consistent with ADFcalculations for [Ru(bpy)2PT3-PC](PF6) showing the HOMO-1 to have a 56% Ru contribution, but not with oxidation from the HOMO which has only a 3% Ru contribution. Taking all this data into account does not allow a conclusive assignment to be made of the cation, but a mixed parentage cation with both metal and PT3 ligand character is most likely, thus the observed excited state is characterized as a mixed metalligand to ligand CT (3MLL'CT) state. The broad but very weak absorbance tail around 650 nm in [Ru(bpy)2PT3-PC](PF6) and [Ru(phen)2PT3-PC](PF6) is characteristic of the presence of an anion,177, 178 cation179, 180 or a charge transfer transition.181 The TA and emission lifetimes are similar for [Ru(bpy)2PT3-PC](PF6) suggesting that it is possible that these states are close in energy and in thermal equilibrium. The excited state spectrum of [Os(bpy)2PT3-PS](PF6)2 appears to be similar, with the clear presence of a transition assigned to the bpy anion. Transitions that could be assigned to a cation are not observed. [Os(bpy)2PT3-PS](PF6)2 absorbs to 700 nm, so the 69  bleaching that is observed in the TA spectrum of this complex may hide weaker absorptions from a cationic species if these are present. The lifetime of this species is short, 2 ns under either nitrogen (Appendix Figure A-8), or oxygen. The measured lifetime is shorter than the emission lifetime, and it is possible that the weak TA spectrum introduces error and these states are also close in energy as in [Ru(bpy)2PT3-PS](PF6)2. Other Ru and Os bipyridyl complexes show similar transient spectra. Excited state Ru(bpy)32+ is reported to have absorption bands at 360 nm and above 525 nm, with a bleach centered at 440.182 Excited state Os(dmb)32+ has an absorption around 350 nm, and a strong bleach from 420-500 nm, with a weaker bleach extending past 650 nm.183  70  0.20  (a) 10 ns 20 ns 30 ns 40 ns 50 ns 70 ns 100 ns  0.15 0.10 0.05 0.00 -0.05 -0.10 0.15  (b)   Abs.  0.10  12 ns 40 ns 65 ns 95 ns  0.05 0.00 -0.05 0.10 0.08 0.06  (c)  0.75 ns 2.50 ns 5.00 ns 7.00 ns 9.50 ns  0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure 2-16 Time-resolved transient absorption spectra of (a) [Ru(bpy)2PT3-PC](PF6), (49), (b) [Ru(phen)2PT3-PC](PF6), (53), and (c) [Os(bpy)2PT3-PC](PF6), (55), in CH3CN. ex = 355 nm. The photophysical results for these complexes can be summarized by consideration of the qualitative energy diagram shown in Figure 2-17. For the PS bound complexes, excitation at 355 nm results in simultaneous population of both 1MLL'CT and 1  LC states. Some emission from the 1LC state is observed for both complexes. Internal  conversion followed by intersystem crossing populates the 3MLL'CT or 3LL'CT state, from which some emission is observed for the [Os(bpy)2PT3-PS](PF6)2 complex. For the 71  Ru(II) complexes, the MC state lies close enough in energy to be thermally populated resulting in a photoreaction, and this does not occur in [Os(bpy)2PT3-PS](PF6)2. In the PS bound complexes, the 3LC state is lower in energy than the 3MLL'CT or 3LL'CT state, resulting in triplet energy transfer and the observation of a transient species attributed to the 3LC state.  This coordination mode results in only a small perturbation in the  electronic structure of the PT3 ligand, possibly due to the weakly coordinated thiophene sulfur. In the PC bound complexes, population of both 1MLL'CT and 1LC states occurs, and some emission from the 1LC states is observed. Here, the 3MLL'CT state is also populated, and emission from this state is observed.  Figure 2-17 Qualitative energy diagram for [Ru(bpy)2PT3-PS](PF6)2, (48), [Ru(bpy)2PT3PC](PF6), (49), [Ru(phen)2PT3-PS](PF6)2, (52), [Ru(phen)2PT3-PC](PF6), (53), [Os(bpy)2PT3-PS](PF6)2 (54), and [Os(bpy)2PT3-PC](PF6) (55). Abbreviations used indicate metal center and binding mode of the complexes.  Section 2.4‒ Conclusions Four new group 8 diimine complexes were synthesized incorporating PT3 as a ligand: [Ru(phen)2PT3-PS](PF6)2, [Ru(phen)2PT3-PC](PF6), [Os(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PC](PF6). The obtained solid-state structures are similar to the previously synthesized [Ru(bpy)2PT3-PS](PF6)2 and [Ru(bpy)2PT3-PC](PF6) complexes. DFT 72  studies indicated that for the [Ru(bpy)2PT3-PS](PF6)2 and [Os(bpy)2PT3-PS](PF6)2 complexes both the HOMO and HOMO-1 have no metal contributions, while the [Ru(bpy)2PT3-PC](PF6) and [Os(bpy)2PT3-PC](PF6) complexes have minor metal character for the HOMO and nearly equal metal and PT3 contributions for the HOMO-1. The electrochemistry reveals PT3 or mixed PT3 – metal oxidation waves, while the reduction waves are assigned as diimine based. The spectroscopic properties of [Ru(phen)2PT3-PS](PF6)2 and [Ru(phen)2PT3-PC](PF6) complexes are akin to the [Ru(bpy)2PT3-PS](PF6)2 and [Ru(bpy)2PT3-PC](PF6) analogues. The absorption spectra are dominated by π→π* transitions for all complexes, and the MLCT band was not shifted a lot between the Ru and Os complexes. The Os analogues had a broader absorption than the Ru complexes due to enhanced spin orbit coupling. Changing the coordination mode of the PT3 ligand (from PS to PC coordination) resulted in broader absorption across the UV-vis region. A new band in the absorption spectrum of [Os(bpy)2PT3-PC](PF6) was observed at ~400 nm. Enhanced photostability of the Os complexes was observed. Weak emission was recorded for all complexes. A shift in the excited state observed by TA spectroscopy from a 3LC triplet localized on the PT3 group in the PS bound complexes to a mixed metal-ligand to ligand CT state in the case of the PC bound complexes was also reported. These results have important implications for the design of dyes for DSSCs and other related applications. In the PC bound complexes the MLL'CT excited state involves charge transfer from the PT3 localized HOMO to the bipyridyl localized LUMO.  Adsorption of these complexes to nanostructured TiO2  should allow charge injection from the LUMO and hole transport away from the metal center via the conjugated ligand.  73  CHAPTER 3 CYCLOMETALATED IRIDIUM (III) PHOSPHINO(TERTHIOPHENE) COMPLEXES  Section 3.1‒ Introduction Cyclometalated iridium (III) complexes have received a great deal of interest in the past several years due to their interesting photophysical properties. Luminescent cyclometalated Ir(III) complexes commonly exhibit short phosphorescence lifetimes relative to organic luminophores184 (microseconds compared to milliseconds) at room temperature and have high quantum yields.185 They are most notably known for their use as emissive dopants in organic light emitting diodes (OLEDs).186-190 More recently, complexes of this type have been shown to have useful applications in a number of different fields, including as photocatalysts,191 oxygen sensors,192,  193  biological  labels,194,195 in light emitting electrochemical cells (LECs)196 and in dye sensitized solar cells (DSSCs).93, 197, 198 As previously discussed (Introduction), Ru(II) polypyridyl systems have dominated the DSSC field to date. Ir (III) complexes isoelectronic with Ru(II) and Os(II) complexes have good chemical stability, and have potential for application in DSSCs as well. Ir(III) terpyridine complexes have been used as photosensitizers, and exhibit charge-separated states with lifetimes of 100 s in air equilibrated solution.197 Their long lifetime in air, coupled with their lower reduction potentials and higher lying excited states (than analogous Ru(II) terpy complexes) are beneficial attributes. Cyclometalated Ir(III) complexes have also been shown to possess similar spectroscopic and electronic properties to Ru(II) bpy complexes. Due to the wide ligand set available, and enhanced spin orbit coupling of the Ir(III) complexes (the one electron spin-orbit coupling constants, δc, for Ru(II) and Ir(III) are 1051 cm-1 and 4430 cm-1, respectively),199 absorption can span a wide range of the visible/NIR spectrum. Mayo et al. have shown that Ir(III) dyes (56 and 57 Chart 3-1) can sensitize TiO2 in a DSSC.93 These complexes have a low energy LLCT state which allows for large spatial separation between holes and electrons. This can facilitate injection into TiO2 while still possessing reduction potentials sufficient to oxidize I-. 74  Chart 3-1 Ref.93  Investigations of Ir (III) complexes have focused on homo- and heteroleptic cyclometalated complexes, with the majority having the general form [Ir(C^N)3] or [Ir(C^N)2(XY)]n+(A-)n (where A- represents a monoanionic counterion, and n = 0, 1). A wide variety of bidentate XY ligands and cyclometalated (C^N) ligands have been coordinated to Ir(III) metal centers. The XY ligand may be neutral or anionic (Chart 3-2 (a) and (b) respectively), resulting in cationic or neutral complexes, respectively. Likewise, numerous aryl and heteroaryl bidentate C^N ligands have been used in homoleptic and heteroleptic complexes. Examples include phenylpyridine (ppy),185, 188, 200 phenylpyrazole  (ppz),200,201  thienyl  phenylisoquinoline,205,206 phenyl-imidazole,207  pyridine,202,203  phenylthiophene,204  and derivatives thereof, among others  (Chart 3-3).  75  Chart 3-2  Chart 3-3  [Ir(C^N)2(XY)]n+ (n=0,1) species can exist as various stereoisomers, however, the major stereoisomer is typically the one with the two cyclometalating carbon atoms mutually cis, and the nitrogen atoms on these ligands mutually trans (A, Scheme 3-1). Scheme 3-1  76  The substituents on the C^N ligand affect the emission energy of the complexes, as do the ancillary XY ligands. Further tuning is possible by adding electron donating or electron withdrawing substituents at various positions on the XY and/or C^N ligands. Therefore, a large number of possible complexes can be made by choosing different C^N and XY ligand combinations. This is useful in DSSC applications as it may allow for broader absorption across the visible spectrum, potentially leading to increased efficiency. In this chapter, six new complexes using PT3 as a ligand are described: Ir(ppz)2PT3Cl-P, [Ir(ppz)2PT3-PS](PF6), Ir(ppz)2PT3-PC, Ir(ppy)2PT3Cl-P, [Ir(ppy)2PT3PS](PF6), and Ir(pp)2PT3-PC (Chart 3-4). The influence of binding mode of the ancillary PT3 ligand on torsion angles, emission and excited state are investigated. The properties of these Ir complexes are compared to the Os complexes discussed in Chapter 2. Chart 3-4 PF6 N  N  N Cl  S  S  Ir N  N  N  S  S  S  P Ph2  N  N  N  N N  P Ph2  S  S  [Ir(ppz)2PT3-PS](PF6)  Ir(ppz)2PT3Cl-P 58  S  Ir  Ir P Ph2  N  S  Ir(ppz)2PT3-PC 60  59 PF6  N  Cl  Ir  Ir P Ph2  S  S  Ir N  N  N S  S S  N  P Ph2  N  S P Ph2 S  S S  Ir(ppy)2PT3Cl-P 61  [Ir(ppy)2PT3-PS](PF6) 62  Ir(ppy)2PT3-PC 63  77  Section 3.2 ‒ Experimental Section 3.2.1 ‒ General All reactions were performed under N2 (99.0%) or Ar (99.997%). The compounds PT3,109 [Ir(ppz)2Cl]2,208 and [Ir(ppy)2Cl]2208, 209 were synthesized according to literature procedures. All other reagents were purchased from Aldrich and Strem and used as received.  1  H and  31  P{1H} NMR spectra were collected on either a Bruker AV-300 or  AV-400 spectrometer. 1H NMR spectra were referenced to residual solvent, and 31P{1H} NMR spectra referenced to external 85% H3PO4. ESI mass spectra were recorded on a Bruker Esquire-LC ion trap mass spectrometer equipped with an electrospray ion source.  The solvent for the ESI-MS experiments was either methanol or  dichloromethane/methanol and the concentration of the compound was ~10 M. High resolution mass spectra were recorded on a Waters Micromass LCT time-of-flight mass spectrometer equipped with an electrospray ion source. CHN elemental analyses were performed using an EA1108 elemental analyzer, using calibration factors. The calibration factor was determined by analyzing a suitable certified organic standard (OAS) of a known elemental composition. All mass spectrometry and microanalysis results were obtained by the staff at the UBC Mass Spectrometry Centre. Cyclic voltammetry experiments were carried out on an Autolab PG STAT 12 potentiostat or a Pinechem potentiostat using a Pt disk working electrode, Pt mesh counter electrode and a silver wire reference electrode with 0.1 M [(n-Bu)4N]PF6 supporting electrolyte which was recrystallized 3 times from ethanol and dried under vacuum at 100 °C for 3 days. Decamethylferrocene was used as an internal reference to correct the measured potentials with respect to the saturated calomel electrode (SCE). UV-vis spectra were obtained on a Varian Cary 5000 UV-Vis-NIR spectrophotometer in HPLC grade solvent. Emission spectra were obtained on a PTI Quantamaster fluorimeter. Transient absorption measurements and fluorescence lifetimes were carried out on an Princeton Instruments Spectra Pro 2300i Imaging Triple Grating Monochrometer/Spectrograph with a Hamamatsu Dynamic Range Streak Camera (excitation source: EKSPLA Nd:YAG laser, λ = 355 nm). Solutions of the complexes in CH3CN having an optical density of 1 at 355 nm were prepared. The UV-vis spectra were obtained before and after each TA 78  experiment to ensure the bulk of the sample did not change, due to sample degradation or another process. Microwave reactions were carried out on a Biotage Initiator 2.5 microwave synthesizer.  Section 3.2.2 ‒ Procedures Ir(ppz)2PT3Cl-P, (58). [Ir(ppz)2Cl]2 (0.045 g) and PT3 (0.042 g) were added to a 2-5 mL microwave vial. EtOH (4 mL) was added and the mixture was stirred and sparged with N2 for 5 minutes. The mixture was heated in a 2.2 GHz microwave synthesizer at 100°C for 30 minutes. Upon removal from the microwave, the mixture was centrifuged, and the supernatant was reduced in volume. A mixture of Ir(ppz)2PT3Cl-P and [Ir(ppz)2PT3-PS]Cl was obtained. The Ir(ppz)2PT3Cl-P was slightly soluble in ether. The mixture was washed thoroughly with ether, which was then removed by rotary evaporation, and the residue dissolved in DCM and layered with hexanes to produce yellow crystals of Ir(ppz)2PT3Cl-P (16.4 mg, 20 %). 1H NMR (300 MHz, CD2Cl2): δ 5.82 (d, J = 7.3 Hz, 1H), 5.91 (t, J = 6.1 Hz, 1H), 6.24-6.29 (m, 1H), 6.32-6.39 (m, 2H), 6.48(d, J = 7.3 Hz, 1H), 6.56 (br.s., 1H), 6.69-6.83 (m, 2H), 6.91 (d, J = 5.5 Hz, 2H), 7.01-7.08 (m, 3H), 7.14 (d, J = 4.1 Hz, 2H), 7.20 (d, J = 9.1 Hz, 2H), 7.26 (d, J =5.9 Hz, 2H), 7.34-7.41 (m, 3H), 7.73 (s, 1H), 7.76-7.83 (m, 3H), 8.12-8.18 (m, 1H). 31P{1H} NMR (121 MHz, CD2Cl2): δ -15.6 (s). m/z [M-Cl]+ 911. HRMS (ESI) Calcd for C42H31N4PS3Ir (m/z [M-Cl]+): 909.1055; Found: 909.1061. Anal. C42H31ClIrN4PS3 requires C, 53.29; H, 3.30; N, 5.92. Found C, 52.02; H, 3.50; N, 5.34%.  [Ir(ppz)2PT3-PS](PF6), (59). [Ir(ppz)2Cl]2 (0.045 g) and PT3 (0.042 g) were added to a 2-5 mL microwave vial along with AgBF4 (0.018 g). EtOH (4 mL) was added and the mixture was stirred while sparging with N2 for 5 minutes. The mixture was heated in a 2.2 GHz microwave synthesizer at 100°C for 30 minutes. Upon removal from the microwave, the mixture was centrifuged, and the supernatant was removed. The solid was rinsed and centrifuged again. The supernatant was combined, reduced in volume and added dropwise to an 79  aqueous ammonium hexafluorophosphate solution (0.284 g in 17 mL H2O). After stirring for 30 minutes, the solid was collected by filtration and rinsed well with water and diethyl ether to yield 65.5 mg (71 %) of a yellow solid. 1H NMR (300 MHz, CD2Cl2): δ 6.10 (ddd, J = 7.5, 5.1, 1.3 Hz, 1H), 6.20 (d, J = 7.5 Hz, 1H), 6.31 (t, J = 2.7 Hz, 1H), 6.38 (dd, J = 5.5, 0.9 Hz, 1H), 6.50 (d, J = 2.3, 1H), 6.58 (t, J = 2.6 Hz, 1H), 6.68-6.75 (m, 2H), 6.78-6.90 (m, 4H), 7.01-7.03 (m, 2H), 7.05-7.10 (m, 3 H), 7.12 (d, J = 2.5 Hz, 1H), 7.23 (d, J = 2.7 Hz, 1H), 7.26 (dd, J = 3.7, 1.1, 1H), 7.30 (d, J = 1.1 Hz, 1H), 7.31-7.36 (m, 3H), 7.37-7.45 (m, 3H), 7.49-7.56 (m, 1H), 7.62 (s, 1H), 7.78 (d, J = 1.8 Hz, 1H), 8.01 (d, J = 3.0 Hz, 1H). 31P{1H} NMR (121 MHz, CD2Cl2): δ -29.6 (s), -143.6 (septet, JPF = 708 Hz, PF6) m/z [M-PF6]+ 911. HRMS (ESI) Calcd for C42H31N4PS3Ir (m/z [MPF6]+): 909.1055; Found: 909.1049. Anal. C42H31F6IrN4P2S3 requires C, 47.77; H, 2.96; N, 5.31. Found C, 47.52; H, 3.05; N, 4.92%.  Ir(ppz)2PT3-PC, (60). Complex 59 (50 mg) was added to a solution of NaOH (0.20 g) in degassed methanol (5 mL) and heated to reflux under nitrogen, with stirring, for 36 hours. The solution was cooled to room temperature, and the MeOH was removed in vacuo. The precipitate was redissolved in 2 mL MeOH, and the resulting solution added dropwise to a solution of ammonium hexafluorophosphate (0.284 g) in H2O (17 mL) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and diethyl ether to yield 28 mg (65 %) of a yellow solid. 1H NMR (300 MHz, CD2Cl2): δ 6.07-6.13 (m,2H), 6.37 (t, J = 2.6 Hz, 1H), 6.48 (d, J = 2.7 Hz, 1H), 6.49-6.57 (m, 3H), 6.59 (d, J = 4.8 Hz, 1H), 6.72-6.88 (m, 5H), 6.90-6.99 (m, 4H), 7.07-7.13 (m, 3H), 7.14-7.21 (m, 2H), 7.24-7.27 (m, 1H), 7.30-7.44 (m, 3H), 7.66-7.74 (m, 2H), 7.84 (d, J = 3.2 Hz, 1H), 7.97 (d, J = 2.7 Hz, 1H).  31  P{1H} NMR (121 MHz,  CD2Cl2): δ -17.9 (s), m/z [M+H]+ 911. HRMS (ESI) Calcd for C42H31N4PS3Ir (m/z [M+H]+): 909.1055; Found: 909.1052. Anal. C42H30IrN4PS3 requires C, 55.43; H, 3.32; N, 6.16. Found C, 55.45; H, 3.55; N, 5.38%.  80  Ir(ppy)2PT3Cl-P, (61). [Ir(ppy)2Cl]2 (0.045 g) and PT3 (0.042 g) were added to a 2-5 mL microwave vial. EtOH (4 mL) was added and the mixture was stirred and sparged with N2 for 5 minutes. The mixture was heated in a 2.2 GHz microwave synthesizer at 100°C for 30 minutes. Upon removal from the microwave, the mixture was centrifuged, and the supernatant was reduced in volume. A mixture of Ir(ppy)2PT3Cl-P and [Ir(ppy)2PT3-PS]Cl was obtained. The Ir(ppy)2PT3Cl-P was slightly soluble in ether. The mixture was washed thoroughly with ether, which was then removed by rotary evaporation, and the residue dissolved in DCM and layered with hexanes to produce yellow crystals of Ir(ppy)2PT3Cl-P (8.1 mg, 10 %). 1H NMR (300 MHz, CD2Cl2): δ 5.74-5.82 (m,1H), 5.94 (d, J = 7.8 Hz, 1H), 6.18 (d, J = 3.0 Hz, 1H), 6.33 (dd, J = 5.0, 3.7 Hz, 1H), 6.52-6.58 (m, 1H), 6.68-6.77 (m, 2H), 6.86-6.93 (m, 5H), 7.00-7.10 (m, 7H), 7.17-7.25 (m, 4H), 7.37 (d, J = 3.4 Hz, 1H), 7.447.56 (m, 2H), 7.59 (d, J = 8.2 Hz, 1H), 7.64 (d, J = 8.0 Hz, 1H), 7.77-7.85 (m, 1H), 7.938.02 (m, 2H), 8.93 (d, J = 5.3 Hz, 1H), 9.19 (d, J = 5.9 Hz, 1H).  31  P{1H} NMR (121  MHz, CD2Cl2): δ -14.0 (s). m/z [M-Cl]+ 933. HRMS (ESI) Calcd for C46H33N2PS3Ir (m/z [M-Cl]+): 931.1150; Found: 931.1144. Anal. C46H33ClIrN2PS3·H2O requires C, 56.00; H, 3.58; N, 2.84. Found C, 55.75; H, 3.54; N, 2.76%  [Ir(ppy)2PT3-PS](PF6), (62). [Ir(ppz)2Cl]2 (0.047 g), PT3 (0.045 g) and with AgBF4 (0.018 g) were added to a 2-5 mL microwave vial. EtOH (4 mL) was added and the mixture stirred and sparged with N2 for 5 minutes. The mixture was heated in a 2.2 GHz microwave synthesizer at 100°C for 30 minutes. Upon removal from the microwave, the mixture was centrifuged, and the supernatant was removed. The solid was rinsed and centrifuged again. The supernatant was combined, reduced in volume and added dropwise to an aqueous ammonium hexafluorophosphate solution (0.284 g in 17 mL H2O). After stirring for 30 minutes, the solid was collected by filtration and rinsed well with water and diethyl ether to yield 62 mg (66 %) of a yellow solid. 1H NMR (400 MHz, CD2Cl2): δ 6.05-6.11 (m, 2H), 6.36 (d, J = 5.5 Hz, 1H), 6.70 (d, J = 7.9 Hz, 1H), 6.67 (d, J = 7.9 Hz, 1H), 6.736.78 (m, 2H), 6.80-6.92 (m, 3H), 7.01-7.08 (m, 6H), 7.12 (d, J = 3.4 Hz, 1H), 7.20-7.27 (m, 4H), 7.32 (td, J = 7.9, 5.3 Hz, 3H), 7.45 (t, J = 7.2 Hz, 1H), 7.50-7.57 (m, 1H), 7.63 81  (d, J = 7.9 Hz, 1H), 7.69 (d, J = 7.9 Hz, 1H), 7.72-7.77 (m, 1H), 7.81 (t, J = 7.9 Hz), 7.89 (d, J = 7.9 Hz, 1H), 8.06 (d, J = 5.8 Hz, 1H), 8.67 (d, J = 5.8 Hz, 1H). P{1H} NMR (161 MHz, CD2Cl2): δ -23.0 (s), -143.6 (septet, JPF = 708 Hz, PF6) m/z [M-PF6]+ 933. HRMS (ESI) Calcd for C46H33N2PS3Ir (m/z [M-PF6]+): 931.1150; Found: 931.1140. Anal. C46H33F6IrN2P2S3 requires C, 51.25; H, 3.09; N, 2.60. Found C, 51.54; H, 3.16; N, 2.38 %.  Ir(ppy)2PT3-PC, (63). Complex 62 (50 mg) was added to a solution of NaOH (0.20 g) in degassed methanol (5 mL) and heated to reflux under nitrogen, with stirring, for 36 hours. The solution was cooled to room temperature, and the MeOH was removed in vacuo. The precipitate was redissolved in 2 mL MeOH, the resulting solution was added dropwise to a solution of ammonium hexafluorophosphate (0.284 g) in H2O (17 mL) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and diethyl ether to yield 18 mg (42 %) of yellow solid. 1H NMR (300 MHz, CD2Cl2): δ 6.06 (dd, J = 7.5, 4.80 Hz, 1H), 6.29-6.35 (m, 1H), 6.42-6.50 (m, 3H), 6.62-6.68 (m, 2H), 6.75-6.84 (m, 7H), 6.85-6.92 (m, 1H), 6.96-7.04 (m, 2H), 7.09 (d, J = 3.7 Hz, 1H), 7.15 (d, J = 5.0 Hz, 1H), 7.24-7.30 (m, 2H), 7.37-7.43 (m, 2H), 7.50-7.54 (m, 1H), 7.57-7.64 (m, 4H), 7.72 (dd, J = 9.7, 8.3 Hz, 2H), 7.81 (d, J = 8.2 Hz, 1H), 8.73 (d, J = 5.9 Hz, 1H).  31  P{1H} NMR (121 MHz, CD2Cl2): δ -16.1 (s), m/z [M+H]+ 933.  HRMS (ESI) Calcd for C46H33N2PS3Ir (m/z [M+H]+): 931.1150; Found: 931.1151. Anal. C46H32IrN2PS3·2CH3OH requires C, 57.87; H, 4.05; N, 2.81. Found C, 57.73; H, 3.73; N, 3.14%.  Section 3.2.3 ‒ X-Ray Crystallography Suitable  crystals  of  Ir(ppz)2PT3Cl-P,  (58),  [Ir(ppz)2PT3-PS](BF4),  (59),  Ir(ppz)2PT3-PC, (60), and Ir(ppy)2PT3Cl-P, (61), were grown from solution. The X-ray data were collected and solved by Dr. B.O. Patrick. In all cases, the crystals were mounted on a glass fiber and a Bruker APEX DUO diffractometer with graphite monochromated Mo-Κα radiation was used for all measurements. Data were collected 82  and integrated using the Bruker SAINT113 software package. Data were corrected for absorption effects using the multi-scan technique (SADABS).116 The data were corrected for Lorentz and polarization effects. The structures were solved by direct methods.118 Solid-state diagrams were visualized using Mercury.119  Ir(ppz)2PT3Cl-P, (58). Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 5.0 second exposures. The crystal to detector distance was 39.96 mm. The data were collected to a maximum 2ζ value of 56.3°. Of the 61356 reflections that were collected, 9518 were unique (Rint = 0.063); equivalent reflections were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),116 with minimum and maximum transmission coefficients of 0.585 and 0.681, respectively. The material crystallizes with one thiophene ring (C9→S3) disordered in two orientations by rotation about the C8 – C9 bond. All non-hydrogen atoms except C9B were refined anisotropically. All hydrogen atoms were placed in calculated positions. The final cycle of full-matrix least squares refinement120 on F2 was based on 9518 reflections and 526 variable parameters and converged (largest parameter shift was 0.00 times its esd).  [Ir(ppz)2PT3-PS](BF4), (59). Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 3.0 second exposures. The crystal to detector distance was 40.08 mm. The data were collected to a maximum 2ζ value of 60.1°. Of the 78800 reflections that were collected, 13494 were unique (Rint = 0.058); equivalent reflections (Excluding Friedel pairs) were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),116 with minimum and maximum transmission coefficients of 0.725 and 0.935, respectively. The material crystallizes with two molecules of CH2Cl2 in the asymmetric unit. One solvent molecule is disordered, and was modeled in three orientations. Restraints were applied to maintain reasonable geometries for all three fragments, and the ISOR and SIMU commands were employed to maintain reasonable anisotropic  displacement  parameters.  All  non-hydrogen  atoms  were  refined  anisotropically. All hydrogen atoms were placed in calculated positions. The final cycle 83  of full-matrix least squares refinement120 on F2 was based on 13494 reflections and 611 variable parameters and converged (largest parameter shift was 0.00 times its esd).  Ir(ppz)2PT3-PC, (60). Data were collected in a series of ϕ and ω scans in 0.50° oscillations using 3.0 second exposures. The crystal to detector distance was 37.87 mm. The data were collected to a maximum 2ζ value of 60.2°. Of the 62011 reflections that were collected, 10385 were unique (Rint = 0.034); equivalent reflections were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),116 with minimum and maximum transmission coefficients of 0.330 and 0.447, respectively. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions. The final cycle of full-matrix least squares refinement120 on F2 was based on 10385 reflections and 450 variable parameters and converged (largest parameter shift was 0.00 times its esd).  Ir(ppy)2PT3Cl-P, (61). Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 3.0 second exposures. The crystal to detector distance was 40.11 mm. The data were collected to a maximum 2ζ value of 60.2°. Of the 52461 reflections that were collected, 11558 were unique (Rint = 0.062); equivalent reflections were merged. Data were corrected for absorption effects using multi-scan the technique (SADABS),116 with minimum and maximum transmission coefficients of 0.754 and 0.864, respectively. Two of the thiophene rings are disordered and each was modeled in two orientations. The atoms of the major disordered component were refined anisotropically, while the atoms of the minor disordered components were refined isotropically. All hydrogen atoms were placed in calculated positions. The material also crystallizes with one molecule of CH2Cl2 in the asymmetric unit. The absolute configuration was determined on the basis of the refined Flack X-parameters.210,  211  The final cycle of full-matrix least squares  refinement120 on F2 was based on 11558 reflections and 543 variable parameters and converged (largest parameter shift was 0.00 times its esd).  84  Section 3.3 ‒ Results and Discussion Section 3.3.1 ‒ Synthesis Cyclometalated Ir (III) complexes are typically made by one of three methods (Scheme 3-2). One technique involves reacting Ir(acac)3 with 3 equivalents of ligand in refluxing glycerol.212 Tris cyclometalated complexes can also be prepared from a βdiketonate derivative, of the type [Ir(C^N)(O^O)] by heating the Ir complexes with 2-3 equivalents of C^N ligand in refluxing glycerol.185,186 A third method, similar to the second, uses chloro-bridged dimers of the type [Ir(C^N)2Cl]2.213 Early investigations reported needing 30 molar equivalents of cyclometallating ligand to make homoleptic complexes from the dimer,214 but 2-6 equivalents are commonly required in more recent literature.200, 212, 215 Scheme 3-2  Typically, the chloro-bridged dimers and β-diketonate derivatives are easily prepared in high yield from IrCl3•H2O. Additionally, with these methods of preparation, homoleptic or heteroleptic complexes can be synthesized. This can be accomplished either through use of a different cyclometalating ligand, or another ancillary bidentate ligand. Synthesis of tris-heteroleptic complexes requires an alternative method.216 Recently the chloro-bridged dimers have been made in even higher yield using microwave irradiation.208 Microwave reactions can drastically decrease the reaction times, resulting in increased yield and purity of the desired product by reducing side reactions. As there is direct and uniform heating from molecular friction, outside heating sources are not required. Microwave reactions can occur under pressure, and can bring lower boiling solvents above their boiling points at higher pressures, which can result in 85  increased reaction rates. The chloro-bridged dimers were synthesized as precursors for the desired Ir complexes. These dimers are known and characterization data was consistent with previously published work.209, 217 Initial attempts to synthesize [Ir(ppz)2PT3-PS](PF6) resulted in a mixture of products. The reaction of the chloro-bridged Ir dimer and PT3 yielded Ir(ppz)2PT3Cl-P and [Ir(ppz)2PT3-PS]Cl. The formation of a mono-chlorinated species was not surprising here, as it has been reported that breaking the last Ir – Cl bond requires a significant barrier to be overcome.218 It was previously observed that the chloro-bridged dimers cleave to produce a neutral mono-chloro, mono-solvated complex. Removal of the final chloro group was only achieved when Ag+ was added.218 Adding silver tetrafluoroborate to the reaction mixture here, followed by salt metathesis with ammonium hexafluorophosphate, resulted in a single product, [Ir(ppz)2PT3-PS](PF6), (59), with the thiophene ring bound to the Ir via the sulfur. McGee and Mann previously reported a complex containing a thienyl-pyridine ligand, bound to the Ir in an S^N motif, and upon heating (80-100 °C) the complex isomerized to the cyclometalated C^N species. Carrying out the reaction here at 100 °C yielded the [Ir(ppz)2PT3-PS](PF6) complex; cyclometalation did not occur until the PS bound complex and NaOH were dissolved in methanol and heated to reflux (Scheme 3-3). Adding trifluoroacetic acid to the cyclometalated (PC bound) Ir(ppz)2PT3-PC complex immediately resulted in reversion to the original complex (Figure 3-1). Heating to reflux with base resulted in a change in coordination mode to the PC complex once again. After carrying out this switching reaction several times, free ligand was also observed. The ligand could be removed by rinsing with ether. The ppy complexes were prepared analogously. Under these conditions, there was no evidence of the pyrazole or pyridine ring undergoing a change in binding mode.  86  Scheme 3-3  sm-jan252011-ItPCpur_002000fid.esp  (a)  (b)  (c)  (d) 250  200  150  100 50 Chemical Shift (ppm)  0  -50  -100  Figure 3-1 31P{1H} NMR spectra showing switching between [Ir(ppz)2PT3-PS](PF6), (59), ((a) and (c)) and Ir(ppz)2PT3-PC, (60), ((b) and (d)). Heating the PS bound complex (a) to reflux with base produced the PC bound complex (b). Addition of trifluoroacetic acid resulted in the sample switching back to the PS bound complex (c). Finally, heating to reflux with base again yielded the PC complex (d).  87  Section 3.3.2 ‒ Solid-State Molecular Structures Crystals of some of the cyclometalated iridium complexes suitable for X-ray diffraction were grown from appropriate solvents. The structures demonstrate the effects of the binding mode of the terthiophene ligand on the torsion angles of the thiophene rings and the metal – phosphorous distance. In all the solid-state structures, the Ir(III) metal center is in a slightly distorted octahedral environment. Single crystals of Ir(ppz)2PT3Cl-P were grown from a CH2Cl2 – hexanes solution, and the solid-state structure is shown in Figure 3-2. Disorder was present in the thiophene ring containing S3. The ppz ligands are bound with the nitrogen atoms trans to one another, while the bound carbon atoms are cis with respect to the Ir(III) center, (A, Scheme 3-1) as they are arranged in the dimer. This bonding motif was observed in all three solid-state structures containing the ppz ligand. All Ir – C and Ir – N bond lengths are similar to those in previously reported complexes.185, 215, 219 In Ir(ppz)2PT3Cl-P, the Ir – Cl bond (2.4716(9) Å, Table 3-1) is longer than some of those reported, but falls within the average range for Ir – Cl bonds trans to a carbon. This difference in length is presumably due to the trans effect of a cyclometalating ligand. The Ir – P distance of 2.4075(10) Å is quite typical. The torsion angles between adjacent thiophene rings of 45.3(4)° and 136.2 (14)° (Table 3-1) are less than the calculated value for terthiophene (147.6°).220 This indicates less π-orbital overlap of the adjacent thiophene rings due to their decreased co-planarity. Weak π-stacking is observed between N1 ppz ring and the C19 phenyl ring (distance between centroids = 3.552 Å).  88  Figure 3-2 Solid-state structure of Ir(ppz)2PT3Cl-P, (58). Hydrogen atoms and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability.  Table 3-1 Selected bond lengths and angles for Ir(ppz)2PT3Cl-P,(48). Bond Lengths (Å) Ir1 – Cl1  2.4716(9)  S1 – C1  1.704(4)  Ir1 – P1  2.4075(10)  C1 – C2  1.360(6)  Ir1 – N1  2.026(3)  C2 – C3  1.405(6)  Ir1 – N3  2.037(3)  C3 – C4  1.420(5)  Ir1 – C33  2.016(4)  C4 – S1  1.727(4)  Ir1 – C42  2.057(4)  C4 – C5  1.464(5)  45.3(4)  S2 – C8 – C9 – S3  136.2(14)  Torsion Angles (°) S1 – C4 – C5 – S2  Single crystals of [Ir(ppz)2PT3-PS](BF4) were grown from a CH2Cl2 – hexanes solution, and the solid-state structure is shown in Figure 3-3. Thiophene has previously 89  been shown to weakly coordinate to Ir(III) through its sulfur atom,204, 218 although it more commonly coordinates via carbon.203,  221, 222  The Ir – S bond was 2.4402 Å in length  (Table 3-2), which is long, but in the range expected for a weakly coordinating atom. Other S bound thiophene rings to Ir have a similar bond length.218, 223-226 The strong Ir – C bond in the ppz ligands facilitates and stabilizes the thiophene coordination, allowing for the CˆS or non-cyclometallating (NˆS) S bound species.204 The sulfur of the S-bound thiophene ring adopts an sp3 hybridization, resulting in the thiophene ring being tilted out of the equatorial plane. The tilt angle of the thiophene away from the Ir – S bond is 59.2° in the [Ir(ppz)2PT3-PS](PF6) complex. This tilting reorients the lone pair of electrons on the sulfur, allowing for a reduction in the unfavorable π antibonding interactions.150, 151 The coordination of a second thiophene ring to the Ir center greatly affects the torsion angles. The S1 – C4 – C5 – S2 and the S2 – C8 – C9 – S3 torsion angles are 163.4(2)° and 167.7(2)°, respectively. The increased co-planarity of the rings indicates more π – orbital overlap. Weak π-stacking may occur between the tilted thiophene ring (containing S1) and the ppz ring (containing N4) (distance between centroids = 3.767 Å) as well as between the N1 ppz ring and the C13 phenyl ring (3.790 Å).  90  Figure 3-3 Solid-state structure of [Ir(ppz)2PT3-PS](BF4), (59). Hydrogen atoms, counterions, and solvent in lattice removed for clarity. Thermal ellipsoids are drawn at 50% probability.  Table 3-2 Selected bond lengths and angles for [Ir(ppz)2PT3-PS](BF4), (59). Bond Lengths (Å) Ir1 – S1  2.4402(10)  S1 – C1  1.739(4)  Ir1 – P1  2.3746(10)  C1 – C2  1.338(6)  Ir1 – N1  2.028(3)  C2 – C3  1.428(6)  Ir1 – N4  2.045(3)  C3 – C4  1.369(5)  Ir1 – C33  2.023(4)  C4 – S1  1.742(4)  Ir1 – C34  2.059(4)  C4 – C5  1.445(5)  163.4(2)  S2 – C8 – C9 – S3  167.7(2)  Torsion Angles (°) S1 – C4 – C5 – S2  91  The Ir – S bond length of [Ir(ppz)2PT3-PS](BF4) (2.4402(10) Å) is significantly longer than the Os – S bond (2.3543(11) Å) in the [Os(bpy)2PT3-PS](PF6)2 structure (54, Chapter 2)), as is the metal – P bond. However, the tilt angle of the thiophene ring plane away from the metal – S bond is almost identical. The torsion angle of the two bound thiophene rings is larger in the Ir complex compared to the Os complex (163.4(2)° vs 154.9(3)°). Again, the increased co-planarity of the rings results in increased π-orbital overlap of the adjacent thiophene rings. Single crystals of Ir(ppz)2PT3-PC were grown from a MeOH solution (Figure 3-4). The Ir – C1 (carbon of the thiophene ring) bond length of 2.1318(19) Å is slightly longer, but comparable to other complexes where a thiophene ring is bonded to an Ir(III) center via a carbon.218,  222, 223  This bond is longer than the other Ir – C bonds in the  complex (to the ppz), suggesting a destabilized bonding orbital.204 There are only a few examples known where a cyclometalated C^P ligand is coordinated to an Ir(III) center in a bidentate fashion.227, 228,229 Ir – P bonds 2.248 to 2.336 Å in length for cyclometalated ligands have been reported. Ir – P bonds that are not in bidentate ligands have been shown to be longer, up to 2.426(2) Å in complexes such as Ir(ppy)2Cl(PPh3).219 In Ir(ppz)2PT3-PC, the torsion120 angles are 13.83°  and 164.26°. The thiophene rings  become more co-planar once a second ring is also bound to the metal (from Ir(ppz)2PT3Cl-P (135°) to [Ir(ppz)2PT3-PS](BF4) and Ir(ppz)2PT3-PC (165°)) and the Ir – P bond gets shorter (from 2.4075(10) to 2.3203(5) Å). The tilt of the carbon bound thiophene ring away from the Ir – C bond is 5.68° in the Ir(ppz)2PT3-PC complex. Weak π-stacking is observed between the N3 ppz ring and the C13 phenyl ring (distance between centroids = 3.526 Å). Comparing Ir(ppz)2PT3-PC to [Os(bpy)2PT3-PC](PF6) (Chapter 2), there are several differences. The metal – carbon and metal – phosphorous bonds are longer in the Ir(III) complex. Additionally, the torsion angle of the two bound thiophene rings are more co-planar in the iridium complex, but the torsion angle with the unbound thiophene indicates greater co-planarity for the osmium complex. The tilt angle of the bound ring away from the metal – carbon bond is almost identical for Ir(ppz)2PT3-PC and [Os(bpy)2PT3-PC](PF6).  92  Figure 3-4 Solid-state structure of Ir(ppz)2PT3-PC, (60). Hydrogen atoms removed for clarity. Thermal ellipsoids drawn at 50% probability.  Table 3-3 Selected bond lengths and angles for Ir(ppz)2PT3-PC, (60). Bond Lengths (Å) Ir1 – C1  2.1318(19)  C1 – C2  1.426(3)  Ir1 – P1  2.3203(5)  C2 – C3  1.335(3)  Ir1 – N1  2.0324(16)  C3 – S1  1.709(2)  Ir1 – N3  2.0235(16)  S1 – C4  1.7447(19)  Ir1 – C33  2.0546(19)  C4 – C1  1.387(3)  Ir1 – C34  2.0794(19)  C4 – C5  1.451(3)  13.8(2)  S2 – C8 – C9 – S3  164.26(11)  Torsion Angles (°) S1 – C4 – C5 – S2  93  Figure 3-5 Solid-state structure of Ir(ppy)2PT3Cl-P, (61). Hydrogen atoms and solvent in lattice are removed for clarity. Thermal ellipsoids drawn at 50% probability. For comparison, a single crystal of Ir(ppy)2PT3Cl-P was also obtained (Figure 3-5), grown from a CH2Cl2 – hexanes solution. Disorder was present in two of the thiophene rings (those not bound to the metal center, containing S1 and S3). While very similar to the analogous ppz complex, some differences in bond lengths and angles are observed. In general, most bonds are slightly longer in this complex. The Ir – Cl bond (2.4965(9)) Å) is still within the average range for Ir – Cl bonds trans to a carbon. The torsion angles between adjacent thiophene rings of 99.8(3)° and 139.2 (2)° (Table 3-4) indicate that one ring is almost entirely out of plane with the other and therefore there is less π-orbital overlap.  94  Table 3-4 Selected bond lengths and angles for Ir(ppy)2PT3Cl-P, (61). Bond Lengths (Å) Ir1 – Cl1  2.4965(9)  S1 – C1  1.711(5)  Ir1 – P1  2.4218(9)  C1 – C2  1.354(9)  Ir1 – N1  2.062(3)  C2 – C3  1.403(8)  Ir1 – N2  2.050(3)  C3 – C4  1.351(7)  Ir1 – C35  2.047(3)  C4 – S1  1.730(4)  Ir1 – C46  2.007(3)  C4 – C5  1.482(4)  99.8(3)  S2 – C8 – C9 – S3  139.5(2)  Torsion Angles (°) S1 – C4 – C5 – S2  Section 3.3.3 ‒ Cyclic Voltammetry The electrochemical properties of [Ir(ppz)2PT3-PS](PF6), Ir(ppz)2PT3-PC, [Ir(ppy)2PT3-PS](PF6), and Ir(ppy)2PT3-PC were probed at room temperature using cyclic voltammetry. Each complex shows three irreversible oxidation waves (Table 3-5). Commonly for cyclometalated iridium complexes the HOMO is centered on the metal with substantial contribution from the ligand.222 The difference in oxidation potentials between the PS bound and PC bound complexes indicates the HOMO is affected by the binding mode of the PT3 ligand. Unfortunately, reliable reduction potentials could not be obtained for these complexes. Cyclic voltammetry experiments were not carried out on Ir(ppz)2PT3Cl-P and Ir(ppy)2PT3Cl-P due to difficulty in obtaining sufficient amounts of pure material. The cyclic voltammograms of the Ir(ppz)PT3 complexes are shown in Figure 3-6 while the analogous ppy complexes are shown in Figure 3-7. The first oxidation potential is assigned to a PT3 based oxidation, with the others believed to be mixed metal – phenyl based and mixed metal – PT3 based oxidations. Although, as Ir(ppz)3 and Ir(ppy)3 exhibit similar oxidation potentials to the first oxidation of the PC bound complexes,215, 230 some contribution of the metal or metal – phenyl moiety cannot be entirely ruled out. The voltammograms of the PS bound complexes are similar, as are the voltammograms for  95  the PC bound complexes. The second oxidation is not as apparent in the ppz complexes as it is for the ppy complexes, suggesting the second oxidation involves the C^N ligands. Coordination of the PT3 ligand in the PC binding mode results in a lowering of the oxidation potentials. This may be partly due to the more co-planar arrangement of the thiophene rings (compared to in the PS coordination) allowing for easier π donation, which is reflected in the oxidation potentials.204 Additionally, in the PC bound complex, the ligand has a formal negative charge, compared to the PS bound complex where the ligand is formally neutral. The negative charge on the ligand in the PC bound complex is expected to lead to lower ligand-based oxidation potentials. This is also echoed in the lower energy transition observed in the absorption spectra (see below). Comparing the [Ir(ppz)2PT3-PS](PF6) and [Ir(ppy)2PT3-PS](PF6) complexes, as well as the Ir(ppz)2PT3PC and Ir(ppy)2PT3-PC complexes it is observed that oxidations of the ppz complex occur at more positive potentials than those of the ppy complex. This may be due to the more electron-withdrawing character of the pyrazole ring compared to the pyridine ring. DFT calculations would be beneficial to support the assignment of these oxidation waves.  96  Table 3-5 Cyclic voltammetry data of [Ir(ppz)2PT3-PS](PF6), (59), Ir(ppz)2PT3-PC, (60), [Ir(ppz)2PT3-PS](PF6), (62), and Ir(ppz)2PT3-PC (63).a Compound  Ep ±0.01 V vs. SCE  [Ir(ppz)2PT3-PS](PF6) (59)  +1.35 +1.60 +1.85  Ir(ppz)2PT3-PC(60)  +0.82 +1.21 +1.31  [Ir(ppy)2PT3-PS](PF6) (62)  +1.27 +1.47 +1.75  Ir(ppy)2PT3-PC (63)  +0.71 +1.07 +1.29  a  Measurements carried out in CH3CN solution containing 0.1 M [(n-Bu)4N]PF6 supporting electrolyte. Attempts to electropolymerize these complexes proved unsuccessful. The steric bulk of the diphenylphosphine moiety may prevent the complexes from oxidatively coupling at the terminal -positions of the PT3 backbone. The use of a longer oligomer could remove some of the steric bulk from the -position of the terminal thiophenes which may allow for electrochemical polymerization. The oxidation peak observed for [Os(bpy)2PT3-PS](PF6)2 (1.23 V (vs SCE), Chapter 2) is similar to that obtained for the [Ir(ppy)2PT3-PS](PF6) complex. The [Os(bpy)2PT3-PC](PF6) complex had 2 reversible oxidation peaks (0.28 and 0.95 V (vs SCE), Chapter 2) The higher oxidation potentials for the Ir (III) complexes may be due to a larger ionic charge (compared to Os(II)), making the metal centered oxidation more difficult.197 The overall charge of the complexes (+2 and +1 for the Os(II) and Ir(III) PS 97  bound complexes, respectively, and +1 and for neutral PC bound complexes) did not have an effect on the ability of these complexes to electropolymerize.  8  (a)  Current (A)  6  4  2  0  0.0  0.5  1.0  1.5  2.0  Volts (V) vs SCE 1.2  (b)  Current (A)  1.0 0.8 0.6 0.4 0.2 0.0 -0.2 0.5  1.0  1.5  Volts (V) vs SCE Figure 3-6 Cyclic voltammetry of (a) [Ir(ppz)2PT3-PS](PF6), (59), and (b) Ir(ppz)2PT3PC, (60), on a Pt disk electrode (scan rate 100 mv/s), electrolyte = 0.1 M [n-Bu4N](PF6), solvent = CH3CN.  98  8 7  (a)  Current (A)  6 5 4 3 2 1 0 -1 0.0  0.5  1.0  1.5  2.0  Volts (V) vs SCE 1.4  (b)  1.2  Current (A)  1.0 0.8 0.6 0.4 0.2 0.0 -0.2 0.0  0.5  1.0  1.5  Volts (V) vs SCE Figure 3-7 Cyclic voltammetry of (a) [Ir(ppy)2PT3-PS](PF6), (62), and (b) Ir(ppy)2PT3PC, (63), on a Pt disk electrode (scan rate 100 mv/s), electrolyte = 0.1 M [n-Bu4N](PF6), solvent = CH3CN.  99  Section 3.3.4‒ Electronic Absorption Spectra The UV-vis absorption spectra of the Ir(ppz)2PT3 complexes in CH3CN are shown in Figure 3-8. The absorption spectra contain two major bands, one at approximately 250 nm and a lower energy band the maximum absorption of which shifts depending on binding mode; from 343 nm for Ir(ppz)2PT3Cl-P, to 360 nm for [Ir(ppz)2PT3-PS](PF6), and to 412 nm for the Ir(ppz)2PT3-PC complex. The tris(phenylpyrazole) Ir(III) complex, Ir(ppz)3, exhibits absorption bands between 230-365 nm. In that complex, the bands above 270 nm are attributed to the π → π* transition of the ppz ligand, while the lower energy bands are assigned as MLCT transitions.201, 215, 231 Based on these comparisons, the band near 250 nm in the Ir(ppz)2PT3 complexes (PS, -PC, and Cl-P bound) is assigned as the π → π* transition of the ppz group. The lower energy band observed between 343-412 nm is assigned as a PT3 ligand based π → π* transition, as this band matches that of the ligand closely. The large shift observed for the PC bound complex can be accounted for at least in part by the reduction in overall charge from the PS to PC bound complex (as the PT3 ligand is formally neutral in the PS bound complex and monoanionic in the PC bound complex). In the [Ir(ppz)2PT3-PS](PF6) and Ir(ppz)2PT3PC complexes, there is a shoulder around 310 nm possibly due to an MLCT or LLCT transition. This was not observed in the Ir(ppz)2PT3Cl-P species.  100  PT3  Normalized Absorbance  2.5  Ir(ppz)2PT3Cl-P (58) [Ir(ppz)2PT3-PS](PF6) (59) Ir(ppz)2PT3-PC (60)  2.0  1.5  1.0  0.5  0.0 250  300  350  400  450  500  550  600  Wavelength (nm)  Figure 3-8 Solution absorption spectra of PT3, Ir(ppz)2PT3Cl-P, (58), [Ir(ppz)2PT3PS](PF6), (59), Ir(ppz)2PT3-PC, (60) in CH3CN. Tris(2-phenylpyridine)iridium, Ir(ppy)3, shows intense bands between 240-350 nm assigned to the π → π* transition of the ppy ligands. Additionally, bands between 350-450 nm have been assigned as both 1MLCT and 3MLCT transitions in the spectra of Ir(ppy)3.215 The spectra of the Ir(ppy)2PT3Cl-P, [Ir(ppy)2PT3-PS](PF6) and Ir(ppy)2PT3PC complexes are very similar to the analogous ppz complexes. There are also two major absorption bands present, the band at approximately 260 nm is assigned as the ppy π → π* transition, while the band occurring at lower energy is also assigned as a π → π* transition of the PT3 ligand. The shoulder around 310 nm is still observed in both the PS and PC bound complexes, but is not as apparent in Ir(ppy)2PT3-PC as it was in the analogous ppz complex. There is a shoulder around 300 nm in the Ir(ppy)2PT3Cl-P complex. Additionally, a lower energy shoulder at 425 nm is observed in the Ir(ppy)2PT3Cl-P complex which was not observed in the analgous ppz complex. This 101  may be a 3MLCT or 3LLCT transition. The Ir(ppy)2PT3-PC complex has a broader, lower energy band than the Ir(ppy)2PT3-PC complex, likely due to overlapping bands, as Ir(ppy)3 exhibits lower energy absorption bands than Ir(ppz)3.  3.5  PT3 Ir(ppy)2PT3Cl-P (61)  Normalized Absorbance  3.0  [Ir(ppy)2PT3-PS](PF6) (62) Ir(ppy)2PT3-PC (63)  2.5  2.0  1.5  1.0  0.5  0.0 250  300  350  400  450  500  550  600  Wavelength (nm)  Figure 3-9 Solution absorption spectra of PT3, Ir(ppy)2PT3Cl-P, (61), [Ir(ppy)2PT3PS](PF6), (62), Ir(ppy)2PT3-PC, (63), in CH3CN. The absorption spectra of the PS bound complexes are very comparable to the Ru(II) and Os(II) diimine complexes discussed in Chapter 2, with greater differences observed for the PC complexes. Whereas no absorption is observed above 475 nm for the Ir complexes, absorption occurs out to 650 and 800 nm for the Ru and Os PC species, respectively. The absence of the lower energy bands in the Ir(III) complexes may be due to the Ir center being more difficult to oxidize,197 or a difference in the nature of the transitions observed.  102  Section 3.3.5 ‒ Emission Spectra The emission wavelength of cyclometalated Ir(III) complexes can be tuned by varying either the cyclometalating ligand and/or the XY ligand. Additionally, the electronic effects of the substituents and their position can significantly influence the photophysical properties. The effect of coordination mode of the PT3 ligand to the cyclometalated Ir(III) centers on the emission properties was explored. The ppz complexes showed weak emission when excited into the lowest energy absorbance band. The Ir(ppz)2PT3Cl-P, [Ir(ppz)2PT3-PS](PF6) and Ir(ppz)2PT3-PC complexes showed emission bands with λmax at 442, 450 and 485 nm respectively (Figure 3-10). The emission lifetimes of all species are short, under 50 ns, and not sensitive to the presence of oxygen. Emission quantum yields are 0.002 and 0.003 for the [Ir(ppz)2PT3PS](PF6)  and Ir(ppz)2PT3-PC complexes respectively, while the  Ir(ppz)2PT3Cl-P  complex had a slightly higher quantum yield (0.068). PT3 has a short-lived emission centered at 435 nm (Table 3-6), attributed to radiative decay of the singlet  state. mer-Ir(ppz)3 in solution has a very weak emission at room temperature, however, at 77 K, it shows emission at 427 nm, and a lifetime on the order of tens of microseconds. facIr(ppz)3 emits at 414 nm with a similar lifetime.  215  Based on these observations, the  emission band in the iridium ppz complexes is assigned to emission from a terthiophenelocalized singlet state.  103  PT3  1.0  Ir(ppz)2PT3Cl-P (58)  Normalized Emission  [Ir(ppz)2PT3-PS](PF6) (59) Ir(ppz)2PT3-PC (60)  0.8  0.6  0.4  0.2  0.0 400  450  500  550  600  650  Wavelength (nm)  Figure 3-10 Emission spectra of PT3, Ir(ppz)2PT3Cl-P, (58), [Ir(ppz)2PT3-PS](PF6), (59), Ir(ppz)2PT3-PC, (60), in CH3CN. The coordination mode of the PT3 ligand to the Ir center resulted in changes in emission for the ppy complexes as well. [Ir(ppy)2PT3-PS](PF6) displays emission at 453 nm, as was observed for [Ir(ppy)2PT3-PS](PF6). The cyclometalated ppy PC bound complex has the lowest emission at 493 nm, slightly lower than the analogous ppz complex. In addition, a low energy band at 700 nm is sometimes observed. The emission quantum yields of the ppy complexes are similar to those of the ppz complexes (Table 36), and once again the emission lifetimes are short. This suggests that the HOMO is located on the terthiophene moiety. Ir(ppy)3 shows emission at room temperature at 510 nm, while at 77 K the emission maximum shifts to 492 nm. The mer species has a broad emission with weak emission at room temperature, while the fac isomer is highly luminescent at room temperature and gives a structured emission profile.  104  Table 3-6 Photophysical data for cyclometalated Ir(III) - PT3 complexesa Abs max (nm)  Em max (nm)  QY  τTA(s)  Ir(ppz)2PT3Cl-P  434  442  0.068  6.21  Ir(ppz)2PT3-PS  360  450  0.002  0.33  Ir(ppz)2PT3-PC  412  485  0.003  2.73  Ir(ppy)2PT3Cl-P  349  454  0.009  7.10  Ir(ppy)2PT3-PS  359  452  0.002  0.40  Ir(ppy)2PT3-PC  400  493  0.004  4.00b  Compound  a  Measurements carried out in Ar sparged CH3CN solution. b It was noted the lifetime of Ir(ppy)2PT3-PC changes with concentration.  1.0  PT3  Normalized Emission  Ir(ppy)2PT3Cl-P (61) [Ir(ppy)2PT3-PS](PF6) (62) 0.8  Ir(ppy)2PT3-PC (63)  0.6  0.4  0.2  0.0 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure 3-11 Emission spectra of PT3, Ir(ppy)2PT3Cl-P, (61), [Ir(ppy)2PT3-PS](PF6), (62), Ir(ppy)2PT3-PC, (63), in CH3CN.  105  Section 3.3.6‒ Transient Absorption Spectra The nature of the excited states in these complexes was further probed using transient absorption (TA) spectroscopy. Excitation of Ir(ppz)2PT3Cl-P results in a broad TA band between 400-600 nm (Figure 3-12 (a)), strongly resembling the TA of T3 (Chapter 2). This species decays monoexponentially with a lifetime of 6.2 μs in nitrogensparged acetonitrile (Appendix, Figure A-9), which is significantly reduced in the presence of oxygen. The TA spectrum of Ir(ppz)2PT3-PC is similar, (Figure 3-12 (b)) but shows a shoulder growing in at 550 nm. In argon-sparged solutions, this species has a lifetime of 2.73 μs (Appendix, Figure A-10), which decays monoexponentially. The peak and the shoulder have the same decay lifetime, suggesting they originate from the same species. [Ir(ppz)2PT3-PS](PF6) also shows an intense, broad TA with two bands between 400-650 nm (Figure 3-12(c)). The two bands in the TA spectra of this complex resemble the bands in the TA spectrum of PT3 (Chapter 2), although slightly red-shifted. The TA decays monoexponentially with a lifetime of 330 ns under argon (Appendix, Figure A11), which decreases under O2. The dependence of the lifetime and intensity of these bands on oxygen supports the conclusion that these are all due to triplet states, and the similarity of the TA spectra to that of PT3 suggests that a PT3 ligand-centered triplet state (3LC) is being observed.  106  0.12  (a)  0.10  1 s 3 s 5 s 7 s 9 s 12 s 15 s 20 s  0.08 0.06 0.04 0.02 0.00 -0.02 0.08  0.5 s 1 s 1.5 s 2 s 3 s 4 s 5 s  (b)  Abs.  0.06 0.04 0.02 0.00 -0.02 0.05  0.1 s 0.2 s 0.3 s 0.4 s 0.5 s 0.7 s 1.0 s  (c)  0.04 0.03 0.02 0.01 0.00 350  400  450  500  550  600  650  700  750  Wavelength (nm) Figure 3-12 Transient absorption spectra of (a) Ir(ppz)2PT3Cl-P,(58), (b) Ir(ppz)2PT3-PC, (60), and (c) [Ir(ppz)2PT3-PS](PF6), (59), in argon-sparged CH3CN. Since complexes with ppy ligands generally have a lower energy LUMO than complexes with ppz ligands, there is the possibility that using ppy as the cyclometalating ligand would result in the observation of a different excited state. However, the transient absorption spectra of the iridium ppy complexes appear similar to those of the ppz complexes, and thus, the PT3 ligand. The lifetimes of the ppy complexes are slightly longer than those of their ppz analogues. The transient absorption of Ir(ppy)2PT3Cl-P 107  (Figure 3-13(a)) has a lifetime of 7.10 µs under argon, and this absorbance decays monoexponentially (Appendix, Figure A-12). The lifetime decreases when oxygen is present. The absorption for this complexes is broader than for Ir(ppz)2PT3Cl-P. The Ir(ppy)2PT3-PC transient spectra look similar to those for the ppz analogue. However, the peak at approximately 465 nm is not as pronounced (Figure 3-13 (b)). This also decays monoexponentially, (Appendix, Figure A-13) and the introduction of oxygen decreases the lifetime. It was noted that the excited state lifetime of Ir(ppy)2PT3-PC changes with concentration; the higher the concentration, the shorter the lifetime. Aggregation can affect excited state lifetimes,232, 233 and may be causing the reduced lifetimes here. Small changes were also observed in the ground state absorption spectrum with concentration, supporting the possibility of aggregation. [Ir(ppy)2PT3-PS](PF6) is similar to the ppz analogue (Figure 3-13 (c)), and decays monoexponentially with a lifetime of 400 ns under argon (Appendix, Figure A-14), which decreases under O2. Excited state absorption spectra of Ir(ppy)3 show an absorption feature at 370 nm, with a shoulder occurring around 500 nm.234 As these features are not observed in the TA spectra for [Ir(ppy)2PT3-PS](PF6) and Ir(ppy)2PT3-PC, this supports the conclusion that the excited state observed in the TA spectra of the species do not have MLCT character, but are largely ligand-based. This is in contrast to Os(bpy)2PT3 spectra, where the PS species shows a ligand localized excited state, and a charge-separated excited state was observed for the PC complex. Presumably, the fact that a charge-separated state is not observed for these Ir complexes is a consequence of differences in the relative energy levels of these complexes, compared to the Os complexes.  108  0.12 0.10  (a)  1 s 3 s 3 s 7 s 9 s 13 s 19 s  (b)  1 s 2 s 3 s 4 s 6 s 8 s  (c)  0.08 s 0.20 s 0.30 s 0.40 s 0.50 s 0.60 s 1.00 s  0.08 0.06 0.04 0.02 0.00 -0.02   Abs.  0.015 0.010 0.005 0.000 -0.005 0.04 0.03 0.02 0.01 0.00 -0.01  350  400  450  500  550  600  650  700  750  Wavelength (nm) Figure 3-13 Transient absorption spectra of (a) Ir(ppy)2PT3Cl-P, (61), (b) Ir(ppy)2PT3PC, (63), and (c) [Ir(ppy)2PT3-PS](PF6), (62), in argon-sparged CH3CN.  Section 3.4‒ Conclusions Six cyclometalated iridium(III) diphenylphosphinoterthiophene complexes were synthesized: Ir(ppz)2PT3Cl-P, [Ir(ppz)2PT3-PS](PF6), Ir(ppz)2PT3-PC, Ir(ppy)2PT3Cl-P, [Ir(ppy)2PT3-PS](PF6), and Ir(ppz)2PT3-PC. The effect of the coordination mode to the electronic and photophysical properties was investigated. The solid-state structures indicate the torsion angles are highly dependent on binding mode. Cyclic voltammetry 109  was used to determine the oxidation potentials of four of these complexes. Attempts to electropolymerize the PS and PC bound complexes were unsuccessful. The absorption spectra were dominated by π→π* transitions, and the thiophene based π→π* transition was shifted in relation to coordination mode; the PC binding mode gave the lowest energy band. All of the complexes were weakly emissive, and a red shift in emission was observed from the Cl-P to PS to PC bound species. The emission lifetimes were very short, and assigned as PT3 ligand-based. Transient absorption spectra show all complexes had a ligand localized excited state. However, the lifetime of the excited state varied greatly depending upon coordination: Ir(ppz)2PT3-P had the longest lifetime, while Ir(ppz)2PT3-PS had the shortest, within the series of ppz complexes investigated.  110  CHAPTER 4 COPPER(I) MIXED-LIGAND COMPLEXES CONTAINING A PHOSPHINO(TERTHIOPHENE) LIGAND  Section 4.1‒ Introduction Recent research on the photophysical and electrochemical properties of phenanthroline and bipyridine based copper(I) complexes has demonstrated their potential application in organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs),235, 236 as well as dye sensitized solar cells (DSSCs).237-239 The excited state lifetime of first row transition metal complexes are often short compared to their second and third row analogues, as low lying metal d-d states often allow non-radiative decay of the MLCT state. Research investigating first row transition metals as sensitizers in DSSCs has been limited, as charge injection from the dye to the semiconductor is often not achieved, leading to inefficient DSSCs. Cu(I) complexes can display longer excited state lifetimes due to their d10 configuration.240 Emission from complexes with open d shells (d<10) can be affected by thermal population of MC states from the MLCT state, leading to non-radiative decay or photochemical degradation. Closed shell d10 copper complexes do not exhibit non-radiative decay via this pathway, although deactivation through other pathways, such as exciplex formation, is possible. Copper (I) complexes with substituted diimine ligands possess similar properties to (Ru(bpy)3)2+ salts.241-243 Additionally, copper is more abundant than ruthenium, and has a much lower cost (approximately $0.08/g for Cu compared to $4.00/g for Ru).244, 245 Cu sensitizers for photoelectrochemical cells date back to 1994.246 Early investigations into Cu(I) sensitizers focused on bis-(phenanthroline) Cu(I) complexes. Substitution in the 2 and 9 positions of the phenanthroline ligands proved useful to sterically constrain the molecule, minimizing the geometry change from distorted tetrahedral to tetragonally flattened, which occurs upon excitation or oxidation (going from a formally Cu(I) to Cu(II) metal center) (Scheme 4-1).243,  247  The geometry change can allow nucleophilic attack,  leading to a five-coordinate (exciplex) species, 244, 245 which then deactivates by non-emissive deactivation pathways.  111  Scheme 4-1 Ref.243  Substituted bipyridines, such as 6,6ʹ-dimethyl-2,2ʹ-bipyridyl-4,4ʹ dicarboxylic acid  and corresponding methyl esters, as well as analogues with extended conjugation have been investigated (Chart 4-1, (64)-(67)).238 These allow for attachment to TiO2, while still sterically constraining the molecule from geometrical reorganization. The efficiency of  DSSCs using these Cu(I) substituted bipyridyl complexes is lowered compared to those with Ru(II) complexes, but the cost is drastically reduced as well. Additionally, the methods used to improve Ru(II) based dyes work also with these Cu(I) complexes. Constable has since made several Cu(I) complexes using 6,6ʹ-disubstituted 2,2ʹbipyridine dicarboxylic acids (Chart 4-1 (68)-(71)).239 Iminopyridine based complexes have also been investigated (Chart 4-1 (72) and (73)).248 These complexes allow the Cu center to be almost tetrahedral in geometry, and allow both carboxylate groups to anchor to the TiO2 surface. These iminopyridine complexes, however, were less efficient as sensitizers than the 6,6ʹ-disubstituted 2,2ʹ-bipyridine dicarboxylic acids complexes this group previously investigated.  112  Chart 4-1 Ref.238, 239, 248  Copper complexes with mixed-ligand systems have recently gained attention, specifically, mixed-ligand complexes using diimine and phosphine ligands.94,  240, 249-256  When considering electronic and photophysical properties, these copper complexes are more similar to Ru(II) polypyridine complexes than corresponding homoleptic Cu(I) diimine complexes. Also they possess enhanced luminescence and longer lifetimes than Cu(diimine)2+ complexes.240 It has been observed that bidentate phosphine ligands help suppress ligand dissociation compared to monodentate phosphine ligands.94 Robertson and coworkers240 reported a heteroleptic Cu(I) complex containing a diimine ligand and a bis(2-(diphenylphosphanyl)phenyl)  ether  ligand,  (POP),  (74,  Chart  4-2),  and  demonstrated its use as a sensitizer in a DSSC. The steric strain of the POP ligand can hinder distortion toward a square planar geometry upon MLCT excitation or oxidation. The photocurrents observed were lower than those reported for devices using homoleptic Cu(I) sensitizers,238, 239, 257 believed to be due to poor absorption of the dye in the visible region. This research group is now looking to replacing the POP with a different ligand with improved absorption properties. They were successful in demonstrating that Cu(I)  113  sensitizers can be obtained without the need for the labour intensive 4,4ʹ,6,6ʹ-substituted diimine analogues. Chart 4-2 Ref.240  In this chapter, new mixed-ligand Cu(I) complexes using a diimine ligand and the PT3 ligand, instead of a diphosphine ligand are described. The PT3 ligand has a broader absorption in the visible region than the POP ligand. Poor light absorption by POP was attributed as a cause of low photocurrents. Additionally, absorption can be tuned as PT3 is capable of binding to metal centers in various ways; via P, PS or PC coordination modes. Binding in a PS or PC configuration could help with complex rigidity. This, along with the bulkiness of the ligand may prevent distortion upon excitation that could lead to nonradiative decay pathways. Here, two new complexes are reported: [Cu(dmp)(MeCN)PT3P](PF6) and [Cu(phen)PT3-P](PF6) (Chart 4-3). The absorption, transient absorption, emission, and electrochemical properties, as well as the solid-state structures of the complexes are investigated. Chart 4-3  114  Section 4.2 ‒ Experimental Section 4.2.1 ‒ General All reactions were performed under N2 (99.0%) or Ar (99.997%). PT3 was synthesized according to literature procedures.109 All other reagents were purchased from Aldrich, Alfa Aesar or Strem and used as received. 1H and  31  P{1H} NMR spectra were  collected on a Bruker AV-300 spectrometer. 1H NMR spectra were referenced to residual solvent, and 31P{1H} NMR spectra referenced to external 85% H3PO4. ESI mass spectra were recorded on a Bruker Esquire-LC ion trap mass spectrometer equipped with an electrospray ion source. The solvent for the ESI-MS experiments was either methanol or dichloromethane/methanol and the concentration of the compound was ~10 M. High resolution mass spectra (HRMS) were recorded on a Waters Micromass LCT time-offlight mass spectrometer equipped with an electrospray ion source. CHN elemental analyses were performed using an EA1108 elemental analyzer, using calibration factors. The calibration factor was determined by analyzing a suitable certified organic standard (OAS) of a known elemental composition. All mass spectrometry and microanalysis results were obtained by the staff at the UBC Mass Spectrometry Centre. Cyclic voltammetry experiments were carried out on a Pinechem potentiostat using a Pt working electrode, Pt mesh counter electrode and a silver wire reference electrode with 0.1 M [(nBu)4N]PF6 supporting electrolyte which was re-crystallized 3 times from ethanol and dried under vacuum at 100 °C for 3 days. Decamethylferrocene (-0.125 V vs SCE in CH3CN, -0.070 V vs SCE in CH2Cl2) was used as an internal reference to correct the measured potentials with respect to saturated calomel electrode (SCE). UV-vis spectra were obtained on a Cary 5000 spectrometer in HPLC grade solvent. Emission spectra were obtained on a PTI Quantamaster spectrometer. Transient absorption (TA) measurements and fluorescence lifetimes were carried out on a Princeton Instruments Spectra Pro 2300i Imaging Triple Grating Monochrometer/Spectrograph with a Hamamatsu Dynamic Range Streak Camera (excitation source: EKSPLA Nd:YAG laser, 35 ps pulse duration,  = 355 nm). Solutions of the complexes in CH3CN having an optical density of 1 at 355 nm were prepared. The UV-vis spectra were obtained before  115  and after each TA experiment to ensure the bulk of the sample did not change, due to degradation or another process. Section 4.2.2 ‒ Procedures [Cu(dmp)(MeCN)PT3-P](PF6), (75). [Cu(CH3CN)4](PF6) (0.025 g) and PT3 (0.030 g) were added to 10 mL of N2 sparged CH3CN. The mixture was heated to reflux, with stirring, for 12 hours. The solution was cooled to room temperature and a solution of dmp (0.013 g) in 5 mL of CH3CN/DCM was added dropwise to the copper solution. The volume of the resulting solution was reduced, added dropwise to a solution of ammonium hexafluorophosphate (0.200 g) in H2O (12 mL) and stirred at room temperature for 30 minutes. The precipitate, a mixture of products, was filtered and washed with copious amounts of water and diethyl ether. A small amount of powder was purified, through several washing with hexanes, ethanol and methanol, and the NMR spectrum was recorded on that sample. The remaining mixture was recrystallized by vapour diffusion of ether into a CH3CN/CH2Cl2 solution, to produce yellow crystals of [Cu(dmp)(MeCN)PT3-P](PF6) (6.3 mg, 11%). 1H NMR (300 MHz, CD2Cl2: δ 2.46 (s, 6H), 6.71 (br. s, 2H), 7.03-7.18 (m, 2H), 7.26-7.35 (m, 3H), 7.40-7.56 (m, 10H), 7.73 (d, J=8.5 Hz, 2H), 7.99 (s, 2H), 8.48 (d, J = 8.5 Hz, 2H).  31  P{1H} NMR (121 MHz, CD2Cl2): δ 15.9 (s), -143.6 (septet, JPF = 708 Hz, PF6).  m/z: [M-PF6]+ 703.1. HRMS (ESI) Calcd for C38H29CuN2PS3 (m/z: [M-PF6-MeCN]+): 703.0527; Found: 703.0553. [Cu(phen)PT3-P](PF6), (76). [Cu(CH3CN)4](PF6) (0.050 g) and PT3 (0.060 g) were added to 15 mL of N2 sparged CH3CN. The mixture was heated to reflux, with stirring, for 12 hours. The solution was cooled to room temperature and a solution of phenanthroline monohydrate (0.026 g) in 5 mL of 1:1 CH3CN/DCM was added dropwise to the copper solution. The volume of the resulting solution was reduced, added dropwise to a solution of ammonium hexafluorophosphate (0.284 g) in H2O (17 mL) and stirred at room temperature for 30 minutes. The precipitate was filtered and washed with copious amounts of water and 116  diethyl ether to yield 62 mg (56 %) of a yellow solid. 1H NMR (300 MHz, CD3CN: δ 5.87-5.99 (m, 1H), 6.36 (d, J = 3.4 Hz, 1H), 6.48 (d, J = 4.8, 1H), 6.57 (d, J = 2.7, 1H), 7.02 (dd, J = 5.3, 3.7 Hz, 1H), 7.14 (dd, J = 3.7, 1.1 Hz, 1H), 7.34 (dd, J = 5.1, 1.0 Hz, 1H), 7.51-7.59 (m, 10H), 7.85 (dd, J = 8.1, 4.7 Hz, 2H) 8.05 (s, 2H), 8.57 (d, J = 8.0 Hz, 2H), 8.79 (d, J = 3.4 Hz, 2H). 31P{1H} NMR (121 MHz, CD2 CD2): δ -12.7 (br. s), -143.6 (septet, JPF = 708 Hz, PF6). m/z [M-PF6]+ 675.5. HRMS (ESI) Calcd for: C36H25CuN2PS3 (m/z [M-PF6]+): 675.0214; Found: 675.0224. Anal. C36H25CuF6N2P2S3 requires C, 52.65; H, 3.07; N, 3.41. Found C, 52.78; H, 3.24; N, 3.28. Section 4.2.3 ‒ X-Ray Crystallography Suitable crystals of [Cu(dmp)(MeCN)PT3-P](PF6) and [Cu(phen)PT3-P](PF6) were grown by vapour diffusion or from solution. The X-ray data were collected and solved by Dr. B.O. Patrick. In each case, the crystals were mounted on a glass fiber and a Bruker APEX DUO or Bruker X8 APEX II diffractometer with graphite monochromated Mo-Κα radiation was used for all measurements. Data were collected and integrated using the Bruker SAINT113, effects  using  multi-scan  258  software package. Data were corrected for absorption techniques,  SADABS116  and  TWINABS259  for  [Cu(dmp)(MeCN)PT3-P](PF6) and [Cu(phen)PT3-P](PF6) respectively. The data were corrected for Lorentz and polarization effects. The structures were solved by direct methods.118 Solid-state diagrams were visualized using Mercury.119  [Cu(dmp)(MeCN)PT3-P](PF6), (75). Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 7.0 second exposures. The crystal to detector distance was 40.08 mm. The data were collected to a maximum 2ζ value of 60.1°. Of the 52311 reflections that were collected, 11254 were unique (Rint = 0.041); equivalent reflections were merged. Data were corrected for absorption effects using the multi-scan technique (SADABS),116 with minimum and maximum transmission coefficients of 0.859 and 0.941, respectively. Two thiophene rings (S1 – C4 and S3 – C12) are disordered by 180° rotation about a C – C bond. Restraints were employed to maintain similar geometries and thermal parameters 117  between the major and minor disordered fragments. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions. The final cycle of full-matrix least squares refinement120 on F2 was based on 11254 reflections and 555 variable parameters and converged (largest parameter shift was 0.00 times its esd).  [Cu(phen)PT3-P](PF6), (76). Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 20.0 second exposures. The crystal to detector distance was 40.15 mm. The data were collected to a maximum 2ζ value of 56.2°.The material crystallizes as a three-component „split-crystal‟ with components one and two related by a 4.4° rotation about the (0.08 -0.37 1.00) crystal axis, and component one and three related by a 5.0° rotation about the (1.00 -0.60 0.05) crystal axis. Data were integrated for all twin components, including both overlapped and non-overlapped reflections. In total, 89164 reflections were integrated (28124 from component one only, 28270 from component two only, 27743 from component three only, 5027 overlapped). Data were corrected for absorption effects using multi-scan the technique (TWINABS),259 with minimum and maximum transmission coefficients of 0.733 and 0.880, respectively. The structure was solved by direct methods118 using non-overlapped data from the major twin component. Subsequent refinements were carried out using the HKLF 5 format data set, containing data from component one and all overlaps from components two and three. The material crystalizes with disorder of one thiophene ring about the C4-C5 bond. The major disorder fragment (~78%) has the thiophene sulfur oriented away from the Cu atom, while the minor fragment had the thiophene sulfur bonded to the Cu atom. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions, but not refined. The final cycle of full-matrix least squares refinement120 on F2 was based on 8227 reflections and 490 variable parameters and converged (largest parameter shift was 0.00 times its esd).  118  Section 4.3‒ Results and Discussion Section 4.3.1 ‒ Synthesis Typical  procedure  for  a  mixed-ligand  Cu(I)  complex,  of  type  [Cu(N^N)(P^P)](BF4), involves mixing [Cu(CH3CN)4](BF4) with a diphosphine ligand (P^P) in DCM for two hours, followed by addition of diimine ligand (N^N) dissolved in DCM. After an additional few hours of stirring, the volume is reduced and layered with CH3CN to give [Cu(N^N)(P^P)](BF4) in good yield.94 (Scheme 4-2)  Scheme 4-2  Employing a similar method here, using 2,9-dimethyl-1,10-phenanthroline (dmp) as the diimine ligand, and PT3 instead of a P^P ligand, led to a mixture of products. Based on NMR spectroscopy and mass spectrometry analysis, it is believed the desired [Cu(dmp)PT3](PF6) complex was formed (m/z [M-PF6]+ 703.1, 31P{1H} NMR showed a new peak that did not correspond to ligand or oxidized ligand), along with [Cu(dmp)2](PF6) (m/z [M-PF6]+ 479.2). It has been previously reported that this homoleptic copper(I) diimine complex forms readily, even when not favored stoichiometrically.249, [Cu(dmp)(P^P)](ClO4)  260  Li and coworkers256 found that they could synthesize using  several  P^P  ligands,  including  1,3-  bis(diphenylphosphino)propane (dppp), and 1,2-bis(diphenylphosphino)ethane (dppe), but not when using 1,2-bis(diphenylphosphino)benzene (bdpp). This was attributed to repulsion between the ligands, as there would be more steric crowding in a complex containing the bdpp ligand. Alternatively, failure to isolate the desired product may be 119  due to a kinetic effect of crystallization, as in solution it is likely there is an equilibrium between various species.256 Here, attempts to efficiently separate the desired product from the mixture were unsuccessful. Column chromatography yielded some pure [Cu(dmp)2](PF6), but no evidence of the desired product. Refluxing the PT3 ligand with the [Cu(CH3CN)4](PF6) before adding dmp did not help in preventing the unwanted [Cu(dmp)2](PF6) from forming. Attempted recrystallization from DCM led to the formation of [Cu(dmp)2](PF6), perhaps due to the stability of this complex. Eventually a small amount of material was recrystallized by vapour diffusion of ether into an DCM/CH3CN mixture, and the solidstate molecular structure was determined to be [Cu(dmp)(MeCN)PT3-P](PF6). The MS analysis does not show a peak for the product with coordinated MeCN. However, it is not surprising as MeCN is known to be relatively labile. It is believed that the MeCN is not coordinated in the bulk crude product, and that it binds during recrystallization with acetonitrile, as a peak that could be assigned to bound CH3CN was not observed in the 1H NMR spectrum of the complex before recrystallization (from the small amount that was purified via several washings). It has been reported that copper complexes with larger anions, such as PF6- and V(CO)6-, can yield three-coordinate trigonal planar salts.261 Recrystallization from acetonitrile has produced four coordinate complexes, where an acetonitrile displaced the anion to bind to the copper.261 Here, all spectroscopic investigations were carried out on the crystals of this complex, rather than the bulk material prior to recrystallization. Changing the diimine ligand from dimethylphenanthroline to phenanthroline produced a single mixed-ligand copper(I) complex. In this case, PT3 was heated to reflux with [Cu(CH3CN)4](PF6), followed by addition of phen (Scheme 4-3). No evidence of [Cu(phen)2](PF6) was observed from mass spectrometry analysis, but a peak at m/z = 675.5 indicates the desired complex was present. This suggests steric effects may be a factor in the formation of the mixed-ligand Cu(I) containing dmp complex.  120  Scheme 4-3  Section 4.3.2‒ Solid-State Molecular Structures Single crystals of [Cu(dmp)(MeCN)PT3-P](PF6) were grown from vapour diffusion of diethyl ether into a CH2Cl2 – CH3CN solution. The solid-state structure is shown in Figure 4-1. Disorder was present in the thiophene rings containing S1 and S3. The [Cu(dmp)(MeCN)PT3-P](PF6) complex crystalized in a distorted tetrahedral environment around the Cu center. The N1 – Cu – N2 angle of 81.29(6)° and P1 – Cu – N3 of 111.96(5)° show a substantial distortion from the expected 109.5°. This is common in these complexes, as the rigid ring system of the diimine ligand requires an acute bite angle. In other complexes were a diphosphine ligand is used, the angle varies substantially, with values between 105° and 123° observed.250 Here, the Cu – N3 bond is the shortest Cu – N bond (Table 4-1). This bond is slightly longer than the Cu – N bond lengths in [Cu(CH3CN)4](PF6).262 However, it is considerably longer than the Cu – NMeCN bond in the three-coordinate [Cu(dmp)(MeCN)](PF6) complex,263 potentially due to steric effects. The Cu – Ndmp bonds fall with normal ranges, when compared to similar structures.94, 249, 250 The Cu – P bond, with a length of 2.1989(5) Å, is slightly shorter than that observed for other Cu – P bonds in complexes with either bidentate diphosphine ligands or PPh3 moieties.94, 250, 252, 264 The S1 to S2 and S2 to S3 torsion angles of the thiophene rings are about 140° - 160° (Table 4-1), which are larger than the calculated value for terthiophene (147.6°).220 The increased co-planarity of the rings indicates more π – orbital overlap.  121  Figure 4-1 Solid-state structure of [Cu(dmp)(MeCN)PT3-P](PF6), (75). Hydrogen atoms and counterions were removed for clarity. Thermal ellipsoids are drawn at 50% probability.  Table 4-1 Selected bond lengths and angles for [Cu(dmp)(MeCN)PT3-P](PF6), (75). Bond Lengths (Å) Cu1 – N1  2.0911(15)  C1 – C2  1.358(7)  Cu1 – N2  2.0634(15)  C2 – C3  1.440(13)  Cu1 – N3  2.0414(16)  C3 – C4  1.329(14)  Cu1 – P1  2.1989(5)  C4 – C5  1.455(8)  S1 – C1  1.712(7)  S1 – C4  1.753(11)  N1 – Cu1 – N2  81.29(6)  P1 – Cu1 – N3  111.96(5)  N1 – Cu1 – N3  105.27(6)  P1 – Cu1 – N2  131.75(4)  N2 – Cu1 – N3  99.27(6)  P1 – Cu1 – N1  121.58(4)  41.0(9)  S2 – C8 – C9 – S3  160.0(3)  Bond Angles (°)  Torsion Angles (°) S1 – C4 – C5 – S2  122  Single crystals of [Cu(phen)PT3-P](PF6) were grown from a warm methanol solution, and the solid-state structure is shown in Figure 4-2. Disorder was present in the thiophene ring containing S1. Disorder in unbound thiophene rings has previously been observed with this ligand (Chapters 2 and 3), but in this case there is disorder in a bound thiophene ring. The major component is a three-coordinate Cu(I) complex, where the sulfur of the S1 thiophene ring is oriented away from the Cu center (Figure 4-2 (a)). The minor component has the S1 thiophene rotated so the sulfur is bound to the copper (Figure 4-2 (b)). As the major component is only bound through the phosphorus, it will continue to be referred to as [Cu(phen)PT3-P](PF6) throughout this Chapter. Additionally, this solid-state structure does not necessarily represent the species present in solution. The 31P{1H} NMR spectrum shows a single broad peak, along with the signals from the counter ion. Broadening of the  31  P NMR spectrum is caused by the quadruple  65  63  Cu nuclei, both with I=3/2 and natural abundance of 69% and 31%, respectively.  Cu and  253  In the three-coordinate species, the Cu center is in a distorted trigonal-planar environment. The sum of the bond angles around the Cu(I) center is 349.21° (Table 4-2). The coordinated phosphorus is not in the plane with the Cu and phen ligand, instead it is above the plane by about 28°. The Cu – N bond lengths (Table 4-2) are similar to those reported for other complexes containing Cu – Nphen bonds.94 The Cu – P bond, 2.1793(7) Å in length, is shorter than other Cu – P bonds in either bidentate phosphine or PPh3 ligands,94, 250, 252, 264 as seen for [Cu(dmp)(MeCN)PT3-P](PF6) as well. Here, the Cu – P bond is shorter than in the complex containing dmp, potentially due to steric effects due to the methyl groups in the dmp complex. The torsion angles here are about 48° and 21° for the S1 – C4 – C5 – S2 and S2 – C8 – C9 –S3 angles, respectively (Table 4-2). These values are very similar to those for [Cu(dmp)(MeCN)PT3-P](PF6).  123  Figure 4-2 Solid-state structure of [Cu(phen)PT3-P](PF6), (76), showing (a) the major disorder fragment and (b) the minor fragment. Hydrogen atoms and counterions were removed for clarity. Thermal ellipsoids are drawn at 50% probability.  124  Table 4-2 Selected bond lengths and angles for [Cu(phen)PT3-P](PF6), (76). Bond Lengths (Å) Cu1 – N1  2.047(2)  C1 – C2  1.393(12)  Cu1 – N2  2.036(2)  C2 – C3  1.414(14)  Cu1 – P1  2.1793(7)  C3 – C4  1.398(12)  Cu1 – S1b  2.548(16)  C4 – C5  1.461(3)  S1 – C1  1.729(9)  S1 – C4  1.706(3)  N1 – Cu1 – N2  82.60(9)  P1 – Cu1 – S1b  94.0(3)  N1 – Cu1 – S1b  89.2(3)  P1 – Cu1 – N2  129.15(7)  N2 – Cu1 – S1b  121.4(3)  P1 – Cu1 – N1  137.46(7)  S1 – C4 – C5 – S2  47.7(3)  S2 – C8 – C9 – S3  21.4(3)  S1b – C4b – C5 – S2  132.5  Bond Angles (°)  Torsion Angles (°)  The minor component in the crystal structure, with the ligand bound in a PS mode, forms a distorted tetrahedral environment around the copper. The Cu – S bond is 2.548(16) Å, which is similar to other copper(I) – thiophene bonds,265 although few complexes of this type have been reported. Common Cu – S distances for tetrahedral complexes (where the S is not part of a thiophene ring) are in the range of 2.27-2.5 Å,266 though bonds up to 3.01 Å in length have been reported.265 The bound thiophene ring is tilted out of the plane of the Cu – S bond by 85.38°, greater than what was observed for Ru(II), Os(II) and Ir(III) complexes discussed in previous Chapters. This tilting occurs to reduce unfavorable π antibonding interactions.150, 151 The S1b – C4b – C5 – S2 torsion angle is 132.5°, which is very similar to the torsion angle in of the S1 ring in its other orientation. The binding of the thiophene ring to the copper does not appear to increase the rings‟ co-planarity, and therefore does not alter the amount of π – orbital overlap. Section 4.3.3‒ Cyclic Voltammetry The electrochemical properties of [Cu(phen)PT3-P](PF6) in two different solvents, CH3CN and CH2Cl2, were probed at room temperature using cyclic voltammetry. The 125  cyclic voltamograms display some interesting differences in the different solvents. Attempted electropolymerization in both DCM and CH3CN was unsuccessful. In CH3CN, four irreversible oxidation waves are observed (Table 4-3, Figure 4-3). The waves at 1.19 V and 1.74 V are quite prominent. The wave at 1.62 V appears only as a shoulder on the wave at 1.74 V. Other phosphine dimiine mixed copper(I) complexes in CH3CN show irreversible waves between 0.50 and 1.40 Volts (vs SCE) that are assigned as Cu(I)/Cu(II) oxidation.240 Typically, the Cu(I)/Cu(II) oxidation are the lowest potential oxidation waves observed. However, in the investigations of PT3 complexed to ruthenium, osmium and iridium, the PT3 based redox has been attributed as the lowest potential oxidation wave. Here, ligand-based and copper oxidation waves are both possible. Although it is difficult at present to make definitive assignments, the wave at 1.19 V may be a PT3 based oxidation, and the wave at 1.74 V may be a Cu(I)/Cu(II) oxidation. The untethered PT3 ligand has an oxidation at 1.30 V vs SCE,  56  and in  Chapter 2, the value of the PT3 oxidation ranged from 0.28 V to 1.48 V, dependent on metal center and coordination mode. Repeated scans show a decrease in the current and disappearance of the features. This may be caused by a non-conductive film coating the electrode, or potentially be due to decomposition from an unstable Cu(II) species being produced.  Table 4-3 Cyclic voltammetry data of [Cu(phen)PT3-P](PF6), (76).a Solvent CH3CN  E1/2 ±0.01 V vs. SCE +1.19 b +1.62 b +1.74 b +2.03 b  CH2Cl2  +0.23 +0.62  a  Measurements carried out in solution containing 0.1 M [(n-Bu)4N]PF6 supporting electrolyte bIrreversible wave, Ep. 126  18  [Cu(phen)PT3-P](PF6) in CH3CN  16 14  Current (A)  12 10 8 6 4 2 0 -2 -1.0  -0.5  0.0  0.5  1.0  1.5  2.0  2.5  Volts (V) vs SCE  Figure 4-3 Cyclic voltammogram of [Cu(phen)PT3-P](PF6), (76), in CH3CN, 0.1 M TBAPF6, 100mV/s scan rate, PT disc working electrode, Pt mesh counter electrode and silver wire reference electrode.  In CH2Cl2, on the other hand, quasi-reversible waves are observed. The redox waves occur at 0.23 and 0.62 V vs SCE, with the lower potential wave having greater current associated with it. There may also be two reductions occurring very close together near 0.09 V, as the shape of the peak looks slightly distorted. [Cu(phen)2](PF6) has a reversible wave at 0.54 V vs SCE, attributed to the Cu(II)/Cu(I) redox couple.267 It is possible that the wave at 0.62 V is from a Cu(I)/Cu(II) oxidation, and the wave at 0.23 V is PT3 ligand-based. In the other complexes containing PT3 that have been investigated, the wave occurring at the lowest potential has been assigned to a ligand-based PT3 process. In this case, the binding mode, coordination environment and metal are all different. The [Os(bpy)2PT3-PC](PF6) complex (55, Chapter 2) shows a reversible wave at 0.28 V, that is assigned as PT3 based redox wave, with support of DFT calculations. This is close to the lowest redox wave observed here.  127  12  [Cu(phen)PT3-P](PF6) in DCM  10 8  Current (A)  6 4 2 0 -2 -4 -6 -8 -0.4  -0.2  0.0  0.2  0.4  0.6  0.8  1.0  1.2  Volts (V) vs SCE  Figure 4-4 Cyclic voltammogram of [Cu(phen)PT3-P](PF6), (76), in CH2Cl2, 0.1 M TBAPF6, 100mV/s scan rate, PT disc working electrode, Pt mesh counter electrode and silver wire reference electrode. Alternatively, it is possible that the wave at 0.62 V is a decomposition product, as the current associated with that wave is much smaller than the oxidation at 0.23 V, suggesting that the waves are not both due to one electron processes. Section 4.3.4‒ Electronic Absorption Spectra The UV-vis absorption spectrum of [Cu(dmp)(MeCN)PT3-P](PF6) in CH3CN is shown in Figure 4-5. The absorption spectrum of [Cu(dmp)(MeCN)PT3-P](PF6) contains two major bands, a band at 274 nm assigned to the π → π* transition of the dimethylphenanthroline (dmp) group, and a lower energy band with max = 348 nm, possibly due to a π → π* transition of the terthienyl ligand. This absorption occurs at a similar wavelength to those of the uncomplexed PT3 ligand and the iridium complexes (Chapter 3), that are assigned as ligand-based transitions. The UV-vis spectrum of [Cu(dmp)2](PF6) has a major band at 454 nm assigned as an metal to ligand charge transfer (MLCT) transition, and a band in the UV region assigned as a π → π* transition 128  in the ligand.267 In [Cu(dmp)(MeCN)PT3-P](PF6), there is also a weak band at 450 nm. This has been assigned as a MLCT transition. In other Cu(I) complexes, the intensity of this low energy band has been attributed to the degree of distortion the system undergoes.268-270 It is possible the band at 450 nm is from a small amount of the homoleptic [Cu(dmp)2](PF6) complex forming in solution, but with time, the relative intensity of this band does not change. In DCM, the spectrum is similar, except the intensity of the band at 450 nm is reduced. After several days in solution, slight changes are observed; the band at 350 nm shifts to higher energy, perhaps due to ligand dissociation.  [Cu(dmp)(MeCN)PT3-P](PF6) in CH3CN  3.0  Normalized Absorption (a.u.)  [Cu(dmp)(MeCN)PT3-P](PF6) in DCM 2.5  2.0  1.5  1.0  0.5  0.0 250  300  350  400  450  500  550  600  Wavelength (nm)  Figure 4-5 Solution absorption spectrum of [Cu(dmp)(MeCN)PT3-P](PF6), (75), in CH3CN (black) and CH2Cl2 (red). As with the [Cu(dmp)(MeCN)PT3-P](PF6) complex, [Cu(phen)PT3-P](PF6) exhibits two main absorption bands; one at 350 nm and the other at 265 nm. These bands are possibly due to a π → π* transition of the PT3 ligand, and a π → π* transition of the phenanthroline group, respectively. In CH3CN, a very weak shoulder at 450 nm is observed, assigned as a MLCT transition. The UV-vis spectrum of [Cu(phen)2](PF6) in 129  acetonitrile exhibits a main peak near 458 nm and a lower energy shoulder, both of which are assigned as MLCT states.267,  269  Comparing the UV-vis spectra of [Cu(phen)PT3-  P](PF6) to [Cu(dmp)(MeCN)PT3-P](PF6), there are only a few differences. The π → π* transition of the diimine ligand has shifted, as a different diimine ligand is present, and the band near 450 nm is less intense. The observance of this lower energy band in the [Cu(phen)PT3-P](PF6)  is  further  evidence  that  the  band  at  450  nm  in  [Cu(dmp)(MeCN)PT3-P](PF6) is not from a small amount of [Cu(dmp)2](PF6) forming, but from the complex itself as no evidence of the homoleptic copper(I) phenanthroline complex was observed. The [Cu(phen)PT3-P](PF6) spectra is reminiscent of [Cu(dmp)(MeCN)PT3-P](PF6), and it is possible that a CH3CN group may weakly coordinate to the three-coordinate copper center in [Cu(phen)PT3-P](PF6). In CH2Cl2, the π → π* transition of the phen group appears to red shift slightly. The band near 350 nm does not shift much, and the shoulder at 450 nm vanishes. 2.5  [Cu(phen)PT3-P]PF6 in CH3CN  Normalized Absorbance  [Cu(phen)PT3-P]PF6 in DCM 2.0  1.5  1.0  0.5  0.0 250  300  350  400  450  500  550  600  wavelength (nm)  Figure 4-6 Solution absorption spectra of [Cu(phen)PT3-P](PF6), (76), in CH3CN (black) and CH2Cl2 (red).  130  Section 4.3.5 – Emission Spectra Excitation of [Cu(dmp)(MeCN)PT3-P](PF6) at 350 nm in argon-sparged CH3CN shows weak emission centered at 441 nm, with a shoulder around 550 nm (Figure 4-7). The presence of oxygen did not have a significant effect on the emission. In CH 2Cl2 however, the lower energy shoulder is not observed (Figure 4-7), even in argon-sparged solutions. [Cu(dmp)2](PF6) displays emission at 740 nm in DCM.267 There is no evidence of this band when the solution is excited at 350 nm or 450 nm, even after the solution was left for several days. However, when excited at 450 nm, a very weak band is observed at about 519 nm. Emission of [Cu(phen)PT3-P](PF6) in CH3CN is weak. A peak at 442 nm is observed along with a shoulder at 550 nm, when excited at 350 nm (Figure 4-8). The observed emission is similar to that observed for [Cu(dmp)(MeCN)PT3-P](PF6). It is possible CH3CN is binding weakly to the three-coordinate copper species, in which case spectroscopic similarities to [Cu(dmp)(MeCN)PT3-P](PF6) would be expected. When excited at 350 nm in a DCM solution, the emission is more intense, and the shoulder at lower energy is no longer visible (Figure 4-8). CH3CN is considered a coordinating solvent, while DCM is considered non-coordinating. The emission spectrum of [Cu(phen)PT3-P](PF6) was also obtained in other coordinating solvents, pyridine (py) and methanol (MeOH). No evidence of the lower energy shoulder (at 550 nm) is observed in these solvents (Table 4-4). These bands are not sensitive to the presence of oxygen. No emission is observed for [Cu(phen)2](PF6).267  131  120000  [Cu(dmp)(MeCN)PT3-P](PF6) in CH3CN [Cu(dmp)(MeCN)PT3-P](PF6) in DCM  -1  Emission (Counts s )  100000  80000  60000  40000  20000  0 400  450  500  550  600  650  Wavelength (nm)  Figure 4-7 Emission spectra of [Cu(dmp)(MeCN)PT3-P](PF6), (75), in CH3CN (black) and CH2Cl2 (red).  132  11000  [Cu(phen)PT3-PS]PF6 in CH3CN  10000  [Cu(phen)PT3-PS]PF6 in DCM  -1  Emission (Counts s )  9000 8000 7000 6000 5000 4000 3000 2000 1000 0 400  450  500  550  600  650  Wavelength (nm)  Figure 4-8 Emission spectra of [Cu(phen)PT3-P](PF6), (76), in CH3CN (black) and CH2Cl2 (red). Many complexes of the type [Cu(N^N)(P^P)](PF6) exhibit emission between 560-700 nm in DCM.94 As the emission observed for both [Cu(dmp)(MeCN)PT3-P](PF6) and [Cu(phen)PT3-P](PF6) occurs at higher energy, and is not sensitive to the presence of oxygen, it is likely a singlet ligand-based emission that is observed. Additionally, the emission lifetimes are very short (< 2 ns).  133  Table 4-4 Photophysical data for [Cu(dmp)(MeCN)PT3-P](PF6), (75), and [Cu(phen)PT3-P](PF6), (76), in various solvents. Complex  Solvent  Abs λ (nm)  Em λ (nm)  Φem  τTA(µs)  75  CH3CN  274, 293, 248, 450  441, 550 (sh)  ---  8  75  CH2Cl2  274, 294, 351, 450  448  ---  40  76  CH3CN  267, 286, 350, 449  442, 550 (sh)  0.003  8  76  CH2Cl2  267, 290, 349  447  0.004  50  76  CH3OH  268, 289, 347  430(sh), 447  ---  4  76  Pyridine  348b  448  ---  a  34 b  Measurements carried out in argon-sparged solutions at room temperature Solvent cut off at 330 nm. Section 4.3.6– Transient Absorption Spectra The transient absorption spectra of [Cu(dmp)(MeCN)PT3-P](PF6) in CH3CN is show in Figure 4-9 (a). The TA spectra of [Cu(dmp)2](PF6) shows an absorption near 350 nm, a strong bleach centered near 450 nm and a broad absorption above 500 nm. The absorptions are attributed to reduced ligand.267, 271, 272 In [Cu(dmp)(MeCN)PT3-P](PF6), a bleach is not observed, and the absorption band starts around 400 nm. Additionally, the shape is similar to that observed for the PT3 ligand (Chapter 2). In this case, the complex decays monoexponentially with a lifetime of 8 µs under argon (Appendix, Figure A-15), in a CH3CN solution. In an argon-sparged DCM solution, a new shoulder is observed around 600 nm (Figure 4-9 (b)). The excited state lifetime of the complex is enhanced, and both bands exhibit similar monoexponential decays (Table 4-4, Appendix Figures A16 and A-17). The transient absorption spectra and decay lifetime of PT3 are similar in CH3CN and CH2Cl2 (Appendix, Figures A-18 to A-21), but exhibit longer lifetimes in argon-sparged solution than in nitrogen-sparged solution (Chapter 2).  134  0.010  (a)  0.008  1 s 4 s 8 s 14 s 19 s  0.006 0.004 0.002 0.000   Abs.  -0.002 -0.004 0.10  6 s 16 s 26 s 36 s 46 s 66 s 96 s  (b) 0.08 0.06 0.04 0.02 0.00 -0.02 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure 4-9 Transient absorption spectra of [Cu(dmp)(MeCN)PT3-P](PF6), (75), in (a) argon-sparged CH3CN and (b) argon-sparged CH2Cl2. The transient absorption spectra of [Cu(phen)PT3-P](PF6) obtained in a CH3CN solution show a broad absorption between 400 – 600 nm (Figure 4-10 (a)), reminiscent of that seen for the previous complex, [Cu(dmp)(MeCN)PT3-P](PF6), and thus the PT3 ligand. This complex has a lifetime of 8 µs when sparged with argon (Appendix, Figure A-22). The lifetime decreases in the presence of oxygen, suggesting a triplet state. The transient absorption spectra reported between 500 and 750 nm of [Cu(phen)2](PF6) shows a broad band with a maximum near 550 nm.269 When the TA spectroscopy was performed on the complex in an argon-sparged DCM solution, the bands broadened, with a new shoulder appearing which absorbs out to 135  700 nm (Figure 4-10 (b)). Both bands decay with the same lifetime, suggesting that each band originates from the same species. Again in this case, the lifetime (about 50 µs, Table 4-4, Appendix, Figures A-23 and A-24) is substantially longer than what was observed for the CH3CN solution. Once again, this may be due to the acetonitrile coordinating weakly, allowing for a non-radiative decay pathway. Alternatively, the DCM stabilizies an excited state, allowing for an equilibrium between two excited states to occur.  (a)  0.020  1 s 3 s 5 s 7 s 9 s 11 s 15 s 20 s  0.015 0.010 0.005 0.000   Abs.  -0.005  (b)  0.10  5 s 15 s 20 s 30 s 40 s 70 s 90 s  0.08 0.06 0.04 0.02 0.00 -0.02 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure 4-10 Transient absorption spectra of [Cu(phen)PT3-P](PF6), (76), in (a) argonsparged CH3CN and (b) argon-sparged CH2Cl2.  136  Previous experiments have shown that Cu(I) diimine complexes have shorter lifetimes in strongly coordinated solvents, or weak bases, compared to non-coordinating ones.269 The authors attribute this to exciplex formation (a five coordinate species), followed by non-radiative decay. In this case, the lifetime of [Cu(phen)PT3-P](PF6) in MeOH was decreased (Table 4-4, Appendix Figures A-25 to A-26). Methanol is known to induce solvent quenching in some species.94 This suggests that the ligands in this complex are bulky enough to suppress some exciplex formation (the complex still exhibits a relatively long lifetime), but not bulky enough to completely prevent it. In pyridine, the transient absorption resembles that of the transient in CH3CN (Appendix Figure A-27) but the excited state lifetime is more similar to that in CH2Cl2 (Table 4-4, Appendix Figure A-28). The differences in the lifetimes observed for [Cu(phen)PT3P](PF6) in CH3OH and CH3CN (4 and 8 µs) compared to pyridine and CH2Cl2 (34 and 50 µs) may be related to the dielectric constant of the solvent. Previous work has suggested a decreasing decay constant with increasing dielectric constant is indicative of polar character in the excited state.273 In this case, there may be a charge transfer state close in energy to the triplet ligand state. In polar media, the CT state is stabilized, causing the energy to funnel from the 3LC state to the CT state, which then decays very fast via a non-radiative pathway, thus shortening the observed lifetime of the triplet ligand localized state.  Section 4.4 – Conclusions Two mixed-ligand copper(I) complexes containing the diphenylphosphinoterthiophene ligand were synthesized: [Cu(dmp)(MeCN)PT3-P](PF6) and [Cu(phen)PT3P](PF6). The PT3 ligand bound only through the P in [Cu(dmp)(MeCN)PT3-P](PF6), whereas the solid-state structure of [Cu(phen)PT3-P](PF6) indicated a minor component that exhibited PS coordination, in addition to the monodentate P bound structure. Oxidation potentials of [Cu(phen)PT3-P](PF6) were obtained using cyclic voltammetry in two different solvents, and in each case the complexes did not electropolymerize. The absorption spectra of [Cu(dmp)(MeCN)PT3-P](PF6) and [Cu(phen)PT3-P](PF6) were dominated by π→π* transitions. All of the complexes were weakly emissive and 137  emission was assigned as PT3 ligand-based. In CH3CN, a low energy shoulder was observed in addition to the higher energy band, but the lower energy band was not observed in CH2Cl2. Transient absorption spectra show all complexes had a ligand localized excited state. However, the lifetime of the excited state varied greatly depending upon solvent (about 8 µs for both complexes in CH3CN, and 40 or 50 µs in CH2Cl2 for [Cu(dmp)(MeCN)PT3-P](PF6) and [Cu(phen)PT3-P](PF6), respectively). The shape of the transient absorption spectra also varied with solvent; a shoulder near 600 nm was observed when the spectrum was recorded in CH2Cl2, but not in CH3CN.  138  CHAPTER 5 CONCLUSIONS AND PERSPECTIVES Ru(II), Os(II), Ir(III) and Cu(I) phosphine(terthiophene) complexes were synthesized and their photophysical and electrochemical properties were studied. Type I complexes containing iridium and copper metal centers were obtained when the PT3 ligand bound to the metal via the phosphorus. Bidentate coordination of PT3 to ruthenium, osmium and iridium resulted in the thiophene backbone being directly bound to the metal, via the sulfur or a carbon atom, to produce Type II complexes. The coordination mode of PT3 is central to the properties observed for these complexes. The obtained solid state structures indicate the interannular thiophene torsion angles are highly dependent on binding mode. In general, the PC bound complexes display increased co-planarity, which is partly reflected in the lower energy absorptions and emission bands. The complexed metal group is also important. Changing from a bis(bipyridine) Ru(II) group (Ru(bpy)22+) to an Os(bpy)22+ group leads to an increased absorption across the visible region due to enhanced spin orbit coupling. In comparison, incorporation of an Ir(ppz)2+ group does not result in improved absorption compared to the Ru(II) complexes. These complexes would ideally absorb out to 920 nm. Adding substituents to the bpy, ppy or ppz ligands may improve the absorption across the visible region, and beyond into the near-IR. The cyclic voltammograms of the complexes generally show irreversible oxidation peaks. Upon PC coordination, the PT3 redox potential is lowered, and in the Ru(II) and Os(II) complexes, reversible redox peaks are observed. The phosphorus bound Cu (I) phenanthroline complex displays irreversible oxidation waves in CH3CN but shows quasi-reversible redox waves in DCM. Regardless of the binding mode of PT3 and solvent used, these complexes do not electropolymerize. Changes in the coordination mode are also reflected in the excited state properties. The excited state of the group 8 complexes is altered based on binding mode. For the Ru(II) and Os(II) (phosphine)terthiophene PS complexes, the excited state is a ligand localized triplet state, in contrast to the PC complexes which exhibit a charge 139  separated state (charge transfer from metal/PT3 HOMO to bipyridyl LUMO). In these complexes it is feasible that charge injection could occur when the complexes are attached to a semiconductor, such as TiO2. Unlike the group 8 metal complexes, the transient absorption spectra of all the iridium and copper complexes show a ligand localized excited state, regardless of coordination mode. These complexes would not perform well in a DSSC as charge separation does not occur in ligand localized triplet states. It would be beneficial to probe the application of some of the complexes that have been synthesized as sensitizers in DSSCs. In order to do so, the diimine, ppy or ppz ligands would have to be substituted with carboxylate groups to allow attachment to a TiO2 surface. This could be achieved by first synthesizing the methyl ester derivative as this is easier to characterize than the corresponding acid or carboxylate salt. If the electrochemical and photophysical properties are still favorable, then incorporation into a DSSC could be pursued. Additionally, only one ligand bearing carboxylate groups is required for attachment to TiO2. Therefore, the use of alternative ligands in place of the second bpy/ppz/ppy group could be investigated. Although the specific coordination mode employed doesn‟t result in a change in the excited state in the Ir(III) cyclometalated complexes (all triplet ligand based), the excited state lifetimes are dependent on coordination mode. The complexes in which PT3 is coordinated in a monodentate fashion via the P atom only exhibit the longest lifetimes, presumably since in these complexes the tether is only through a single diphenyl phosphine linker (Type I vs. Type II complexes). In the copper complexes, the solvent used affects the excited state lifetimes, potentially due to exciplex formation or solvent stabilization. The incorporation of a bidentate diphosphine ligand, such as 3,3ʺbis(diphenylphosphino)-2,2ʹ:5ʹ,2ʺ-terthiophene274 (P2T3, Chart 5-1) may be beneficial as binding through both phosphines may induce less strain than binding in a PS fashion. The extra diphenylphosphine group would add extra steric bulk, which could reduce any distortions or prevent exciplex formation.  140  Chart 5-1 Ref.274  Overall, Type II complexes are found to more strongly alter the properties of the substituted terthiophene and display more π orbital overlap compared to a metal group attached only via the pendant diphenylphosphino group (Type I complex). 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[Ru(phen)2PT3-PS] (PF6)2  [Os(bpy)2PT3-PS] (PF6)2  [Os(bpy)2PT3PC] (PF6)  Formula  C51H39N4OF12P3S3Ru C46H37N4S3OsP3F12Cl4 C44H32N4PS3OsPF6  Crystal Colour, Habit  yellow, tablet  red, plate  brown, blade  Dimensions / mm  0.05 × 0.14 × 0.17  0.05 × 0.30 × 0.50  0.03 × 0.20 × 0.45  Temperature / K  173 (1)  173 (1)  173 (1)  Crystal System  Triclinic  monoclinic  monoclinic  Space Group  P -1 (#2)  P 21/c (#14)  C 2/c (#15)  a/Å  10.7574(4)  11.1984(8)  39.8697(9)  b/Å  11.9596(5)  20.8114(16)  9.4270  c/Å  21.2088(9)  21.9881(17)  28.1007  α /deg  104.616(1)  90.0  90  β /deg  103..562(1)  91.752(4)  130.946  γ /deg  94.916(1)  90.0  90  V / Å3  2536.1(2)  5122.0(7)  7977.5(3)  Z  2  4  8  ρcalc / g cm-1  1.626  1.809  1.797  μ (Mo kα)  6.16 cm-1  29.98 mm-1  35.03 mm-1  R1a (I>2.00σ(I))  0.039  0.037  0.030  wR2a (I>2.00σ(I))  0.090  0.088  0.061  Goodness of fit  1.01  1.07  1.01  Function minimized. w(Fo2-Fc2)2, R1 =  ||Fo| - |Fc|| /  |Fo|, wR2 = [(w (Fo2 Fc2)2 )/  w(Fo2)2]1/2 a  159  0.035  decay at 450-525 nm fit t1= 10.28033 ± 0.08774 s  0.030   Abs.  0.025  0.020  0.015  0.010  0.005  0.000 0  5  10  15  20  Time (s)  Figure A-1 Decay of transient signal averaged over the 450 - 525 nm wavelength region for PT3 (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red).  decay at 425-475 nm fit  0.05  t1 = 2.98126 ± 0.01362 s   Abs.  0.04  0.03  0.02  0.01 0  5  10  15  20  Time (s)  Figure A-2 Decay of transient signal averaged over the 425 - 475 nm wavelength region for T3 (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red).  160  0.05  decay At 575-625 nm fit t1 = 120.18427 ± 0.93169 ns   Abs.  0.04  0.03  0.02  0.01  0.00 0  100  200  300  400  500  Time (ns)  Figure A-3 Decay of transient signal averaged over the 575 - 625 nm wavelength region for [Ru(bpy)2PT3-PS](PF6)2, (48), (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red).  0.035  decay at 560-590 nm fit t1 = 124.72449 ± 0.95076 ns  0.030   Abs.  0.025  0.020  0.015  0.010  0.005  0.000 0  100  200  300  400  500  Time (ns)  Figure A-4 Decay of transient signal averaged over the 560 - 590 nm wavelength region for [Ru(phen)2PT3-PS](PF6)2, (52), (black) upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fit (red).  161  0.30  decay at 550-575nm fit t1 = 0.82214 ± 0.00264 s  0.25   Abs.  0.20  decay at 375-400 nm fit 0.15  t1 = 0.91544 ± 0.01211 s  0.10  0.05 0.00  -0.05 0  1  2  3  4  5  Time (s)  Figure A-5 Decay of transient signal averaged over the 550 - 575 nm (black) and 375400 nm (green) wavelength regions for [Os(bpy)2PT3-PS](PF6)2, (54), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red and blue, respectively).  0.04  0.02   Abs.  0.00  decay at 500-525 nm fit  -0.02  t1 = 18.43525 ± 0.25001 ns  -0.04  decay at 425-475 nm fit  -0.06  t1 = 18.94936 ± 0.30336 ns  -0.08 0  20  40  60  80  100  Time (ns)  Figure A-6 Decay of transient signal averaged over the 500 - 525 nm (black) and 425475 nm (green) wavelength regions for [Ru(bpy)2PT3-PC](PF6), (49), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red and blue, respectively).  162  decay at 500-525 nm fit  0.08  t1 = 62.41716 ± 1.00838 ns  0.06   Abs.  0.04 0.02 0.00 -0.02 -0.04  decay at 425-475 nm fit  -0.06  t1 = 51.26091 ± 0.78995 ns  -0.08 0  20  40  60  80  100  Time (ns)  Figure A-7 Decay of transient signal averaged over the 500 - 525 nm (black) and 425475 nm (green) wavelength regions for [Ru(phen)2PT3-PC](PF6), (53), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red and blue, respectively).  0.01 0.00   Abs.  -0.01  decay at 465-485 nm fit  -0.02  t1 = 2.76434 ± 0.04038 ns  -0.03  decay at 550-575 nm fit  -0.04  t1 = 3.08317 ± 0.08966 ns  -0.05  decay at 650-675 nm fit t1 = 2.74622 ± 0.04703 ns  -0.06 0  1  2  3  4  5  6  7  8  9  10  Time (ns)  Figure A-8 Decay of transient signal averaged over the 465-485 nm (black), 550 - 575 nm (green) and 650-675 nm (orange) wavelength regions for [Os(bpy)2PT3-PC](PF6), (55), upon excitation at 355 nm in N2 sparged CH3CN, and the monoexponential fits (red, blue, and purple, respectively).  163  Table A-2 Selected crystallographic data for Ir(ppz)2PT3Cl-P, (58), [Ir(ppz)2PT3PS](BF4), (59), and Ir(ppz)2PT3-PC, (60).  Ir(ppz)2PT3Cl-P  [Ir(ppz)2PT3-PS](BF4)  Ir(ppz)2PT3-PC  Formula  C43H33N4PS3IrCl3  C44H35BN4F4PS3IrCl4  C42H30IrN4PS3  Crystal Colour, Habit  yellow, irregular  yellow, blade  brown, prism  Dimensions / mm  0.10 × 0.10 × 0.15  0.02 × 0.10 × 0.35  0.20 × 0.28 × 0.29  Temperature / K  90 (1)  90(1)  100(1)  Crystal System  Triclinic  orthorhombic  monoclinic  Space Group  P -1 (#2)  P 212121 (#19)  P 21/n (#14)  a/Å  9.8502(11)  9.1409(8)  9.9313(3)  b/Å  13.0136(14)  20.640(2)  17.0695(4)  c/Å  16.0601(17)  24.406(2)  20.9214(5)  α /deg  78.905(6)  90  90  β /deg  76.782(7)  90  91.624(1)  γ /deg  89.430(7)  90  90  V / Å3  1965.4(4)  4604.7(7)  3545.2(2)  Z  2  4  4  ρcalc / g cm-1  1.743  1.684  1.705  μ (Mo kα) /cm-1  38.40  33.56  40.26  R1a (I>2.00σ(I))  0.032  0.031  0.020  wR2a (I>2.00σ(I))  0.077  0.071  0.042  Goodness of fit  1.06  1.04  1.03  a  2  2 2  2  2 2  Function minimized. w(Fo -Fc ) , R1 =  ||Fo| - |Fc|| /  |Fo|, wR2 = [(w (Fo - Fc ) )/  2 2 1/2  w(Fo ) ]  164  Table A-3 Selected crystallographic data for Ir(ppy)2PT3Cl-P, (61). Ir(ppy)2PT3Cl-P Formula  C47H35N2PS3IrCl3  Crystal Colour, Habit  yellow, irregular  Dimensions / mm  0.04 × 0.06 × 0.16  Temperature / K  90 (1)  Crystal System  Monoclinic  Space Group  P n (#7)  a/Å  11.420(1)  b/Å  11.204(1)  c/Å  16.843(1)  α /deg  90o  β /deg  106.532(2)  γ /deg  90o  V / Å3  2065.8(3)  Z  2  ρcalc / g cm-1  1.694  μ (Mo kα) /cm-1  36.54  R1a (I>2.00σ(I))  0.036  wR2a (I>2.00σ(I))  0.052  Goodness of fit  0.874  a  2  2 2  2  2 2  Function minimized. w(Fo -Fc ) , R1 =  ||Fo| - |Fc|| /  |Fo|, wR2 = [(w (Fo - Fc ) )/  2 2 1/2  w(Fo ) ]  165  0.09  decay at 450-475 nm fit  0.08  t1 = 6.2042 ± 0.01505 s  0.07   Abs.  0.06 0.05 0.04 0.03 0.02 0.01 0.00 0  5  10  15  20  Time (s)  Figure A-9 Decay of the transient signal averaged over the 450 - 475 nm wavelength region for Ir(ppz)2PT3Cl-P, (58), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red).  0.07  decay at 450-500 nm fit t1 = 2.72768 ± 0.01323 s  0.06   Abs.  0.05  0.04  0.03  0.02  0.01 0  1  2  3  4  5  Time (s)  Figure A-10 Decay of the transient signal averaged over the 450 -500 nm wavelength region for Ir(ppz)2PT3-PC, (60), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red).  166  decay at 450-500 nm fit  0.05  t1 = 0.33486 ± 0.00125 s   Abs.  0.04  0.03  0.02  0.01  0.00 0.0  0.2  0.4  0.6  0.8  1.0  Time (s)  Figure A-11 Decay of the transient signal averaged over the 450 -500 nm wavelength region for [Ir(ppz)2PT3-PS](PF6), (59), (black) upon excitation at 355 nm in argonsparged CH3CN, and the monoexponential fit (red).  decay at 460-485 nm fit  0.12  t1 = 7.1462 ± 0.0208 s  0.10   Abs.  0.08  0.06  0.04  0.02  0.00 0  5  10  15  20  time (s)  Figure A-12 Decay of the transient signal averaged over the 460 -485 nm wavelength region for Ir(ppy)2PT3Cl-P, (61), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red).  167  decay at 475-525 nm fit  0.020  t1 = 4.00051 ± 0.05338 s   Abs.  0.015  0.010  0.005  0.000 0  2  4  6  8  10  time, microseconds (s)  Figure A-13 Decay of the transient signal averaged over the 475 -525 nm wavelength region for Ir(ppy)2PT3-PC, (63), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red).  0.040  decay at 475-525 nm fit  0.035  t1 = 0.39028 ± 0.0021 s  0.030   Abs.  0.025 0.020 0.015 0.010 0.005 0.000 0.0  0.2  0.4  0.6  0.8  1.0  Time (s)  Figure A-14 Decay of the transient signal averaged over the 475-525 nm wavelength region for [Ir(ppz)2PT3-PS](PF6), (62), (black) upon excitation at 355 nm in argonsparged CH3CN, and the monoexponential fit (red).  168  Table A-4 Selected crystallographic data for [Cu(dmp)(MeCN)PT3-P](PF6), (75), and [Cu(phen)PT3-P](PF6), (76). [Cu(dmp)(MeCN)PT3-P](PF6)  [Cu(phen)PT3-P](PF6)  C40H32N3P2F6 S3Cu  C36H25N2F6P2S3Cu  Crystal Colour, Habit  yellow, rod  yellow, irregular  Dimensions / mm  0.07 × 0.12 × 0.30  0.13 × 0.22 × 0.25  Temperature / K  90 (1)  100 (1)  Crystal System  monoclinic  triclinic  Space Group  P 21/c (#14)  P -1 (#2)  a/Å  11.5178 (9)  12.137(1)  b/Å  9.1509(7)  12.343(1)  c/Å  36.983(3)  13.457(1)  α /deg  90  74.841(5)  β /deg  98.276(1)  80.130(5)  γ /deg  90  61.167(4)  V / Å3  3857.4(5)  1702.0(3)  Z  4  2  ρcalc / g cm-1  1.533  1.602  μ (Mo kα)  8.76 cm-1  9.84 cm-1  R1a (I>2.00σ(I))  0.039  0.045  wR2a (I>2.00σ(I))  0.078  0.103  Goodness of fit  1.06  1.04  Formula  a  2  2 2  2  2 2  Function minimized. w(Fo -Fc ) , R1 =  ||Fo| - |Fc|| /  |Fo|, wR2 = [(w (Fo - Fc ) )/  2 2 1/2  w(Fo ) ]  169  decay at 450-500 nm fit  0.008  t1 = 8.00705 ± 0.13237 s   Abs.  0.006  0.004  0.002  0.000 0  5  10  15  20  Time (s)  Figure A-15 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(dmp)(MeCN)PT3-P](PF6), (75), (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red). 0.10  decay 475-525 nm fit   Abs.  0.08  t1 = 37.03517 ± 0.15144 s  0.06  0.04  0.02  0.00 0  20  40  60  80  100  Time (s)  Figure A-16 Decay of the transient signal averaged over the 475-525 nm wavelength region for [Cu(dmp)(MeCN)PT3-P](PF6), (75), (black) upon excitation at 355 nm in argon-sparged CH2Cl2, and the monoexponential fit (red).  170  0.06  decay 550-600 nm fit 0.05  t1 = 41.5668 ± 0.23397 s   Abs.  0.04  0.03  0.02  0.01  0.00 0  20  40  60  80  100  Time (s)  Figure A-17 Decay of the transient signal averaged over the 550-600 nm wavelength region for [Cu(dmp)(MeCN)PT3-P](PF6), (75), (black) upon excitation at 355 nm in argon-sparged CH2Cl2, and the monoexponential fit (red).  0.025  2 s 10 s 20 s 36 s 48 s  0.020   Abs.  0.015  0.010  0.005  0.000  -0.005  -0.010 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure A-18 Transient absorption spectra of PT3 in argon-sparged CH3CN.  171  0.020  decay 475-525 nm fit t1 = 26.01411 ± 0.28581 s   Abs.  0.015  0.010  0.005  0.000 0  10  20  30  40  50  time (s)  Figure A-19 Decay of the transient signal averaged over the 475-525 nm wavelength region for PT3 (black) upon excitation at 355 nm in argon-sparged CH3CN, and the monoexponential fit (red).  5 s 10 s 15 s 20 s 30 s 40 s 60 s 80 s 99 s  0.10  0.08   Abs.  0.06  0.04  0.02  0.00  -0.02 350  400  450  500  550  600  650  700  750  Wavelength (nm)  Figure A-20 Transient absorption spectra of PT3 in argon-sparged CH2Cl2.  172  0.10  decay 475-525 nm fit 0.08  t1 = 26.99102 ± 0.15795 s   Abs  0.06  0.04  0.02  0.00 0  20  40  60  80  100  time (s)  Figure A-21 Decay of the transient signal averaged over the 475-525 nm wavelength region for PT3 (black) upon excitation at 355 nm in argon-sparged CH2Cl2, and the monoexponential fit (red).  decay at 475-525 nm fit  0.020  t1 = 8.65679 ± 0.09175 s  Abs.  0.015  0.010  0.005  0.000 0  2  4  6  8  10  12  14  16  18  20  Time (s)  Figure A-22 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH3CN, and the monoexponential fit (red).  173  0.11  decay at 465-495 nm fit  0.10  t1 = 45.64 ± 0.14647 s  0.09 0.08   Abs.  0.07 0.06 0.05 0.04 0.03 0.02 0  20  40  60  80  100  Time (s)  Figure A-23 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH2Cl2, and the monoexponential fit (red).  decay at 575-600 nm fit  0.06  t1 = 50.22189 ± 0.29072 s  0.05   Abs.  0.04  0.03  0.02  0.01  0.00 0  20  40  60  80  100  Time (s)  Figure A-24 Decay of the transient signal averaged over the 575-600 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH2Cl2, and the monoexponential fit (red).  174  0.04  1 s 3 s 5 s 7 s 10 s 15 s 19 s   Abs.  0.03  0.02  0.01  0.00  -0.01 400  450  500  550  600  650  700  750  Wavelength (nm)  Figure A-25 Transient absorption spectra of [Cu(phen)PT3-P](PF6), (76), in argonsparged CH3OH.  0.035  decay 450-500 nm fit 0.030  t1 = 4.45736 ± 0.01973 s   Abs.  0.025  0.020  0.015  0.010  0.005  0.000 0  5  10  15  20  Time (s)  Figure A-26 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged CH3OH, and the monoexponential fit (red).  175  0.05  5 s 15 s 30 s 50 s 70 s 95 s  0.04   Abs.  0.03  0.02  0.01  0.00  -0.01 400  450  500  550  600  650  700  750  Wavelength (nm)  Figure A-27 Transient absorption spectra of [Cu(phen)PT3-P](PF6), (76), in argonsparged pyridine.  0.05  decay at 500-550 nm fit t1 = 34.29754 ± 0.14943 s   Abs.  0.04  0.03  0.02  0.01  0.00 0  20  40  60  80  100  Time (s)  Figure A-28 Decay of the transient signal averaged over the 450-500 nm wavelength region for [Cu(phen)PT3-P](PF6), (76), (black) upon excitation at 355 nm in argonsparged pyridine, and the monoexponential fit (red).  176  

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