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Bis-cyclometallated iridium(III) complexes bearing pyridineimine and salicylimine ancillary ligands :… Howarth, Ashlee Joanna 2014

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BIS-CYCLOMETALLATED IRIDIUM(III) COMPLEXES BEARING PYRIDINEIMINE AND SALICYLIMINE ANCILLARY LIGANDS: SYNTHESIS, CHARACTERIZATION AND APPLICATIONS  by Ashlee Joanna Howarth  B.Sc. Chemistry, The University of Western Ontario, 2009  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemistry)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  July 2014  © Ashlee Joanna Howarth, 2014 ii  Abstract   Two stable diastereomeric atropisomers of a cyclometallated iridium complex containing a pyrene functionalized pyridineimine ligand have been isolated. These are the first fully characterized examples of metal containing atropisomers in which the rotational axis is not between two chelating atoms. The atropisomers can be converted thermally via a rocking motion of the pyrene moiety.  A new mechanism for enhanced phosphorescence emission in the solid state (EPESS) in cyclometallated Ir complexes with the general formula [Ir(C^N)2(N^O)] involving distortion of the six-membered chelate ring of the ancillary ligand is proposed. Photophysical and computational studies show that neither π-stacking nor restricted rotation cause the observed EPESS in these complexes and that ligand distortions in the triplet excited state are responsible for EPESS.  Bis-cyclometallated Ir(III) complexes with the general formula Ir(ppz)2(N^XPyrene) where X = N or O are shown. Modifications on the ancillary ligand containing pyrene drastically affect the emission lifetimes observed (2 μs to 104 μs).  Extended emission lifetimes in these complexes compared to model complexes result from reversible electronic energy transfer or the observation of pyrene (3LC) phosphorescence. A combination of steady state and time-resolved spectroscopic techniques are used to observe reversible electronic energy transfer between the cyclometallated iridium core and the pyrene moiety in the complexes [Ir(ppz)2(N^NPyrene)][PF6]. Replacing the N^NPyrene ligand with an N^OPyrene ligand results in long-lived pyrene phosphorescence. Reversible electronic energy transfer as well as 3pyrene emission is observed and characterized in a PMMA film. iii  Preface   In all chapters, Professor Michael O. Wolf acted in a supervisory role. Chapters 2-4 involved a collaboration with Professor David L. Davies from the Department of Chemistry at the University of Leicester in Leicester, England as well as Francesco Lelj from the Dipartimento di Scienze at the Università della Basilicata in Potenza, Italy.  Sections of Chapter 1 have been published as a review: Howarth, A. J.; Majewski, M. B.; Wolf, M. O. Coord. Chem. Rev. 2014, In Press, Accepted Manuscript. I am the primary author of this work. Dr. Marek B. Majewski contributed to material included in sections 1.4 and 1.4.1.  A version of Chapter 2 has been previously published as a communication: Howarth, A. J.; Davies, D. L.; Lelj, F.; Wolf, M. O.; Patrick, B.O. Dalton Trans. 2012, 41, 10150-10152. I am the primary author of this work and carried out all the experiments. All DFT calculations were performed by Professor Francesco Lelj. Dr. Brian Patrick collected the data and solved all the X-ray crystal structures.  A version of Chapter 3 has been published as a full paper: Howarth, A. J.; Patia, R.; Davies, D. L.; Lelj, F.; Wolf, M. O.; Singh, K. Eur. J. Inorg. Chem. 2014, In Press, Accepted Manuscript.  I am the primary author of this work and carried out all the experiments, except where noted. Raissa Patia from the University of Leicester grew the single crystals of complexes 57-59 and assigned the 1H and 13C NMR spectrum of 56-59.  All DFT calculations were performed by Professor Francesco Lelj. Kuldip Singh collected the data and solved all the X-ray crystal structures. iv   A version of Chapter 4 has been submitted for publication as a full paper: Howarth, A. J.; Davies, D. L.; Lelj, F.; Wolf, M. O.; Patrick, B. O. submitted.  I am the primary author of this work and carried out all the experiments. All DFT calculations were performed by Professor Francesco Lelj. Dr. Brian Patrick collected the data and solved all the X-ray crystal structures.    v  Table of Contents  Abstract ................................................................................................................................... ii Preface .................................................................................................................................... iii Table of Contents .....................................................................................................................v List of Tables .......................................................................................................................... ix List of Figures ........................................................................................................................ xi List of Symbols and Abbreviations .................................................................................... xvi List of Charts....................................................................................................................... xxii List of Equations ................................................................................................................ xxiii List of Schemes ................................................................................................................... xxiv Acknowledgements ..............................................................................................................xxv Dedication .......................................................................................................................... xxvii Chapter 1: Introduction ..........................................................................................................1 1.1 Overview................................................................................................................... 1 1.2 An Introduction to Photophysical Processes ............................................................ 1 1.2.1 Photophysics of Aromatic Hydrocarbons ............................................................. 3 1.2.2 Photophysics of Transition Metal Complexes ...................................................... 6 1.3 Cyclometallated Iridium Complexes ........................................................................ 8 1.3.1 Bis-cyclometallated Iridium Complexes ............................................................ 10 1.4 Pyrene and Pyrene-Containing Coordination Complexes ...................................... 11 1.4.1 Reversible Energy Transfer Involving a Pyrene-based 3LC State ...................... 13 1.4.2 3π-π* Emission from Pyrene ............................................................................... 17 vi  1.5 Overview of Microwave Synthesis ......................................................................... 19 1.6 Overview of Transient Absorption Spectroscopy .................................................. 22 1.7 Goals and Scope ..................................................................................................... 23 Chapter 2: Atropisomeric bis-cyclometallated Ir(III) complexes bearing pyridineimine ligands for applications in molecular switches ....................................................................25 2.1 Introduction............................................................................................................. 25 2.2 Experimental ........................................................................................................... 26 2.2.1 General ................................................................................................................ 26 2.1.1 Methods .............................................................................................................. 28 2.1.2 X-Ray Crystallography ....................................................................................... 35 2.2 Results and Discussion ........................................................................................... 38 2.2.1 Synthesis and Characterization ........................................................................... 38 2.2.2 Solid-State Molecular Structures ........................................................................ 45 2.2.3 Calculation of the Rotational Energy Barrier in Complex 37 ............................ 49 2.2.4 DFT Calculations following the Rotation in Complex 37 and 38 ...................... 51 2.2.5 Photophysical Properties of Complex 37 and 38 in Solution ............................. 53 2.3 Conclusions ............................................................................................................ 55 Chapter 3: Elucidating the origin of enhanced phosphorescence emission in the solid state (EPESS) in bis-cyclometallated Ir(III) complexes .....................................................57 3.1 Introduction............................................................................................................. 57 3.2 Experimental ........................................................................................................... 61 3.2.1 General ................................................................................................................ 61 3.2.2 Methods .............................................................................................................. 64 vii  3.2.3 X-Ray Crystallography ....................................................................................... 73 3.3 Results and Discussion ........................................................................................... 75 3.3.1 Synthesis and Characterization ........................................................................... 75 3.3.2 Solid-State Molecular Structures ........................................................................ 76 3.3.3 Photophysical Properties .................................................................................... 80 3.3.4 Effects of Restricted Rotation ............................................................................. 82 3.3.5 Effects of π-Stacking .......................................................................................... 84 3.3.6 DFT Calculations ................................................................................................ 86 3.4 Conclusions ............................................................................................................ 95 Chapter 4: Tuning the emission lifetimes of bis-cyclometallated Ir(III) complexes bearing pyridineimine and salicylimine ancillary ligands .................................................96 4.1 Introduction............................................................................................................. 96 4.2 Experimental ........................................................................................................... 99 4.2.1 General ................................................................................................................ 99 4.2.2 Methods ............................................................................................................ 101 4.2.3 X-ray Crystallography ...................................................................................... 104 4.3 Results and Discussion ......................................................................................... 106 4.3.1 Synthesis and Characterization ......................................................................... 106 4.3.2 Solid-State Molecular Structures ...................................................................... 107 4.3.3 Photophysical Properties .................................................................................. 108 4.3.4 DFT Calculations .............................................................................................. 121 4.4 Conclusions .......................................................................................................... 123 Chapter 5: Conclusions and future work ..........................................................................124 viii  5.1 Conclusions and Future Work .............................................................................. 124 References .............................................................................................................................128 Appendices ...........................................................................................................................144   ix  List of Tables  Table 1-1. Select photophysical properties of 1-4. ...................................................................5 Table 3-1. Select photophysical properties of 45, 46, 49 and 53-59.......................................84 Table 4-1. Photophysical properties of iridium complexes 37 and 62-65 in dichloromethane   and PMMA. ..................................................................................................................112 Table A1-1. Selected crystal structure data for NNHPyr (36) ...............................................144 Table A1-2. Selected bond lengths and angles for NNHPyr (36) ..........................................145 Table A1-3. Selected crystal structure data for [Ir(NNMePyr)(ppz)2][PF6] (37a) and               [Ir(NNMePyr)(ppz)2][PF6] (37b) ..................................................................................146 Table A1-4. Selected bond lengths and angles for [Ir(NNMePyr)(ppz)2][PF6] (37a) ............147 Table A1-5. Selected bond lengths and angles for [Ir(NNMePyr)(ppz)2][PF6] (37b)............148 Table A1-6. Selected crystal structure data for [Ir(NNMeNapht)(ppz)2][PF6] (42) ...............149 Table A1-7. Selected bond lengths and angles for [Ir(NNMeNapht)(ppz)2][PF6] (42a) ........150 Table A1-8. Selected bond lengths and angles for [Ir(NNMeNapht)(ppz)2][PF6] (42b) .......151 Table A1-9. Selected crystal structure data for Ir(ppz)2(NOiProp2Ph) (57) .........................152 Table A1-10. Selected bond lengths and angles for Ir(ppz)2(NOiProp2Ph) (57) ..................153 Table A1-11. Selected crystal structure data for Ir(ppy)2(NOiProp) (58) ............................154 Table A1-12. Selected bond lengths and angles for Ir(ppy)2(NOiProp) (58) .......................155 Table A1-13. Selected crystal structure data for Ir(ppy)2(NOiProp2Ph) (59) .......................156 Table A1-14. Selected bond lengths and angles for Ir(ppy)2(NOiProp2Ph) (59)..................157 Table A1-15. Selected crystal structure data for [Ir(NNMePyrMe)(ppz)2][PF6] (62). ...........158 Table A1-16. Selected bond lengths and angles for [Ir(NNMePyrMe)(ppz)2][PF6] (62). .....159 x  Table A1-17. Selected crystal structure data for Ir(NOPyr)(ppz)2 (63) ................................160 Table A1-18. Selected bond lengths and angles for Ir(NOPyr)(ppz)2 (63) ..........................161       xi  List of Figures  Figure 1-1. Jablonski energy diagram.......................................................................................2 Figure 1-2. Simplified molecular orbital diagram illustrating possible excited state transitions in a d6 metal complex in an octahedral environment with (a) strongly destabilized eg (M) and (b) small d-d splitting .................................................................6 Figure 1-3. Jablonski diagram for a bichromophoric system with 3MLCT and 3LC states of nearly the same energy. Dashed arrows to the ground state represent nonradiative decay pathways ..............................................................................................................14 Figure 2-1. 1H-NMR spectrum of the crude reaction product of 37a/b in CD3CN ................39 Figure 2-2. (a) 1H-NMR spectrum of 38 at room temperature in CD3CN and (b) 1H-NMR spectrum of 38 at -35°C in CD3CN.. ..............................................................................41 Figure 2-3. (a) 1H-NMR spectrum of 42 in CD3CN before attempts at separating individual atropisomers (1:1.1 ratio of 42a:42b) and (b) 1H-NMR spectrum of 42 in CD3CN after washing with methanol in an attempt to separate individual atropisomers (1:2 ratio of 42a:42b). ........................................................................................................................44 Figure 2-4. Solid state structure of NNHPyr (36). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms are omitted for clarity ......................................................45 Figure 2-5. Solid state structure of [Ir(NNMePyr)(ppz)2][PF6] (37a). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms, counterions and solvent molecules are omitted for clarity ...........................................................................................................46 xii  Figure 2-6. Solid state structure of [Ir(NNMePyr)(ppz)2][PF6] (37b). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms, counterions and solvent molecules are omitted for clarity ...........................................................................................................47 Figure 2-7. Solid state structure showing the major atropisomer of [Ir(NNMeNapht)(ppz)2][PF6] (42b). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and counterions are omitted for clarity ...............................................48 Figure 2-8. Solid state structure showing the minor atropisomer of [Ir(NNMeNapht)(ppz)2][PF6] (42a). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and counterions are omitted for clarity... ............................................48 Figure 2-9. Eyring plot for reaction kinetics of 37b→37a from 100°C - 140°C.. .................49 Figure 2-10. ln[1bt-1be] vs. time plots for 37b→37a from 100°C to 140°C.. ........................50 Figure 2-11. Reaction coordinate diagram showing ΔE vs. torsion angle (^C9-C6) for complexes 37 (---) and 38 (—). Transition state structures are shown for complex 37.  Experimental value shown in red. Top center inset: definition of ϕ... ..........................52 Figure 2-12. Reaction coordinate showing the Ir-N2 bond length vs. torsion angle (^C9-C6) for complexes 37 (---) and 38 (—) .................................................................................53 Figure 2-13. Ground state absorption spectrum of 37a, 37b and 38 ......................................54 Figure 2-14. Emission spectrum of 37b following photoirradiation at 294 nm. Inset: 1H-NMR spectrum showing the formation of an acetonitrile-bound complex at δ 2.77 .....55 Figure 3-1. Solid state structure of Ir(ppz)2(NOiProp2Ph) (57). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent molecules are omitted for clarity... .77 Figure 3-2. Solid state structure of Ir(ppy)2(NOiProp) (58). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent molecules are omitted for clarity.... ....78 xiii  Figure 3-3. Solid state structure of Ir(ppy)2(NOiProp2Ph) (59). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent molecules are omitted for clarity.... 79 Figure 3-4. Selected packing diagrams of 57-59 showing minimal evidence for π-stacking .80 Figure 3-5. Normalized absorption spectra of 45, 46, 49 and 53-59 ......................................81 Figure 3-6. Emission spectra of 56, 57 and 58 in dichloromethane purged with argon, λex = 400 nm ............................................................................................................................81 Figure 3-7. Solid state emission spectra of 45, 46, 49 and 53-59, λex = 400 nm.... ................82 Figure 3-8. Solid state emission spectra of 45, 46, 49 and 53-59 in PMMA, λex = 400 nm.... ...............................................................................................................................85 Figure 3-9. HOMO and LUMO pictures (ground state) of 45, 46, 49 and 53-59 ..................87 Figure 3-10. HSOMO-1 and HSOMO pictures (excited triplet state) of 45, 46, 49 and 53-59.... ................................................................................................................................88 Figure 3-11. Computed energy profile for the excited triplet state geometry of 53 relative to the half chair inversion of the six membered ring. The green plane is the equatorial plane and the red plane is the phenol imine ligand plane. Blue arrows show the transition vectors related to the interconversion between minima and are associated with the imaginary frequency of 23.72i cm-1 .................................................................90 Figure 3-12. Excited triplet state geometry of 45, 46, 49, and 54-59 showing ligand distortions. In each case the ‘tilted up’ version is shown. The green plane is the equatorial plane and the red plane is the phenol imine ligand plane..............................91 Figure 3-13. Excited triplet state geometry of 47-48 and 60-61 showing ligand distortions. The green plane is the equatorial plane and the red plane is the acac ligand plane .......93 xiv  Figure 3-14. (a) Ground state HOMO-LUMO pictures of 47-48 and 60-61 (b) Triplet state HSOMO-1 - HSOMO pictures of 47-48 and 60-61 .......................................................94 Figure 4-1. Solid state structure of [Ir(NNMePyrMe)(ppz)2][PF6] (62). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms, solvent and counterions are omitted for   clarity ............................................................................................................................107 Figure 4-2. Solid state structure of Ir(ppz)2(NOPyr) (63). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent are omitted for clarity ............................108 Figure 4-3: (a) Normalized absorption spectrum of 37 and 62-63 in dichloromethane (b) Normalized absorption spectrum of 64 and 65 in dichloromethane ............................109 Figure 4-4. (a) Emission spectrum and (b) transient absorption spectrum of 2 wt% of 37 in a PMMA film at time delays shown; λex = 355 nm .........................................................111 Figure 4-5. (a) Time resolved emission spectrum of 2 wt% of 37 in PMMA with intensity in arbitrary units. (b) Time resolved emission spectrum of 2 wt % of 37 in PMMA with normalized intensity .....................................................................................................111 Figure 4-6. (a) Emission spectra of 62 in dichloromethane in air and with argon and (b) emission spectrum of 2 wt% of 62 in a PMMA film ...................................................113 Figure 4-7: (a) Transient absorption spectrum of 62 in dichloromethane at time delays shown; λex = 355nm. (b) Transient absorption spectrum of 62 in PMMA at time delays shown; λex = 355nm ......................................................................................................114 Figure 4-8. Rise time following the growth of triplet pyrene in 62 in dichloromethane…...114 Figure 4-9. (a) Time resolved emission spectrum of 2 wt% of 62 in PMMA with intensity in arbitrary units. (b) Time resolved emission spectrum of 2 wt% of 62 in PMMA with normalized intensity .....................................................................................................116 xv  Figure 4-10. (a) Time resolved emission spectrum of 62 in dichloromethane with intensity in arbitrary units. (b) Time resolved emission spectrum of 62 in dichloromethane with normalized intensity .....................................................................................................117 Figure 4-11. (a) Time resolved emission spectrum of 64 in PMMA. (b) Time resolved emission spectrum of 65 in PMMA .............................................................................118 Figure 4-12.  (a) Ground state geometry of complex 63 and (b) Triplet state geometry of complex 63 showing ligand distortion .........................................................................120 Figure 4-13. (a) Emission spectrum and (b) transient absorption spectrum of 2 wt% of 63 in a PMMA film at a time delay of 18-90μs; λex = 355 nm ..............................................120 Figure 4-14. Natural transition orbitals representing the lowest lying triplet states T1 and T2 for complexes 37 and 62-65 computed from TD-DFT at the SDD09/D95(d)/M06/DCM level of theory...............................................................................................................122  xvi  List of Symbols and Abbreviations  1 singlet state 3 triplet state α fraction of pyrene-like triplets Δ crystal field splitting energy Δ difference or heat δ chemical shift ΔA absorbance difference ΔOD optical density difference θ angle of diffraction  λ wavelength λem wavelength of emission λex wavelength of excitation λmax wavelength at peak maximum μ X-ray linear absorption coefficient Σ the sum of σ standard deviation of the X-ray intensity τ lifetime τMLCT decay of MLCT state τPyr decay of pyrene state φ quantum yield φ X-ray rotation axis ω angle the X-ray source makes with the crystal xvii  acac acetylacetone ACQ aggregation caused quenching AIE aggregation induced emission bpy 2,2'-bipyridine br broad (NMR) C^N cyclometallating ligand COSY correlated spectroscopy CT charge transfer d doublet (NMR) DCM dichloromethane ddd doublet of doublets of doublets (NMR) dfppy 2-(2,4-difluorophenyl)pyridine dfppz 1-(2,4-difluorophenyl)pyrazole DFT density functional theory DMSO dimethyl sulfoxide EA elemental analysis EADFT theoretically calculated activation energy EAEXP experimentally calculated activation energy EPESS enhanced phosphorescence emission in the solid state ESI electrospray ionization EtOAc ethyl acetate  EtOH ethanol F2 X-ray scattering factor fac facial xviii  Fluor fluoranthene  HOMO highest occupied molecular orbital HR high resolution HSOMO highest singly occupied molecular orbital HSQC heteronuclear single quantum correlation IL intraligand ILCT intraligand charge transfer  iPrOH isopropanol  iProp isopropyl IR infrared IUPAC International Union of Pure and Applied Chemistry J indirect dipole-dipole coupling kb rate constant of back energy transfer keq equilibrium rate constant kf rate constant of forward energy transfer  kisc rate constant of intersystem crossing  kLC rate constant of decay from the ligand-centered state  kLM rate constant of energy transfer from the LC to the MLCT state  kML rate constant of energy transfer from the MLCT to the LC state  knr rate constant of non-radiative decay  kr rate constant of radiative decay L ligand L^X generic bidentate ligand LC ligand centered xix  LEEC light emitting electrochemical cell LLCT ligand-to-ligand charge transfer LMCT ligand-to-metal charge transfer  LUMO lowest unoccupied molecular orbital M metal m multiplet (NMR) MC metal centered Me methyl MeCN acetonitrile MeOH methanol mer meridional MLCT metal-to-ligand charge transfer MLLCT metal-ligand-to-ligand charge transfer MO molecular orbital MS mass spectrometry Napht naphthalene NLO non-linear optic NMR nuclear magnetic resonance NOE nuclear overhauser effect NOESY nuclear overhauser effect spectroscopy npz 1-(1-naphthalenyl)pyrazole OLED organic light emitting diode ORTEP Oak Ridge thermal ellipsoid plot Ph phenyl xx  PMMA poly (methyl methacrylate)  PMO periodic mesoporous organosilica ppy 2-phenylpyridine ppz 1-phenylpyrazole pyr pyrene q quartet (NMR) Rint linear regression goodness of fit RIR restricted intramolecular rotation s singlet (NMR) or second S0 ground state S1 first excited singlet state S2 second excited singlet state SBLCT sigma bond-to-ligand charge transfer sept septet (NMR) t triplet (NMR) T1 first excited triplet state T2 second excited triplet state td triplet of doublets (NMR) TD-DFT time-dependent density functional theory tfmppz 1-(4-(trifluoromethyl)phenyl)-1H-pyrazole Tg glass transition temperature TOCSY total correlation spectroscopy tpy 2-p-tolylpyridine trpy 2,2':6',2"-terpyridine xxi  TS transition state TV transition vector UDFT unrestricted density functional theory UV ultraviolet vis visible Z number of molecules in a crystallographic unit cell   xxii  List of Charts  Chart 1-1. ..................................................................................................................................4 Chart 1-2. ..................................................................................................................................6 Chart 1-3. ..................................................................................................................................9 Chart 1-4. ................................................................................................................................10 Chart 1-5. ................................................................................................................................15 Chart 1-6. ................................................................................................................................16 Chart 1-7. ................................................................................................................................18 Chart 1-8. ................................................................................................................................18 Chart 1-9. ................................................................................................................................19 Chart 1-10. ..............................................................................................................................20 Chart 3-1. ................................................................................................................................59 Chart 3-2. ................................................................................................................................60 Chart 3-3. ................................................................................................................................61 Chart 3-4. ................................................................................................................................92 Chart 4-1. ................................................................................................................................98       xxiii  List of Equations  Equation 4-1. ........................................................................................................................112 Equation 4-2. ........................................................................................................................112   xxiv  List of Schemes  Scheme 2-1. .............................................................................................................................38 Scheme 2-2. .............................................................................................................................42 Scheme 2-3. .............................................................................................................................43 Scheme 3-1. .............................................................................................................................76 Scheme 4-1. .............................................................................................................................99    xxv  Acknowledgements   First and foremost I would like to thank my supervisor Mike Wolf. I have learned so much in my time at UBC and I owe it all to you. Thank you for being incredibly supportive of everything I have done and for being the best mentor anyone could ask for. To my collaborator Dai Davies, I am very grateful for all of your help. Your passion for chemistry is contagious. To my collaborator Francesco Lelj, thank you for teaching me so much about computational chemistry and for always being available for a Skype chat when I needed help. Thank you to Chris Orvig for reading my thesis in a very short timeframe and making helpful suggestions and corrections throughout.  To all my colleagues over the years, Tim – for showing me how to run my first NMR at UBC and for teaching me to dance to east coast tunes; Matt – for patiently showing me how to pack my first column and being a great desk-mate; Angela – for teaching me things about lab safety that I never would have thought of and for the coffee maker that has gotten me through grad school; Steph – for patiently answering all of my questions and being a great crossword puzzle coach; Glen – for being a great team player, whether it be making a run to stores for the group or on the football field (and thanks for being a great dancer too…haha); Lyndsey – for being a great desk-mate, for telling it how it is, for organizing breakfast at Jethros (ladies only of course) and for being a great friend; Renee – for answering all my computer questions and introducing me to all the great food that Richmond has to offer.  To all my “junior” colleagues, thank you for making my last few years in the Wolf group just as enjoyable as my first. To Chris for always coming to my desk for a polite chat, Elise for always xxvi  being down for a competition and Janet for her incredibly positive attitude, crazy dreams and for never saying no to a beer.   Thank you to all the shops and services people at UBC. This thesis would not have been possible without you. Special thanks to Marshall for always being so friendly and making my trips to the mass spec lab so enjoyable.  Thanks to Angela and Tamara for being great mentors and for getting me involved in things outside of research. My involvement in the CGSS, Outreach activities, TA-ing Chem111/113 and Girl Guides was all thanks to you! Thanks for being great friends as well as great leaders.  A special thank you to Marek for teaching me so much about myself, chemistry and life. You made my time in Vancouver so enjoyable and I can’t wait for the adventures that lie ahead for us.  To my mom, thank you for being so supportive even though you didn’t appreciate the 3600km between us. I promise I’ll move closer to home soon. To my dad, thank you for kindling my interest in chemistry and for making me the person that I am today, I know you would be proud.   xxvii  Dedication          To my Mom and Dad1  Chapter 1: Introduction  1.1 Overview   Luminescent transition-metal complexes are of interest for their utility in diverse applications.1,2 The applicability of a complex in a specific role is dictated by its excited state properties which can be manipulated synthetically. Early work in this field focused primarily on [Ru(bpy)3]2+ and its derivatives, but the ability to colour tune the emission from these complexes is limited.3 Ir(III) complexes however, offer broader tuning capabilities and as a result have displaced Ru(II) complexes at the forefront of many photophysical and photochemical applications. Ir(III) complexes often show reversible electrochemical behavior, synthetic versatility and are chemically and thermally robust which makes them appealing for a number of different applications.4   Ir(III) complexes have been prepared for applications in organic light emitting diodes (OLEDS),5,6,7 light emitting electrochemical cells (LEECs),8,9 luminescence-based sensing,10 nonlinear optics (NLOs),11,12 photocatalysis13 and bioimaging.14,15 In this work, a series of new bis-cyclometallated Ir(III) complexes is presented, demonstrating that minor synthetic modifications can vastly change the structural and photophysical properties of these complexes, thereby changing their potential utility.  1.2 An Introduction to Photophysical Processes   A photophysical process is defined as the physical outcome resulting from the electronic excitation of a molecule or system of molecules by electromagnetic radiation 2  (photons). The basic photophysical processes that can occur in an isolated molecule include: (1) radiative excitation (absorption) where a molecule is excited from a lower to a higher electronic state by absorption of a photon; (2) radiative de-excitation (fluorescence or phosphorescence) where a molecule returns to the ground state by emission of a photon and; (3) radiationless transitions between isoenergetic vibrational levels of different electronic states (internal conversion and intersystem crossing).16 These photophysical processes can be illustrated with a classical Jablonski diagram (Figure 1-1) which was first illustrated by Aleksander Jablonski in 1933.17   Figure 1-1. Jablonski energy diagram with time scales. Adapted from Ref.18   Fluorescence is the emission of light resulting from spin-allowed transitions between states with the same multiplicity (ie. S1→S0) whereas phosphorescence is the emission of light 3  resulting from spin-forbidden transitions between states with different multiplicity (ie. T1→S0). In general, phosphorescence is only observed from organic molecules at low temperatures where non-radiative decay is minimized or with the presence of a heavy atom to induce spin-orbit coupling and enhance the probability of the spin-forbidden transition.16  Electronic transitions are very fast (as illustrated in Figure 1-1) and are most probable if the vibrational wave functions involved in the transition have similar nuclear geometries (as described by the Franck-Condon Principle).19 In many cases, rapid non-radiative processes efficiently dissipate the energy absorbed and molecules return to the ground state without the emission of light. Molecules with rigid structures however, have restricted vibrational motions and therefore decreased rates of non-radiative relaxation.20 This allows the slower radiative processes like fluorescence and phosphorescence to compete with the faster non-radiative processes. Rigid structures can result from extended π-conjugation or fixed coordination geometries which accounts for luminophores often containing π-conjugated or aromatic moieties.   1.2.1 Photophysics of Aromatic Hydrocarbons   According to IUPAC, an aromatic hydrocarbon or arene is a compound having a chemistry typified by benzene.21 More specifically, this refers to a cyclically conjugated molecular entity with a stability (due to delocalization) significantly greater than that of a hypothetical localized structure (e.g. Kekulé structure22). Chart 1-1 shows the aromatic hydrocarbons that are used as ligand substituents in this thesis.    4  Chart 1-1.    There have been several different nomenclatures based on the symmetry of orbitals, symmetry of states and intensity of absorptions that have been used to designate transitions between various molecular orbitals of aromatic hydrocarbons. These include the Clar,23 Platt24 and basic symmetry25 notation. Details of these notations are beyond the scope of this thesis and instead the important lowest singlet and triplet states are denoted S0, S1, S2, T1 and T2. Table 1-1 includes relevant photophysical properties of aromatic hydrocarbons 1-4.           5  Table 1-1. Select photophysical properties of 1-4. Data from Ref.16 Compound E1a (cm-1) τ1b (s) ϕ1c Eexcimer (cm-1) E3d (cm-1) τ3e (s) Benzene (1) 37000 2.9 x 10-8 0.058 31300 29500 16 Naphthalene (2) 32000 9.6 x 10-8 0.22 25550 21300 2.4 Fluoranthene (3) 25300 5.3 x 10-8 0.25 ----- 18550 0.85 Pyrene (4) 26500 4.5 x 10-7 0.65 21100 16900 0.50 a Energy of S1 corresponding to the 0,0 emission b Lifetime of S1 in cyclohexane c Emission quantum yield of S1 in cyclohexane d Energy of T1 corresponding to the 0,0 emission e Lifetime of T1   In general, the emission spectrum of aromatic hydrocarbons is concentration dependent. Strong monomer emission is observed in dilute solutions and becomes quenched as the molar concentration of the solution is increased. In some cases, such as benzene (1), naphthalene (2) and pyrene (4) for example, this concentration dependent quenching is accompanied by the appearance of broad, structureless excimer fluorescence occurring at lower energy than the corresponding monomer emission (Table 1-1).16 The term excimer was first introduced by Stevens and Hutton to describe an excited dimer which is associated in an electronic excited state and dissociated in the ground state.26  Most organic molecules that emit light at room temperature, including aromatic hydrocarbons 1-4, do so from excited singlet states. Incorporation of a second or third row transition metal ion (Ru(II) or Ir(III) for example) can induce intersystem crossing via spin-orbit coupling interactions which increases the probability of emission being observed from triplet excited states in coordination complexes compared to organic molecules.27 6  1.2.2 Photophysics of Transition Metal Complexes    To understand the photophysical processes that can occur in d6 transition metal complexes such as Ru(bpy)3Cl2 (5) or Ir(ppy)3 (6), it is helpful to consider a simplified molecular orbital diagram of the excited states (Figure 1-2).  Chart 1-2.    Figure 1-2. Simplified molecular orbital diagram illustrating possible excited state transitions in a d6 metal complex in an octahedral environment with (a) strongly destabilized eg (M) and (b) small d-d splitting. Adapted from Ref.28,29,30   7   In transition metal complexes such as 5 and 6, the octahedral crystal field of the ligands splits the five degenerate d-orbitals into a triply degenerate t2g level and a doubly degenerate eg* level. This splitting arises from the different spatial orientations of the d-orbitals in relationship to the ligands. The magnitude of the splitting (Δ) is determined by the crystal field strength of the ligands and the central metal ion.31 Altering the ligands, geometry and metal center can therefore have a significant effect on the luminescence properties observed. In a strong field configuration (ie. when Δ is large), it is energetically favourable to pair electrons in the t2g level according to Hund’s rule.32 Weak field systems are generally not favourable for luminescence and therefore, in the following discussion on luminescent transitions in d6 coordination complexes, only the strong field (low spin) systems are considered, where all six d electrons are paired and fill the t2g orbitals.   In the ground state of a low spin d6 coordination complex, all spins are paired which constitutes a singlet state (S0). The lowest excited states are derived from promoting one of these paired electrons to an unoccupied orbital. The classification of the resulting excited state is determined by the source and destination orbital.32 There are three types of excited states: metal centered (MC) states from a d-d transition, ligand centered (LC) states from a π-π* transition and charge transfer (CT) states from metal-ligand (ML), ligand-metal (LM) or ligand-ligand´ (LL´) transition.33 In all of these cases, the excited state can be either singlet or triplet in nature with the triplet state being lower in energy than the corresponding singlet state.   Charge transfer states (LM or ML) involve both the organic ligand and the metal and they arise from promoting an electron from a metal orbital to a ligand orbital (t2g5π*1 configuration) or from a ligand orbital to a metal orbital (π1eg*1). The former are called metal-to-ligand charge transfer (MLCT) states and the latter are called ligand-to-metal charge 8  transfer (LMCT) states. CT transitions are often more strongly allowed than d-d transitions which leads to shorter radiative lifetimes and makes CT transitions less susceptible to intramolecular or environmental quenching.32  The following criteria must be met for a metal complex to be luminescent:32 (i) the lowest excited state must be a CT state or ligand π-π* state to circumvent photochemical instability associated with the d-d excited states, (ii) the lowest d-d excited state must be high enough in energy to avoid thermal population from the emitting state, (iii) spin-orbit coupling should be high enough to increase the probability of emission and permit radiative decay to compete effectively with non-radiative decay, (iv) pure π-π* phosphorescence tends to be too long-lived for efficient emission to occur and therefore spin-orbit coupling or mixing with an allowed CT state must be used to increase the probability of π-π* phosphorescence, (v) the emitting state cannot be too low in energy due to the energy gap law which states that non-radiative decay becomes more efficient as the emitting state approaches the ground state.34  1.3 Cyclometallated Iridium Complexes   In 1985, Watts et al. reported the synthesis of fac-Ir(ppy)3 (6) which was the first tris-cyclometallated complex of ppy.35,36 This initial report led to a surge of research interest in the development of phosphorescent cyclometallated Ir(III) complexes. In 1999, Thompson, Forrest et al. demonstrated the first example of an organic light emitting diode (OLED) that incorporated fac-Ir(ppy)3 (6) as a phosphorescent dopant in the emitting layer.5     Ir(III) tris-complexes with asymmetric chelating ligands can adopt either a facial (fac) or meridional (mer) structure which have N,N-cis and N,N-trans configurations respectively. The kinetic product (mer) can be converted to the thermodynamic product (fac) both thermally 9  and photochemically. Thompson et al. reported the first selective synthesis of mer and fac tris-cyclometallated Ir(III) complexes (Chart 1-3) and described the pronounced differences in the photophysical and electrochemical behavior of the facial and meridional isomers. The major differences found in this study include (i) the meridional complexes have oxidation potentials approximately 50-100 mV less positive than the corresponding facial complexes (ii) the MLCT absorption bands are less sharply defined in the meridional isomers and have lower extinction coefficients than those in the facial isomers and (iii) the meridional isomers display broader, more red-shifted emission in comparison to the facial isomers.37   Chart 1-3. Adapted from Ref 37    The coexistence of mer and fac isomers is common in homoleptic, tris-cyclometallated Ir(III) complexes. In contrast, heteroleptic, bis-cyclometallated Ir(III) complexes are generally 10  free from isomeric contamination due to the strong preference of the N,N-trans configuration and conversion from the mer to fac isomer typically requires temperatures >200°C.29,37  1.3.1 Bis-cyclometallated Iridium Complexes   Substitution of one C^N cyclometallating ligand in 7/8 with either a bidentate L^X ancillary ligand or two monodentate L and L´ ligands gives rise to heteroleptic bis-cyclometallated iridium complexes. This section will focus on bis-cyclometallated Ir(III) complexes containing bidentate ancillary ligands [Ir(C^N)2(L^X)]n (15).   Chart 1-4.    The charges on Ir(III) complexes can be controlled by choosing a neutral, dianionic or monoanionic ancillary ligand (ie. N^N, C^C or O^O acetylacetonato-type ligand respectively).29 In 2001, Thompson et al. showed that emission from a series of bis-cyclometallated Ir(III) complexes containing acac ancillary ligands could be tuned from green to red by changing the nature of the cyclometallating ligand.38,39 Additional studies showed that the photophysical properties of Ir(III) complexes, and specifically the lowest excited state, could be tuned by altering the ancillary ligand.40 The two principle transitions that are observed 11  in the excited state of bis-cyclometallated iridium complexes are MLCT and LC in nature (see section 1.2.2). As a consequence of the strong spin-orbit coupling of the Ir(III) center, intersystem crossing can occur and facilitate the formation of an emissive, mixed triplet excited state which often contains both 3MLCT and 3LC character.41 Generally, the cyclometallating ligand is associated with the 3LC transition and the ancillary ligand with the 3MLCT transition. The highly mixed nature of the lowest triplet excited state allows for fine control when tailoring the emission properties of these complexes.4,42  The role of the ancillary ligand in tuning the emission in these complexes can be confirmed by electrochemical measurements. In complexes containing the same cyclometallating ligand, altering the ancillary ligand structure is shown to shift the oxidation potentials, whereas the reduction potentials remain relatively constant. Therefore, the ability to tune the emission by changing the ancillary ligand structure is caused by changes in the HOMO energy, while the LUMO energy is relatively unperturbed. 40,43     Fine tuning of the excitation pathway in bis-cyclometallated iridium complexes has garnered widespread interest and makes these complexes potentially useful in a variety of different applications (see section 1.1 for examples of specific applications).   1.4 Pyrene and Pyrene-Containing Coordination Complexes   Pyrene has become one of the most widely studied organic molecules in the field of photochemistry and photophysics. Its unique properties have inspired research in many scientific fields and as a result, pyrene has become the fluorophore of choice in both fundamental and applied photochemical research44. There have been numerous studies on the photophysical properties of pyrene, including its electronic spectrum and state 12  assignments,45,46,47 kinetic details of excimer formation,16,48 formation and kinetics of excited states,49,50 photoionization,51,52 delayed luminescence53 and the sensitivity of its excitation spectrum to environmental changes.54 Pyrene monomer emission typically occurs between 370-420 nm and is a characteristic violet colour. Pyrene is one of few polycyclic aromatic hydrocarbons that show vibronic structure in its monomer fluorescence spectrum in solution.54 The relative intensities of the vibronic bands in the emission spectrum are dictated by the relative positions of the potential energy surfaces of the excited singlet states relative to the ground state singlet and by the Franck-Condon principle.54 Like many fluorophores, pyrene fluorescence becomes quenched as the molar concentration of the solution is increased. This concentration dependent quenching is accompanied by the appearance of broad, structureless excimer fluorescence which typically occurs around 475 nm.16 The formation of a pyrene excimer requires the encounter of an electronically excited pyrene with a second pyrene in a ground electronic state. Consequently, the two pyrenes must be sufficiently far apart when light is absorbed, so that excitation is localized on only one of them. The observation of excimer emission therefore indicates that diffusive encounter between pyrenes has occurred.55 Pyrene phosphorescence is much less commonly observed than fluorescence, due to the spin forbidden nature of the triplet transition. Special conditions such as cooling to 77K in rigid media or the presence of a heavy atom to induce spin-orbit coupling are often required to observe pyrene phosphorescence.56   Coordination of pyrene-containing ligands to metal centers further expands upon the rich photophysics of pyrene. Because of the structural and electronic properties of the pyrene moiety, it can play many roles in coordination complexes and subsequent applications, broadly falling under three categories: (1) to act as an easily detectable fluorescent label or probe in 13  sensing;57,58,59 (2) to extend the emission or excited state lifetimes of coordination complexes through the triplet reservoir effect (section 1.4.1) or via 3IL emission (section 1.4.2) and; (3) to provide a readily observable π-stacking interface for structural purposes.60,61,62,63  1.4.1 Reversible Energy Transfer Involving a Pyrene-based 3LC State   It is not uncommon for complexes bearing ligands with low-lying triplet states to exhibit photophysical behavior arising from interactions of both triplet ligand centered (3LC) and 3MLCT states. In systems where electronic coupling between the peripheral ligand and metal center is significant, phosphorescence may appear with characteristics of neither pure 3LC or 3MLCT states. In systems with weak electronic coupling, the two components may interact through energy transfer.64,65 Generally, in complexes where 3MLCT and 3LC states are weakly interacting and are similar in energy, excitation energy can be disseminated between both states via reversible energy transfer. Aromatic hydrocarbon based LC states typically have a larger singlet-triplet energy gap than MLCT states. It is therefore possible to prepare complexes bearing ligands incorporating aromatic hydrocarbon moieties where excitation is allowed into both the 1MLCT state (in the visible regime) and the 1LC state (in the UV regime) separately, but where a small energy gap exists between the corresponding two triplet excited states. In this scenario, excitation into the visible 1MLCT transition will give intersystem crossing to the 3MLCT state. Relaxation of this state to the ground state will be governed by the magnitude of the rate constants for reversible energy transfer to the 3LC state (Figure 1-3). This energy transfer often leads to an extension of the 3MLCT state lifetime, and therefore, incorporating ligands with low-lying 3LC states like pyrene (3LCpyr), is one strategy for 14  extending the lifetime of charge-separated states. There have been several excellent review articles published that discuss this ‘triplet energy reservoir’ effect in detail.64,65,66  Figure 1-3. Jablonski diagram for a bichromophoric system with 3MLCT and 3LC states of nearly the same energy. Dashed arrows to the ground state represent nonradiative decay pathways. Adapted from Ref.64   The first example of a triplet reservoir observed through the equilibration of 3LC states and 3MLCT states was reported by Ford and Rodgers in a heteroleptic Ru2+ complex bearing a single 1,10-phenanthroline amide-linked pyrene ligand (16) where the rate of back energy transfer (kLM, Figure 1-3) between the 3LCpyr and 3MLCT states is 18-fold lower than the forward rate of transfer (kML, Figure 1-3). This arrangement results in an exceptionally long excited state lifetime of 11.2 μs in CH3OH.67 Examples of this behavior are found in heteroleptic complexes 17 and 18 which incorporate similar ligand motifs, homoleptic 15  complexes 19 and 20, as well as in the directly linked homoleptic complex 21. Complex 17 exhibits a long excited state lifetime (τ = 5.23 μs), while 18 exhibits a 60-fold lifetime enhancement over the pyrene-free parent complex.68,69,70,71,72,73 Interestingly, the triplet reservoir is preserved even when 17 is hosted in mesoporous organosilica (PMO) and a zeolite (NaY).69  Chart 1-5. Ref.67,68,69,70,71,72,73    Castellano et al. have reported light-harvesting complex 19, where irrespective of excitation wavelength, the complex exhibits emission arising from the [Ru(bpy)3]2+ moiety suggesting that the 1LC state localized on pyrene is quantitatively quenched by the MLCT state in this complex giving rise to sensitized MLCT-based emission.71 In addition, the equilibration of a 3LCpyr and 3MLCT state gives rise to an extended excited state lifetime of 9.0 μs. Analogous behavior was also observed by Castellano et al. in complex 21, where via this excited state equilibration, the emission lifetime was reported to be τ = 148 μs at room 16  temperature.72 It is clear that the directly bound nature of the pyrene chromophore in 21 enhances the triplet reservoir effect. This is further supported by a study from Campagna et al. on complex 20, where incorporating a longer saturated linker affords an emission lifetime of only 7.9 μs.73 The effect of the nature of the linkage is also evident in complexes 22 and 23 where the intramolecular energy transfer processes between two chromophores with varying separation distance was studied. For example, complex 23 has an extended conformation where the distance between chromophores is as long as 21 Å. However, equilibration between the 3MLCT and 3pyrene states results in a luminescence lifetime of τ ≈ 9 μs in both 22 and 23. This is attributed to the folding properties of the poly(ethylene glycol) linkage which influence the rates of forward (kML) and reverse (kLM) triplet-triplet equilibration such that through space energy transfer was allowed to proceed.74 In complex 24, despite the relative isolation of the Ru2+ center from the pyrene chromophore via the hemicage ligand, energy transfer is still observed to proceed, elongating the emission lifetime to 2.1 μs at room temperature.75  Chart 1-6. Ref.74,75     17  1.4.2 3π-π* Emission from Pyrene   There have been numerous studies on coordination complexes with excited state behaviour which is dictated by a triplet metal-to-ligand charge transfer (3MLCT) state. Emission from a 3π-π* state of a coordinating ligand is rare because these states typically lie much higher in energy than the corresponding 3MLCT states. Complexes can be designed, however, such that the 3π-π* state lies lower in energy than the 3MLCT state. In these instances, with the help of the internal heavy atom effect, 3π-π* emission can be observed. This concept has been demonstrated a few times using pyrene as the low-lying 3π-π* emitter. Castellano et al. reported a square planar, Pt(II) diimine bis(pyrenylacetylide) complex (25) that displays long-lived (48.5 μs) 3π-π* (3IL) pyrene-based emission at room temperature in solution.76 In this example, direct excitation into the MLCT excited state leads to the rapid formation of the triplet intraligand (3IL) state (τisc = 240 ± 40 fs). The formation of the 3IL state in 25 occurs significantly faster than intersystem crossing to the 3IL state in a model complex (26) which is lacking an MLCT excited state. This suggests that the presence of the MLCT state enables fast triplet sensitization.77 Room temperature pyrene 3π-π* emission is also observed in a related example, where the pyrene group is separated from the acetylide linker via a fluorene bridge (27).78    18  Chart 1-7. Ref.76,77,78  McMillin et al. studied a series of Pt(trpy)Ph+ complexes (trpy = 2,2':6',2''- terpyridine) with electron-rich groups at the 4' position of the trpy ligand.79 In general, Pt(trpy)Ph+ complexes are not emissive in solution due to non-radiative decay from a sigma-bond-to-ligand charge transfer (3SBLCT) state. Electron-rich groups on the 4' position of the trpy ligand alter the lowest-lying excited state in these complexes and promote emission by introducing intraligand charge-transfer (ILCT) character. Attaching pyrene at the 4' position (28) had the most significant effect on the orbital parentage of the emitting state. Unlike the other complexes in the series, 28 did not give rise to ILCT character, but instead the emission spectrum was dominated by pyrene 3π-π* emission with a lifetime of 45 μs.   Chart 1-8. Ref.79  19    Ziessel et al. synthesized a series of Ru(II) complexes with bipyridine and terpyridine ligands containing multiple acetylide bridged pyrene moieties (29-33).80 In all cases the emission spectrum is dominated by pyrene 3π-π* emission at room temperature in solution. In contrast, replacing the pyrene moieties with toluene groups yields 3MLCT emission from Ru-bpy or Ru-trpy excited states.   Chart 1-9. Ref.80  1.5 Overview of Microwave Synthesis   The first examples of cyclometallated Ir(III) complexes and dichloro-bridged dimers (34) prepared using microwave irradiation were reported by Konno et al. in 2003.81 In 2011, 20  Davies et al. reported an optimized procedure for the dichloro-bridged Ir(III) dimers as well as the synthesis of heteroleptic complexes [Ir(C^N)2(bpy)][PF6] using microwave irradiation.82  Chart 1-10.     The microwave region of the electromagnetic spectrum corresponds to wavelengths of 1 cm to 1 m (30 GHz to 300 MHz). Commercially available microwave systems for domestic and chemical purposes generally operate at 2.45 GHz (12.2 cm) to avoid interference with radar and telecommunications.83,84   In 1986, Gedye85 and Majetich86 and their coworkers showed that a range of organic reactions could be accelerated by using microwave dielectric heating. There are now over 2000 papers describing the application of microwave irradiation in organic,85,86 and organometallic87,88 chemistry. The use of microwave chemistry raised many questions and speculations concerning the mechanism by which chemical reactions were accelerated. Before the scientific fundamentals of microwave-accelerated chemical reactions could be understood however, it was necessary to solve the technical problems associated with containment of flammable organic liquids, often under pressurized conditions, which required the 21  development of accurate and reliable temperature measurements.89 The introduction of specially designed microwave equipment in the 1990s countered these problems and the application of microwaves in synthesis has increased dramatically since this time.90    Today, it is widely accepted that the major reason for the observed rate enhancements of chemical reactions under microwave irradiation is a result of a thermal/kinetic effect. This is a consequence of the high reaction temperatures that can rapidly be achieved when irradiating polar materials in a microwave field.90 This phenomenon is known as microwave dielectric heating and it relies on the ability of a solvent or reagent to absorb microwave energy and convert it to heat. Microwave irradiation causes heating by two main mechanisms: dipolar polarization and ionic conduction. Irradiation of a sample with microwaves causes the dipoles in a material to align in the applied electric field. As this applied field oscillates, the dipoles attempt to realign with the alternating electric field and energy is lost in the form of heat. The amount of heat generated is related to the ability of the dipole field to align itself with the applied field. If the dipole field does not have enough time to realign or it realigns too quickly, then no heating occurs. The frequency of 2.45 GHz used most commonly in commercial systems gives the molecular dipole sufficient time to align in the field.84,90,91 Traditional syntheses are carried out by conductive heating which is most commonly achieved with a hot plate and oil bath. This is an inefficient method of heating as it depends on the thermal conductivity of the various materials that must be penetrated. Conductive heating results in the temperature of the reaction vessel being higher than that of the reaction mixture whereas microwave irradiation achieves efficient internal heating by direct coupling of microwave energy with the materials that are present in the reaction mixture. The reaction vessels used in microwave chemistry are typically made out of microwave-transparent materials (ie. 22  borosilicate glass, quartz, or Teflon) and therefore an inverted temperature gradient results compared to conventional thermal heating.90   All of the dichloro-bridged Ir(III) dimers as well as the bis-cyclometallated Ir(III) complexes studied in this thesis were prepared using microwave irradiation. These synthesis were used because they give high yields in short reaction times.  1.6 Overview of Transient Absorption Spectroscopy   Transient absorption spectroscopy is used in this work to elucidate the origin of the lowest lying triplet excited state in a series of bis-cyclometallated Ir(III) complexes (Chapter 4). This also gives insight into the lifetime of these triplet excited states as well as the time it takes to populate these states.  Transient absorption spectroscopy was developed by Porter and Norrish in 194992 for which they won the Nobel Prize in 1967. It has since become an essential tool for investigating the mechanism and dynamics of photoinduced processes.   Transient absorption spectroscopy is a pump-probe technique. The ‘pump’ or excitation pulse promotes a fraction of the molecules in a sample to an electronically excited state while the ‘probe’ is a low intensity pulse that is sent through the sample with a delay time τ with respect to the pump pulse. This pump-probe sequence allows for a difference absorption spectrum to be calculated. The difference in absorption (ΔA or ΔOD) is given by the absorption spectrum of the sample in the excited state minus the absorption spectrum of the sample in the ground state. By changing the time delay τ or by use of a streak camera (see section 4.2.1 for details) a difference absorption spectrum as a function of τ and wavelength λ can be obtained. This spectrum can offer insight into the origin of the excited states in a sample as well as 23  information on dynamic processes like electron migration, energy transfer and photochemical reactions.93   In general, a difference absorption spectrum is comprised of contributions from: (i) ground-state bleaching, which appears as a negative signal, and is a consequence of the ground-state absorption being lower in the excited sample than it is in the non-excited sample (ii) stimulated emission which occurs when a photon from the probe pulse induces emission of a photon from the excited sample (iii) excited-state absorptions where transitions from the excited states of a chromophore to excited states that are higher in energy are observed and (iv) product absorptions from a photoinduced reaction that may result in a long-lived molecular state, for example triplet states or charge-separated states.93 The extinction coefficients of the species involved in these processes will determine if the difference spectrum contains a net bleach (negative signal) or net absorption (positive signal).94   In the study of fast (seconds) to ultrafast (femtosecond or even attosecond) processes like excitation, isomerization, internal conversion, intersystem crossing, electron/energy transfer, excimer formation, fluorescence and phosphorescence, transient absorption has proved to be an invaluable tool.   1.7 Goals and Scope   The primary goal of this thesis is the synthesis and characterization of novel bis-cyclometallated Ir(III) complexes with both pyridineimine and salicylimine ancillary ligands.   Chapter 2 discusses the synthesis of Ir(III) complexes incorporating pyridineketimine and pyridinealdimine ancillary ligands containing bulky ligand substituents. The role of the 24  steric bulk of the ancillary ligand substituent as well as the role of the aldimine vs. ketimine ancillary ligand backbone in generating atropisomeric Ir(III) complexes is explored.    Chapter 3 discusses the synthesis of Ir(III) complexes incorporating salicylimine ancillary ligands with variations in the steric bulk of the ligand substituents. The role of the steric bulk of the ancillary ligand substituent as well as the role of solid state interactions in the photophysical properties of these complexes is explored.   Chapter 4 discusses the synthesis of Ir(III) complexes incorporating both pyridineketimine and salicylimine ancillary ligands containing pyrenyl ligand substituents. The role of pyrene as well as the role of the salicylimine vs. pyridineketimine ligand backbone in the photophysical properties of these complexes is explored.  In general, this thesis looks at how the structural and photophysical properties in bis-cyclometallated Ir(III) complexes are affected by minor synthetic modifications to ancillary ligand frameworks.   25  Chapter 2: Atropisomeric bis-cyclometallated Ir(III) complexes bearing pyridineimine ligands for applications in molecular switches    2.1  Introduction   Molecular switches in which internal rotary motions result in conversion between enantiomers95,96 or diastereomers can be used to drive switching between states in liquid crystals,97,98,99 non-destructive optically readable switches for molecular electronics100,101 and may be used as components of molecular motors.102,103,104  Restricted cis/trans, syn/anti or meso/rac atropisomerization is often a key functional feature of organic molecular switches.105,106,107 A weakness of organic atropisomeric systems is that the atropisomers are often unstable and difficult to separate and purify.108 Metal complexes offer several features of interest for molecular switches, in that ligand exchange allows for the development of modular systems and coordination numbers >4 allow for the construction of more complex architectures relative to organic systems.  Metal based molecular switches involving linkage isomerism have been studied, for example systems based on conversion of O to S- bound sulfoxides.109  An alternate approach involves restricted rotation about an axis external to a coordinated ligand, rather than between two donor atoms in a chelate ring. In this case the metal coordination sphere presents a scaffold, allowing a sterically-confined pocket to be constructed in which a ligand can reside in two or more orientations.  If rotation between the orientations is restricted, stable atropisomers can result. This approach offers the possibility of interconversion between atropisomers, which 26  may be induced chemically, thermally, photochemically or electrochemically.110,111,112 Currently, there are very few examples of this type; these involve diimine113,114 or bisiminopyridine115,116,117 ligands with di-orthosubstituted phenyl susbtituents on the imine N atom. The most well characterized examples are bisiminopyridine complexes of FeX2 which can exist as syn or anti rotamers.116 In this chapter a bidentate pyridineimine ligand combined with a chiral metal coordination sphere leading to the synthesis and facile separation of stable diastereomeric atropisomers of a thermally-switchable cyclometallated iridium complex is discussed. In contrast to previous examples, both atropisomers have been crystallographically characterized and a full investigation of their thermal interconversion is discussed.  2.2 Experimental  2.2.1 General   All experiments were performed under an inert nitrogen atmosphere, using standard Schlenk-line techniques. Toluene was dried over activated alumina with a copper catalyst. All other solvents and reagents were obtained from commercial sources and used as received. Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc. Chloro(1-phenylpyrazole)iridium(III) dimer [IrCl(ppz)2]2,82 1-nitropyrene,118 and 1-aminopyrene119 were prepared according to literature procedures. 1H NMR and 13C NMR spectra were obtained using a Bruker AV-300 or AV-400 spectrometer and referenced to the residual protonated solvent peak. Electrospray ionization mass spectrometry data were obtained on a Bruker Esquire LC ion trap mass spectrometer. Microwave reactions were performed on a Biotage Initiator 2.5 microwave synthesizer. Absorption spectroscopy data were obtained on 27  a Varian Cary 5000 UV-vis-near-IR spectrophotometer. Fluorescence spectroscopy data were collected on a Photon Technology International QuantaMaster fluorimeter. Photoirradiation was performed using a Rayonet photochemical reactor containing three G8T5 Germicidal UV fluorescent bulbs with emission at 254 nm.  DFT computations were performed by Professor Francesco Lelj and applied by using the meta-hybrid xc functional known as M06120 as implemented in the Gaussian09 suite of programs.121 Geometry optimizations were performed using the Dunning/Huzinaga double-ζ (D95) basis sets,122 with additional polarization functions for C and N atoms. The most recent Stuttgart/Dresden ECP basis set including the f polarization function was used for Ir, taking into account relativistic effects.123 Default gradient and displacement thresholds were used for the geometry optimization convergence criteria. The dichloromethane (DCM) solvent environment was modeled according to the IEPCM124 model. To confirm that the obtained geometries are relative minima or transition states (TS), analytical computation of the Hessian matrix with respect to the nuclear coordinates at the same level of theory was performed. The program GaussView 5.0.8 125 was used to draw chemical structures and generate movies of the normal mode of vibration corresponding to the transition vector (TV), i.e. the normal mode associated with the imaginary frequency.      28  2.1.1 Methods  NNMePyr (35)  2-Acetylpyridine (0.026 mL, 0.23 mmol) and 2 drops of formic acid catalyst were added to a solution of 1-aminopyrene (0.100 g, 0.460 mmol) in 5 mL of degassed benzene. The yellow-brown solution was heated to reflux under nitrogen for 18 hours and then allowed to cool to room temperature. Benzene was removed in vacuo to give a red-yellow oil. The product was recrystallized from hot hexanes to yield yellow crystals (0.042 g, yield 57%). 1H NMR (CDCl3, 400 MHz): δ 8.67 (1H, d, J = 4.8, H4), 8.19 (1H, d, J = 7.5, H9), 8.13 (1H, d, J = 7.5, H1), 8.07-7.82 (7H, m, H10,15,19,20,21,22,23), 7.78 (1H, td, H3), 7.44-7.41 (2H, m, H2,14), 2.75 (3H, s, H7).13C NMR (CD3CN, 100 MHz): 169.2 (C4), 157.0 (C3), 147.7-140.1 (C10,15,19,20,21,22,23), 147.3 (C2), 147.1 (C1), 144.7 (C9), 133.5 (C14), 45.1 (C7). HR ESI-MS: Calcd for C23H17N2: 321.1392; Found: 321.1392 [M+H]+.  NNHPyr (36)  2-Pyridinecarboxaldehyde (0.088 mL, 0.92 mmol) was added to a solution of 1-aminopyrene (0.200 g, 0.921 mmol) in 20 mL of toluene. The yellow solution was heated to reflux under nitrogen for 18 hours and then allowed to cool to room temperature. The solution was dried over MgSO4. Toluene was removed in vacuo to give an orange-yellow oil. The product was recrystallized from hot hexanes to yield orange needle crystals (0.244 g, yield 86%). 1H NMR (CDCl3, 300 MHz, hydrogen numbering is the same as in the X-ray structure): δ 8.91 (1H, s, 29  H6), 8.81-8.78 (1H, m, H4), 8.74 (1H, d, J = 9.5, H9), 8.54 (1H, d, J = 8.0, H1), 8.24-8.00 (7H, H10,15,19,20,21,22,23), 7.94 (1H, td, J = 7.5, 7.5, 1.5, H3), 7.86 (1H, d, J = 8.0, H14), 7.45 (1H, ddd, J = 7.5, 5.0, 1.5, H2).13C NMR (CD3CN, 100 MHz): 150.4 (C4), 137.0 (C3), 127.6-125.2 (C10,15,19,20,21,22,23), 125.5 (C2), 123.3 (C9), 122.1 (C1), 115.3 (C14), 110.8 (C6). HR ESI-MS: Calcd for C22H15N2: 307.1235; Found: 307.1230 [M+H]+.  [Ir(NNMePyr)(ppz)2][PF6] (37)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), 2-acetylpyridine (0.017 mL, 0.15 mmol), 1-aminopyrene (0.0326 g, 0.150 mmol) and potassium hexafluorophosphate (0.025 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in a microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting deep red solution was passed through a Celite pad and the filtrate reduced in volume.  Layering with hexanes yielded the desired product as a mixture of diasteromers. The mixture was purified by column chromatography using MeCN to elute any unreacted 1-aminopyrene and then MeCN:H2O:KNO3(aq) (96:3:1) to elute the diastereomers (0.041 g, yield 76%). Diastereomer 37a was separated by precipitation from methanol. 37a and 37b were each dissolved in DCM and layered with hexanes to yield red crystals suitable for X-ray crystallographic analysis.  37a: 1H NMR (CD3CN, 400MHz, hydrogen numbering is the same as in the X-ray structure): δ 8.45 (1H, d, J = 8.0, H4), 8.41 (1H, d, J = 3.0, H35), 8.27 (1H, d, J = 7.0, H3), 8.24-8.23 (1H, m, H9), 8.17 (1H, d, J = 8.0, 30  H21), 8.13 (1H, d, J = 2.5, H33), 8.06-8.05 (1H, m, H1), 7.76 (1H, d, J = 3.0, H26), 7.70-7.68 (1H, m, H2), 7.65 (1H, d, J = 9.5, H15), 8.18-7.64 (5H, m, H10,19,20,22,23),7.45 (1H, d, J = 7.5, H37), 7.40 (1H, d, J = 2.5, H24), 7.03-7.01 (1H, m, H38), 6.82-6.80 (1H, m, H39), 6.78 (1H, s, H34), 6.72 (1H, t, J = 2.5, H25), 6.65 (1H, d, J = 9.5, H14), 6.24-6.22 (1H, m, H30), 6.19-6.17 (1H, m, H28), 6.15-6.13 (1H, m, H40), 6.12-6.10 (1H, m, H29), 5.92-5.90 (1H, m, H31), 2.54 (3H, s, H7abc). 13C NMR (CD3CN, 100 MHz): 153.0 (C3), 141.6 (C33), 140.9 (C9), 140.5 (C24), 134.5 (C31), 133.9 (C40), 131.4 (C2), 130.7 (C4), 129.9 (C35), 129.3-127.9 (overlap 4 × CPyr), 128.9 (C15), 128.7 (CPyr), 127.8 (C39), 126.6 (C21), 126.2 (C30), 126.0 (CPyr), 124.5 (C38), 122.8 (C29), 121.4 (C26), 121.0 (C14), 113.5 (C37), 111.0 (C28), 109.8 (C34), 109.3 (C25), 19.2 (C7). HR ESI MS: Calcd for C41H30IrN6: 797.2138; Found: 797.2152 [M]+. 37b: 1H NMR (CD3CN, 400MHz): δ 8.46 (1H, d, J = 8.0, H4), 8.40 (1H, d, J = 2.5, H26), 8.34 (1H, dd, J = 9.5, 3.0, H35), 8.30-8.28 (1H, m, H3), 8.26-8.23 (1H, m, H1), 8.15-8.13 (1H, m, H14), 8.09-8.08 (1H, m, H33), 7.93 (1H, d, J = 9.0, H15), 7.72-7.69 (1H, m, H10), 7.66-7.64 (1H, m, H2), 8.30-7.59 (5H, m, H19,20,21,22,23),7.41 (1H, d, J = 8.0, H37), 7.35-7.34 (1H, m, H24),  7.02-6.99 (1H, m, H38), 6.94-6.91 (1H, m, H28), 6.82 (1H, m, H25), 6.79-6.77 (1H, m, H39), 6.69 (1H, d, J = 1.0, H34), 6.23 (1H, td, J = 7.5, 1.5, H29), 6.11 (1H, d, J = 7.5, H40), 6.04 (1H, d, J = 7.0, H9), 5.73 (1H, t, J = 8.0, H30), 5.52 (1H, d, J = 7.5, H31), 2.60 (3H, s, H7abc). 13C NMR (CD3CN, 100 MHz): 153.4 (C14), 143.2 (overlap 4 × CPyr), 140.9 (C24), 140.7 (C3), 134.3 (C9), 133.7 (C40), 133.2 (C31), 132.6 (CPyr), 131.2 (C2), 131.0 (C4), 130.3 (C26), 130.1 (C33), 129.7 (C10), 128.9 (C35), 128.0 (C15), 127.8 (C25), 127.2 (C1), 126.8 (C39), 126.0 (C30), 124.7 (C38), 124.5 (C28), 123.3 (C29), 113.5 (C37), 109.1 (C34), 19.7 (C7). HR ESI-MS: Calcd for C41H30IrN6: 797.2138; Found: 797.2134 [M]+.  31  [Ir(NNHPyr)(ppz)2][PF6] (38)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), 2-pyridinecarboxaldehyde (0.014 mL, 0.15 mmol), 1-aminopyrene (0.0326 g, 0.150 mmol) and potassium hexafluorophosphate (0.025 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in a microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting deep red solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a dark orange precipitate. The product was purified by column chromatography using MeCN to elute any unreacted 1-aminopyrene and then MeCN:H2O:KNO3(aq) (96:3:1) to elute complex 38 (0.021 g, yield 40%). 1H NMR (CD3CN, 400 MHz): δ 9.42 (1H, s, H6), 8.43 (1H, d, J = 3.0, H35), 8.39 (1H, d, J = 8.0, H4), 8.26 (1H, t, J = 7.5, H3), 8.21 (1H, d, J = 8.0, H1), 8.28-8.01 (8H, m, H9,10,19,20,21,22,23,33), 7.90 (1H, s br., H26), 7.77 (1H, s br., H15), 7.70-7.66 (1H, m, H2), 7.47 (1H, d, J = 8.0, H24), 7.45 (1H, s br., H37), 7.08-7.03 (1H, m, H38),  6.92 (1H, s br., H14), 6.86 (1H, t, J = 7.5, 7.5, H39), 6.77 (1H, s, H34), 6.74 (1H, s, H25), 6.54 (1H, s br., H28), 6.32 (2H, s br., H29,30), 6.22 (1H, d, J = 7.5, H40), 6.01 (1H, s br., H31). 13C NMR (CD3CN, 100 MHz): 152.1 (CPyr), 140.6 (CPyr), 140.2 (C1), 139.8 (C37), 133.3 (C31), 132.7 (C40), 131.3 (C4), 130.5 (C2), 130.3 (C15), 128.5 (C35), 128.4 (C33), 127.4-136.9 (overlap 4 × CPyr), 126.6 (C39), 125.7 (C30), 125.5 (CPyr), 124.4 (C26), 123.9 (C38), 123.3 (C6), 122.3 (C29), 111.9 (C24), 110.7 (C28), 109.0 32  (C25), 108.5 (C34), 108.1 (C14). HR ESI-MS: Calcd for C40H28IrN6: 783.1981; Found: 783.1975 [M]+.  1-(1- Naphthalenyl)-1H-pyrazole (39)   39 was made using modified literature procedures126 where pyrazole (0.61 g, 9.0 mmol), copper(I) oxide (0.087 g, 0.60 mmol), KOH (0.69 g, 12 mmol) and 1-iodonaphthalene (1.52 g, 6.00 mmol) were suspended in DMSO in a round-bottom flask. The suspension was heated to reflux for 14 hours and upon heating a red-brown solution was obtained. The solution was filtered through silica on a fine frit and dichloromethane was used to elute the product from the silica layer. The red-brown filtrate was reduced in volume via rotary evaporation and the final product was obtained via column chromatography using 1:1 DCM:Hexane followed by 3:2 Hexane:EtOAc (0.47 g, yield 41%). 1H NMR resonances match those reported in literature. 1H NMR (CDCl3, 400 MHz): δ 7.91 - 7.98 (2H, m), 7.85 - 7.89 (1H, m), 7.78 - 7.85 (2H, m), 7.51 - 7.60 (4H, m), 6.53 - 6.59 (1H, m).   [IrCl(npz)2]2 (40)   IrCl3·3H2O (0.172 g, 0.575 mmol) and 39 (0.335 g, 1.73 mmol) were added to a microwave vial with 4.5 mL of 2:1 2-propanol:water. The vial was placed in a microwave reactor and heated under microwave irradiation for 90 min at 110 °C (1bar, 235W).  The yellow-green precipitate was filtered through a medium frit and washed with hexanes (0.28 g, yield 40%). The resulting dimer 40 was used without further purification. 1H NMR (CD3CN, 400 MHz): δ 8.93 (1H, d, J = 3.05), 8.33 (1H, d, J = 8.83), 8.09 (1H, d, J = 2.13), 7.62 (1H, d, 33  J = 7.92 Hz), 7.42 - 7.56 (1H, m), 7.24 (1H, t, J = 7.31), 6.99 (1H, d, J = 8.53), 6.88 (1H, t,  J = 2.44),  5.99 (1H, d, J = 8.22). MS: 1193.4 [M-Cl]+  [Ir(NNMePyr)(npz)2][PF6] (41)   [IrCl(npz)2]2 (0.070 g, 0.057 mmol), 2-acetylpyridine (0.014 mL, 0.13 mmol), 1-aminopyrene (0.027 g, 0.13 mmol) and potassium hexafluorophosphate (0.021 g, 0.12 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in a microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting red-brown solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a dark orange precipitate. The product was purified by column chromatography using MeCN to elute any unreacted 1-aminopyrene and then MeCN:H2O:KNO3(aq) (96:3:1) to elute complex 41 as a mixture of diasteromers (0.054 g, yield 46%). 1:1.1 mixture of diastereomeric atropisomers, integrations have been rounded down to the nearest whole number. 1H NMR (CD3CN, 400 MHz): δ 9.08 (1H, d, J = 3.05), 9.00 (1H, d, J = 2.74), 8.88 (1H, d, J = 2.74), 8.34 - 8.54 (4H, m), 8.01 - 8.29 (13H, m), 7.66 - 7.85 (7H, m), 7.49 - 7.66 (10H, m), 7.17 - 7.44 (8H, m), 7.05 (1H, s), 6.88 - 7.01 (3H, m), 6.67 - 6.87 (6H, m), 6.50 (1H, d, J = 9.14), 6.34 (1H, d, J = 7.31), 6.14 - 6.27 (3H, m), 6.04 - 6.07 (1H, m), 5.84 (1H, d, J = 7.92), 2.69 (3H, s), 2.64 (3H, s). HR ESI-MS: Calcd for C49H34IrN6: 897.2451; Found: 897.2451 [M]+.   34  [Ir(NNMeNapht)(ppz)2][PF6] (42)   [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), 2-acetylpyridine (0.017 mL, 0.15 mmol), 1-naphthylamine (0.021 g, 0.15 mmol) and potassium hexafluorophosphate (0.025 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in a microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting red solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a dark orange precipitate. The product was purified by column chromatography using MeCN to elute any unreacted 1-aminopyrene and then MeCN:H2O:KNO3(aq) (96:3:1) to elute complex 42 as a mixture of diasteromers (0.050 g, yield 43%). 1:1.1 mixture of diastereomeric atropisomers, integrations have been rounded down to the nearest whole number. 1H NMR (CD3CN, 400 MHz): δ 8.36 - 8.44 (3H, m), 8.33 (2H, d, J = 2.74), 8.18 - 8.27 (3H, m), 8.08 (1H, d, J = 5.18), 7.78 (1H, d, J = 8.53), 7.96 (1H, d, J = 1.83), 7.51 (3H, t, J = 7.61),  7.98 (1H, d, J = 1.83), 7.91 (1H, d, J = 8.22), 7.83 (1H, d, J = 2.74), 7.56 - 7.71 (4H, m), 7.38 - 7.45 (2H, m), 7.35 (1H, t, J = 7.46), 7.26 - 7.32 (3H, m), 7.19 (1H, d, J = 7.31), 6.92 - 7.08 (5H, m), 6.74 - 6.84 (3H, m), 6.69 - 6.74 (1H, m), 6.61 - 6.68 (2H, m), 6.47 - 6.57 (2H, m), 6.38 - 6.45 (2H, m), 6.34 (1H, t, J = 7.46 Hz), 6.01 - 6.14 (3H, m), 5.85 (1H, d, J = 7.61), 5.53 (1H, d, J = 7.61), 5.45 (1H, d, J = 7.61), 2.54 (3H, s), 2.51 (3H, s). HR ESI-MS: Calcd for C35H28IrN6: 723.1981; Found: 723.1982 [M]+.    35  2.1.2 X-Ray Crystallography   All crystals were mounted on a glass fiber. The crystal structure data were obtained and the structures were solved by Dr. Brian Patrick. All measurements were made using a Bruker X8 Apex II CCD diffractometer with graphite monochromated Mo-Kα radiation. Data were collected and integrated using the Bruker SAINT127 software package. Data were corrected for absorption effects using the multi-scan technique (SADABS128). The data were corrected for Lorentz and polarization effects. The structures were solved by direct methods.129   NNHPyr (36)   An orange needle crystal of C22H14N2 having approximate dimensions of 0.02 x 0.02 x 0.20 mm was used. The data were collected at a temperature of -183.0 + 0.1°C to a maximum 2θ value of 132.4°. Data were collected in a series of ϕ and ω scans in 1.0° oscillations using 30.0-second exposures. The crystal-to-detector distance was 40.00 mm. Of the 9525 reflections that were collected, 3853 were unique (Rint = 0.030; Friedels not merged) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.837 and 0.988, respectively. The material crystallizes with two crystallographically independent molecules in the asymmetric unit. The final cycle of full-matrix least-squares refinement on F2 was based on 3853 reflections and 434 variable parameters and converged.  [Ir(NNMePyr)(ppz)2][PF6] (37a)   An orange tablet crystal of [C41H30N6Ir][PF6]·CH2Cl2 having approximate dimensions of 0.16 x 0.25 x 0.60 mm was used. The data were collected at a temperature of -173.0 + 0.1°C 36  to a maximum 2θ value of 55.9°. Data were collected in a series of ϕ and ω scans in 0.50° oscillations with 7.0-second exposures. The crystal-to-detector distance was 39.87 mm. Of the 53222 reflections that were collected, 9224 were unique (Rint = 0.045) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.445 and 0.554 respectively. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions. The material crystallizes with one disordered molecule of CH2Cl2 in the lattice. This solvent molecule is disordered over three sites and the final occupancies were refined such that the sum of all three fragments was 1.0.  Additionally the fluorine atoms of the PF6 ˉ anion are disordered and were modeled in two orientations. The final cycle of full-matrix least-squares refinement on F2 was based on 9224 reflections and 564 variable parameters and converged.  [Ir(NNMePyr)(ppz)2][PF6] (37b)   An orange tablet crystal of [C41H30N6Ir][PF6] having approximate dimensions of 0.14 x 0.24 x 0.30 mm was used. The data were collected at a temperature of -173.0 + 0.1°C to a maximum 2θ value of 60.1°. Data were collected in a series of ϕ and ω scans in 0.50° oscillations with 7.0-second exposures. The crystal-to-detector distance was 37.92 mm. Of the 73988 reflections that were collected, 12853 were unique (Rint = 0.044) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.526 and 0.638 respectively. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions. The material crystallizes with two half-PF6 counterions residing at different sites on the mirror plane (making one complete PF6). In addition, one complete solvent hexane molecule is found over three different sites in the 37  asymmetric unit (also on the crystallographic mirror plane). The three sites consist of one half-molecule and two quarter-molecules. The final cycle of full-matrix least-squares refinement on F2 was based on 12853 reflections and 582 variable parameters and converged.   [Ir(NNMeNapht)(ppz)2][PF6] (42a/b)   An irregular orange crystal of [C35H28N6Ir][PF6], having approximate dimensions of 0.03 x 0.08 x 0.13 mm was used. The data were collected at a temperature of -183.0 + 0.1°C to a maximum 2θ value of 60.4°. Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 10.0-second exposures. The crystal-to-detector distance was 40.07 mm. Of the 83882 reflections that were collected, 9573 were unique (Rint = 0.064) and equivalent reflections (excluding Friedel pairs) were merged. The minimum and maximum transmission coefficients were 0.739 and 0.880 respectively. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in calculated positions. The material crystallizes as a disordered mixture of isomers, where the isomers are related by 180° rotation about the N2 – C14 bond.  The two isomers are present in an 80:20 ratio.  The presence of the two isomers causes what amounts to ‘whole-molecule disorder’. The EADP command was employed between pairs of similarly situated atoms. Finally, as the crystal packs in a non-centrosymmetric space group, the absolute configuration was determined on the basis of the value of refined Flack x-parameter (-0.001(5)).  The final cycle of full-matrix least-squares refinement on F2 was based on 9573 reflections and 607 variable parameters and converged.   38  2.2 Results and Discussion  2.2.1 Synthesis and Characterization   The sterically-confined pocket in 37 was designed by first attaching two phenylpyrazole (ppz) ligands to an Ir center, then self-assembling a pyrene-functionalized pyridineketimine ligand into the remaining coordination sites at the Ir (Scheme 2-1 where R = Me).  Scheme 2-1. Synthesis of complex 37a/b (R = Me) and 38 (R = H).   The crude reaction product shows 1H NMR signals corresponding to two isomers, and integration of the methyl signals in the spectrum show that the two isomers are present in a 1:1.3 ratio (37a:37b) (Figure 2-1).  The non-symmetric substitution at pyrene results in two possible orientations of the bound pyrene ligand due to the steric constraints imposed by a ppz ligand and the methyl imine group. The two isomers have different solubilities in MeOH allowing easy separation and crystallization. X-ray crystal structures show that 37a and 37b are diastereomers resulting from chirality at the metal and atropisomerism due to restricted rotation about the N2-C8 bond (see Section 2.2.2).  This restricted rotation is caused by steric hindrance, whereby the pyrene moiety cannot rotate 360° due to interactions between the 39  hydrogen atoms (H9, H14) and the methyl group (C7) and interaction with one of the cyclometallated ppz ligands.            Figure 2-1. 1H-NMR spectrum of the crude reaction product of 37a/b in CD3CN.   The 1H NMR spectra of 37a and 37b have been assigned using a combination of TOCSY, COSY, NOESY and HSQC experiments. Some key features of the solution spectra indicate the solution structures are close to the solid state structures. In all cases, the TOCSY spectra show correlations between hydrogens in a given ring system. This aids in assigning the signals for the phenyl, pyrazole and pyridine hydrogens. Correlations between all nine hydrogens in the pyrene ring system are weak and therefore not readily observed in these spectra. In addition to the TOCSY data, there are a few diagnostic signals in the NOESY spectra which help to confirm these assignments. In both isomers the phenyl hydrogens closest to the iridium center (H40 and H31) are shifted upfield82 and show NOEs to the pyrazole Chemical Shift (ppm) AJH088_002000fid.esp8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5Chemical Shift (ppm)AJH088_002000fid.esp8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5Chemical Shift (ppm)40  hydrogens of the other ppz (H24 and H33 respectively). The ketimine hydrogen (H7) shows a strong NOE to pyridine H4 and a weaker NOE to pyrene H14.  The differing orientations of the pyrene ligand, with respect to the rest of the complex in the two diastereomers, results in pyrene H14 being shifted upfield in 37a compared to 37b (δ 6.65 vs. 8.14). This is because H14 lies side-on over the center of a pyrazole ring in 37a and is shielded by a ring current, while in 37b H14 lies over the methyl group and is unaffected by ring current.  For H9 the situation is reversed, it points end-on towards the center of a pyrazole ring in 37b so is observed at δ 6.04 whereas in 37a it lies over a phenyl hydrogen and is shifted downfield to  8.23. Other notable differences in the spectra include the upfield shift of phenyl H26 in 37a compared to 37b (7.76 - 7.77 ppm vs. 8.40 – 8.41 ppm). In 37a, H26 lies over the pyrene ring system and is therefore affected by ring current, whereas in 37b H26 is on the opposite side of the complex to the pyrene.   Replacing the ketimine group with an aldimine group significantly reduces the barrier to rotation of the pyrene group (see section 2.2.4 for more details) and as a result, stable atropisomers cannot be isolated at room temperature.  This is demonstrated by complex 38 (Scheme 2-1 where R = H) prepared analogously to 37a/b using 2-pyridinecarboxaldehyde.  Complex 38 did not crystallize, and the 1H NMR spectrum at room temperature contains broadened peaks (Figure 2-2a), suggesting that the pyrene moiety undergoes partially restricted rotation at this temperature. At low temperature (-35°C) the NMR signals sharpen (Figure 2-2b) and the peaks for the major conformer can be assigned. However, NOE exchange peaks are still observed at low temperature, suggesting rotation, though restricted, is still taking place at -35°C. The chemical shifts of pyrene H14, H9 and phenyl H26 for 38 are similar to those for 37a. This supports the conclusion that the major conformer of 38 is analogous to 37a with 41  respect to the orientation of the pyrene group relative to the other ligands on Ir. The major and minor conformers of 38 are present in a 10:1 ratio based on integration of the imine hydrogen signals in the 1H NMR spectrum at -35°C.  Figure 2-2. (a) 1H-NMR spectrum of 38 at room temperature in CD3CN and (b) 1H-NMR spectrum of 38 at -35°C in CD3CN.  AJH049Inv_001000fid.esp9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0Chemical Shift (ppm)-35_000000fid9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0Chemical Shift (ppm)(b) (a) 42   Complexes 41 and 42 were prepared for comparison with 37 and 38.  [IrCl(npz)2]2 (40) was synthesized by reacting 3 equivalents of 1-(1-naphthalenyl)-1H-pyrazole (39) with IrCl3·3H2O under microwave irradiation at 110°C for 90 min. The pyrene-functionalized pyridineketimine ligand was then self-assembled into the remaining coordination sites at Ir using the same procedures as for 37 to give complex 41 (Scheme 2-2).    Scheme 2-2. Synthesis of 41.   42 was synthesized using a similar procedure as for 37 where 1-naphthylamine was used in place of 1-aminopyrene (Scheme 2-3).   43  Scheme 2-3. Synthesis of 42   Attempts at separating and purifying the atropisomers of complex 41 and 42 were unsuccessful. In contrast to complex 37, washing with methanol as well as other common organic solvents (ethanol, dichloromethane, acetonitrile and ethyl acetate) was not sufficient to allow for isolation of the individual atropisomers of 41 and 42. Upon washing 42 (original ratio = 1:1.1 of 42a:42b) with methanol, a 1:2 ratio (42a:42b) of atropisomers was achieved as evidenced by integration of the methyl signals in the 1H-NMR spectrum (Figure 2-3). A single crystal grown from this mixture of 42a/b (see section 2.2.2) showed a 1:4 ratio of 42a:42b. Due to the inability to separate and purify individual atropisomers, 41 and 42 were not studied further.  44   Figure 2-3. (a) 1H-NMR spectrum of 42 in CD3CN before attempts at separating individual atropisomers (1:1.1 ratio of 42a:42b) and (b) 1H-NMR spectrum of 42 in CD3CN after washing with methanol in an attempt to separate individual atropisomers (1:2 ratio of 42a:42b). AJH115s.001.esp8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5Chemical Shift (ppm)1.102.028.448.428.358.358.238.027.997.987.797.607.537.517.447.327.307.307.077.057.006.996.786.786.776.646.536.426.126.106.055.555.535.475.452.542.52AJH115.001.esp8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5Chemical Shift (ppm)1.001.088.438.418.398.348.237.997.967.667.607.547.527.447.317.287.207.016.996.976.956.796.786.786.776.726.456.366.126.106.065.875.855.555.535.475.452.542.51(a)(b)45   2.2.2 Solid-State Molecular Structures   Single crystals of NNHPyr (36) suitable for X-ray diffraction were grown from a solution of 36 in hot hexanes which was cooled to 0°C. The molecule crystalizes in the P21 space group with two crystallographically independent molecules in the asymmetric unit. See Table A1-2 for selected bond lengths and angles.  Figure 2-4. Solid state structure of NNHPyr (36). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms are omitted for clarity.    Single crystals of [Ir(NNMePyr)(ppz)2][PF6] (37a) suitable for X-ray diffraction were grown from a concentrated solution of 37a in dichloromethane which was layered with hexanes at 0°C and then slowly warmed to room temperature. The X-ray crystal structure confirms that 37a is the “pyrene-down” diastereomeric atropisomer. See Table A1-4 for selected bond lengths and angles. 46   Figure 2-5. Solid state structure of [Ir(NNMePyr)(ppz)2][PF6] (37a). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms, counterions and solvent molecules are omitted for clarity.    Single crystals of [Ir(NNMePyr)(ppz)2][PF6] (37b) suitable for X-ray diffraction were grown from a concentrated solution of 37b in dichloromethane which was layered with hexanes at 0°C and then slowly warmed to room temperature. The X-ray crystal structure confirms that 37b is the “pyrene-up” diastereomeric atropisomer. See Table A1-5 for selected bond lengths and angles.  47    Figure 2-6. Solid state structure of [Ir(NNMePyr)(ppz)2][PF6] (37b). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms, counterions and solvent molecules are omitted for clarity.    Single crystals of  [Ir(NNMeNapht)(ppz)2][PF6] (42a/b) suitable for X-ray diffraction were grown from a concentrated solution of a mixture of diasteromers 42a/b in dichloromethane which was layered with hexanes at 0°C and then slowly warmed to room temperature. The X-ray crystal structure shows that the diastereomeric atropisomers of 42a/b are present in a 1:4 (42a:42b) ratio in the crystal that was grown. See Table A1-7 and A1-8 for selected bond lengths and angles. 48   Figure 2-7. Solid state structure showing the major atropisomer of [Ir(NNMeNapht)(ppz)2][PF6] (42b). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and counterions are omitted for clarity.  Figure 2-8. Solid state structure showing the minor atropisomer of [Ir(NNMeNapht)(ppz)2][PF6] (42a). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and counterions are omitted for clarity. 49   2.2.3 Calculation of the Rotational Energy Barrier in Complex 37   Thermal conversion of diastereomer 37b to 37a occurs only at temperatures of 90°C or higher, as determined by 1H NMR spectroscopy. The experimental energy barrier to conversion of 37b to 37a (EAexp = 100.6 ± 9.8 kJ/mol) was calculated by constructing an Eyring plot (Figure 2-9) from reaction rates obtained by following the conversion at different temperatures (100 - 140°C) using 1H NMR spectroscopy. First-order reaction kinetics were observed and rate constants were obtained from the slope of a plot of ln[1bt-1be] vs. time at different temperatures, where 1bt = concentration of 37b at time t and 1be = concentration of 37b at equilibrium (Figure 2-10).  Figure 2-9. Eyring plot for reaction kinetics of 37b→37a from 100°C - 140°C.  y = -12099x + 27.122R² = 0.9299-5.5-4.5-3.5-2.5-1.50.0024 0.00245 0.0025 0.00255 0.0026 0.00265 0.0027ln(k/T)1/T (K-1)Eyring Plot50    Figure 2-10. ln[1bt-1be] vs. time plots for 37b→37a from 100°C to 140°C.  y = -2E-05x - 5.5134R² = 0.9822-6-5.8-5.6-5.4-5.2-1000 1000 3000 5000 7000 9000 11000 13000ln[1bt-1be]Time (s) ln[1bt-1be] vs. Time @ 100 Cy = -3E-05x - 5.5831R² = 0.9603-6.4-6.2-6-5.8-5.6-5.4-5.2-1000 1000 3000 5000 7000 9000 11000 13000ln[1bt-1be]Time (s) ln[1bt-1be] vs. Time @ 110 Cy = -4E-05x - 5.6649R² = 0.9485-6.2-6-5.8-5.6-5.4-500 500 1500 2500 3500 4500 5500 6500ln[1bt-1be]Time (s) ln[1bt-1be] vs. Time @ 120 Cy = -0.0002x - 5.6988R² = 0.9739-7.5-7-6.5-6-5.5-5-500 500 1500 2500 3500 4500 5500 6500ln[1bt-1be]Time (s) ln[1bt-1be] vs. Time @ 130 Cy = -0.0003x - 5.4088R² = 0.9848-7.5-7-6.5-6-5.5-5-500 500 1500 2500 3500 4500ln[1bt-1be]Time (s)ln[1bt-1be] vs. Time @ 140 C51  2.2.4 DFT Calculations following the Rotation in Complex 37 and 38   DFT calculations by Professor Francesco Lelj show two barriers (TS1 and TS2, Figure 2-11) to interconversion of the atropisomers of 37 and 38. In complex 37, rotation of the less sterically bulky side of the pyrene moiety (C13) past the methyl group (C7) (via TS1 in Figure 2-11) occurs with a computed energy barrier (EADFT) of 108 kJ/mol which agrees well with the experimental value (EAexp = 100.6 ± 9.8 kJ/mol). Rotation of the pyrene in the opposite direction, with the more bulky side (C9) going past the methyl group (C7) (via TS2, Figure 2-11) occurs with a larger computed energy barrier (EADFT = 136 kJ/mol), comparable to that calculated for the uncomplexed ketimine ligand (EADFT = 149 kJ/mol). Since the barrier to rotation is lower in complex 37a and 37b than in the free ligand it suggests that the metal coordination sphere is actually raising the energy of the minima more than the transition states. Interconversion of the atropisomers 37a and 37b requires only a rocking motion of the pyrene group via TS1.  Similar calculations for complex 38 show two barriers, close in energy to each other, that are both significantly lower than those for 37 (EADFT = 55 and 64 kJ/mol) (Figure 2-11). These barriers are consistent with the observation of fluxionality on the NMR timescale at room temperature and do not allow for separation of stable atropisomers of 38. Comparison of the relative energy barriers of 37 and 38 suggests that the “trapping” role is mainly due to the influence of the methyl substituent of the ketimine moiety. In 38 the hydrogen substituent on the aldimine provides a lower barrier and the major steric hindrance to rotation is determined by one of the ppz ligands. 52   Figure 2-11. Reaction coordinate diagram showing ΔE vs. torsion angle (^C9-C6) for complexes 37 (---) and 38 (—). Transition state structures are shown for complex 37.  Experimental value shown in red. Top center inset: definition of ϕ.   Both transition states TS1 and TS2 in 37 and 38 show significant changes in geometry. The Ir-N2 distance lengthens substantially (Δ 0.5 Å), and a large reorientation of the pyridine moiety with respect to the rest of the complex occurs (Figure 2-12).   53   Figure 2-12. Reaction coordinate diagram showing the Ir-N2 bond length vs. torsion angle (^C9-C6) for complexes 37 (---) and 38 (—).  2.2.5 Photophysical Properties of Complex 37 and 38 in Solution   The ground state absorption spectrum of complex 37a, 37b and 38 shows absorptions below 270 nm which are assigned to phenylpyrazole and pyrene based π-π* transitions. Absorptions between 270 – 350 nm are assigned to pyrene π-π* transitions. The weak, low energy absorptions are assigned to spin forbidden 3MLCT and 3LLCT transitions (Figure 2-13).  54  300 400 500 600 700020000400006000080000  Molar Absorptivity M-1cm-1Wavelength (nm) 37a 37b 38 Figure 2-13. Ground state absorption spectrum of 37a, 37b and 38.   Iridium(III) complexes bearing pyridineimine ancillary ligands typically show 3MLCT emission in solution between 640 – 780 nm.130 In contrast, complexes 37a, 37b and 38 do not show any emission in this region in solution. The lack of 3MLCT emission can be attributed to distortions of the Ir-Nimine bond in solution130 as well as Ir-Nimine bond lability which can lead to non-radiative decay. This bond lability in the excited state is supported by the formation of an acetonitrile-bound complex (δ 2.77) upon photoirradiation of 37b in acetonitrile. Emission spectra taken following photoirradiation at 294 nm show growth of a weak 3MLCT emission band at 620 nm attributed to the formation of an acetonitrile-bound complex (Figure 2-14). Details on the emission properties of 37a in the solid state will be discussed in Chapter 4.   55   Figure 2-14. Emission spectrum of 37b following photoirradiation at 294 nm. Inset: 1H-NMR spectrum showing the formation of an acetonitrile-bound complex at δ 2.77.  2.3 Conclusions   In conclusion, atropisomers of an iridium complex functionalized with a bulky pyrene pyridineimine ligand have been isolated. These are the first fully characterized examples of metal containing atropisomers in which the rotational axis is not between two chelating atoms.   The sterically confined pocket created by the methyl group of the imine ligand and one of the ppz ligands traps the complex in one of two possible rotamers during the synthesis. The atropisomers can be converted thermally via a rocking motion of the pyrene around the N2-C8 axis. Replacement of the methyl group with a hydrogen results in a lower barrier to rotation and in this case interconversion of the atropisomers occurs on the NMR timescale at room temperature.  This metal-ligand assembly provides an excellent platform for the preparation of 400 450 500 550 600 6500.00.51.01.52.02.5  Normalized EmissionWavelength (nm) Before Irradiation After 30 min After 90 min After 150 min After 210 min After 270 minNONAME002.8 2.7 2.6Chemical Shift (ppm)2.772.602.5456  molecular switches of this type. The ease of synthesis and isolation of these complexes allows modular changes to be easily made. 57  Chapter 3: Elucidating the origin of enhanced phosphorescence emission in the solid state (EPESS) in bis-cyclometallated Ir(III) complexes   3.1 Introduction   Organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LEECs) require molecules that emit intensely in the solid state.131 Interactions between molecules in the solid state are known to influence emission behaviour. Typically, molecules that are strongly emissive in dilute solution become less emissive in concentrated solutions or in the solid state due to “aggregation caused quenching” (ACQ).16 In 2001, Tang and coworkers reported a series of substituted 2,3,4,5–tetraphenylsiloles in which aggregation caused an enhancement in emission in the solid state compared to dilute solution, a phenomenon they dubbed “aggregation induced emission” (AIE).132,133 Since this discovery, many organic chromophores exhibiting AIE have been reported.134,135 Recently, coordination complexes of iridium,136 platinum137 and rhenium138 that show AIE have also been reported.  In such complexes, emission often arises from states with triplet character, so AIE in this class of compounds is also called enhanced phosphorescence emission in the solid state (EPESS). The performance of solid state molecular devices depends strongly on the molecular assembly of components. As a consequence, understanding and controlling molecular arrangements in the solid state is pertinent for these applications.139  EPESS in metal complexes has been attributed to a variety of causes including restricted intramolecular rotation (RIR),140 or π-stacking,136 however the complexity of the 58  excited state manifolds in these complexes makes unambiguous determination of the origin of EPESS difficult. Cyclometallated iridium complexes are of particular interest due to their high photoluminescence efficiencies and the ability to colour tune their emission.39 Two different mechanisms have been proposed as the possible origin of EPESS in cyclometallated iridium complexes. One mechanism involves restricted intramolecular rotations of substituents on the bidentate ancillary ligand (N^O140 or N^N141) and the other involves π-stacking of cyclometallating phenylpyridine ligands.136,142,143   Park et al. proposed that restricted intramolecular rotation around the N-aryl bond of salicylimine ligands in the solid state suppresses a non-radiative decay pathway giving rise to EPESS.140 The solid state absorption and luminescence properties of 43-46 (Chart 3-1) were studied in neat films as well as in various polymer films.140 Due to the presence of strong solid state emission in the polymer films of 43-46, it was concluded that the solid state emission does not arise from an excimeric or aggregated state.140 Instead, a combination of low temperature emission and TD-DFT studies were used to conclude that rotation around the N-aryl bond in solution gives rise to a non-radiative decay pathway causing these complexes to be non-emissive in solution.140 It was proposed that this pathway is slowed down or shut off in the solid state giving rise to the observed emission.140       59  Chart 3-1. Ref.140    Li et al. have suggested that π-stacking of phenylpyridine ligands lowers the energy of an emissive 3MLLCT state below that of a non-emissive triplet ligand (3L) state, resulting in an increase in emission in the solid state compared to solution.136 This explanation was first proposed from studies on 47-49 (Chart 3-2), where 47 does not show EPESS in contrast to 48 and 49.136  The triplet energies of the ancillary ligands (3L) of 47-49 were measured and 48 and 49 were determined to have low-lying triplet energies.136 From these results, it was proposed that π-stacking lowers an emissive 3MLLCT state below the low-lying, non-emissive 3L state (in 48 and 49) giving rise to emission in the solid state.136 Follow-up studies on 50-52 (Chart 3-2) were used to dispute the theory of restricted rotation proposed by Park et al. as 50 and 51 have ancillary ligand substituents which are not free to rotate but still show EPESS.143 Li et al. used X-ray crystallography136,143 as well as emission spectroscopy on micro-aggregates formed in acetonitrile/water mixtures,136 to suggest that the phenylpyridine ligands π-stack and give rise to the solid state emission observed.  60  Chart 3-2. Ref.136,143    There are some contradictory results in the data reported by Park and Li respectively which suggest that neither of the interpretations proposed by these groups is correct. Park et al. show that strong solid state emission is observed in polymer films140 (when π-stacking interactions are diminished144), inconsistent with the interpretation put forward by Li et al. as the cause of EPESS. The studies by Li et al. in which strong solid state emission is observed in complexes with ancillary ligand substituents which are not free to rotate143 do not agree with Park’s interpretation as the cause of EPESS. In this chapter, a new mechanism for EPESS in cyclometallated Ir complexes with the general formula [Ir(C^N)2(N^O)] (45, 46, 49 and 53-59; Chart 3-3) is proposed. A combination of photophysical and computational studies show that neither π-stacking nor restricted rotation of ancillary ligand substituents cause the observed EPESS in these complexes. Instead, the cause of EPESS in these complexes is attributed to a distortion of the bonding of the six-membered chelate ring of the ancillary ligand 61  to the metal. This mechanism can also be applied to [Ir(C^N)2(O^O)] complexes and hence is consistent with all the experimental observations made previously by Park140 and Li136,143 and may apply more widely in other transition metal complexes.  Chart 3-3.   3.2 Experimental  3.2.1 General   All experiments were performed under an inert nitrogen atmosphere, using standard Schlenk-line techniques. Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc. Chloro(1-phenylpyrazole)iridium(III) dimer [IrCl(ppz)2]2,130 chloro(2-62  phenylpyridine)iridium(III) dimer [IrCl(ppy)2]2,130 2-((phenylimino)methyl)phenol (NOPh),140 2-((1-naphthalenylimino)methyl)phenol (NONapht),140 2-((3-fluoranthenylimino)methyl)phenol (NOFluor),136 and 2-[[[2,6-bis(1-methylethyl)phenyl]imino]methyl]-phenol (NOiProp2Ph)145 were prepared according to literature procedures. 2-[[(1-methylethyl)imino]methyl]-phenol (NOiProp) was prepared by a typical Schiff base condensation reaction in ethanol.  All other solvents and reagents were obtained from commercial sources and used as received. 1H NMR and 13C NMR spectra were obtained using a Bruker AV-400 spectrometer and referenced to the residual protonated solvent peak. NMR spectra were assigned using a combination of COSY, NOESY, TOCSY and HSQC experiments. Electrospray ionization mass spectrometry data were obtained on a Bruker Esquire LC ion trap mass spectrometer. Elemental analyses were performed by Derek Smith from the UBC mass spectrometry/microanalysis lab on a Carlo Erba Elemental Analyzer EA 1108. Microwave reactions were performed on a Biotage Initiator 2.5 microwave synthesizer. Fluorescence spectroscopy data were collected on a Photon Technology International QuantaMaster fluorimeter. Solid state emission spectra were obtained at 298 K by drop casting a dichloromethane solution of each complex onto a glass slide. Absolute quantum yields were determined using an integrating sphere coupled to the PTI fluorimeter. Neat solid quantum yields were obtained from drop casting a 1:1 dichloromethane:hexane solution of each complex. PMMA matrix quantum yields were drop cast from dichloromethane.  Complexes 45-49, and 53-61 were studied by ab initio DFT and TD-DFT calculations performed by Professor Francesco Lelj.  Preliminary calculations were performed using the hybrid xc functional B3LYP;146 this has been shown to have some drawbacks because of the wrong asymptotic behavior; therefore the 1 parameter xc functionals mPW1PW91147 and the 63  PB1PBE148 and the more recent M06120 meta-hybrid functional were also used. For all second period atoms the Dunning122 all electron basis set augmented by a set of d polarization functions (D95(d)) was used. Hydrogen atoms not involved in any hydrogen bond, were described by the same Dunning basis set that does not include p polarization functions.  For Ir the new double ζ Stuttgart123 basis set including f polarization functions and relativistic effects by a fully relativistic small core pseudopotential148 (SDD09)  were used and not the default SDD as included in Gaussian09c01. The ultrafine option with 99590 grid points was used thoroughly for the integral calculations for all atoms except Ir where a total of 1566228 grid points were used.  The first triplet state structure was computed using the unrestricted approach. All energy minimized structures were characterized by the calculation of the Hessian matrix in order to check that they were minima and not simple stationary points on the molecular Born-Oppenheimer energy surface. Wavefunctions were checked against possible internal instability.149,150 TD-DFT calculations were performed by increasing the initial configuration space for the Davidson151 diagonalization, unlike the default option in the program. A dichloromethane solvent environment was simulated by the self-consistent reaction field.152 Vibrational band structure was evaluated by computing the Frank-Condon contribution153,154 between the ground state S0 structure and T1 structures and their harmonic vibrational properties. Further T1 structures were computed constraining the O^N-Ph ligand conformation of the N-Ir-O-C and C-N-Ir-O dihedral angle as in the ground state while optimizing all the remaining geometrical parameters to simulate the effect of the solid state constraining those internal degrees of freedom. All calculations were performed using Gaussian09,155 version C01.  64  3.2.2 Methods  Ir(ppy)2(NOPh) (45)    This complex has been reported previously140 using different synthetic procedures. [IrCl(ppy)2]2 (0.070 g, 0.065 mmol), NOPh (0.028, 0.14 mmol) and sodium carbonate (0.015 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as an orange-yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOPh and then EtOAc:CH2Cl2 (1:1) to elute complex 45 (0.026 g, yield 29%). 1H NMR resonances match those reported in literature. HR ESI-MS: Calcd for C35H27IrN3O: 696.1760; Found: 696.1746 [M+H]+. Anal. Calcd for (C35H26IrN3O)·CH4O: C, 59.32; H, 4.15; N, 5.77. Found: C, 59.39; H, 3.95; N, 5.48.  Ir(ppy)2(NOFluor) (46)    This complex has been reported previously140 using different synthetic procedures. [IrCl(ppy)2]2 (0.070 g, 0.065 mmol), NOFluor (0.046, 0.14 mmol) and sodium carbonate (0.015 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was 65  then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-brown solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a dark orange precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOFluor and then EtOAc:CH2Cl2 (1:1) to elute complex 46 (0.040 g, yield 38%). 1H NMR resonances match those reported in literature. HR ESI-MS: Calcd for C45H31IrN3O: 820.2073; Found: 820.2074 [M+H]+.  Ir(ppy)2(NONapht) (49)    This complex has been reported previously140 using different synthetic procedures. [IrCl(ppy)2]2 (0.070 g, 0.065 mmol), NONapht (0.035, 0.14 mmol) and sodium carbonate (0.015 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-orange solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NONapht and then EtOAc:CH2Cl2 (1:1) to elute complex 49 (0.036 g, yield 37%). 1H NMR resonances match those reported in literature. HR ESI-MS: Calcd for C39H29IrN3O: 746.1917; Found: 746.1094 [M+H]+. Anal. Calcd for (C39H28IrN3O)·C2H6O: C, 62.18; H, 4.20; N, 5.31. Found: C, 61.96; H, 3.91; N, 5.53.  66  Ir(ppz)2(NOPh) (53)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), NOPh (0.030, 0.15 mmol) and sodium carbonate (0.016 g, 0.15 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a bright orange precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOPh and then EtOAc:CH2Cl2 (1:1) to elute complex 53 (0.031 g, yield 34%).  1H NMR (CD2Cl2, 400 MHz): δ 8.10 (1H, d, J = 2.8, H25), 8.07 (1H, s, H7), 8.07 (1H, d, J = 2.7, H14), 7.78 (1H, d, J = 2.0, H23), 7.73 (1H, d, J = 2.1, H16), 7.25-7.21 (2H, m, H2,18),  7.15 (1H, d, J = 1.7, H4), 6.90 (1H, t, J = 8.0, 8.6, H19), 6.84-6.79 (4H, m, H10,11,12,27), 6.70 (1H, d, J = 9.2, H20), 6.67-6.62 (3H, m, H1,15,24), 6.57 (1H, t, J = 7.7, 5.3, H28),  6.41-6.34 (2H, m, H3,29), 6.26-6.24 (3H, m, H9,13,21), 5.94 (1H, d, J = 7.1, H30). 13C NMR (CD2Cl2, 100 MHz): 162.9 (C7), 139.1 (C23), 138.4 (C16), 136.5 (C4), 135.5 (C30), 135.1 (C21), 134.5 (C18), 128.3-125.0 (C10,11,12), 126.6 (C25), 126.1 (C14), 125.7 (C20), 125.4 (C3), 123.9 (C24), 122.9-122.0 (C9,13), 121.9 (C19), 120.8 (C28), 113.4 (C29), 111.1 (C2), 110.2 (C27), 107.6 (C15), 107.2 (C1). HR ESI-MS: Calcd for C31H25IrN5O: 674.1649; Found: 674.1665 [M+H]+. Anal. Calcd for (C31H24IrN5O): C, 55.18; H, 3.58; N, 10.38. Found: C, 55.40; H, 3.68; N, 9.98.   67  Ir(ppz)2(NONapht) (54)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), NONapht (0.037, 0.15 mmol) and sodium carbonate (0.016 g, 0.15 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-orange solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a bright yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NONapht and then EtOAc:CH2Cl2 (1:1) to elute complex 54 (0.029 g, yield 29%). 1H NMR (CD2Cl2, 400 MHz): δ 8.20 (1H, s, H7), 8.13 (1H, d, J = 2.8, H18), 7.99 (1H, d, J = 2.2, H19), 7.89 (1H, d, J = 2.2, H27), 7.56 (1H, d, J = 8.1, H13), 7.49 (1H, d, J = 2.9, H29),  7.32-7.27 (3H, m, H3,15,32), 7.21 (1H, d, J = 8.9, H9), 7.14 (1H, dd, J = 7.8, 2.0, H34), 7.08 (1H, d, J = 8.1, H16), 6.98-6.86 (3H, m, H1,4,14), 6.74 (1H, d, J = 9.3, H10),  6.70-6.65 (3H, m, H2,20,31), 6.63 (1H, t, J = 4.9, H28), 6.41 (1H, t, J = 7.3, H33), 6.29 (1H, d, J = 7.7, H22), 6.24-6.20 (2H, m, H23,24), 6.10 (1H, d, J = 7.6, H11), 5.90 (1H, d, J = 7.9, H25). 13C NMR (CD2Cl2, 100 MHz): 138.7 (C19), 137.5 (C27), 136.2 (C34), 135.2 (C25), 134.8 (C3), 133.8 (C11), 127.3 (C13), 126.5 (C18), 126.4 (C7), 125.2 (C31), 125.1 (C1,29), 124.9 (C32), 124.7 (C24), 124.3 (C2,16), 121.9 (C4), 121.3 (C20), 120.1 (C22), 119.2 (C14), 113.1 (C33), 110.8 (C15), 110.5 (C9), 108.7 (C23), 106.9 (C10), 106.8 (C28). HR ESI-MS: Calcd for C35H27IrN5O: 724.1822; Found: 724.1818 [M+H]+.   68  Anal. Calcd for (C35H26IrN5O)·CH4O: C, 57.20; H, 3.87; N, 9.27. Found: C, 57.25; H, 3.96; N, 9.57.  Ir(ppz)2(NOFluor) (55)   [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), NOFluor (0.048, 0.15 mmol) and sodium carbonate (0.016 g, 0.15 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-brown solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a dark orange precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOFluor and then EtOAc:CH2Cl2 (1:1) to elute complex 55 (0.046 g, yield 43%). 1H NMR (CD2Cl2, 400 MHz): δ 8.30 (1H, s, H7), 8.20 (1H, d, J = 2.7, H35), 8.06 (1H, d, J = 1.7, H33), 7.89-7.87 (2H, m, H21,22), 7.82-7.80 (2H, m, H23,24), 7.55 (1H, d, J = 7.1, H10),  7.50 (1H, d, J = 2.5, H26), 7.38-7.36 (3H, m, H16,20,39), 7.28 (1H, d, J = 7.9, H1), 7.24-7.20 (2H, m, H4,37), 7.07 (1H, d, J = 7.5, H9), 6.94 (1H, t, J = 7.4, H2),  6.78-6.66 (5H, m, H3,14,25,34,40), 6.46 (1H, t, J = 7.4, H38), 6.32-6.29 (1H, m, H30), 6.24-6.19 (3H, m, H15,28,29), 6.06 (1H, d, J = 7.6, H31) . 13C NMR (CD2Cl2, 100 MHz): 164.5 (C7), 139.6 (C33), 138.4 (C21), 136.9 (C4), 135.7 (C31), 135.2 (C39), 134.9 (C29), 128.0 (C37), 127.91 (C20), 127.1 (C35), 126.1 (C26), 126.0 (C34), 125.2 (C30), 124.9 (C40), 122.5 (C2), 122.4 (C9), 122.1 (C3), 121.9-121.7 (C16,22,24), 120.7 (C15), 120.4 (C23), 119.7 (C10), 113.9 (C38), 111.1 (C1), 109.7 69  (C28), 107.9 (C14), 107.7 (C25). HR ESI-MS: Calcd for C41H29IrN5O: 798.1978; Found: 798.1984 [M+H]+. Anal. Calcd for (C41H28IrN5O)·CH4O: C, 60.71; H, 3.88; N, 8.43. Found: C, 60.62; H, 3.59; N, 8.56.  Ir(ppz)2(NOiProp) (56)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), NOiProp (0.024, 0.15 mmol) and sodium carbonate (0.016 g, 0.15 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-brown solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOiProp and then EtOAc:CH2Cl2 (1:1) to elute complex 56 (0.040 g, yield 46%). 1H NMR (CDCl3, 500 MHz): δ 8.06 (1H, s, H7), 8.04 (1H, d, J = 2.6, H20), 7.95 (1H, d, J = 2.6, H11), 7.66 (1H, d, J = 1.9, H22), 7.47 (1H, d, J = 1.9, H13), 7.17 (1H, ddd, J = 1.9, 6.8, 8.6, H2 or 3), 7.13 (1H, dd, J = 0.8, 7.9, H15 or 24), 7.08 (2H, t, J = 8.0, H15 or 24 and 4), 6.82-6.78 (2H, m, H16, 25), 6.68-6.65 (2H, m, H1,17,), 6.61 (1H, td, J = 1.1, 7.3, H26), 6.58 (1H, t, J = 2.6, H21), 6.46 (1H, t, J = 2.6, H12), 6.38 (1H, t, J = 7.3, H2 or 3), 6.25 (1H, dd, J = 0.9, 7.5, H27 ), 6.18 (1H, d, J = 0.9, 7.6, H18), 3.72 (1H, sept, J = 6.6, H8), 1.18 (3H, d, J = 6.7, H9/10), 0.55 (3H, d, J = 6.7, H9/10). 13C NMR (CDCl3, 125 MHz): δ 166.5 (C7), 159.2, 144.2 (C22), 143.9 (C13), 138.5 (C4), 138.2, 134.9, 134.8 (C2/3), 134.2, 133.5, 131.5, 125.9 (C11), 125.6 (C17/26), 125.6 70  (C17/26), 125.2 (C20), 123.5 (C1), 122.1, 121.7 (C16/25), 120.8 (C16/25), 112.9(C2/3), 110.5 (C15/24), 110.4 (C15/24), 107.0 (C21), 106.8 (C12), 58.3 (C8), 23.0 (C9/10), 22.8 (C9/10). HR ESI-MS: Calcd for C28H27IrN5O: 642.1845; Found: 642.1849 [M+H]+.  Ir(ppz)2(NOiProp2Ph) (57)   [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), NOiProp2Ph (0.042, 0.15 mmol) and sodium carbonate (0.016 g, 0.15 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting orange-brown solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as an orange-yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOiProp2Ph and then EtOAc:CH2Cl2 (1:1) to elute complex 57 (0.027 g, yield 26%). 1H NMR (CDCl3, 500 MHz): δ 8.05 (1H, d, J = 2.1, H20), 7.98 (1H, d, J = 2.9, H31), 7.91 (1H, s, H7), 7.83 (1H, d, J = 2.7, H22), 7.65 (1H, d, J = 2.1, H29), 7.16 (1H, ddd, J = 1.9, 6.8, 8.5, H2), 7.08 (1H, d, J = 7.5, H33), 7.06 (1H, dd, J = 1.8, 7.8, H4), 6.88-6.83 (2H, m, H13/14/15), 6.78 (1H, td, J = 1.1, 7.6, H34), 6.74 (1H, dd, J = 0.9, 7.8, H24), 6.70-6.68 (2H, m, H21 + H13/14/15), 6.60-6.57 (2H, m, H35, 1), 6.54 (1H, td, J = 1.1, 7.6, H25), 6.46-6.42 (2H, m, H30,26), 6.40 (1H, t, J = 7.3, H3), 6.23 (1H, dd, J =1.1, 7.8, H27), 5.58 (1H, dd, J = 1.1, 7.8, H36), 3.48 (1H, sept, J = 6.6, H10 or 17), 2.68 (1H, sept, J = 6.7, H10 or 17), 1.18 (3H d, J = 6.5, H11/12/18/19), 1.03 (3H, d, J = 6.5, H11/12/18/19), 0.87 (3H, d, J = 6.9, H11/12/18/19), 0.62 (3H, d, 71  J = 6.9, H11/12/18/19) 13C NMR (CDCl3, 125 MHz): δ 168.6, 166.0 (C7), 149.2, 143.7, 141.4, 139.9, 139.8 (C29), 138.2 (C20), 134.5, 136.4 (C27), 135.0 (C4), 134.5 (C2), 133.5 (C36), 132.5, 127.7, 126.0, 125.8 (C22), 125.7 (C31), 125.6, 124.9 (C26), 123.9, 123.0, 122.0, 121.9 (C34), 121.7, 120.3 (C25), 113.6 (C3), 110.4 (C33), 109.3, 108.1, 106.2 (C30), 27.7 (C10/17), 27.2 (C10/17) 27.4 (C11/12/18/19), 25.7 (11/12/18/19), 23.3 (C11/12/18/19), 21.8 (C11/12/18/19). HR ESI-MS: Calcd for C37H37IrN5O: 760.2628; Found: 760.2626 [M+H]+.  Ir(ppy)2(NOiProp) (58)   [IrCl(ppy)2]2 (0.070 g, 0.065 mmol), NOiProp (0.023, 0.14 mmol) and sodium carbonate (0.015 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-brown solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOiProp and then EtOAc:CH2Cl2 (1:1) to elute complex 58 (0.037 g, yield 43%). 1H NMR (CDCl3, 400 MHz): δ 8.92 (1H, d, J = 5.1, H11), 8.49 (1H, d, J = 5.1, H22), 8.15 (1H, s, H7), 7.83 (1H, d, J = 8.37, H14), 7.80 (1H, d, J = 8.0, H25), 7.73 (1H, td, J = 1.2, 7.5, H13), 7.62 (1H, t, J = 7.8, H24), 7.58 (1H, d, J = 7.7, H17), 7.52 (1H, d, J = 7.1, H32), 7.16-7.06 (3H, m, H12,2,4), 6.93 (1H, t, J = 6.3, H23), 6.80 (2H, q, J = 6.4, H18,31), 6.71 (1H, td, J = 0.9, 7.4, H19 or 30), 6.65 (1H, td, J = 1.1, 8.4, H19 or 30), 6.62 (1H, d, J = 8.6, H1), 6.37 (2H, t, J = 7.4, H3, 20 or 29), 6.15 (1H, d, J = 72  7.4, H20 or 29), 3.54 (1H, sept, J = 6.7, H8), 1.12 (3H, d, J = 6.7, H9/10), 0.53 (3H, d, J = 6.6, H9/10). 13C NMR (CDCl3, 100 MHz): δ 168.5, 158.8 (C7), 152.8, 151.2, 149.2 (C11), 148.9 (C22), 144.4, 136.8 (C14), 136.5 (C24), 134.6 (C13), 133.5, 133.1 (C20/29), 131.9 (C20/29), 129.4 (C19/30)  129.2 (C19/30), 124.2, 123.8 (C17), 123.7 (C32), 121.9, 121.6, 121.3, 121.2 (C23), 120.1, 118.9 (C25), 118.0 (C14), 113.1 (C3), 57.2 (C8), 23.3 (C9/10), 23.2 (C9/10). HR ESI-MS: Calcd for C32H29IrN3O: 664.1940; Found: 664.1935 [M+H]+.  Ir(ppy)2(NOiProp2Ph) (59)   [IrCl(ppy)2]2 (0.070 g, 0.065 mmol), NOiProp (0.040, 0.14 mmol) and sodium carbonate (0.015 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting yellow-orange solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as an orange precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOiProp2Ph and then EtOAc:CH2Cl2 (1:1) to elute complex 59 (0.037 g, yield 37%). 1H NMR (CDCl3, 400 MHz): δ 9.25 (1H, d, J = 5.1, H31), 8.82 (1H, d, J = 5.4, H20), 8.01 (1H, s, H7), 7.80 (1H, d, J = 7.6, H34), 7.66-7.61 (2H, m, H22,33), 7.57 (1H, d, J = 7.6, H23), 7.50 (1H, d, J = 7.9, H37), 7.19-7.14 (2H, m, H32 + H1/2/3), 7.05 (2H, m, H26,4), 6.93 (1H, td, J = 1.3, 6.6, H21), 6.86 (1H, t, J = 7.6, H14), 6.80 (1H, dd, J = 0.9, 7.6, H13/15), 6.75 (1H, t, J = 7.1, H38), 6.64-6.59 (3H, m, H39 + H1/2/3 + H13/15), 6.50 73  (2H, m, H28,27), 6.40 (1H, t, J = 7.1, H2/3), 6.17 (1H, d, J = 7.6, H29), 5.59 (1H, d, J = 7.6, H40), 3.33 (1H, sept, J = 6.7, H10/17), 2.48 (1H, sept, J = 6.4, H10/17), 1.14 (3H, d, J = 7.0, H11/12/18/19), 0.89 (3H, d, J = 6.7, H11/12/18/19), 0.88 (3H, d, J = 6.9, H11/12/18/19), 0.39 (3H, d, J = 6.7, H11/12/18/19). 13C NMR (CD2Cl2, 100 MHz): δ 168.4, 168.1, 167.3, 164.8 (C7), 149.7 (C20), 149.4, 148.1 (C31), 147.9, 146.2, 143.3, 143.1, 140.6, 139.0, 135.9 (C22/33), 135.7 (C22/33), 134.1, 133.5 (C29), 129.9 (C40), 128.3, 127.8, 124.7, 123.3 (C26), 122.7, 121.9, 121.7, 121.0, 120.9, 120.7, 120.1 (C21), 118.7 (C23), 118.5 (C34), 117.7, 117.3, 112.6, 26.9 (C10/17) , 26.7(C10/17), 26.6 (C11/12/18/19), 24.5 (C11/12/18/19), 21.6 (C11/12/18/19), 20.6 (C11/12/18/19). HR ESI-MS: Calcd for C41H39IrN3O: 782.2723; Found: 782.2726 [M+H]+.  3.2.3 X-Ray Crystallography   The crystal structure data were obtained and the structures were solved by Kuldip Singh. Data were collected on a Bruker Apex 2000 CCD diffractometer using graphite monochromated Mo-K radiation,  = 0.7107 Å. The data were corrected for Lorentz and polarisation effects and empirical absorption corrections were applied. The structure was solved by direct methods and with structure refinement on F² employed SHELXTL version 6.10.156 Hydrogen atoms were included in calculated positions (CH = 0.95 – 1.00 Å, OH = 0.84 Å). All non-hydrogen atoms were refined with anisotropic displacement parameters without positional restraints.      74  Ir(ppz)2(NOiProp2Ph) (57)    A crystal having approximate dimensions of 0.29 x 0.20 x 0.10 mm was used. The data were collected at a temperature of -123.0 ± 0.1 °C to a maximum 2θ value of 54°. Of the 14776 reflections that were collected, 7431 were unique (Rint = 0.049) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.532 and 0.831 respectively. The material crystalizes with two crystallographically independent molecules in the asymmetric unit. The final cycle of full-matrix least-squares refinement on F2 was based on 7431 reflections and 446 variable parameters and converged.   Ir(ppy)2(NOiProp) (58)    A crystal having approximate dimensions of 0.22 x 0.13 x 0.07 mm was used. The data were collected at a temperature of -123.0 ± 0.1 °C to a maximum 2θ value of 52°. Of the 28190 reflections that were collected, 7270 were unique (Rint = 0.169) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.520 and 0.831 respectively. The final cycle of full-matrix least-squares refinement on F2 was based on 7270 reflections and 363 variable parameters and converged. Disordered solvent was removed using the Squeeze option in PLATON.157  Ir(ppy)2(NOiProp2Ph) (59)    A crystal having approximate dimensions of 0.32 x 0.10 x 0.04 mm was used. The data were collected at a temperature of -123.0 ± 0.1 °C to a maximum 2θ value of 52°. Of the 14864 reflections that were collected, 7274 were unique (Rint = 0.071) and equivalent reflections were 75  merged. The minimum and maximum transmission coefficients were 0.526 and 0.831 respectively. The material crystalizes with two crystallographically independent molecules in the asymmetric unit. The final cycle of full-matrix least-squares refinement on F2 was based on 7274 reflections and 475 variable parameters and converged.  3.3 Results and Discussion  3.3.1 Synthesis and Characterization   Complexes 45, 46, 49 and 53-59 were studied to test the effect of restricted N-aryl and N-alkyl rotations as well as π-stacking on EPESS. Increasing steric bulk of the -R group from benzene to fluoranthene to 2,6-diisopropylbenzene was used to test the effects of restricted N-R rotation. Ir(III) complexes with phenylpyrazole cyclometallating ligands were used as a starting point to test the effects of π-stacking on EPESS, since phenylpyrazole ligands have been shown to be less likely than phenylpyridine ligands to π-stack in the solid state.158,159,160,161,162,163,164 Complexes 45, 46, 49 and 53-59 were prepared by reacting the appropriate Ir(III) dimer and corresponding salicylimine proligand under microwave irradiation for 30 minutes at 100°C (Scheme 3-1). All complexes were characterized by high resolution mass spectrometry and 1H NMR spectroscopy (COSY, NOESY, TOCSY and HSQC) allowing full assignment of all resonances. X-ray crystal structures were also obtained for 57-59 (see section 3.3.2).    76  Scheme 3-1.     3.3.2 Solid-State Molecular Structures   The X-ray structures of 57-59 have been determined and they all show the expected atom connectivities. The Ir-N(salicylimine) bond lengths, where the N atom is trans to C of the cyclometallating ligand, is much longer than the Ir-N(ppy/ppz) bond lengths.   Single crystals of Ir(ppz)2(NOiProp2Ph) (57) suitable for X-ray diffraction were grown by Raissa Patia from a solution of 57 in chloroform which was layered with methanol. In complex 57 the phenylpyrazole of one molecule is coplanar with that of another though the two planes are considerably offset with only minor overlap of the two pyrazole rings (centroid-centroid distance of 3.42 Å). The plane of the N^O ligand (N,C,C,C,O) is considerably distorted from the IrC2 plane forming an interplanar angle of 27.6. See Table A1-10 for selected bond lengths and angles. 77   Figure 3-1. Solid state structure of Ir(ppz)2(NOiProp2Ph) (57). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent molecules are omitted for clarity.    Single crystals of Ir(ppy)2(NOiProp) (58) suitable for X-ray diffraction were grown by Raissa Patia from a concentrated solution of 58 in chloroform. In complex 58, the phenylpyridine ligands in adjacent molecules are almost coplanar but are hardly overlapped (centroid-centroid distance of pyridine in one molecule and pyridine in another is 3.80 Å).  The angle between the plane of the N^O ligand and IrC2 plane is 22.2. See Table A1-12 for selected bond lengths and angles. 78   Figure 3-2. Solid state structure of Ir(ppy)2(NOiProp) (58). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent molecules are omitted for clarity.    Single crystals of Ir(ppy)2(NOiProp2Ph) (59) suitable for X-ray diffraction were grown by Raissa Patia from a solution of 59 in chloroform which was layered with methanol. Complex 59 shows some π-stacking of the phenylpyridine ligands which are at an angle of 7.1 to each other though again the rings are offset from one another (centroid-centroid distance of pyridine in one molecule and phenyl in another is 4.16 Å).  The angle between the plane of the N^O ligand and IrC2 plane is 24.5. See Table A1-14 for selected bond lengths and angles. 79   Figure 3-3. Solid state structure of Ir(ppy)2(NOiProp2Ph) (59). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent molecules are omitted for clarity.    Overall, there is very little evidence in any of these structures for a significant degree of π-stacking (Figure 3-4). A notable feature in all three cases is the bending of the N^O plane away from the IrC2 plane. The reasons for this are not obvious, however, there are a number of weak interactions between molecules in the solid state. For example, in 57 there are close contacts between the salicylimine phenol ring and the CH bond of a pyrazole, and of an isopropyl group, from two different adjacent molecules. In all cases, these short contacts suggest that there will be restricted motion of the molecules in the solid state. 80   Figure 3-4. Selected packing diagrams of 57-59 showing minimal evidence for π-stacking.  3.3.3 Photophysical Properties    The ground state absorption spectrum of 45, 46, 49 and 53-59 shows absorptions below 270 nm which are assigned to phenylpyrazole π-π* transitions. Absorptions between 270 – 400 nm are assigned to π-π* transitions on the salicylimine ancillary ligand. The weak, low energy absorptions are assigned to spin forbidden 3MLCT and 3LLCT transitions (Figure 3-5).    (a) (b) (c) Parallel View Parallel View Parallel View Perpendicular Perpendicular Perpendicular 57 59 58 81   Figure 3-5. Normalized absorption spectra of 45, 46, 49 and 53-59.   Complexes 45, 46, 49 and 53-59 show either very weak or no phosphorescence at room temperature in dichloromethane solution (Figure 3-6).  Figure 3-6. Emission spectra of 56, 57 and 58 in dichloromethane purged with argon, λex = 400 nm. 300 400 500 600 7000.00.20.40.60.81.0  Normalized AbsorbanceWavelength (nm) 53 54 55 56 57300 400 500 600 7000.00.20.40.60.81.0  Normalized AbsorbanceWav length (nm) 45 49 46 58 59500 550 600 650 700 7500200040006000800010000120001400016000  Counts (s-1)Wavelength (nm) 58550 600 650200400600800100120014001600  Counts (s-1)Wavel ngth (nm) 56 5782    In stark contrast to this observation, all of the complexes display enhanced phosphorescence emission in the solid state with λmax between 580–635 nm, measured at 298 K by drop casting a dichloromethane solution of each complex onto a glass slide (Figure 3-7). See section 3.3.6 for a detailed discussion on the origin of the emission in these complexes. Figure 3-7. Solid state emission spectra of 45, 46, 49 and 53-59, λex = 400 nm, in air.  3.3.4 Effects of Restricted Rotation   Previously, restricted intramolecular rotation around the N-aryl bond of the salicylimine ligand in the solid state was proposed to suppress a non-radiative decay pathway giving rise to EPESS.140 Contrary to this proposal, our results show that there is no correlation between the size of the substituent on the salicylimine ligand and the presence or absence of emission in solution. In addition, there is no correlation between size and the emission quantum yield of the complex in the solid state (Table 3-1). If rotation around the N-aryl (or N-alkyl) bond was giving rise to a non-radiative pathway, then complexes in which rotation is hindered 500 550 600 650 7000.00.20.40.60.81.0  Normalized EmissionWavelength (nm) 53 54 55 56 57550 600 7000.00.20.40.60.81.0  Normalized EmissionWav length (nm) 45 9 46 58 5983  or fixed would be expected to be emissive in solution and hence not show significant EPESS. The 1H-NMR spectrum of 57 shows four inequivalent doublets (δ 1.18, 1.03, 0.87 and 0.62) corresponding to the methyl groups of the isopropyl substituents as well as two septets (δ 3.48 and 2.68) corresponding to the CH groups of the isopropyl substituents, complex 59 shows similar features. The observation of inequivalent diisopropyl substituents on the diisopropylphenyl moiety confirms that there is no rotation of the N-aryl substituent on the NMR timescale, yet complexes 57 and 59 still demonstrate EPESS. These results, as well as others reported in the literature showing complexes with fixed substituents that display EPESS,143 confirm that restricted rotation around the N-aryl bond is not the major cause of EPESS in these complexes.              84   3.3.5 Effects of π-Stacking   To test the possible effects of π-stacking136,143 or aggregation in complexes 45, 46, 49 and 53-59, 2 wt% of each complex was dispersed in a PMMA matrix (Figure 3-8), allowing isolation of the molecules from one another in the solid state.144 The solid state emission maxima in all ten complexes in PMMA are blue-shifted by 21–47 nm compared to the corresponding complexes in the undiluted solid state (Table 3-1). Red-shifts in solid-state absorption and emission spectra are typically observed due to intermolecular interactions,165 Table 3-1. Select photophysical properties of 45, 46, 49 and 53-59. Measurements taken in air. Solution measurements taken in dichloromethane. Complex Solution λem (nm) Solution ϕem Solid λem (nm) Solid ϕem PMMA λem (nm) PMMA ϕem Ir(ppy)2(NOPh) (45) --- --- 609 0.058 570 0.134 Ir(ppy)2(NOFluor) (46) --- --- 633 0.012 604 0.097 Ir(ppy)2(NONapht) (49) --- --- 600 0.045 576 0.096 Ir(ppz)2(NOPh) (53) --- --- 602 0.080 578 0.086 Ir(ppz)2(NONapht) (54) --- --- 598 0.044 574 0.139 Ir(ppz)2(NOFluor) (55) --- --- 632 0.014 604 0.086 Ir(ppz)2(NOiProp) (56) 589 0.013 580 0.028 559 0.047 Ir(ppz)2(NOiProp2Ph) (57) 593 <<0.001a 592 0.049 569 0.099 Ir(ppy)2(NOiProp) (58) 584 <<0.001a 581 0.036 534 0.117 Ir(ppy)2(NOiProp2Ph) (59) --- --- 607 0.028 570 0.109 aQuantum yield was too low to be accurately measured      85  and the blue-shifts observed here confirm that intermolecular solid state interactions are less prevalent when the complexes are placed in the polymer matrix (i.e. the molecules are more isolated). In addition, in each case, the emission quantum yield of the complex in PMMA is higher than that of the solid (Table 3-1), demonstrating that the solid state emission is partially quenched in the aggregated form. These results are consistent with the more common aggregation caused quenching (ACQ) effect16 and demonstrate that π-stacking or aggregation of these complexes in the solid state is not giving rise to EPESS. In fact, π-stacking or aggregation is actually detrimental to the enhancement of the emission observed. In addition, the π-stacking that has been reported previously136,143 always involves phenylpyridine cyclometallating ligands. We also observe EPESS behaviour in complexes bearing phenylpyrazole ligands which typically do not to show long-range π-stacking in the solid state.158,159,160,161,162,163,164 Figure 3-8. Solid state emission spectra of 45, 46, 49 and 53-59 in PMMA, λex = 400 nm, in air.   500 550 600 650 7000.00.20.40.60.81.0  Normalized EmissionWavelength (nm) 53 54 55 56 57500 550 600 650 7000.00.20.40.60.81.0  Normalized EmissionWav length (nm) 45 49 46 58 5986  3.3.6 DFT Calculations   To better understand the emission observed in complexes such as 45, 46, 49 and 53-59 detailed DFT calculations were performed by Professor Francesco Lelj. TD-DFT calculations show that the lowest energy triplet consists mainly of a LUMO-HOMO transition (Figure 3-9) justifying the use of an unrestricted DFT (UDFT) approach to study the first triplet state. UDFT calculations of 45, 46, 49 and 53-59 reveal that the highest singly occupied molecular orbital (HSOMO) and HSOMO-1 contain both Ir metal character as well as contributions from each of the three ligands (Figure 3-10), consistent with emission from a 3MLLCT state. This suggests that the nature of both the cyclometallating ligands as well as the ancillary N^O ligand is important for the observed emission. DFT results show that the emission from 46 and 55 is red shifted relative to the other complexes while 56 and 58 are blue shifted. This is due to a shift in the LUMO from being localized on the salicylimine portion of the N^O ancillary ligand (blue shift) to delocalized onto the N-aryl moiety of the N^O ancillary ligand (red shift).  87  Figure 3-9. HOMO and LUMO plots (ground state) of 45, 46, 49 and 53-59.  HOMO HOMO HOMO HOMO HOMO HOMO HOMO HOMO LUMO LUMO LUMO LUMO LUMO LUMO 56 49 58 57 46 59 LUMO LUMO 54 55 HOMO HOMO LUMO LUMO 45 53 88   Figure 3-10. HSOMO-1 and HSOMO plots (excited triplet state) of 45, 46, 49 and 53-59.  HSOMO HSOMO HSOMO HSOMO HSOMO HSOMO HSOMO HSOMO HSOMO-1 HSOMO-1 HSOMO-1 HSOMO-1 HSOMO-1 HSOMO-1 56 49 58 57 46 59 HSOMO-1 HSOMO-1 54 55 HSOMO HSOMO-1 HSOMO HSOMO-1 45 53 89   DFT and UDFT calculations were performed to help understand the cause of EPESS. For complex 53, the ground state calculation shows that in the most stable structure the plane of the phenol imine ligand and the equatorial plane are almost coplanar (angle between planes = 5.94°). The equatorial plane refers to the plane defined by the cyclometallated phenyl carbons, Ir and the nitrogen and oxygen atoms of the salicylimine ligand (see planes in green and red in Figure 3-11). In the triplet excited state the phenol imine tilts with respect to the equatorial plane leading to two stable conformations of this state (tilted up (43.54°) or down (-25.65)). The cause of this distortion can be rationalised since the LUMO has antibonding character between Ir and the phenol imine ligand. Thus, the plane of the phenol imine tilts with respect to the equatorial plane to reduce the antibonding interaction and allow population of this orbital in the triplet excited state (T1). Hence, the conformers do not arise from a distortion of the phenol imine ancillary ligand, rather the distortion is in how this ligand bonds to the metal. This ligand distortion does not require a rotatable imine substituent, therefore EPESS in complexes that do not have rotatable groups can also be explained by this mechanisim. The largest barrier separating the two conformers in 53 is only 15.7 kJ/mol (Figure 3-11) and as a result, they can rapidly interconvert in solution at room temperature. This geometrical change in the excited state gives rise to a non-radiative decay pathway which deactivates the 3MLLCT state in solution at room temperature. Similar distortions were observed in complexes 45, 46, 49 and 53-59 (Figure 3-12), suggesting that the non-radiative decay pathway has the same origin in all cases. Ligand distortions in solution have been reported as the cause of non-radiative decay in a series of EPESS-active Pt complexes containing similar N^O chelating ligands.166,167 Calculations that simulate a solid state matrix, show that the T1 state is much less distorted than in solution. This leads to an enhancement in the contribution of the Franck 90  Condon factor for the 3MLLCT emission and hence makes this transition more probable in the solid state.  Figure 3-11. Computed energy profile for the excited triplet state geometry of 53 relative to the half chair inversion of the six membered ring. The green plane is the equatorial plane and the red plane is the phenol imine ligand plane. Blue arrows show the transition vectors related to the interconversion between minima and are associated with the imaginary frequency of 23.72i cm-1. 91   Figure 3-12. Excited triplet state geometry of 45, 46, 49, and 54-59 showing ligand distortions. In each case the ‘tilted up’ version is shown. The green plane is the equatorial plane and the red plane is the phenol imine ligand plane.   In addition to Ir(III) complexes with N^O ligands, complexes with O^O ancillary ligands have also been shown to demonstrate EPESS and to be of interest in OLED 54 55 56 57 45 49 46 58 59 92  applications.39,136, 160,168,169  To further test this theory, calculations were performed on a series of known complexes 47-48 and 60-61 (Chart 3-2 and 3-4) containing bidentate O^O ancillary ligands. These complexes also contain ancillary ligands with 6-membered chelate rings and 48, 60 and 61 have been shown to demonstrate EPESS.39,136,160,168  Chart 3-4. Ref.39,160,168    Complex 60 demonstrates EPESS160,168 whereas complex 47 is strongly emissive in both solution and the solid state39,136 so therefore it does not demonstrate EPESS. Calculations on 60 show that ligand distortions occur in the excited triplet state which is in agreement with our interpretation (Figure 3-13). Calculations on 47 however, show that ligand distortions do not occur in the excited triplet state, and instead the acac ancillary ligand remains planar with respect to the equatorial plane (Figure 3-13). This is convincing evidence demonstrating that excited state ligand distortions are the cause of EPESS. Complexes 48 and 61 both demonstrate EPESS39,136,168 and consistent with our interpretation, calculations show that both of these complexes show excited state ligand distortions (Figure 3-13).  93               Figure 3-13. Excited triplet state geometry of 47-48 and 60-61 showing ligand distortions. The green plane is the equatorial plane and the red plane is the acac ligand plane.   In the complexes which demonstrate EPESS (45, 46, 48, 49 and 53-61) the ground state HOMO and/or LUMO must contain significant contribution from the N^O or O^O ancillary ligand (Figure 3-9 and Figure 3-14a). In complex 47, which does not show EPESS, the HOMO and LUMO do not show any contribution from the acac ancillary ligand. While the origin of the excited state ligand distortions is very complex, these results suggest that involvement of the ancillary ligand in the frontier MOs may be causing it to distort.  60 47 61 48 94   Figure 3-14. (a) Ground state HOMO-LUMO plots of 47-48 and 60-61 (b) Triplet state HSOMO-1 - HSOMO plots of 47-48 and 60-61. HOMO LUMO HOMO LUMO 60 47 HOMO LUMO  HOMO LUMO 61 48 (a) HSOMO HSOMO-1 HSOMO HSOMO -1 60 47 HSOMO HSOMO -1 HSOMO HSOMO -1 61 48 (b) 95  3.4 Conclusions   In conclusion, most examples of EPESS-active iridium complexes in the literature contain ancillary ligands bound through a flexible 6-membered chelate ring,136,142,143 suggesting that distortions of the ancillary ligand relative to the equatorial plane may apply more widely as the origin of EPESS in these complexes. The use of 6-membered rings may therefore be a useful design criterion for the synthesis of EPESS active complexes. The few EPESS-active complexes that contain a 5-membered chelate,141,170,171 have very bulky ancillary ligand substituents and in these cases EPESS is almost certainly due to restricted rotation. The relative energies of the cyclometallating and ancillary ligands are likely also important since the emission results from a 3MLLCT state which involves orbitals on all three ligands. Additionally, it is important for the frontier molecular orbitals to contain significant ancillary ligand character.  For example, it is important to ensure that the transition involves orbitals which have a significant contribution from the atoms of the 6-membered chelate ring and not orbitals exclusively on the C^N ligands and/or the periphery of the complex.        96  Chapter 4: Tuning the emission lifetimes of bis-cyclometallated Ir(III) complexes bearing pyridineimine and salicylimine ancillary ligands   4.1 Introduction   Coordination complexes with long-lived excited states are of interest for applications in lifetime based imaging to increase signal to noise ratios,172,173,174 photoredox catalysis13,175,176 and upconversion to enable efficient diffusion-based quenching of a sensitizer.177 These applications are all currently limited by the lack of materials with appropriate emission or excited state lifetimes. For example, coordination complexes embedded in polymer nanoparticles have been used in time-resolved luminescence bioimaging techniques,166,178 however the dynamic range of these techniques is currently limited by the lifetime of the phosphors, and species with longer lifetimes in the microsecond or millisecond time regime that emit in a solid state polymer environment are being sought. In general, organic chromophores show very long phosphorescence lifetimes but are very poorly emissive due to the spin-forbidden nature of the triplet-singlet transition.179 In contrast, coordination complexes with strong spin-orbit coupling often exhibit reasonably intense phosphorescence (3MLCT or 3LLCT), but the emission lifetimes are typically short (<1 μs). To overcome these inherent limitations, two approaches can be considered for the design of long lifetime phosphorescent dyes. One approach involves using a ligand-based triplet energy reservoir to extend the lifetime of an emissive 3MLCT state. This tactic has been demonstrated in ruthenium polypyridyl complexes in solution,67,180 but has rarely been reported for iridium 97  complexes181 and has never been fully explored in a solid state matrix. A second approach involves taking advantage of spin-orbit coupling to increase the quantum yield of formally spin forbidden phosphorescence from an organic emitter. Using this approach, long lived pyrene phosphorescence has been observed in the solid state by the addition of a mercury trifunctional Lewis acid to pyrene, creating a sandwich complex,182 as well as in coordination complexes in solution where the organic emitter is directly coordinated to the metal.183   For bioimaging applications, an important goal is to obtain coordination complexes with long emission lifetimes. In these applications, coordination complexes are often delivered to target tissues encapsulated in a polymeric vessel to help minimize toxicity as well as increase cellular uptake and provide target specificity.184 Cyclometallated iridium complexes 37 and 62-63 (Chart 4-1) containing pyrene based ancillary ligands, Ir(ppz)2(N^XPyrene) (X = N or O) were designed in order to demonstrate how systematic changes in ancillary ligand structure can be used to tune the photophysical properties. Cyclometallated iridium complexes can demonstrate a range of emissive states including MLCT, ILCT and LLCT states,185 allowing the emission energy to be easily tuned. Pyrene is a well-studied polyaromatic hydrocarbon, however the lowest energy singlet state (S1) is the focus of most applications involving pyrene while phosphorescence from the lowest energy triplet state (T1) has rarely been harnessed.186 The design strategy reported herein, involves tuning the relative energies of the charge transfer states involving the metal (3MLCT) and the pyrene-based 3π-π* states to obtain the desired emission behavior.  With this design motif, three scenarios are possible: (a) the 3MLCT state lies lower in energy than the 3pyrene state, (b) the 3MLCT and 3pyrene states are very close in energy or (c) the 3pyrene state lies lower than the 3MLCT state (Scheme 4-1). Complexes in categories (b) or (c) are expected to have extended emission lifetimes compared to those in 98  category (a), as a result of contributions to the excited state lifetime from the long-lived 3pyrene chromophore. In this chapter, it is shown that altering the pyrene-containing ligand can affect the relative energies of the 3MLCT and 3pyrene states to elicit long lived phosphorescence emission. This is accomplished by utilizing the “triplet reservoir” effect in both solution and a polymer host (scenario b) as well as using spin orbit coupling effects to achieve very long lived pyrene-based phosphorescence in the solid state as well as in a polymer matrix (scenario c).    Chart 4-1. Complexes 37 and 62-65.      99  Scheme 4-1. Three scenarios for relative 3MLCT and 3pyrene (π-π*) energy levels.   4.2 Experimental  4.2.1 General   All experiments were performed under an inert nitrogen atmosphere, using standard Schlenk-line techniques. Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc.  Chloro(1-phenylpyrazole)iridium(III) dimer [IrCl(ppz)2]2,82 1-nitropyrene,118 1-aminopyrene,119 NOPyr187 and [Ir(NNiProp)(ppz)2][PF6] (65)130 were prepared according to literature procedures. The synthesis of [Ir(NNMePyr)(ppz)2][PF6] (37) is described in section 2.1.1.  All other solvents and reagents were obtained from commercial sources and used as received. 1H NMR and 13C NMR spectra were obtained using a Bruker AV-400 spectrometer and referenced to the residual protonated solvent peak. Electrospray ionization mass spectrometry data were obtained on a Bruker Esquire LC ion trap mass spectrometer. Microwave reactions were performed on a Biotage Initiator 2.5 microwave synthesizer. Absorption spectroscopy data were obtained on a Varian Cary 5000 UV-vis-near-100  IR spectrophotometer. Fluorescence spectroscopy data were collected on a Photon Technology International QuantaMaster fluorimeter. Transient absorption spectroscopy data were collected using a Princeton Instruments Spectra Pro 2300i Imaging Triple Grating Monochromator/Spectrograph with a Hamamatsu Dynamic Range Streak Camera (excitation source: EKSPLA Nd:YAG laser, λex = 355nm, (fwhm = 35 ps). X-ray crystallographic analyses were performed by Dr. Brian Patrick using a Bruker X8 Apex CCD diffractometer.  DFT calculations were performed by Professor Francesco Lelj using the widely diffused hybrid xc functional B3LYP.146 This has been shown to have some drawbacks because of the wrong asymptotic behavior; therefore the 1 parameter xc functionals mPW1PW91147 and PB1PBE148 as well as M06, M02X120 and the asymptotic corrected hybrid functional CAM-B3LYP were also applied.188 For all second period atoms the Dunning122 all electron basis set augmented by a set of d polarization functions (D95(d)) were used. Hydrogen atoms not involved in any hydrogen bond, were described by the same Dunning basis set that does not include p polarization functions. For Ir the new double ζ Stuttgart123 basis set including f polarization functions and relativistic effects by a fully relativistic small core pseudopotential148 (SDD09) were used and not the default SDD as included in Gaussian09c01. The ultrafine option with 99590 grid points was used for the integral calculations for all atoms except Ir where a total of 1566228 grid points were used. The first triplet state geometries were computed at the unrestricted level. Singlet and triplet excitations were computed with the TD-DFT linear response approach in the Random Phase Approximation.189 Analysis of the multideterminental wavefunctions involved in the transitions has been performed using the natural transition orbital approach.190 All calculations were performed using Gaussian09,191 version C01 and D01. 101  4.2.2 Methods  Synthesis of [Ir(NNMePyrMe)(ppz)2][PF6] (62)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), 2-acetylpyridine (0.017 mL, 0.15 mmol), 1-pyrenemethylamine hydrochloride (0.0402 g, 0.150 mmol) and potassium hexafluorophosphate (0.025 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting deep red solution was passed through a Celite pad and the filtrate reduced in volume.  Layering with hexanes yielded the desired product as a red powder. The product was purified by column chromatography using MeCN to elute any unreacted 1-pyrenemethylamine and then MeCN:H2O:KNO3(aq) (96:3:1) to elute complex 62 (0.030 g, yield 46%). 1H NMR (CD3CN, 400 MHz, hydrogen numbering is the same as in the X-ray structure): δ 8.41 (1H, d, J = 8.3, H4),  8.36 (1H, d, J = 3.1, H26), 8.38-7.94 (9H, m, H3,29,1,11,23,24,20,21,22), 7.84 (1H, d, J = 2.2, H25), 7.76 (1H, d, J = 9.4, H10), 7.63 (1H, t, J = 7.7, H2), 7.55 (1H, d, J = 8.1, H16), 7.47 (1H, d, J = 2.9, H34), 7.40-7.38 (1H, m, H38), 7.01 (1H, d, J = 2.4, H36), 6.99-6.95 (1H, m, H39), 6.77-6.73 (2H, m, H40,27), 6.61 (1H, d, J = 7.9, H15), 6.58 (1H, t, J = 2.2, H35), 6.36-6.32 (1H, m, H31), 6.13-6.11 (3H, m, H8a,8b,30), 6.00 (1H, dd, J = 7.6, 1.2, H41), 5.69 (1H, d, J = 4.0, H32), 2.90 (3H, s, H7abc). 13C NMR (CD3CN, 100 MHz): 139.83-124.16 (overlap C3,29,1,11,23,24,20,21,22), 139.0 (C25),  138.6 (C36), 132.9 (C41), 132.6 (C30), 129.4 (C2), 128.6 (C4), 127.8 (C26), 126.9 102  (C34), 126.6 (C27), 126.5 (C31), 123.8 (C39), 123.4 (C16), 122.6 (C10), 121.4 (C15), 111.3 (C38), 110.1 (C32), 108.5 (C35), 108.1 (C40), 57.1 (C8a/b), 16.1 (C7). HR ESI MS: Calcd for C42H32N6Ir: 811.2294; Found: 811.2289 [M]+.  Synthesis of Ir(ppz)2(NOPyr) (63)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), NOPyr (0.048, 0.15 mmol) and sodium carbonate (0.016 g, 0.15 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting dark yellow solution was passed through a Celite pad and the filtrate reduced to approximately 2 mL in volume.  Layering with hexanes yielded the desired product as a dark yellow precipitate. The product was purified by column chromatography using CH2Cl2 to elute any unreacted NOPyr and then EtOAc:CH2Cl2 (2:1) to elute complex 63 (0.027 g, yield 50%). 1H NMR (CD2Cl2, 400 MHz, hydrogen numbering is the same as in the X-ray structure): δ 8.30 (1H, s, H7), 8.17 (1H, d, J = 2.6, H26), 8.13-8.11 (2H, m, H21,24), 8.06 (1H, d, J = 7.3, H22), 7.98-7.92 (3H, m, H15,23,35), 7.86 (1H, d, J = 8.7, H14),  7.76 (1H, d, J = 8.1, H19), 7.59 (1H, d, J = 9.3, H10), 7.52 (1H, d, J = 8.1, H20), 7.36-7.33 (2H, m, H2,33), 7.25 (1H, d, J = 8.1, H37), 7.16 (1H, d, J = 7.8, H4),  7.03 (1H, d, J = 9.3, H9), 6.88 (1H, t, J = 7.7, 7.5, H38), 6.77-6.74 (2H, m, H1,25), 6.68-6.65 (2H, m, H34,39), 6.43 (1H, t, J = 7.3, 7.3, H3), 6.19-6.14 (2H, m, H28,40), 6.03-5.99 (2H, m, H29,30), 5.90 (1H, d, J = 8.3 H31). 13C NMR (CD2Cl2, 100 MHz): 139.5 (C24), 137.9 (C35), 136.4 (C4), 135.7 (C30), 135.1 (C2), 134.4 (C40), 127.5 (C14), 103  127.3 (C15), 127.1 (C10), 127.0 (C26), 126.9 (C23), 125.9 (C33), 125.8 (C34), 125.0 (C21), 124.9 (C28), 124.7 (C22), 124.5 (C25), 123.9 (C19), 122.2 (C20), 122.1 (C38), 121.3 (C9), 120.4 (C29), 113.9 (C3), 111.3 (C37), 109.4 (C31), 107.6 (C1), 107.3 (C39). HR ESI-MS: Calcd for C41H29N5OIr: 798.1978; Found: 798.1966 [M+H]+.   Synthesis of [Ir(ppz)2(NNMePh)][PF6] (64)  [IrCl(ppz)2]2 (0.070 g, 0.068 mmol), 2-acetylpyridine (0.017 mL, 0.15 mmol), aniline (0.014 mL, 0.150 mmol) and potassium hexafluorophosphate (0.025 g, 0.14 mmol) were placed in a microwave vial with 3.5 mL of ethanol. The suspension was degassed with nitrogen for 4 minutes. The vial was placed in the microwave reactor and heated under microwave irradiation for 30 minutes at 100 °C (18 bar, 155 W). The solvent was then removed in vacuo and the solid residue dissolved in 10 mL CH2Cl2. The resulting orange solution was passed through a Celite pad and the filtrate reduced in volume.  Layering with hexanes yielded the desired product as a orange powder. The product was purified by column chromatography using MeCN to elute any unreacted aniline and then MeCN:H2O:KNO3(aq) (96:3:1) to elute complex 64 (0.053 g, yield 48%). 1H NMR (CD3CN, 400 MHz): δ 8.41 (1H, d, J = 2.7, H25),  8.34 (1H, d, J = 8.0, H4), 8.27 (1H, d, J = 2.7, H16), 8.21-8.12 (3H, m, H1,3,23), 7.77 (1H, d, J = 2.2, H14), 7.59 (1H, t, J = 6.7, H2), 7.44 (1H, d, J = 7.8, H18), 7.36 (1H, d, J = 8.0, H27), 7.09-7.03 (2H, m, H11,19), 7.01-6.90 (2H, m, H12,28), 6.90-6.79 (2H, m, H20,24), 6.76-6.65 (3H, m, H13,15,29), 6.46 (1H, t, J = 5.3, H10), 6.25 (1H, dd, J = 7.4, 1.2, H21), 6.02 (1H, dd, J = 7.6, 1.2, H30), 5.84 (1H, dd, J = 7.4, 1.0, H9), 2.57 (3H, s, H7abc). 13C NMR (CD3CN, 100 MHz): 151.6 (C1 or 3 or 23), 147.5 (C18), 140.4 (C1 or 3 or 23), 139.5 104  (C14), 138.3 (C1 or 3 or 23), 132.9 (C21), 132.4 (C30), 131.6 (C9), 129.6 (C2), 129.1 (C4), 128.7 (C11 or 19), 127.5 (overlap C16 and 25), 126.6 (C20 or 24), 126.2 (C11 or 19), 125.8 (C20 or 24), 125.4 (C13 or 15 or 29), 124.6 (C10), 122.9 (C12 or 28), 122.1 (C13 or 15 or 29), 111.2 (C27), 107.9 (C13 or 15 or 29), 18.4 (C7). HR ESI MS: Calcd for C31H26N6Ir: 673.1825; Found: 673.1827 [M]+.  4.2.3 X-ray Crystallography   All crystals were mounted on a glass fiber. The crystal structure data were obtained and the structures were solved by Dr. Brian Patrick. All measurements were made using a Bruker Apex DUO diffractometer with graphite monochromated Mo-Kα radiation. Data were collected and integrated using the Bruker SAINT127 software package. Data were corrected for absorption effects using the multi-scan technique (TWINABS192) or (SADABS128) for 62 and 63 respectively. The data were corrected for Lorentz and polarization effects. The structures were solved by direct methods.129   [Ir(NNMePyrMe)(ppz)2][PF6] (62)   An orange needle crystal C42H32N6F6PIr.CH2Cl2·1/4H2O having approximate dimensions of 0.02 x 0.04 x 0.20 mm was used. The data were collected at a temperature of -183.0 + 0.1°C to a maximum 2θ value of 55.9°. Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 10.0-second exposures. The crystal-to-detector distance was 59.65 mm. Of the 63183 reflections that were collected, 20728 were unique (Rint = 0.058) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.673 and 0.930, respectively. The material crystallizes as a two-component ‘split-105  crystal’ with components one and two related by a 2.4º rotation about the real axis.  Data were integrated for both twin components, including both overlapped and non-overlapped reflections. Subsequent refinements were carried out using an HKLF 5 format data set containing complete data from both components one and two, including overlaps.  One molecule of solvent CH2Cl2 is in the asymmetric unit, as well as a small (~0.25 eq) of H2O.  The CH2Cl2 molecule is disordered and is modeled in two orientations using mild restraints to maintain reasonable geometries. All non-hydrogen atoms were refined anisotropically.  All hydrogen atoms were placed in calculated positions, however no hydrogen atoms were located for the water molecule.  The final formula includes 0.25 oxygen and 0.5 hydrogen atoms.   The final cycle of full-matrix least-squares refinement on F2 was based on 20728 reflections and 571 variable parameters and converged.  Ir(ppz)2(NOPyr) (63)   A yellow flake crystal of C41H28N5OIr·1/2H2O having approximate dimensions of 0.02 x 0.16 x 0.18 mm was used. The data were collected at a temperature of -183.0 + 0.1°C to a maximum 2θ value of 53.0°. Data were collected in a series of ϕ and ω scans in 0.5° oscillations using 30.0-second exposures. The crystal-to-detector distance was 40.17 mm. Of the 33283 reflections that were collected, 12990 were unique (Rint = 0.054) and equivalent reflections were merged. The minimum and maximum transmission coefficients were 0.693 and 0.918, respectively. The original solution, consisting of two Ir-complexes and one water molecule, could not be reasonably refined with a final R1 = 0.19, large residual electron density peaks and holes (ranging from +12e to -20e) and many atoms with NPD displacement parameters 106  after anisotropic refinement.  The program ROTAX suggested possible pseudo-merohedral twinning about the (1 0 0) direct lattice direction.  Using the appropriate twin law, including racemic twinning, resulted in a stable refinement with R1 = 0.057 and residual electron density in the +/-2.4e range.  The RIGU and ISOR restraints were also used to generate more reasonable ADP’s.  All non-hydrogen atoms were refined anisotropically.  All hydrogen atoms were placed in calculated positions. The final cycle of full-matrix least-squares refinement on F2 was based on 32005 unmerged reflections and 874 variable parameters and converged.  4.3 Results and Discussion  4.3.1 Synthesis and Characterization   Complexes 37 and 62-63 were synthesized by reacting [IrCl(ppz)2]2 and the corresponding ligand or ligand precursors under microwave irradiation for 30 minutes at 100 °C (similar to procedures used in Chapters 2 and 3). For comparison with 37 and 62-63, model complex 64 was synthesized in an analogous fashion and 65 was synthesized as previously reported.130 The syntheses were carried out under microwave irradiation81,82 giving high yields in short times. The complexes were then purified by column chromatography eluting with KNO3(aq) and then converted by metathesis back to PF6 salts. 37 is characterized in section 2.1.1 and 65130 has been characterized previously. 62-64 were characterized by high resolution mass spectrometry and 1H NMR (COSY, NOESY, TOCSY and HSQC) allowing full assignment of all resonances. X-ray crystal structures of 62 and 63 were also obtained (see section 4.3.2).  107  4.3.2 Solid-State Molecular Structures   Single crystals of [Ir(NNMePyrMe)(ppz)2][PF6] (62) suitable for X-ray diffraction were grown from a concentrated solution of 62 in dichloromethane which was layered with hexanes at 0°C and then slowly warmed to room temperature. The X-ray crystal structure shows the expected atom connectivities for 62 and shows that the pyrene moiety undergoes weak intramolecular pi-stacking with a phenylpyrazole ligand (centroid-centroid distance = 3.87Å). See Table A1-16 for selected bond lengths and angles.  Figure 4-1. Solid state structure of [Ir(NNMePyrMe)(ppz)2][PF6] (62). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms, solvent and counterions are omitted for clarity.    Single crystals of Ir(ppz)2(NOPyr) (63) suitable for X-ray diffraction were grown from a concentrated solution of 63 in dichloromethane which was layered with hexanes at 0°C and then slowly warmed to room temperature. The X-ray crystal structure shows the expected atom 108  connectivities for 63. The plane of the salicylimine ligand is nearly coplanar with the plane of the rest of the molecule, with a torsion angle O(1)-Ir(1)-N(1)-C(7) of 2.5(4)°. See Table A1-18 for selected bond lengths and angles.   Figure 4-2. Solid state structure of Ir(ppz)2(NOPyr) (63). Thermal ellipsoids are drawn at 50 % probability. Hydrogen atoms and solvent are omitted for clarity.  4.3.3 Photophysical Properties   The absorption spectra of 37 and 62-63 show phenylpyrazole π-π* transitions below 300 nm as well as pyrene π-π* transitions from 270-375 nm. The low energy absorptions above 400 nm are assigned to spin forbidden 3MLCT and 3LLCT transitions (Figure 4-3a). Similar 109  phenylpyrazole π-π* transitions below 300 nm as well as spin forbidden 3MLCT and 3LLCT transitions are observed in model complexes 64 and 65 (Figure 4-3b).  It is important to note that the pyrene π-π* transitions are well resolved from the 3MLCT transitions in 37 and 62-63 and retain strong vibronic coupling, characteristic of pyrene, suggesting weak electronic coupling between the two components. Figure 4-3: (a) Normalized absorption spectrum of 37 and 62-63 in dichloromethane (b) Normalized absorption spectrum of 64 and 65 in dichloromethane.   Complex 37 is not emissive in solution due to a distortion of the imine N in this complex which gives rise to a non-radiative decay pathway.130 37 shows very weak emission from the 3MLCT state130 centered at 631 nm when dispersed in a PMMA film (Figure 4-4). Below the glass transition temperature of PMMA (Tg = 114°C), molecules dispersed in this polymer are separated and behave as if they are isolated molecules in the solid state.144 A biexponential fit of the emission decay from 37 in PMMA gives two components with lifetimes of 329 ns and 2.4 μs, respectively. The transient absorption spectrum of 37 in a PMMA film 300 400 500 600 7000.00.20.40.60.81.0  Normalized AbsorbanceWavelength (nm)  64  65300 400 500 600 7000.00.20.40.60.81.0  Normalized AbsorbanceWavel ngth (nm)  37  62  63(a) (b) 110  shows features attributed to a pyrene radical anion as well as bands attributed to triplet pyrene, indicating that the 3MLCT and 3pyrene states coexist, and can be assumed to lie close in energy. In addition, the solid state time-resolved emission spectrum shows two different bands which decay separately (Figure 4-5).  This ‘dual emission’ results from slow energy transfer between the 3MLCT and 3pyrene states at equilibrium. The rates of forward (kf) and back (kb) energy transfer can be estimated using equations 4-1 and 4-2, where τMLCT and τPyr correspond to the decay of the excited iridium and pyrene moieties respectively. τ2 is the observed emission lifetime, α is the fraction of excited triplet states which are pyrene-like while (1 – α) is the fraction of excited triplet states which are MLCT-like. It was found that kf = 2.8 × 106 s-1 and kb = 2.4 × 105 s-1 in PMMA (Table 4-1), confirming that energy transfer in 37 is slow in PMMA. Dual emission has previously been observed in a pyrene-Ru(II) diimine dyad as a result of slow energy transfer.193 It was suggested that this unusual behaviour was a consequence of molecular rigidity, where back-folding of the pyrene ligand is not possible and therefore only one conformation is present. This rigidity leads to a fixed orientation of the two interacting triplet states which can affect the electronic coupling as well as the transition dipole moments of the two states.194 It has been shown that this triplet energy transfer proceeds via a Dexter mechanism,195 and therefore the rates of forward and back energy transfer are in part, due to electronic coupling. Complex 37 is rigid as a result of dispersion in a solid state PMMA matrix,196 which gives rise to the slow forward and back energy transfer observed. While the lifetimes of 37 in PMMA are relatively short (329 ns and 2.4 μs), they are significantly extended in comparison to model complex 64 in PMMA (45.8 ns and 198 ns), where the pyrene 111  substituent is replaced with a phenyl group. This further confirms that the pyrene group is contributing to the long lifetime observed for 37.  Figure 4-4. (a) Emission spectrum and (b) transient absorption spectrum of 2 wt% of 37 in a PMMA film at time delays shown; λex = 355 nm. Figure 4-5. (a) Time resolved emission spectra of 2 wt% of 37 in PMMA with intensity in arbitrary units. (b) Time resolved emission spectra of 2 wt % of 37 in PMMA with normalized intensity.  550 600 650 700 750400006000080000  Counts (s-1)Wavelength (nm)400 450 500 550 60 650 700-200002000400060008000  ODWav length (nm) 0.4 - 1.0 s 1.6 - 2.2 s 5.0 - 5.5 s 8.4 - 9.1 s(a) (b) 500 550 600 650 70020000400006000080000100000120000140000160000180000200000220000  Intensity (a.u)Wavelength (nm) 647 ns 895 ns 1.22 s 2.45 s 8.58 s500 550 600 650 7000.0.20.40.60.81.0  Normalized IntensityWav length (nm) 647 ns 89  ns 1.22 s 2.45 s 8.58 s(a) (b) 112  1𝜏2= 𝛼1𝜏Pyr+ (1 −  𝛼)1𝜏MLCT                                                     𝟒 − 𝟏 𝛼(1 −  𝛼)= 𝐾eq = 𝑘f𝑘b                                                             𝟒 − 𝟐  Table 4-1. Photophysical properties of iridium complexes 37 and 62-65 in dichloromethane and PMMA.  λem (DCM, nm) τem (DCM, μs) λem (PMMA, nm) τem1 (PMMA, μs) τem2 (PMMA, μs) keq kf (s-1) kb (s-1) ΔE (cm-1) 37 ----- ----- 631 0.329 2.4 11.5a 2.8 × 106 a 2.4 × 105 a 505a 62 615 2.7 610 2.0 28.1 30.3a 13.3b 4.8 × 105 a 1.9 × 108 b 1.6 × 104 a 1.4 × 107 b 706a 536b 63 ----- ----- 615 18.0 104 ----- ----- ----- ----- 64 ----- ----- 583 0.046 0.198 ----- ----- ----- ----- 65 590 0.145 572 0.460 0.877 ----- ----- ----- ----- aCalculated using data obtained from a PMMA film bCalculated using data obtained from a DCM solution   Changing the nature and length of the linker between the pyrene and metal in 37 is expected to affect the 3MLCT and 3pyrene state energies as well as the degree of electronic coupling between the states. Therefore, the pyrene directly bonded to the coordinated nitrogen was replaced with one linked via a methylene spacer (complex 62), as it is known that spacer length can affect reversible energy transfer.74,181  In contrast to 37, complex 62 shows 3MLCT emission in solution (Figure 4-6a) at 615 nm with a lifetime of 2.7 μs. This emission lifetime is much longer than that observed for complex 65 with an N-isopropyl substituent in place of the N-methylenepyrenyl substituent 113  which has a lifetime of 145 ns in solution.130 The solution transient absorption spectrum of 62 shows features attributed to the triplet pyrene state (Figure 4-7a). These data suggest that reversible energy transfer between 3MLCT and 3pyrene states is occurring in solution, giving rise to an extended 3MLCT emission lifetime. The rates of forward and back energy transfer (kf = 1.9 × 108 s-1 and kb = 1.4 × 107 s-1, Table 4-1) between the 3MLCT and 3pyrene states of 62 in dichloromethane can be estimated by using the rise time (Figure 4-8) for the formation of 3pyrene which gives the rate of establishment of the equilibrium.  Figure 4-6. (a) Emission spectra of 62 in dichloromethane in air (black line) and under argon (red line) and (b) emission spectrum of 2 wt% of 62 in a PMMA film.        400 450 500 550 600 650020004000600080001000012000140001600018000  Counts (s-1)Wavelength (nm) under air  under argon500 550 600 650 700 7500.00.20.40.60.81.01.2  Normalized EmissionWav length (nm)(a) (b) 114  Figure 4-7: (a) Transient absorption spectrum of 62 in dichloromethane at time delays shown; λex = 355nm. (b) Transient absorption spectrum of 62 in PMMA at time delays shown; λex = 355nm.  Figure 4-8. Rise time following the growth of triplet pyrene in 62 in dichloromethane.    20 30 40 50 60 70 80 90 10050001000015000200002500030000  ODTime Delay (ns)= 5.3 ns400 450 500 550 600 650 70002000400068000 OD  Wavelength (nm) 4-11 s 92-99 s500 550 600 650 7000200040006000800010000  ODWavel ngth (nm) 456 - 952 ns 3.25 - 3.76 s 9.49 - 9.98 s(a) (b) 115   In a PMMA film, complex 62 shows broad 3MLCT emission centered at 610 nm with weak shoulders (Figure 4-6b), with lifetimes of 2.0 and 28.1 μs obtained from a biexponential fit of the emission decay data. Similar to 37, the two observed lifetimes for 62 can be attributed to slow forward and back energy transfer between the 3MLCT and 3pyrene states in the polymer film (kf = 4.8 × 105 s-1 and kb = 1.6 × 104 s-1, Table 4-1). This slow energy transfer is reflected in the solid state time-resolved emission spectrum which shows two distinct bands that decay separately (Figure 4-9). The mono-exponential emission decay of 62 in solution, as well as the presence of one band in the time-resolved emission spectrum (Figure 4-10) and the estimated values of kf and kb (Table 4-1), confirms that energy transfer is fast in solution compared to the PMMA film. The emission lifetime of the corresponding complex without pyrene is also longer in PMMA than in solution (for example, the lifetime of 65 is 145 ns in solution and biexponential in PMMA with components of 460 ns and 877 ns).  This is likely a consequence of deactivation of non-radiative decay pathways in the solid state which are operative in solution.197  However, the absolute lifetimes for 37 and 62 in PMMA are much longer than those for the corresponding complexes without pyrene. These observations demonstrate that while energy transfer is slower, the triplet reservoir has been retained in the solid state. Complexes 37 and 62 are the first examples of coordination complexes where reversible energy transfer has been characterized in a polymer film. 116  Figure 4-9. (a) Time resolved emission spectra of 2 wt% of 62 in PMMA with intensity in arbitrary units. (b) Time resolved emission spectra of 2 wt% of 62 in PMMA with normalized intensity.          450 500 550 600 650 70030000400005000060000700008000090000100000110000  Intensity (a.u)Wavelength (nm) 418 ns 3.95 s 6.00 s 70.01 s450 500 550 600 650 7000.0.20.40.6.81.0  418 ns 3.95 s 6.00 s 7 .01 s  Normalized IntensityWav length (nm)(a) (b) 117  Figure 4-10. (a) Time resolved emission spectra of 62 in dichloromethane with intensity in arbitrary units. (b) Time resolved emission spectra of 62 in dichloromethane with normalized intensity.   It is important to note that the biexponential decay in 37 and 62 has been attributed to slow forward and back energy transfer between 3MLCT and 3pyrene states occurring in PMMA. This is in agreement with time-resolved emission data in the polymer films which show two distinct bands that decay separately. These two bands are assigned to a pre-equilibrium 3MLCT198 and equilibrium 3MLCT state respectively. Studies on luminescent metal complexes embedded in polymer matrices have previously shown multiexponential emission decay curves. These multiexponential decay kinetics have been attributed to different microenvironments within the polymer matrix resulting in different emission lifetimes. In these examples, distinct bands are not observed in the time-resolved emission spectra but instead a slight blue shift of a single emission band is observed with time.199 Model complexes 64 and 65 also show biexponential emission decay curves in PMMA but do not show two 500 550 600 650 7002000020500  Intensity (a.u)Wavelength (nm) 513 ns 665 ns 857 ns 1.89 s 3.52 s500 550 600 650 7000.00.20.40.60.81.0  Normalized IntensityWav length (nm) 513 ns 665 ns 857 ns 1.89 s 3.52 s(a) (b) 118  distinct bands in the time-resolved emission spectra (Figure 4-11). While the possibility of different polymer microenvironments giving rise to the observed biexponential decay in 37 and 62 cannot be ruled out, the time-resolved emission data in addition to comparisons with model complexes and literature data suggest that the lifetimes originate from one state before and after equilibration as opposed to one state in different environments inside the polymer host. Figure 4-11. (a) Time resolved emission spectra of 64 in PMMA. (b) Time resolved emission spectra of 65 in PMMA.   In principle, if the energy of the 3MLCT state of a coordination complex is sufficiently increased in relation to that of a 3pyrene state, there may no longer be efficient reversible energy transfer between the 3MLCT and the 3π-π* state. This is expected to result in a purer, long lived 3pyrene emission assuming that spin orbit coupling is sufficiently large. An increased 3MLCT energy in complexes such as 37 and 62 can be achieved by changing the pyridineimine for a salicylimine in the ligand backbone. In general, iridium complexes 540 560 580 600 620 640 6602050021000215002200022500230002350024000  Intensity (a.u.)Wavelength (nm) 25-34 ns 43-52 ns 67-76 ns 90-99 ns 128-137 ns525 550 575 600 625 650404004060040800410004120041400416004180042 004220042400  Intensity (a.u.)Wav length (nm) 26-38 ns 37-49 ns 52-64 ns 67-79 ns 87-99 ns(a) (b) 119  containing salicylimine ligands have been shown to emit from a 3MLCT based state at higher energies than iridium complexes containing analogous pyridineimine ligands (Chapter 3). This is a consequence of the electron donating nature of the oxygen chelator compared to nitrogen which effectively raises the LUMO energy in these complexes. Complex 64, for example, emits at 620 nm in the solid state whereas the analogous salicylimine complex Ir(ppz)2(NOPh) emits at 602 nm (Chapter 3).   Complex 63 is structurally similar to 37 but with a salicylimine-based ancillary ligand. Complex 63 is not emissive in solution at room temperature. This lack of emission is attributed to non-radiative decay caused by distortions of the 6-membered N^O chelate ring relative to the equatorial plane of the molecule (See discussion in Chapter 3). DFT calculations show that 63 undergoes similar distortions (Figure 4-12), which is consistent with the lack of emission at room temperature in solution. The N^O-aryl complexes shown in Chapter 3 display broad phosphorescence emission in the solid state and in PMMA arising from a 3MLLCT type state. In contrast, 63 shows weak, structured phosphorescence in the solid state centered at 615 nm. When dispersed in PMMA, 63 shows stronger structured phosphorescence with a lifetime of 104 μs at 615 nm, consistent with emission from a 3π-π* pyrene state (Figure 4-13a). The transient absorption spectrum of 63 in a PMMA film shows an excited state absorption typical of 3pyrene, supporting this state as the origin of the phosphorescence (Figure 4-13b). In addition, the structured emission and very long lifetime suggest that the emission predominantly originates from a 3pyrene (3IL) state. The emission lifetime of 63 is shorter than the reported lifetime for free pyrene phosphorescence in a frozen glass (0.7 s). The shortened lifetime compared to that of free pyrene can be attributed to the strong spin orbit coupling effect of iridium enabling decay from the triplet pyrene state, and leading to shorter lifetimes 120  than expected from pyrene itself in which the transition is spin forbidden.182 Interestingly, this is the first example of pyrene phosphorescence at room temperature in the solid state from a coordination complex.        Figure 4-12.  (a) Ground state geometry of complex 63 and (b) Triplet state geometry of complex 63 showing ligand distortion. Figure 4-13. (a) Emission spectrum and (b) transient absorption spectrum of 2 wt% of 63 in a PMMA film at a time delay of 18-90μs; λex = 355 nm.   (a) (b) 550 600 650 700 7500.00.20.40.60.81.0  Normalized EmissionWavelength (nm)400 450 500 550 600 650 700-4000-2000020004 00  ODWav length (nm) 18-90 s(a) (b) 121  4.3.4 DFT Calculations   DFT calculations were performed on 37 and 62-65 to obtain the natural transition orbitals which give insight into the origin of the lowest lying triplet states (T1 and T2). Natural transition orbitals190 can be used to visualize the origin and destination orbitals involved in monoelectronic excitations. Natural transition orbital analysis generates a new set of orbitals that allows description of the electronic transition in terms of two of these new orbitals, one describing the hole resulting from the expulsion of one electron and the other describing the orbital housing the expelled electron. In complexes 37 and 62, the lowest lying triplet state (T1, Figure 4-14) is localized on the pyrene moiety, consistent with T1 being exclusively 3pyrene in nature. In complexes 37 and 62, T2 is a mixed charge transfer state from a mixed metal + a ligand orbital to a ligand orbital (Figure 4-14). It is not uncommon for the emissive state (typically T1) in bis-cyclometallated Ir(III) complexes to be attributed to a combination of decay from 3MLCT and 3LLCT states200,201,202 or alternatively to a 3MLLCT state.159 It is more rare however, to observe a T1 that is purely ligand localized (3LC).203 These calculations support what is observed experimentally and fit the criteria necessary for the triplet reservoir effect to be observed, that is T1 is a π-π* state on pyrene while T2 has significant MLCT character.  In complex 63, the calculations show that the lowest lying triplet (T1) is localized on pyrene, whereas T2 is calculated to be a mixed charge transfer state from a mixed metal + ligand orbital to a ligand orbital involving only the pyridineimine moiety of the ancillary ligand. In contrast to complexes 37 and 62, the phenylpyrazole ligands do not contribute to the calculated T1 or T2 states in complex 63. In model complexes 64 and 65, T1 is found to be a mixed charge transfer state from a metal + ligand to ligand orbital (Figure 4-14), analogous to 122  T2 in complexes 37 and 62, and similar to what is observed most commonly as the T1 state in bis-cyclometallated Ir(III) complexes.159,200 This is consistent with the lowest lying triplet state of 64 and 65 having significant 3MLCT character. Figure 4-14. Natural transition orbitals representing the lowest lying triplet states T1 and T2 for complexes 37 and 62-65 computed from TD-DFT at the SDD09/D95(d)/M06/DCM level of theory. 62 63 T1 hole T1 electron T2 hole T2 electron 37 T1 hole T1 electron T2 hole T2 electron  64 65 T1 hole T1 hole T1 hole T1 electron T1 electron T1 electron T2 hole T2 hole T2 hole T2 electron T2 electron T2 electron 123  4.4 Conclusions   In summary, complexes 37 and 62 represent significant additions to the small family of iridium complexes showing extended lifetimes due to excited-state equilibration. This reversible energy transfer has been characterized in solution and for the first time, the equilibration process has been characterized in a solid state polymer film. Additionally, complex 63 has been rationally designed to achieve the first example of long lived pyrene phosphorescence from a coordination complex in the solid state as well as in a polymer film. The ability to rationally tune excited state lifetimes in coordination complexes is relevant to photoredox catalysis and upconversion applications. In addition, the kinetic inertness of low spin d6 octahedral complexes such as 37 and 62-63, large Stokes shifts (>100 nm) and microsecond emission lifetimes makes these complexes potential candidates for time-resolved bioimaging techniques.    124  Chapter 5: Conclusions and future work  5.1 Conclusions and Future Work   Scientists continue to be captivated by the relationship between the structure of materials and their resulting properties. By understanding structure-property relationships, materials can be improved or tailored for specific applications and new materials can be rationally designed. In this thesis, a number of different structure-property relationships have been developed and explored.   To better understand structure-property relationships, it is helpful to synthesize and study a series of materials that differ by only small modifications. By observing how minor synthetic modifications affect the properties of a material, trends can be revealed. These trends can be rationalized by comparison to known materials or through the use of computational chemistry.  To this end, each chapter of this thesis explores the effect of relatively small changes to ancillary ligand frameworks on the structural and electronic properties of bis-cyclometallated iridium complexes. Despite the minor nature of these modifications, significant changes in properties were found to result in some cases.  Iridium complexes functionalized with bulky pyrene containing pyridineimine ligands are studied in Chapter 2. Here, the effect of replacing an aldimine with a ketimine ligand framework is explored as well as the effect of changing the sterics of the imine ligand substituent. It is shown that replacing the methyl group of the pyridineketimine ligand with a hydrogen results in a lower barrier to rotation and leads to the interconversion of atropisomers on the NMR timescale at room temperature. Understanding how the structure of these 125  complexes affects their atropisomeric behaviour is fundamentally important for applications in molecular switches. A molecular switch requires a molecule that exists in two or more stable states that can be reversibly switched between those states. An understanding of the structural relationship governing the rotational energy barrier in these bis-cyclometallated iridium complexes allows for the rational design of coordination complexes that exist in two or more stable states. Additional changes to the ancillary ligand substituent may be explored in the future to obtain iridium complexes that switch reversibly between atropisomeric forms using various stimuli. For example, the use of a photoswitchable substituent such as an azobenzene derivative to achieve photochemical switching or the use of a substituent that can be protonated/deprotonated to achieve pH switching may be interesting.  A series of bis-cyclometallated (ppz or ppy) iridium complexes bearing salicylimine or acetylacetonate ligands are studied in Chapter 3. The effect of both the cyclometallating ligand as well as the ancillary ligand framework on the resulting photophysical properties is examined. It is shown that the cyclometallating ligand does not have a significant effect on the emission properties observed and that the lack of emission in solution results from excited state ancillary ligand distortions which are favoured due to the presence of a flexible, six-membered chelating ring. Understanding how the structure of these complexes affects their solution and solid state emission behaviour gives rise to a series of design principles that are required to prepare complexes that display enhanced phosphorescence emission in the solid state (EPESS). Learning how solid state interactions affect emission behaviour is fundamentally important for solid state device technologies such as OLEDs. The performance of a solid state device relies on the properties of the component materials when assembled on a molecular level. As a consequence, an understanding of how molecular arrangements affect the properties 126  of these materials is imperative when designing a device. Additional DFT calculations to determine the exact cause of the excited state ancillary ligand distortions occurring in these complexes would allow for a more thorough understanding of the mechanism of EPESS. This may give rise to additional criteria necessary for the design of complexes that show EPESS or alternatively, to specifically design complexes that do not show this phenomenon which is necessary for applications that require complexes that emit in solution. Studying additional complexes both experimentally and theoretically that contain 5-membered (ie. less flexible) chelate rings but still show EPESS may also be of interest to determine if the mechanism is equivalent.   Iridium complexes bearing pyrene-containing pyridineimine and salicylimine ligands are studied in Chapter 4. The effect of the ancillary ligand framework on the resulting emission lifetimes is explored. It is shown that an increase in the tether length between the nitrogen and pyrene moiety of a pyrenyl pyridineketimine ancillary ligand increases the emission lifetime in these complexes by enhancing the triplet reservoir effect. By applying structure-property relationships learned from the work reported in Chapters 2 and 3, an iridium complex with long-lived pyrene phosphorescence is rationally designed by replacing the pyridineimine with a salicylimine framework. Understanding how the structure of these complexes affect the emission and excited state lifetimes observed is relevant to applications in photoredox catalysis, upconversion and time-resolved bioimaging techniques. In these applications, materials with extended excited state or emission lifetimes are needed to enhance photocatalytic activity, enable efficient diffusion-based quenching of a sensitizer or increase signal to noise ratios respectively. Additional changes to the length of the tether between the imine nitrogen and the pyrene moiety, the effect of aldimine vs. ketimine ligand frameworks 127  as well as testing these complexes in biological applications such as oxygen sensing and luminescence imaging may be of interest.   Overall, the work presented in this thesis demonstrates that synthetic modifications to ancillary ligands in bis-cyclometallated iridium complexes give rise to very different structural and photophysical properties. As a consequence, the complexes reported in this work have potential to be used in a wide variety of applications from molecular switches and motors to OLEDs as well as photocatalysis, upconversion and bioimaging.  The work in Chapters 2-4 expands upon the catalogue of bis-cyclometallated iridium complexes reported in the literature. Additional contributions to this field continue to further our understanding of the molecular parameters that govern that nature of triplet excited states affiliated with phosphorescent emission from these complexes. This work provides further insight into the structure-property relationships of iridium complexes that are relevant when rationally designing complexes of this type for their many diverse applications.      128  References 1. 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Chem. Soc. 2004, 126, 14129-14135. 203. Constable, E. C.; Neuburger, M.; Rösel, P.; Schneider, G. E.; Zampese, J. A.; Housecroft, C. E.; Monti, F.; Armaroli, N.; Costa, R. D.; Ortí, E. Inorg. Chem. 2013, 52, 885-897.       144   Appendices  Appendix 1 Crystallography Data Table A1-1. Selected crystal structure data for NNHPyr (36)  NNHPyr formula C22H14N habit orange, needle dimensions/ mm 0.02 x 0.02 x 0.2 temperature/ K 90 cryst syst monoclinic space group P21 a/ Å 4.9767(2) b/ Å 19.5560(7) c/ Å 15.5719(5) α/ ° 90 β/ ° 92.554(3) γ/ ° 90 V/ Å3 2661.3(3) Z 4 μ/ cm-1 6.16 R[F2 > 2σ(F2)]a 0.057 Rw (F2)a 0.126 goodness of fit 1.02 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2  145   Table A1-2. Selected bond lengths and angles for NNHPyr (36) Bond Lengths (Å)  C(1)-N(1)                      1.340(4) N(1)-C(5) 1.338(4) C(6)-N(2) 1.270(4) C(7)-N(2) 1.412(4) C(5)-C(6) 1.468(4) Angles (°)  N(1)-C(1)-C(2) 123.5(3) C(5)-N(1)-C(1) 117.2(3) N(1)-C(5)-C(4) 122.9(3) N(1)-C(5)-C(6) 115.0(3) N(2)-C(6)-C(5) 121.6(3) C(8)-C(7)-N(2) 124.2(3) C(12)-C(7)-N(2) 116.8(3) Torsion Angles (°)  C(5)-C(6)-N(2)-C(7) 179.8(3) N(1)-C(5)-C(6)-N(2) 177.2(3)        146   Table A1-3. Selected crystal structure data for [Ir(NNMePyr)(ppz)2][PF6] (37a) and [Ir(NNMePyr)(ppz)2][PF6] (37b)  [Ir(NNMePyr)(ppz)2][PF6]  · CH2Cl2 (a) [Ir(NNMePyr)(ppz)2][PF6]  · C6H14 (b) formula C42H32N6Cl2IrPF6 C47H44N6IrPF6 habit orange, tablet orange, tablet dimensions/ mm 0.16 x 0.25 x 0.60 0.14 x 0.24 x 0.30 temperature/ K 100 100 cryst syst monoclinic monoclinic space group P21/n C2/m a/ Å 12.333(1) 17.731(2) b/ Å 12.691(1) 23.624(2) c/ Å 25.377(2) 21.585(2) α/ ° 90 9 β/ ° 102.052(5) 107.697(4) γ/ ° 90 90 V/ Å3 3884.6(6) 8613(2) Z 4 8 μ/ cm-1 36.86 32.05 R[F2 > 2σ(F2)]a 0.074 0.049 Rw (F2)a 0.166 0.079 goodness of fit 1.30 1.07 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2    147   Table A1-4. Selected bond lengths and angles for [Ir(NNMePyr)(ppz)2][PF6] (37a) Bond Lengths (Å)  Ir(1) – N(1)   2.122(7)   Ir(1) – N(2)   2.125(6)   Ir(1) – N(3)   2.021(7)   Ir(1) – N(5)   2.026(7)   Ir(1) – C(32)   2.021(8)   Ir(1) – C(41)   2.031(8)   C(1) – N(1)   1.339(10)   C(1) – C(2)   1.382(12)   C(5) – N(1)   1.370(9)   C(5) – C(6)   1.474(11)   C(6) – N(2)   1.308(10)   C(8) – N(2)   1.436(10)   Angles (°)  N(3) – Ir(1) – C(32)   80.3(3)   N(1) – Ir(1) – N(2)   76.6(2)   C(1) – N(1) – C(5)   118.4(7)   C(1) – N(1) – Ir(1)   126.9(5)   C(5) – N(1) – Ir(1)   114.5(5)   C(6) – N(2) – C(8)   121.4(6)   C(6) – N(2) – Ir(1)   116.9(5)   C(8) – N(2) – Ir(1)   121.6(5)   Torsion Angles (°)  C(9) – C(8) – N(2) – C(6)   110.1(8)     148   Table A1-5. Selected bond lengths and angles for [Ir(NNMePyr)(ppz)2][PF6] (37b) Bond Lengths (Å)  Ir(1) – N(1)   2.131(3)   Ir(1) – N(2)   2.173(2)   Ir(1) – N(3)   2.013(3)   Ir(1) – N(5)   2.035(3)   Ir(1) – C(32)   2.023(3)   Ir(1) – C(41)   2.009(3)   C(1) – N(1)   1.343(4)   C(1) – C(2)   1.384(5)   C(5) – N(1)   1.359(4)   C(5) – C(6)   1.486(4)   C(6) – N(2)   1.300(4)   C(8) – N(2)   1.446(4)   Angles (°)  N(3) – Ir(1) – C(32)   80.01(12)   N(1) – Ir(1) – N(2)   75.86(10)   C(1) – N(1) – C(5)   118.7(3)   C(1) – N(1) – Ir(1)   125.3(2)   C(5) – N(1) – Ir(1)   116.0(2)   C(6) – N(2) – C(8)   118.8(3)   C(6) – N(2) – Ir(1)   116.3(2)   C(8) – N(2) – Ir(1)   124.6(2)   Torsion Angles (°)  C(9) – C(8) – N(2) – C(6)   -110.0(3)     149   Table A1-6. Selected crystal structure data for [Ir(NNMeNapht)(ppz)2][PF6] (42)  [Ir(NNMeNapht)(ppz)2][PF6] (a) and (b) formula C35H28N6IrPF6 habit orange, irregular dimensions/ mm 0.03 x 0.08 x 0.13 temperature/ K 90 cryst syst orthorhombic space group P 212121   a/ Å 12.8573(7) b/ Å 13.1060(7) c/ Å 19.1905(10) α/ ° 90 β/ ° 90 γ/ ° 90 V/ Å3 3233.7(3) Z 4 μ/ cm-1 42.50 R[F2 > 2σ(F2)]a 0.034 Rw (F2)a 0.056 goodness of fit 1.09 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2      150   Table A1-7. Selected bond lengths and angles for [Ir(NNMeNapht)(ppz)2][PF6] (42a) Bond Lengths (Å)  Ir(1)-C(26) 2.006(6) Ir(1)-N(5) 2.021(4) Ir(1)-C(35) 2.023(5) Ir(1)-N(3) 2.031(4) Ir(1)-N(2) 2.136(3) Ir(1)-N(1) 2.158(9) N(1)-C(1)                      1.330(6) N(1)-C(5) 1.355(5) C(1)-C(2) 1.383(6) C(6)-C(5) 1.513(12) C(6)-N(2) 1.296(6) Angles (°)  N(2)-Ir(1)-N(1) 76.7(3) C(6)-N(2)-Ir(1) 117.1(3) C(1)-N(1)-C(5) 119.0(4) C(5)-N(1)-Ir(1) 114.6(6) C(1)-N(1)-Ir(1) 126.3(6) Torsion Angles (°)  C(13)-C(14)-N(2)-C(6) 87.1(5)      151   Table A1-8. Selected bond lengths and angles for [Ir(NNMeNapht)(ppz)2][PF6] (42b) Bond Lengths (Å)  Ir(1B)-C(26B) 2.05(2) Ir(1B)-N(5B) 2.011(18) Ir(1B)-C(35B) 2.01(2) Ir(1B)-N(3B) 2.104(17) Ir(1B)-N(2B) 2.147(16) Ir(1B)-N(1B) 1.91(4) N(1B)-C(1B)                      1.3900 N(1B)-C(5B) 1.3900 C(1B)-C(2B) 1.3900 C(6B)-C(5B) 1.27(5) C(6B)-N(2B) 1.24(3) Angles (°)  N(2B)-Ir(1B)-N(1B) 71.1(15) C(6B)-N(2B)-Ir(1B) 117.4(15) C(1B)-N(1B)-C(5B) 120.0 C(5B)-N(1B)-Ir(1B) 119(3) C(1B)-N(1B)-Ir(1B) 120(3) Torsion Angles (°)  C(13B)-C(14B)-N(2B)-C(6B) -115(2)      152   Table A1-9. Selected crystal structure data for Ir(ppz)2(NOiProp2Ph) (57)  Ir(ppz)2(NOiProp2Ph)·CHCl3 formula C38H37Cl3IrN5O  dimensions/ mm 0.29 x 0.20 x 0.10 temperature/ K 150 cryst syst triclinic space group P-1  a/ Å 9.447(4) b/ Å 11.680(5) c/ Å 16.245(7) α/ ° 84.814(7) β/ ° 78.207(7) γ/ ° 81.115(7) V/ Å3 1730.4(13) Z 2 μ/ cm-1 41.29 R[F2 > 2σ(F2)]a 0.0365 Rw (F2)a 0.0715 goodness of fit 0.969 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2       153   Table A1-10. Selected bond lengths and angles for Ir(ppz)2(NOiProp2Ph) (57) Bond Lengths (Å)  Ir(1)-N(1) 1.99(4)  Ir(1)-C(9) 1.99(6) Ir(1)-N(3) 2.01(8) Ir(1)-O(1) 2.13(1) Ir(1)-N(5) 2.13(8) Ir(1)-C(18) 1.98(9) N(5)-C(25) 1.28(4) C(25)-C(24) 1.42(6) C(24)-C(19) 1.42(7) C(19)-O(1) 1.29(3) Angles (°)  Ir(1)-N(5)-C(25) 121.7(2) N(5)-C(25)-C(24) 128.6(5) C(25)-C(24)-C(19) 123.0(8) C(24)-C(19)-O(1) 124.7(1) C(19)-O(1)-Ir(1) 123.8(5) Torsion Angles (°)  O(1)-Ir(1)-N(5)-C(25) 26.9(1) N(5)-Ir(1)-O(1)-C(19) -32.6(4)      154   Table A1-11. Selected crystal structure data for Ir(ppy)2(NOiProp) (58)  Ir(ppy)2(NOiProp)·CH2Cl2 formula C33H30Cl2IrN3O dimensions/ mm 0.22 x 0.13 x 0.07 temperature/ K 150 cryst syst monoclinic space group C2/c   a/ Å 27.764(14) b/ Å 14.918(8) c/ Å 18.083(9) α/ ° 90 β/ ° 98.371(9) γ/ ° 90 V/ Å3 7410(7) Z 8 μ/ cm-1 37.90 R[F2 > 2σ(F2)]a 0.0725 Rw (F2)a 0.1736 goodness of fit 0.929 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2       155   Table A1-12. Selected bond lengths and angles for Ir(ppy)2(NOiProp) (58) Bond Lengths (Å)  Ir(1)-C(14) 2.00(9) Ir(1)-N(2) 2.08(8) Ir(1)-C(25) 2.00(7) Ir(1)-N(3) 2.06(0) Ir(1)-N(1) 2.15(7) Ir(1)-O(1) 2.16(1) O(1)-C(1) 1.29(6) C(1)-C(6) 1.43(3) C(6)-C(7) 1.44(5) C(7)-N(1) 1.28(6) Angles (°)  Ir(1)-N(1)-C(7) 122.6(5) N(1)-C(7)-C(6) 128.6(7) C(7)-C(6)-C(1) 126.2(5) C(6)-C(1)-O(1) 121.7(8) C(1)-O(1)-Ir(1) 126.6(8) Torsion Angles (°)  O(1)-Ir(1)-N(1)-C(7) 20.1(5) C(1)-O(1)-Ir(1)-N(1) -29.1(9)      156   Table A1-13. Selected crystal structure data for Ir(ppy)2(NOiProp2Ph) (59)  Ir(ppy)2(NOiProp2Ph)·CHCl3·CH3OH formula C43H43Cl3IrN3O2 dimensions/ mm 0.32 x 0.10 x 0.04 temperature/ K 150 cryst syst triclinic space group P-1 a/ Å 9.460(3) b/ Å 12.796(3) c/ Å 15.498(4) α/ ° 90.953(5) β/ ° 94.117(5) γ/ ° 90.670(5) V/ Å3 1870.9(9) Z 2 μ/ cm-1 38.25 R[F2 > 2σ(F2)]a 0.0481 Rw (F2)a 0.0780 goodness of fit 0.888 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2       157   Table A1-14. Selected bond lengths and angles for Ir(ppy)2(NOiProp2Ph) (59) Bond Lengths (Å)  Ir(1)-C(11) 1.98(8) Ir(1)-C(22) 1.97(7) Ir(1)-N(2) 2.02(2) Ir(1)-N(1) 2.04(4) Ir(1)-N(3) 2.15(9) Ir(1)-O(1) 2.16(0) O(1)-C(23) 1.29(4) C(23)-C(28) 1.41(5) C(28)-C(29) 1.42(4) C(29)-N(3) 1.29(3) Angles (°)  Ir(1)-N(3)-C(29) 122.5(1) N(3)-C(29)-C(28) 128.6(0) C(29)-C(28)-C(23) 124.3(6) C(28)-C(23)-O(1) 123.7(3) C(23)-O(1)-Ir(1) 123.2(2) Torsion Angles (°)  O(1)-Ir(1)-N(3)-C(29) 19.7(3) N(3)-Ir(1)-O(1)-C(23) -36.1(0)      158   Table A1-15. Selected crystal structure data for [Ir(NNMePyrMe)(ppz)2][PF6] (62)  [Ir(NNMePyrMe)(ppz)2][PF6] ·CH2Cl2·1/4H2O formula C43H34.5O0.25N6F6PIrCl2 habit orange, needle dimensions/ mm 0.02 x 0.04 x 0.20 temperature/ K 90 cryst syst monoclinic space group P 21/n   a/ Å 9.083(2) b/ Å 15.227(4) c/ Å 28.551(7) α/ ° 90 β/ ° 92.521(5) γ/ ° 90 V/ Å3 3945(2) Z 4 μ/ cm-1 36.32 R[F2 > 2σ(F2)]a 0.039 Rw (F2)a 0.074 goodness of fit 1.01 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2      159   Table A1-16. Selected bond lengths and angles for [Ir(NNMePyrMe)(ppz)2][PF6] (62) Bond Lengths (Å)  Ir(1)-N(5) 2.00(6) Ir(1)-C(33) 2.01(2) Ir(1)-N(2) 2.13(4) Ir(1)-N(3) 2.01(6) Ir(1)-C(42) 2.02(3) Ir(1)-N(1) 2.11(9) C(6)-N(2) 1.28(8) N(2)-C(8) 1.46(5) C(8)-C(9) 1.51(2) Angles (°)  C(6)-N(2)-C(8) 122.4(3) N(2)-C(8)-C(9) 112.5(5) C(8)-C(9)-C(10) 120.6(0) C(8)-C(9)-C(14) 119.4(2) N(2)-C(6)-C(5) 115.4(8) Torsion Angles (°)  Ir(1)-N(2)-C(8)-C(9) -77.5(8) N(2)-C(8)-C(9)-C(10) -28.5(2)       160   Table A1-17. Selected crystal structure data for Ir(NOPyr)(ppz)2 (63)  Ir(NOPyr)(ppz)2 ·1/2H2O formula C82H58N10O3Ir2 habit yellow, flake dimensions/ mm 0.02 x 0.16 x 0.18 temperature/ K 90 cryst syst monoclinic space group P 21 a/ Å 8.6566(11) b/ Å 25.000(4) c/ Å 14.566(2) α/ ° 90 β/ ° 90.169(3) γ/ ° 90 V/ Å3 3152.3(7) Z 2 μ/ cm-1 42.81 R[F2 > 2σ(F2)]a 0.056 Rw (F2)a 0.124 goodness of fit 1.04 aFunction minimized by R = Σ ‖Foǀ - ǀFc‖ / ΣǀFoǀ, Rw = [Σ(w(Fo2-Fc2)2)/Σw(Fo2)2]1/2      161   Table A1-18. Selected bond lengths and angles for Ir(NOPyr)(ppz)2 (63) Bond Lengths (Å)  Ir(1)-N(1) 2.15(0) Ir(1)-O(1) 2.17(5) Ir(1)-N(4) 2.02(7) Ir(1)-C(41) 2.04(0) Ir(1)-C(32) 2.03(4) Ir(1)-N(2) 1.94(4) N(1)-C(7) 1.03(8) C(7)-C(5) 1.45(9) C(5)-C(6) 1.41(1) C(6)-O(1) 1.31(5) Angles (°)  Ir(1)-O(1)-C(6) 125.0(0) O(1)-C(6)-C(5) 127.7(0) C(6)-C(5)-C(7) 125.6(7) C(5)-C(7)-N(1) 127.3(4) C(7)-N(1)-Ir(1) 125.4(1) Torsion Angles (°)  O(1)-Ir(1)-N(1)-C(7) 2.5(4) N(1)-Ir(1)-O(1)-C(6) -2.4(3)  

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