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Metallated, beta-substituted phosphine-oligothiophenes Moorlag, Carolyn Patricia 2006

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METALLATED, BETA-SUBSTITUTED PHOSPHINE-OLIGOTHIOPHENES by  C A R O L Y N PATRICIA M O O R L A G B.Sc. (Honours, Co-op), Chemistry, University of Victoria, Canada, 1997^ M.Sc, Metals and Materials Engineering, University of British Columbia, Canada, 2000  A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY in  the Faculty of Graduate Studies (CHEMISTRY)  THE UNIVERSITY OF BRITISH C O L U M B I A January 2006  © Carolyn Patricia Moorlag, 2006  Abstract The synthesis and characterization of transition metal complexes combined with rc-conjugated chains to yield hybrid metal-organic materials with new structural, chemical, and electronic properties are reported. P-Phosphinothiophene ligands (9, 11, 13-15, 21-22, 27) were prepared  by metal-catalyzed coupling reactions, thienyl backbone conformations  were  determined by X-ray crystallography, and electronic properties were characterized by absorption and emission spectroscopy and electrochemical methods. Transition metal groups were attached in close proximity to rc-conjugated thienyl chains, at pendent positions or directly to the conjugated backbone, and metal-thienyl interactions were investigated. Pd(II) (29-30) and Au(I) (33-34) complexes were prepared by reaction of the metal groups with bis(phosphino)thiophene ligands. The conformational and electronic properties of the complexes were characterized, and the conjugation of the oligothiophene chains was modified by metal attachment. complexes  (41-46,  47-52)  mono(phosphino)thiophenes.  are  formed  from  bis(bipyridine)  Ru(II)  groups  Ru(II) and  Metal-mediated acid-base reactions change the mode of direct  attachment of Ru(II) with the oligothiophene chains, between P,S and P,C bonding modes, resulting in different structural and electronic properties, as observed by absorption and emission spectroscopy,  electrochemical  oxidation  and  reduction,  X-ray  crystallography,  spectroelectrochemistry, and electron paramagnetic resonance spectroscopy. These two modes of metal bonding to the rc-conjugated backbone constitute a reversible molecular switch. The incorporated bis(bipyridine) Ru(II) groups undergo charge-transfer  transitions, and light  absorption of 51 appears to remove charge from the pentathiophene chain, suggesting possible light-harvesting applications.  Preliminary polymerization studies towards the preparation of  polynuclear, metallated polythiophene poly-46 and a p-polysubstituted polythiophene derivative are reported. Long oligomers were observed by ' H N M R spectroscopy and mass spectrometry, but further studies are required.  PPh  2  CH 6  H  Ph P  13  R  2  H  R  Ph P  R  2  X  X  n  H C 13  6  Ph P 2  P T (9) P hex T (ll) 2  2  2  2  4  n= 0 n=l  PT (13) R = R'=H PMeT (14) R = CH , R' = H PMe T (15) R = R' = CH 3  3  2  3  3  3  n  Phex T (21) R = C H ,X = H 2  5  PDo T (23) 2  5  6  13  R = C H ,X = H 12  25  P B r D o T (27) R = C H , X = Br 2  2  5  12  25  r  H C 13  QH13  6  2  2  2  2  4  2  13  n= 0 n=l  Pd(P T )Cl (29) Pd(P hex T )Cl (30) 2  H C  CH  6  6  (AuCl) P T (33) (AuCl) P hex T (34) 2  2  2  s-N,.  2  2  2  4  13  n=0 n=l  , K  ^Ru\ | ^PPh  2  RuPT -/»S (41) RuPMeT -P,S (42) RuPMezTj-P^ (43) 3  3  RuPhex T -P,5'(44) RuPDo T -7>S (45) 2  5  2  5  R= R'=H R = CH, R' = H R = R' = CH  RuPT -P,C(47) RuPMeT -/» C (48) RuPMe T -/> C (49) 3  3  3  3  2  R = C H ,X=H R = C H ,X = H 6  12  RuPhex T -P,C(50) RuPDo T -J>C(51)  13  2  25  2  s  12  5  2  RuPBr Do T -i',5 (46) R = C H , X = Br 2  3  5  R = R' = H R = CH , R' = H R = R' = CH 3  3  R = C H ,X = H R = Ci H ,X = H 6  13  2  25  RuPBr Do T - P,C(52) R = C H , X = Br  25  2  iii  2  5  J  12  25  Table of Contents Abstract  ii  Table of Contents List of Tables  :  iv  ;  vii  List of Figures  viii  List of Symbols  xi  List of Abbreviations  xii  List of Charts  xvii  List of Schemes  xviii  Acknowledgements CHAPTER 1 1.1 1.2 1.2.1 1.2.2 1.2.3 1.3 1.3.1 1.3.2 1.4 1.5 1.6  CHAPTER 2 2.1 2.2 2.2.1 2.2.2 2.3 2.3.1 2.3.2 2.3.3 2.4 2.5 2.6  -.  Introduction  xix 1  Scope Organic re-Conjugated Materials Structures of it-Conjugated Materials Synthesis of Oligo- and Polythiophenes Properties and Applications of it-Conjugated Materials Metal-Organic Hybrid Materials Metallation of it-Conjugated Organic Materials Properties and Applications of Metal-Organic Hybrid Materials Focus of Present Study Goals References  1 2 2 3 6 9 9 12 15 16 17  Synthesis and Characterization of p-Phosphinothiophene Ligands and Derivatives  20  Introduction Experimental General Experimental Synthesis Results Synthesis Cyclic Voltammetry Electronic Spectroscopy Discussion Conclusions References  20 25 25 25 32 32 38 40 42 44 45  iv  CHAPTER 3 3.1 3.2 3.2.1 3.2.2 3.3 3.3.1 3.3.2 3.3.3 3.4 3.5 3.6 CHAPTER 4 4.1 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.4 4.5 4.6 CHAPTER 5 5.1 5.2 5.2.1 5.2.2 5.2.3 5.2.4 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.3.6 5.4 5.5  Synthesis and Characterization of Au(I) and Pd(II) Complexes Introduction Experimental General Experimental X-ray Crystallographic Analysis Results Synthesis and Crystallographic Studies Cyclic Voltammetry Electronic Spectroscopy Discussion Conclusions References.....  47 ;  47 49 49 50 50 50 54 55 57 59 60  <  Synthesis and Characterization of P.S-Bound Ru(II) Complexes  62  Introduction Experimental General Experimental Synthesis X-ray Crystallographic Analysis Density Functional Theory Calculations Results Synthesis and Crystallographic Studies Density Functional Theory (DFT) Calculations Cyclic Voltammetry Electronic Spectroscopy and Charge-Transfer Correlations Reversible Molecular Switching Discussion Conclusions References  62 67 67 68 71 72 72 72 77 79 81 86 88 92 92  Synthesis and Characterization of P, C-Bound Ru(II) Complexes  96  Introduction Experimental General Experimental Synthesis X-ray Crystallographic Analysis Density Functional Theory Calculations Results Synthesis and Crystallographic Studies Density Functional Theory (DFT) Calculations Cyclic Voltammetry Electron Paramagnetic Resonance Optical Spectroscopy and Charge-Transfer Correlations Spectroelectrochemistry Discussion Conclusions v  •  '.  96 98 98 99 102 103 103 103 106 108 110 113 118 122 127  5.6 CHAPTER 6 6.1 6.2 6.2.1 6.2.2 6.3 6.3.1 6.3.2 6.4 6.5 6.6 CHAPTER 7 7.1 7.2 7.3 Appendix 1  References  128  Preliminary Polymerization Studies  131  Introduction Experimental General Experimental Polymerization Reactions Results Coupling of P-Halogenated Oligothiophenes Coupling of Ru(II)-Complexes Discussion Conclusions References  131 133 133 133 135 135 138 140 141 141  Conclusions and Future Directions  142  Conclusions Suggestions for Future Work References  142 144 147  Crystal Structure Data  148  vi  List of Tables Table 2-1 Cyclic voltammetry data for (3-phosphinothiophene ligands and derivatives, oligothiophenes, and triphenylphosphine  38  Table 2-2 Electronic spectroscopy data for P-phosphinothiophene ligands and derivatives, and oligothiophenes  40  Table 3-1 Selected interatomic distances (A) and angles (°) for Pd(P2hex2T4)2Ci2 (30)  52  Table 3-2 Cyclic voltammetry data of Pd(II)- and Au(I)-bis(phosphino)thiophene complexes.. 54 Table 3-3 Electronic spectroscopy data of Pd(II)- and Au(I)-bis(phosphino)thiophene complexes 56 Table 4-1 Selected interatomic distances (A) and angles (°) for 41 and 43  73  Table 4-2 Selected interatomic distances (A) and angles (°) for RuPDo T -P,5' (45)  76  Table 4-3 Calculated H O M O and L U M O energies for RuPT -P,5 (41)  79  2  5  3  Table 4-4 Cyclic voltammetry data of Ru(II)-phosphinothiophene-i ,5' complexes  81  Table 4-5 Electronic spectroscopy data for Ru(II)-phosphinothiophene-/ ,5' complexes  83  5  >  Table 5-1 Selected interatomic distances (A) and angles (°) for 47 and 49  105  Table 5-2 Calculated H O M O and L U M O energies for RuPT -P, C (47)  106  3  Table 5-3 Cyclic voltammetry data of Ru(II)-phosphinothiophene-/ ,C complexes 5  3  Table 5-4 Electronic spectroscopy data for Ru(II)-phosphinothiophene-/ , C complexes >  109 115  Table 5-5 Spectroelectrochemistry data for P, C Ru(II)-phosphinothiophene complexes and related oligothiophenes 120 Table 6-1 Peaks corresponding to coupled oligomers in the mass spectrum of poly-26T  vii  138  List of Figures Figure 1-1 Selected examples of rc-conjugated organic polymers  2  Figure 1-2 Selected examples of soluble polythiophenes  3  Figure 1-3 Metal-catalyzed coupling reactions used to prepare oligo- and polythiophenes  4  Figure 1-4 Mechanism of oxidative polymerization of thiophene  5  Figure 1-5 Energy band diagram of polyacetylene, as derived from overlapping rc orbitals  6  Figure 1-6 Changes in the irreversible oxidation potential, E (O), and the wavelength, A, x ( A ) with extension of thiophene chain length  7  p  TC—»TC*  absorption  ma  Figure 1-7 Localized distortions on polythiophene chains and the introduction of energy levels into the band gap due to the formation of (a) a polaron, and (b) a bipolaron  8  Figure 1-8 Classes of transition metal-organic hybrid materials  9  Figure 1-9 Metal-oligothiophene and metal-polythiophene hybrid materials, classed as Type I, Type II, and Type III  11  Figure 1-10 Modification of the band gap energy with metallation of rc-conjugated materials, due to inductive effects or chain twisting to increase the band gap (left), and electron donation or chain planarization (right) 13 Figure 1-11 Examples of planar and twisted conformations of an oligothiophene  13  Figure 1-12 The introduction of metal-based H O M O or L U M O levels into the band gap of a rc-conjugated chain, resulting in (a) a metal-to-ligand charge transfer (MLCT) transition, or (b) a ligand-to-metal charge transfer (LMCT) transition 14 Figure 1-13 General strategies for making (a) Type I and (b) Type II metal-oligothiophene hybrid materials using P-phosphinothiophenes  15  Figure 2-1 Bidentate and monodentate modes of bonding that may arise with metallation of bis(phosphino)thiophene chains 22 Figure 2-2 (a) ORTEP view of (PO) T (12). (b) ORTEP view down the C - C axis illustrating the interannular torsion angle  34  Figure 2-3 Cyclic voltammetry of 22 and 24 in C H 2 C I 2  39  2  2  4  5  Figure 2-4 Correlation between the oxidation potentials, Ei/2, , and the number of thienyl rings of the P-phosphinothiophene ligands (+) and the corresponding oligothiophenes (O)  39  Figure 2-5 Correlation between A , and the number of thienyl rings of representative phosphinothiophene ligands (+) and the corresponding oligothiophenes (O)  41  Figure 2-6 The and T  42  ox  ! m a x  7C<-TC*  fluorescence emission of (phosphino)terthiophene ligands 13 and 16,  3  Figure 3-1 ORTEP view of Pd(P hex T4)Cl2 (30)  51  Figure 3-2 (a) ORTEP view of 33 and (b) ORTEP view of 33-tol  53  2  2  viii  Figure 3-3 Cyclic voltammograms of (a) Pd(II) complex 30 and (b) Au(I) complex 34 in CH C1  55  Figure 3-4 Absorption spectra of Pd(P2hex2T4)Cl2 (30) in solvents of different polarity  56  Figure 4-1 Schematic representation of a Gratzel cell  64  2  2  Figure 4-2 Two possible bidentate bonding modes of a P-phosphinothiophene chain attached to a Ru(bpy)2 group, P,S and P,C 65 2+  Figure 4-3 (a) ORTEP view of RuPT -P,S (41) (conformation A) and (b) ORTEP view of RuPMe T -P,S(43) . 3  2  3  73  Figure 4-4 A portion of the unit cell of RuPMe2T3-P,5' (43) viewed normal to the 010 plane... 75 Figure 4-5 X-ray crystal structure of RuPDo Ts-.P,S'(45) (conformation B)  76  2  Figure 4-6 Ordering of the calculated H O M O and L U M O energies of RuPT -i ,5' (41), and depictions of frontier orbitals  78  Figure 4-7 Cyclic voltammograms of (a) 41-43, and (b) 45 in C H 3 C N  80  5  3  Figure 4-8 Solution absorption spectra of Ru(II)-.P S complexes 41-43 and 45 in C H C i 2  82  Figure 4-9 Crystals of (a) RuPT -P,S (41) and (b) RuPDo T -P,5 (45)  82  Figure 4-10 Linear fit of E  84  2  )  3  op  2  versus AE(redox) for R  5  complexes 41-43 and 45  u n D - P S  Figure 4-11 Solid state absorption spectra of Ru(II)-phosphinothiophene-i ,5' complexes 41-43 and 45 3  84  Figure 4-12 (a) Emission and excitation spectra of R u P D o 2 T - P , 5 ' (45) in deaerated C H C N solution, (b) Emission spectra of RuPDo2T5-P,5 (45) obtained at 12 ns, 37 ns, 90 ns and 143 ns average times after the incidence of the laser pulse 85 5  3  Figure 4-13 Emission spectra of RuPDo2T5- P,S' (45) (a) at time = 0 h, and (b) at time = 0, 2.5, and 22 h  86  Figure 4-14 P N M R spectra of RuPDo T -P,5 (45) and RuPDo T -P,C (51). Addition of HPF6 (cone.) to a solution of 51 results in reversion to 45  88  J  3 1  2  5  2  5  Figure 5-1 (a) ORTEP view of RuPT -P,C (47) and (b) ORTEP view of RuPMe T -P,C(49) 3  2  105  3  Figure 5-2 (a) Ordering of the calculated H O M O and L U M O energies of RuPT -P,C (47), and depictions of the frontier orbitals 107 3  Figure 5-3 Cyclic voltammograms of (a) 47-49, and (b) 51 in C H C N  109  Figure 5-4 EPR spectra at room temperature (RT = 298 K ) and low temperature (110 K) of the first oxidized species of (a) RuPT -P, C (47), (b) RuPMeT -P,C (48), and RuMe PT -P,C(49)  112  3  3  2  3  3  Figure 5-5 EPR spectra of the first oxidized species of (a) D02T5 (24) at room temperature (298 K), and (b) RuDo PT -P,C (51) at room temperature (298 K ) and low temperature (110K) 113 2  5  Figure 5-6 Solution absorption spectra of Ru(II)-.P, C complexes 47-49 and 51 in CH2CI?. solution  114  Figure 5-7 (a) RuPT -P, C (47) crystals and (b) RuPDo T -P,C (51) powder  114  3  2  ix  5  (a) Plot of the primary CT optical transition (E ) versus the difference in potential between the first oxidation potentials and first reduction potential (AE) for all Ru(II)-/ , C complexes, and (b) the linear fit for the Ru(II)-(phosphino)terthiophene-P,C complexes  116  Solid state absorption spectra of Ru(II)-P, C complexes 47-49 and 51 drop-cast from solution in acetone  117  Figure 5-10 (a) Emission and excitation spectra of 47 (A. = 456 nm, A, = 748 nm), 48 (A. = 459 nm, X = 751 nm), and 49 (A, = 460 nm, X - 761 nm) in deaerated C H 3 C N . (b) Emission spectra of 47 obtained at 14 ns, 62 ns, 113 ns and 137 ns average times after the incidence of the laser pulse  118  Difference spectra of 49 in deaerated C H 3 C N solution with 0.1 M [(«-Bu)4N]PF6 supporting electrolyte  119  Figure 5-12 Difference spectra of (a) complex 51 and (b) pentathiophene 24 in deaerated C H C N solution with 0.1 M [(«-Bu) N]PF supporting electrolyte  122  Figure 5-13 Proposed energy-level diagram and transitions, Ti and T , for T  125  Figure 5-8  op  5  Figure 5-9  ex  ex  em  ex  em  sm  Figure 5-11  3  4  6  2  + n  Figure 5-14 Proposed molecular orbital diagram for 5 1 and transitions T ' i , T 2 and T'3, with energy levels O1-O4  126  Figure 5-15 Representation of Ru(II)-phosphino(pentathiophene)-P,C complex 51 as a light-harvesting molecular wire  127  +  Figure 6-1 ' H N M R spectra of the aromatic region of (a) heptathiophene 28 and (b) the coupled products of the Suzuki cross-coupling reaction of 26 and thiophene (T), to give poly-26T Figure 6-2  136  M A L D I - T O F mass spectrum of poly-26T, 700-4000 m/z region  Figure 6-3 P N M R (162.0 MHz) spectra in CO(CD ) of products of Ni(0) coupling reaction of 46 at 50°C (a) 2 h, (b) 16 h  137  3 1  3  2  139  List of Symbols Symbol  Description  5  chemical shift (ppm)  A  difference  s  molar absorptivity ( M c m ) _1  _1  quantum yield hapticity X  wavelength (nm)  A-Ern  emission wavelength (nm)  A-Ex  excitation wavelength (nm)  Arnax  wavelength at band maximum (nm) micro energy of X-rays used for crystallographic determination (mm ) -1  V  frequency (s )  9  angle of diffraction  P  density (g cm )  T  lifetime  o  standard deviation  -1  degrees parallel  1  perpendicular  I  the sum of  xi  List of Abbreviations  Abbreviation  Description  A  Angstrom  A  amperes  uA  microamperes  Ac  acetate  Anal.  analysis  aq  aqueous  a.u.  arbitrary units  bpy  bipyridine  Bu  butyl  cm  centimeter  cone.  concentrated  °C  degrees Celsius  Cp  cyclopentadienyl  CT  charge-transfer  d  doublet  dd  doublet of doublets (NMR)  dd  doublet of doublets of doublets (NMR)  DFT  density functional theory  Do  dodecyl  D02T5  3,3 ""-didodecyl-2,2': 5 ',2": 5 ",2"': 5 "',2""-pentathiophi  dppf  1,1 '-bis(diphenylphosphino)ferrocene  dppp  1,3 -bis(diphenylphosphine)propane  DSSC  dye-sensitized solar cell  e~  electron  E  energy  AE(redox)  energy difference between redox couples (eV)  E1/2  half wave redox potential (V)  E ic  redox potential predicted by EL values (V)  EL  ligand electrochemical parameters (V)  E  transition energy (eV)  ca  op  xii  E  o x  peak potential, oxidation process (V)  E  p  peak potential, irreversible wave (V)  E d  peak potential, reduction process (V)  EDOT  3,4-ethylenedioxythiophene  EI  electron ionization  EPR  electron paramagnetic resonance  eq  equivalents  Et  ethyl  eV  electron volts  Fc  ferrocene  F  c  calculated intensity of a reflection from the crystal model  F  0  measured intensity of a reflection in a diffraction pattern  re  g  *  gram  gx  g-value  GOF  goodness of fit indicator  h  Planck's constant  hv  light energy  hex  hexyl  HH  head-to-head  HOMO  highest occupied molecular orbital  HT  head-to-tail  Hz  Hertz  I  symmetry-related reflection (crystallography)  J  magnetic coupling constant, N M R coupling constant  K  Kelvin  L  ligand  LMCT  ligand-to-metal charge transfer  LUMO  lowest unoccupied molecular orbital  m  multiplet  M  metal, molarity (mol L" ), mass  MALDI-TOF  matrix-assisted laser desorption ionization time of flight  MC  metal-centered  Me  methyl  mg  milligram  1  xiii  MHz  Megahertz  mL  milliliter  MLCT  metal-to-ligand charge transfer  mm  millimeter  mmol  millimole  MO  molecular orbital  mol  mole  umol  micromole  MS  mass spectra  mV  millivolts  MW  molecular weight  m/z  mass-to-charge ratio  n  number of units in an oligo- or polymeric chain  n-  normal  NBO  natural bonding orbital  NBS  A^-bromosuccinimide  near-IR  near-infrared  NHE  normal hydrogen electrode  NIS  /V-iodosuccinimide  nm  nanometer  NMR  nuclear magnetic resonance  ns  nanosecond  OLED  organic light emitting diode  ORTEP  Oak Ridge Thermal Ellipsoid Plot  OPO  optical parametric oscillator  PAT  polyalkylthiophene  PBr2Do2Ts  5,5 ""-dibromo-3,3 ""-didodecyl-3 "-diphenylphosphino-2,2':5 ',2": 5 ",2 5 "',2 ""-pentathiophene  P,C  phosphine, thienyl carbon coordination  PDo T 2  3,3""-didodecyl-3"-diphenylphosphino-2,2':5',2":5",2"':5"',2""-  5  pentathiophene PEDOT Ph Phex T 2  pory(3,4-ethylenedioxythiophene)  5  phenyl 3,3""-dihexyl-3"-diphenylphosphino-2,2':5',2":5",2"':5"',2""pentathiophene xiv  PHT  polyhexylthiophene  PMeT3  3'-(diphenylphosphino)-5-methyl-2,2':5'2"-tertW  PMe T 2  5,5Mimethyl-3'-(diphe^  3  (PO)2T  3,3 '-bis(diphenylphosphoryl)-2,2'-bithiophene  ppm  parts per million  PPV  poly(p-phenylenevinylene)  P,S  phosphine, thienyl sulfur coordination  2  PT3  3'-(diphenylphosphino)-2,2':5'2"-terthiophene  ocPT  2-diphenylphosphino-5,2':5',2"-terthiophene  3  P hex T 2  2  4  3,3"'-dihexyl-3',3"'-bis(diphenylphosphino)-2,5':2',2":5",2"'quaterthiophene  PT 2  2  3,3'-bis(diphenylphosphino)-2,2'-bithiophene  q  quartet  R  residual (in crystallography, a measure of agreement between the crystallographic model and the X-ray diffraction data)  RT  room temperature (298 K)  Ru  bis(bipyridyl) Ru(II) group (for complex labels)  s  singlet (NMR data), second  S  Siemens  sat. aq  saturated aqueous  SD  standard deviation  sep  septet  sh  shoulder  SCE  saturated calomel electrode  SOMO  singly occupied molecular orbital  t  triplet  T  temperature, tesla  T  x  T  transition thiophene  T  2  T  3  T  4  bithiophene terthiophene quaterthiophene  T5  pentathiophene  T7  heptathiophene  T„  oligothiophene of indeterminate chain length xv  td  triplet of doublets  THF  tetrahydrofuran  tht  tetrahydrothiophene  tol  toluene  TT  tail-to-tail  UBC  University of British Columbia  V  Volts  V  volume  w  least squares weights  X  halogen  Z  number of molecules in a crystallographic unit cell  xvi  List of Charts Chart 1-1  3  Chart 2-1  ;  Chart 2-2  :  20 21  Chart 2-3  21  Chart 2-4  22  Chart 2-5  23  Chart 2-6  .....  24  Chart 2-7  24  Chart 3-1  48  Chart 3-2  48  Chart 3-3  '.  49  Chart 4-1  62  Chart 4-2  63  Chart 4-3  66  Chart 4-4  66  Chart 4-5  87  Chart 5-1  96  Chart 5-2  108  Chart 5-3  120  Chart 6-1  132  Chart 6-2  132  Chart 6-3  137  Chart 7-1  146  xvii  List of Schemes Scheme 2-1  2  3  Scheme 2-2  3  3  Scheme 2-3  3  4  Scheme 2-4  3  5  Scheme 2-5  3  6  Scheme 2-6  3  7  3  7  Scheme 3-1  5  0  Scheme 3-2  5  3  Scheme 4-1  6  3  Scheme 4-2  6  3  6  5  7  2  7  5  8  7  Scheme 2-7  Scheme 4-3  •  Scheme 4-4  •  .•  •  Scheme 4-5 Scheme 4-6  •  •  • •'  Scheme 4-7  9 1  Scheme 5-1  9  7  Scheme 5-2  1  0  4  Scheme 5-3  1  0  4  Scheme 5-4  1 2 1  Scheme 6-1  1  3  5  Scheme 6-2  1  3  9  Scheme 7-1  1  4  6  Scheme 7-2  1  4  6  xviii  Acknowledgements There are many people whom I would like to thank for helping me to carry out and complete this thesis.  I thank my supervisor, Mike Wolf, for his encouragement, for many  thoughtful discussions, and for supporting me in the many directions that I wanted to take (including overseas) for this work. I appreciated his confidence in me. I would like all my group members, past and present. I was very lucky to have met such extraordinary people, from whom I gained insights about science and life. I especially thank Tracey Stott, who worked on a related project and was always willing to share helpful ideas, and was also a real friend. I thank all the undergraduate students who helped me with this work and contributed towards its final results: Shirley Lam, Mike Bridges, Eagrainie Yuh, Maureen Sam, and Michael Lam.  The  collaborations carried out were also very important toward the development of this thesis and I would like to thank all the people involved, they were: Daniel Leznoff, Cornelia Bohne, Y u Zhang, Alex Wang, Bipro Sarkar, Wolfgang Kaim, and Peter Bauerle. I am very grateful to Prof. Bauerle for not only inviting me to his group to carry out experiments and sharing his perspectives on thiophene chemistry with me, but for also supporting me while I was for three months in Germany. I also thank NSERC and U B C for scholarships. Finally, I thank my husband, Oliver, who was with me when I first decided that after a Master's, I still wanted to stay years more at university pursue a Ph.D. During the time since, his love, support, and understanding was a positive influence for me that would counteract even the most frustrating times. Without him, this thesis would not have been the same.  xix  CHAPTER 1 Introduction  1.1  Scope "Materials chemistry" is a rapidly emerging field of chemistry that as yet does not have a  formal definition, though the Journal of Materials Chemistry describes its content as "the 1  fabrication,  properties  and  applications  characterization and modeling".  of  materials,  including synthesis,  structural  By this description, materials chemistry consequently  2  encompasses many areas of scientific study. In accordance with its designation as a materials chemistry topic, this thesis brings together ideas and experimental methods from the areas of organic, inorganic, and physical chemistry, and electronic engineering, for the purpose of preparing and characterizing new metal-organic hybrid materials. It was desired that the materials targeted by this study would find applications in the area of molecular electronics, an expanding area of chemical research conducted with the aim of producing molecular equivalents for conventional electronic components such as wires, switches 3 5  and transistors. "  The very small dimensions of molecular components would result in  nanoscale devices that would potentially be more energy efficient and transport charge faster than current electronic systems. rc-Conjugated organic materials can conduct current via a delocalized rc-system along an organic molecular chain, and function as "molecular wires". " 6  8  Extensive research has been carried out on the synthesis and characterization of a variety of conductive rc-conjugated materials, with common examples being poly(p-phenylenevinylene) (PPV), polyaniline and polythiophene.  9  Oligo- and polythiophenes were selected for use in this study due to the stability and ease of chemical modification of thiophene chains and their spectroscopic properties such as the absorption and emission of light in the visible region. The conductivity, electrochromism, and electroluminescence displayed for oxidized oligo- and polythiophenes also make these materials very interesting for investigation. " 10  15  Merging transition metal groups with rc-conjugated chains  produces hybrid metal-organic materials with new structural, chemical, and electronic properties. 16-22  1  tr-Conjugated  1.2  Organic  Materials  1.2.1  Structures of ^-Conjugated Materials Organic rc-conjugated materials generally contain alternating double bonds, or linked  aromatic rings that form extended, delocalized rc-systems along oligomer or polymer chains. Selected examples of rc-conjugated organic polymers are shown in Figure 1-1, where polythiophene and polypyrrole are examples of polymerized aromatic rings, P P V incorporates both an aromatic ring and a vinyl group within the monomer unit, and polyaniline forms a conjugated pathway along the phenyl ring and the lone pair on the nitrogen atom of the amine linker group.  9  H  polythiophene  polypyrrole  poly(p-phenylenevinylene)  polyaniline  Figure 1-1 Selected examples of rc-conjugated organic polymers.  Oligo- and polythiophenes are formed of chains of thiophene rings linked at the a positions (Chart 1-1). For chains of n > 7, these materials are insoluble, and a general strategy to increase the solubility in organic solvents is the substitution of organic groups at P positions along the thienyl backbone. Significant research has also been devoted towards the preparation of regioregular or symmetric polythiophenes, since ordered structures exhibit superior properties such as enhanced conjugation, " conductivity. '  26 27  improved alignment in the solid state, '  and higher  Polythiophenes have been functionalized with solubilizing alkyl substituents at  P positions to yield polyalkylthiophenes (PATs). A regioregular structure can be prepared by linking alkythiophenes head-to-tail (HT) to form HT-PATs, such as polyhexylthiophene (HT-PHT) depicted in Figure 1-2.  Polyalkylenedioxythiophenes have also been prepared from  alkylenedioxythiophene monomers to yield a symmetric polymer that is soluble in organic 29 30  solvents, and these materials have been investigated for their interesting electronic properties. ' An  example of a polyalkylenedioxythiophene, poly(3,4-ethylenedioxythiophene) (PEDOT), is  also shown in Figure 1-2. 2  n  PEDOT  HT-PHT Figure 1-2 Selected examples of soluble polythiophenes.  Chart 1-1  1.2.2 Synthesis of Oligo- and Polythiophenes The preparation of oligo- and polythiophenes can be carried out by a variety of synthetic pathways.  Since many synthetic pathways are available, and more routes are continually  developed, only some of the most commonly used techniques are described, and especially those used for this study.  The Handbook of Oligo- and Polythiophenes provides a comprehensive  synopsis of thienyl coupling techniques.  31  Oligo- and polythiophene coupling reactions can be generally grouped into the categories of metal-catalyzed homo- and cross-coupling reactions, and oxidative polymerization. Metalcatalyzed homocoupling is the coupling of aryl halides, and is a straightforward method involving the coupling of a single aryl halide starting material. The method is convenient for the coupling of symmetric monomers, or if a regioregular material is not required. A n example is the Ni(II)-catalyzed coupling of 2-bromothiophene in the presence of zinc to give bithiophene, as depicted in Figure l-3a.  32  Kumada coupling is a metal-catalyzed cross-coupling reaction of aryl halides and Grignard reagents, ' and is an efficient technique that can be used to couple thiophene rings at 33 34  a positions in the presence of reactive P-substituents. '  Kumada coupling is frequently used  for oligothiophene synthesis, commonly employing [PdCbCdppf)] (dppf = l,l'-bis(diphenylphosphino)ferrocene) or [NiC^Cdppp)] (dppp = l,3-bis(diphenylphosphine)propane) as catalysts. 3  The example given in Figure l-3b depicts selective coupling of tribromothiophene at the a positions, leaving the (3-bromo position unsubstituted.  Suzuki coupling is the metal-catalyzed  cross-coupling of halide and boronic ester groups, and is also often used for oligothiophene coupling reactions.  Suzuki coupling reactions are high yielding and display a much higher  activity for the iodo group versus other halides, so that the method can be used to prepare regiospecific oligomers via cross-coupling reactions.  Figure l-3c shows the coupling of an  37,38  a,a-chloroiodoalkylthiophene with a thienyl boronic ester, where the iodo group is reacted, and the remaining chloro group can be converted to a boronic ester for further reaction and chain 37 38  extension. '  Ni(II)-HomocoupIing  (a)  2  ^ - B r  [N**P"bM  ^y^]  Zn, Et NI 4  Kumada Coupling ,S  S  V  [PdCl (dppf)]  x  2  Br  Br Suzuki Coupling  <c) M  , ^  '^_^ Q^\J —~ i x ^ c S  CI +  ^ _ , - ,  /  R  S  X  P ~ \  [  P D  <  P P H  3)4]  „ ,  R  R  R  McCullough Method (d) B r ^ C y - M g B r S  ^(dppp)]  R  -  ^  V  ^ R  Figure 1-3 Metal-catalyzed coupling reactions used to prepare oligo- and polythiophenes.  4  a  The McCullough method for preparing regioregular polyalkylthiophenes makes use of Grignard-halide coupling similarly to that of Kumada coupling with a Ni(II) catalyst, using a single 2-bromo-5-bromomagnesio-3-alkylthiophene monomer. Cross-coupling of the monomer results  in 98-100% HT-HT  HT-PHT. ' ' 28  39  40  coupling, yielding highly regioregular polymers such as  Figure l-3d displays the general procedure for preparing HT-PAT polymers.  An alternative synthetic thienyl coupling method frequently used is Stille coupling, which is a palladium-catalyzed cross-coupling reaction using organotin reagents, ' although this method 41 42  has the disadvantage of handling toxic tin reagents.  Oxidative polymerization occurs by loss of an electron from thiophene or an oligothiophene chain that creates a localized radical at an a position, and polymerization proceeds via a radical mechanism. Shown in Figure 1-4 is the oxidation of thiophene to produce the radical cation, followed by coupling of two thiophene radicals. Subsequent loss of two protons yields bithiophene, and chain extension then continues by repetition of the radical mechanism.  10  Coupling preferentially occurs at the a positions due to the greater relative  reactivity of these positions, though P-couplings can also occur via this technique in a lower ratio than a-coupling. Oxidative polymerization can occur by a chemical redox reaction with the 5  addition of an oxidant such as F e C ^ , surface  4 4  43  or by electrochemical polymerization at an electrode  Thiophenes substituted with electron donating groups or extended oligothiophene  chains are more easily oxidized than thiophene, and are therefore better candidates for polymerization via this approach. The electron-rich EDOT group is an example of a substituted thiophene that is polymerized by oxidative polymerization to give P E D O T .  44  1.2.3 Properties and Applications of 71-Conjugated Materials  A  Conduction Band  LUMO  Energy  Band Gap  HOMO  Valence Band  n=l  n=2  n= 3  n=  oo  Figure 1-5 Energy band diagram of polyacetylene, as derived from overlapping n orbitals.  Organic ^-conjugated materials display interesting properties due to the delocalized ^-electrons of these systems. Overlap of the n-orbitals of the double bonds, adjacent aromatic rings, or lone pairs of extended chains results in multiple bonding and antibonding orbitals of similar energy that form a filled valence band and an empty conduction band, separated by a band gap. This band structure can be likened to that of a semiconductor, and n-conjugated materials exhibit similar properties to semiconductors. The molecular orbital diagram displayed 6  in Figure 1-5 shows the overlap of n and n* orbitals of alternating double bonds, resulting in the formation of multiple n-bonding and antibonding orbitals. The valence and conduction bands that are formed for polyacetylene (n = oo) are separated by a band gap that is lower in energy The TC orbitals of  than the difference between the initial H O M O and L U M O levels. polythiophene overlap in a similar fashion to yield a band structure. Structure-property  relationships  are  established  between  the  composition and  conformation of a material and specific chemical or electronic properties.  The changes in  electronic properties that arise due to chain extension and the overlap of n orbitals include red shifts of the absorption and emission wavelengths, and lower oxidation potentials. Red shifted absorption and emission wavelengths are due to a decreasing energy gap between the H O M O and the L U M O levels, while a higher H O M O energy level results in easier oxidation of long thiophene chains.  Tt-Conjugated chains are also more easily reduced compared with the  monomer species, but as the energies of the L U M O levels are generally still high in energy, reduction of the organic chain is more difficult to carry out than oxidation. Figure 1-6 displays 10  trends observed for the X  max  of the  TC->TC*  transition, and oxidation potentials for oligothiophenes  of n = 2-6.  Number of Thienyl Rings  Figure 1-6 Changes in the irreversible oxidation potential, E (O), and the n—>n* absorption p  31  wavelength, X  max  ( A ) with extension of thiophene chain length. Data from Ref.  7  Substantial interest has been generated for the study of n-conjugated materials that is largely stimulated by their ability to conduct current in the doped form.  7  The conductivity of  regioregular polyalkylthiophenes is increased significantly to maximum conductivities of >1000 Scm" with the introduction of holes (p-doping); ' '  to the same order of magnitude as  that of Cu and Ag. The removal of an electron from the rc-orbitals of polythiophene results in the formation of a polaron, a localized distortion of the backbone that changes the alternation of double bonds over five thiophene units, separating a radical-cation pair (Figure l-7a). Polarons are characterized by the insertion of localized levels within the band gap for which the H O M O level is half-filled, as depicted to the right of Figure l-7a. Two polarons can combine to form a lower energy, doubly-charged bipolaron. The structure of a bipolaron is shown in Figure 1 -7b, and the two empty, localized levels that are inserted between the valence and conduction bands are shown to the right of the structure. A bipolaron is thought to be the more stable state that acts as the primary charge carrier for polythiophene conduction. '  45 46  Figure 1-7 Localized distortions on polythiophene chains and the introduction of energy levels into the band gap due to the formation of (a) a polaron, and (b) a bipolaron.  Due to the introduction of energy levels into the band gap via the creation of polarons and bipolarons with oxidation, the spectroscopic properties of polythiophenes are altered. The colour of polythiophenes is modified with doping and the application of an electrical potential, and this phenomenon is termed electrochromism.  While polythiophene displays an absorption band  between 400-500 nm to yield a dark-red colour, red shifting of the absorption band with 8  electrochemical oxidation results in a green or black colour of the doped material. Electroluminescence occurs when the application of an electric field results in electrons and holes moving in opposite directions that can combine to form an exciton (electron-hole pair), and emit radiation. This property can be exploited to make organic light emitting diode (OLED) devices where the conjugated material is the emissive layer. Polythiophene usually emits orange to red light, but by substitution of the polythiophene chains and modification of the dihedral 47  angles between rings, electroluminescent emission spanning the visible and near-IR regions has been achieved.  1.3  13  Metal-Organic  Hybrid  Materials  1.3.1 Metallation of rc-Conjugated Organic Materials Transition metal groups incorporated into rc-conjugated organic materials can modify the structural, chemical, and electronic properties of the organic component, to generate new classes of metal-organic hybrid materials. Metal groups can be combined with rc-conjugated chains via different attachment modes and with varying proximity to the backbone, and the structural composition and extent of metal-chain interaction strongly affects the resulting properties.  Figure 1-8 Classes of transition metal-organic hybrid materials. Figure adapted from Ref. 9  Metal-organic hybrid materials can be classified into three categories, as shown in Figure 48  1-8.  '  For Type I materials, the transition metal center is spaced from the conjugated backbone  via a typically saturated tether group. The metal group of Type I materials generally exerts little influence on the electronic properties of the organic chain unless the tether is very short. Polymer  l  4 9  is  an  example  of a Type I metal-oligothiophene  electropolymerized from the terthiophene monomer, and 2  material  that was  is a methyl-capped terthiophene  complex used to model a polythiophene chain (Figure 1-9). Both 1 and 2 contain long tether groups separating the metal centers from the thienyl backbones, and metal-chain interactions are not observed for these configurations.  Complex 3  5 0  is a metal-bis(salicylidene)terthiophene  complex where the metal is held in much closer proximity to the conjugated chain. This monomer can be electropolymerized, and the colour of the resulting metallated polythiophene material is dependant on the transition metal center [Ni(II) or Cu(II)]. Binding interactions with cations, occurring near the metal center, also modify the properties of the conjugated chain. The transition metal groups of Type II materials are directly bound to the conjugated backbone without interrupting the conjugation pathway.  Compared to Type I materials, the  bound metals of Type II materials are more likely to interact electronically with the conjugated chain, dependent on the overlap of orbital energies. Type II metal-oligothiophene complexes include 4 , which contains a bis(bipyridine) Ru(II) [Ru(bpy) ] group coordinated via an 2+  19  2  inserted bipyridine segment that modifies the chain properties (Figure 1-9).  Several other  Ru(II)-oligothiophene and Ru(II)-polythiophene hybrid materials have been reported with 20 22 51 52  similar backbone structures incorporating an inserted metal-coordinating group. ' ' '  There  are fewer examples of metals that are bound directly to oligo- or polythiophenes, and those reported generally contain a tethered metal group that encourages interaction of a metal with the thienyl chain. For instance, when the metal group of Type I complex 2 reacts with A g to +  abstract a chloride ligand, the metal then coordinates to a thienyl sulfur to form the Type II complex 5.  18  This research group has demonstrated direct binding of a metal via two modes:  metal-sulfur coordination, and metal-carbon bonding. Using a p-diphenylphosphine linker to promote metal-chain reactions, the Pd(II) complex 6  5 3 , 5 4  electropolymerized to yield metal-crosslinked polythiophenes.  10  was prepared, and could be  Type I  2  1  3 ( M = Ni,Cu)  Type II  5  6  Type I I I  Figure 1-9 Metal-oligothiophene and metal-polythiophene hybrid materials, classed as Type I, Type II, and Type III.  Type III materials can also display strong interactions between metal groups and a conjugated chain, since the transition metal is closely situated to the organic chains and positioned directly in the pathway of conjugation. include Ru(II) complexes 7  55  and 8  56  Type III metal-oligothiophene materials  (Figure 1-9). Complex 7 consists of a hexathiophene chain  that is inserted with conjugated acetylene and metal groups, and displays a low-energy thienyl absorption, and ligand to metal charge transfer (LMCT) absorption bands when oxidized. The 11  binuclear cyclometallated complex 8 is also an example of a Type III material; although the metal is not inserted between conjugated chains, the metal groups are attached via a positions and are in the direction of conjugation. Complexes of this type can also be used as models for extended Type III materials.  17  Interaction of the thienyl chain with the metal groups of 8 is  indicated by an increase in the oxidation potential, though metal-metal interactions via the conjugated chain were not observed.  1.3.2 Properties and Applications of Metal-Organic Hybrid Materials There are a variety of properties that can be altered by the attachment of metals to ^-conjugated materials, and some have already been mentioned in the previous section. In this section, a summary of possible properties modifications that can occur with metallation of conjugated chains is given, along with specific applications that can result. The properties of ^-conjugated materials are generally altered either chemically, structurally, or electronically. Several factors modify electronic properties, including inductive effects, conformation of the conjugated backbone, and the introduction of metal-based orbitals that interact with organic n-orbitals in the hybrid materials. The properties and applications of metal-oligothiophene and metal-polythiophene materials are discussed using the examples given from the previous section. Oligo- and polythiophenes are generally chemically stable; however, the introduction of metal groups can result in new reaction or binding sites that can be exploited for sensing applications.  For example, polymers of the bis(salicylidene)terthiophene monomer 3 appear  green or orange, depending on whether the complexed metal is Cu(II) or Ni(II), respectively. Additionally, the materials produce characteristic shifts of the thienyl-based redox potentials when the crown-ether ring of the complex selectively chelates B a resulting device is a chemosensitive electroactive polymer.  2 +  and M g  2 +  cations, and the  50  Inductive effects occur when there is shifting of the charge density localized at the thienyl chain towards a comparatively electron poor metal center, and can be most often observed as an increase in the oxidation potential of the conjugated chain.  Proximity of the metal to the  conjugated chain mediates the strength of the inductive effect, and hence the effects on the electronic properties.  Comparison between 2 and 5 demonstrates the importance of metal  proximity for the inductive effect.  18  The Type I complex 2 displays A,  max  (353 nm) and E\a  (510 mV vs. Fc/Fc ) values that are near those of the ligand, while the Type II complex 5 shows +  a similar X  m a x  [352 nm, 420 nm (sh)] but an E\a value that is shifted to a higher potential by 12  225 mV.  When significant electron density is removed from a rc-conjugated chain,  derealization is less effective, and the H O M O / L U M O gap is widened for the conjugated system. This effect is observed as increased absorption and emission energies in the electronic spectra.  Conversely, electron donation into the rc-system can occur due to metallation, to  increase the conjugation and reduce the energy gap (Figure 1-10).  Conduction Band Inductive Effect i  or Chain Twisting  Band Gap  Electron Donation  •  or Chain Planarization  Valence Band  Figure 1-10 Modification of the band gap energy with metallation of rc-conjugated materials, due to inductive effects or chain twisting to increase the band gap (left), and electron donation or chain planarization (right).  Planar  Figure 1-11 Examples of planar and twisted conformations of an oligothiophene.  The effective overlap of rc-orbitals largely determines the extent of conjugation, therefore the conformation of the conjugated backbone affects the electronic properties. In the case of a chain composed of aromatic rings, whether the rings are in planar or twisted conformations (Figure 1-11), or some conformation in between, will mediate the conjugation.  The  H O M O / L U M O gap is decreased by coplanar rings, while chain twisting widens the gap (Figure 1-10). Since Type I and Type II metal-thienyl materials may incorporate metal groups in a 13  bidentate mode along the backbone, changes in the conformation of the chain compared to the free ligand or the corresponding oligo- or polythiophene can occur. Complex 5 is a Type II material that deviates from a terthiophene planar conformation in the solid state and displays a dihedral angle between substituted rings that is 21° from planarity.  18  The attachment of metal groups cannot only modify the properties of a rc-conjugated chain, but also introduce new electronic properties into hybrid metal-organic materials. A n interesting characteristic of metals is the occurrence of charge transfer processes.  Charge  transfers with the ligand set and/or with a thiophene chain (Figure 1-12) could occur and would be observed in the electronic spectra. Type II complex 4 displays several changes in properties 2+ due to Ru(bpy)  2  complexation, including a red shift of the  TC—»TC*  absorption band of the  conjugated chain due to planarization of the bipyridyl segment of the chain upon metallation.  19  Donation of electron density from the Ru(II) group could also contribute toward the red shift. Metal-to-ligand charge transfer (MLCT) transitions, both to the conjugated chain and to the bpy ligands, are introduced and result in a much altered absorption spectrum of the material. M L C T transitions from the metal group to the thienyl chain would result in the introduction of electrons into the conduction band (n-doping, Figure l-12a). Ligand-to-metal charge transfer (LMCT) transitions involving a transition from the conjugated chain to the metal group would alternatively create holes in the valence band (p-doping, Figure l-12b).  Both doping  mechanisms create a conductive pathway along a rc-conjugated chain with light absorption, and materials of this type constitute light-harvesting materials, having applications in organic-based solar cells.  Conduction Band  A  MLCT Metal HOMO  Metal LUMO  Band Gap  LMCT  Valence Band  (a)  (b)  Figure 1-12 The introduction of metal-based H O M O or L U M O levels into the band gap of a rc-conjugated chain, resulting in (a) a metal-to-ligand charge transfer (MLCT) transition, or (b) a ligand-to-metal charge transfer (LMCT) transition.  14  1.4  Focus  of Present  Study  This study is focused on the interactions between transition metals and oligothiophenes of the Type I and Type II classes. These types of structures were targeted so that the conjugation of the oligothiophene chains is not interrupted; as well, metal-oligothiophene interactions could be studied without the complication of an inserted conjugated group. Diphenylphosphine linker groups, substituted at P positions on oligothiophene chains, are used to anchor metal groups. Phosphines can coordinate many metals via a lone pair, modify the electronic properties of metals, and participate in charge transfer transitions.  57  These phosphine-oligothiophene ligands  are referred to as P-phosphinothiophenes in this thesis.  The coordination of a P-  phosphinothiophene to a metal group creates a Type I metal-oligothiophene material, where the short phosphine linker allows the metal to lie in close proximity with the conjugated backbone (Figure 1-13a).  Type II  Figure 1-13 General strategies for making (a) Type I and (b) Type II metal-oligothiophene hybrid materials using P-phosphinothiophenes.  Type  II  metal-oligothiophene  hybrid  materials  are  also  prepared  with  P-phosphinothiophene ligands, and are formed when a metal group positioned near the conjugated backbone bonds directly with the adjacent thiophene ring. Metal-thiophene bonding can occur by this strategy either at the sulfur atom or at a P-carbon position (Figure 1-13b). I was especially interested in studying the changes in electronic properties that occur due to close 15  proximity of the attached metal groups, and orbital overlap with the n-conjugated backbone. Both types of metallation can also alter the thienyl backbone structure, with further ramifications on the electronic properties. Once metal groups are attached to the oligothiophene chain, they can also be involved in chemical reactions and the reactivity of the hybrid materials is investigated. These studies, focusing on direct metal-oligothiophene interactions, differ from similar work that has been carried out involving Type II metal-oligothiophene hybrid materials. Most studies have made use of other conjugated groups, inserted into an oligothiophene backbone to directly bond a metal to the conjugated chain, and few instances of direct metal-thienyl interactions along thienyl chains have been reported. The lack of examples in the literature is likely because the thienyl sulfur is a poor coordinating atom, metal-(3-thienyl bonds often require the presence of heat or strong base to form, and both modes usually require chelation for stability. " 58  60  P-Phosphinothiophenes are used in this study to promote metal interactions with  the thienyl backbone via different modes of binding. Oligothiophene chains are used to model polythiophene chains since the metallated materials can be more easily purified and isolated, to prepare well-defined materials and better establish structure-property relationships.  1.5  Goals The goals of this thesis were: (1) to design and synthesize new, metal-oligothiophene and  metal-polythiophene hybrid materials, (2) to investigate the properties of these new materials, and (3) to interpret the results from a perspective of materials applications. The initial goal was to design and synthesize hybrid materials where the attached metal group is in close proximity to the thienyl backbone, and can interact structurally, chemically, or electronically with the conjugated chains. The metals were to be attached at either pendent positions or directly to the backbone, to maintain an uninterrupted ^-conjugated thienyl chain.  The second goal is  comprised of the following objectives: to structurally characterize solid state materials, determine chemical reactivity of the hybrid materials due to the incorporation of metal groups, and to characterize the electronic properties, including the H O M O and L U M O levels, the electronic excitation and emission energies, and oxidation potentials.  The properties of the  metal-organic hybrid materials in the oxidized state were also to be characterized. The final goal was to identify the structure/property relationships established by this work, and evaluate the metal-organic hybrid materials for molecular electronics or materials applications. 16  References Day, P. "Towards defining materials chemistry," IUPAC, Inorganic Chemistry Division (II) and Polymer Division (IV), 2005 (www.iupac.org/projects/2005/2005-001-l200.html). Journal of Materials Chemistry Homepage, (www.rsc.org/Publishing/Journals/jm/About.asp).  RSC  Publishing,  2005  Forrest, S. R. 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Polyhedron 1984, 3, 1037-1057.  19  CHAPTER 2 Synthesis and Characterization of (3-Phosphinothiophene Ligands and Derivatives  2.1  Introduction A  strategy to bring metals into close proximity with thiophene chains is the use of  coordinating "linker" groups. Examples of linker groups that have been incorporated into oligoor polythiophenes are imines, pyridines, and thiols.  Phosphines are useful in coordinating a  variety of transition metals, and my group and others have made use of phosphines to coordinate gold, palladium, 4  5,6  and ruthenium ' centers to ^-conjugated thienyl backbones.  Ligands  7 8  synthesized for this study contain diphenylphosphine linker groups attached to oligothiophenes at the P, or 3- position of a thiophene ring (Chart 2-1), to form P-phosphinothiophene ligands. The  attachment of a linker group at a P position rather than at the a, or 2- position allows  coordination of a metal without alteration of the backbone composition. Phosphinothiophene ligands metallated at the P positions could be used as molecular wires with the end positions available as points of "electrical contact".  Chart 2-1  P h P ^ p, 32  a ,  2  -  ^  S'  ^  P-Phosphinothiophene ligands and derivatives prepared for this study contain 2-7 thiophene  units, based  on bithiophene (T2), terthiophene  pentathiophene (T ) or heptathiophene (T7) 5  (T3),  quaterthiophene  (T4),  chains (Chart 2-2). P T (9) and P h e x T (11) 2  2  2  (Chart 2-3) were first synthesized by Dr. O. Clot in this research group.  2  9  4  These  P-bis(phosphino)thiophene ligands contain two adjacent diphenylphosphine groups that permit bidentate coordination of one metal center, or monodentate coordination of two metal centers (Figure 2-1).  P-Hexyl substituents are attached to the outer thiophene rings of 11 and the 20  brominated precursor 10 to promote solubility in organic solvents.  The (3-phosphine oxide  (PO)2T2 (12) was prepared by the oxidation of 9, and conformational information is extracted from the crystal structure.  Chart 2-2  O  (PO) T (12) 2  P hex T (ll)  2  2  21  2  4  Ph P 7  -  ML  Ph P  PPh,  2ML„  • p - f t 2  pph ML  x  •  p  -  p  -  Ph P PPh i I L M ML  2  2  n  n  2  n  Figure 2-1 Bidentate and monodentate modes of bonding that may arise with metallation of bis(phosphino)thiophene chains.  Monophosphinated ligands, such as previously reported (3-(phosphino)terthiophene ligands 13-15  10  and the a-(phosphino)terthiophene ligand 16,  11  coordinate one metal center  (Chart 2-4). While the metal group coordinated by an a-phosphinothiophene is directed away from the thiophene chain due to the structural design of the ligand, P positioning of a phosphine allows an anchored metal group to bind to the adjacent thiophene ring via a thienyl sulfur or P position, provided a vacant site is available at the metal (Scheme 2-1).  These bidentate  bonding modes employ direct interaction of a metal to a thiophene chain, and have been demonstrated in my group with different metals. ' '  5 6 12  Due to the close interaction of the metals  with the thiophene chains, the steric and electronic properties of thiophene chains are strongly affected by direct bonding modes. Longer p-phosphinothiophene ligands were prepared for this study by first synthesizing the p-substituted bromodihexyl- and bromodidodecyl-pentathiophenes 17 and 18, and subsequently the iodo analogs 19 and 20.  From the P-substituted iodo  derivatives, the new P-(phosphino)pentathiophene ligands 21 and 22 were obtained (Chart 2-5).  Chart 2-4  aPT  3  (16)  22  Scheme 2-1  Chart 2-5  Phex T (21) 2  P D o T (22)  5  2  5  Electron-rich hexa- and pentathiophene derivatives 23-24 (Chart 2-6) were prepared and characterized.  A tridodecylhexathiophene (23) was obtained as a side product via a non-  selective coupling reaction. Didodecylpentathiophene (24) was prepared for comparison of its physical properties to those of the (3-(phosphino)pentathiophene ligand (22).  23  Chart 2-6  The effect that P-substitution and metallation imparts on the properties of polythiophenes is of interest due to the processibility of bulk organic polymers, and for modeling molecular wires.  Towards this goal, reactions were carried out as models for two possible routes of  polymerization: the polymerization of metal complexes, or the polymerization of functionalized oligomers. Precursor pentathiophenes 25 and 26 that are functionalized at both a positions and at one central p position were prepared (Chart 2-7). By exploiting the higher reactivity of the iodo substituents, the a,a-dibrominated ligand 27 was prepared from 25. P-brominated heptathiophene 28 was prepared from 26.  Chart 2-7  24  Likewise, the  2.2 2.2.1  Experimental General Experimental All reactions were performed using standard Schlenk techniques with dry solvents under  nitrogen. Ligands 9 and 14-15 were obtained from Dr. O. Clot, 16 was obtained from Dr. 9  6  Stott, and ligand 11 was previously synthesized by Dr. Tetrabromo-2,2'-bithiophene,  13  T.  11  O. Clot by another procedure.  3'-bromoterthiophene,  12  10  3,5,3',5'-  2-bromo-3-hexylthiophene, 2-bromo14  3-dodecylthiophene, and 2-thienyl-l,3,2-dioxaborinane and 13 were prepared by published 14  procedures.  15  6  A l l other reagents were purchased from  Aldrich  or Strem Chemicals.  A^^Z-dimethylethylenediamine, bis-2-methoxyethylether, and xylenes were distilled before use, and  all other reagents were used as received. ' H and P{'H} NMR 31  experiments were performed  on either a Bruker AC-200E,. Bruker AV-300 or Bruker AV-400 spectrometer, and spectra were 1  31  referenced to residual solvent ( H) or external 85% H3PO4 ( P). Electronic absorption spectra were obtained on an HP8452A diode-array spectrophotometer or on a Cary 5000 in HPLC grade CH2CI2.  Microanalyses (C, H , N) were performed at UBC  by M . Lakha. Electrochemical  measurements were conducted on a Pine AFCBP1 bipotentiostat using a platinum disc working electrode, platinum coil wire counter electrode and a silver wire reference electrode. A n internal reference, either decamethylferrocene (-0.12 V vs. SCE) or ferrocene (0.41 V vs. SCE),  was  added to calibrate the measured potentials with respect to saturated calomel electrode (SCE). The  16  supporting electrolyte was [(n-Bu)4N]PF that was purified by triple recrystallization from 6  ethanol and dried at 90°C under vacuum for three days.  2.2.2  Synthesis  3,3'"-Dihexyl-3 '3 "-dibromo-2,5':2',2":5 ",2 '"-quaterthiophene (10) A solution of 2-bromo-3-hexylthiophene (7.34 g, 30 mmol) in THF (10 mL) was added dropwise to a mixture of magnesium (1.41 g, 58 mmol) and trace iodine in THF (30 mL) at reflux and stirred for 2 h. The resulting solution was transferred dropwise at 25°C via cannula to a mixture of 3,5,3',5'-tetrabromo-2,2'-bithiophene (5.72 g, 12 mmol) and [PdCl2(dppf)]-CH Cl2 2  (200 mg, 0.2 mmol) in Et^O (30 mL) and toluene (20 mL), and heated at reflux for 3 h. The reaction was then quenched with sat. aq N H 4 C I (50 mL), insoluble material.  CH2CI2  phase was extracted with  (50 mL) CH2CI2.  and filtered through Celite to remove  was added, the organic phase was separated and the aqueous The combined organic phases were washed with sat. aq 25  NaHCCh solution and H2O, dried with anhydrous MgSCU, and the solvent was removed to give a thick orange oil. The crude product was purified by column chromatography on silica gel with hexanes as eluent.  The first three bands contained small amounts of unreacted 3,5,3',5'-  tetrabromo-2,2'-bithiophene, 3-hexylthiophene, and monosubstituted terthiophene side product, respectively. The fourth band contained the desired product 10, and removal of solvent left a bright-yellow, waxy solid. subsequent bands.  Penta- and hexathiophene derivatives were also isolated in  Yield: 4.02 g (52%).  5.2 Hz), 2H), 7.09 (s, 2H), 6.96 (d, J  HH  !  H N M R (200.1 M H z , CDCI3):  = 5.2 Hz, 2H), 2.79 (t,  J  HH  5 7.23 (d, J  =  m  = 7.7 Hz, 4H), 1.64 (m, 4H),  1.34 (m, 12H), 0.90 (t, 6.3 Hz, 6H). Anal. C 8H32Br S4 requires C, 51.22; H , 4.91%. found: 2  2  C, 51.34; H , 4.72%.  3,3"'-Dihexyl-3 '3 "-bis(diphenylphosphino)-2,5':2 '2 ":5 "2 '"-quaterthiophene (P2hex2T ) (11 4  To a suspension of 10 (1.0 g, 1.52 mmol) in E t 0 (30 mL) at -78°C was added a solution 2  of «-BuLi (1.6 M , 2.10 mL, 3.35 mmol) in dry THF. The mixture was slowly warmed until the suspended solids dissolved at -30°C to give an orange solution, and PPh Cl (1.34 g, 6.09 mmol) 2  was subsequently added. After 5 min at -30°C, a yellow precipitate formed and the mixture was slowly allowed to warm to room temperature, then stirred for 1 h. The reaction was quenched with H 0 , dried with anhydrous MgSCM and the solvent was removed to leave a dark-yellow 2  solid/liquid mixture. The crude product was purified by chromatography on silica gel using hexanes-CH2Cl (4:1) as eluent. The first two bands contained starting materials, and the third 2  band contained the monosubstituted side product.  Removal of solvent from the fourth band  yielded 11 as a dark-yellow liquid. Yield: 0.91 g (61%). ' H N M R (200.1 MHz, CDC1 ): 5 7.31 3  (m, 20H), 7.10 (d,  J  HH  = 5.1 Hz, 2H), 6.85 (d,  J H H  = 5.1 Hz, 2H), 6.65 (s, 2H), 2.55 (m, 4H),  1.56-1.07 (m, 16H), 0.88 (m, 6H). P{'H} N M R (81.0 MHz, CDC1 ): 8 -25.1 (s). Elemental 31  3  analysis results were obtained by Dr. O. Clot and were reported. 3.3 -Bis(diphenylphosphoryl)-2,2-bithiophene (PO)2T  2  9  (12)  To a solution of 9 (1.0 g) in CHC1 (50 mL) and acetone (50 mL) was added 30% H 0 3  2  2  (0.4 mL). A white solid precipitated immediately and the mixture was stirred for 1 h. The solid was collected by filtration, redissolved in CHCI3, filtered and precipitated with acetone to give a white solid. Yield: 0.54 g (51%). ' H N M R (200.1 MHz, CDCI3): 5 7.71 (ddd, J= 1.6, 8.2, 14.0 Hz, 8H), 7.53-7.36 (m, 12H), 7.18 (dd, J  HH  = 5.4 Hz, J p = 2.2 Hz, 2H), 6.65 (dd, J H  26  HH  = 5.4  Hz, J p = 4.4 Hz, 2H).  31  H  P { ' H } N M R (81.0 MHz,  CDCI3):  5 20.5 (s). Anal.  C32H24O2P2S2  requires C, 67.83; H, 4.27. found: C, 67.59 H, 4.32%. 3 "-Bromo-3,3""-dihexyl-2,2 ':5 '2 ":5 "2 "':5 "',2 ""-pentathiophene (17) Magnesium (0.20 g, 7.5 mmol) and a trace amount of iodine were brought to reflux in THF (15 mL), and a solution of 2-bromo-3-hexylthiophene (0.92 g, 3.7 mmol) in THF (2 mL) was added dropwise by syringe. The mixture was heated at reflux for 2 h and allowed to cool. The Grignard solution was then added dropwise by cannula to a condenser-fitted flask containing a  solution  of  5,3',5"-tribromo-2,2':5',2"-terthiophene  [PdCl2(dppf)]-CH Cl 2  (0.91  g,  1.9  mmol)  and  (40 mg, 0.049 mmol) in Et 0/toluene (22 mL/17 mL). The orange  2  2  solution was heated at reflux for 16 h, and then quenched with sat. aq NH C1 and stirred for 1 h. 4  The crude product was extracted with  CH2CI2,  washed with sat. aq NaHC03 once, then three  times with H 0 to give a bright orange solution that was removed of solvent. The crude product 2  was run through a short silica gel plug with hexanes to remove 3-dodecylthiophene side product and catalyst, and then purified by column chromatography on silica gel using hexanes as eluent. The third band was collected and the solvent was removed to give 17 as a viscous orange liquid. Yield: 316mg(26%). H N M R (400.1 MHz, CDC1 ): 5 7.372 (d, J= 4.0 Hz, 1H), 7.182 (d, J = ]  3  5.2 Hz, 1H), 7.176 ( d , J = 4 . 0 H z , 1H), 7.111 (d,J=4.0 Hz, 1H), 7.075 (s, 1H), 7.065 (d,J=4.0 Hz, 1H), 7.015 ( d , J = 4.0 Hz, 1H), 6.935 (d, J= 5.2 Hz, 1H), 6.932 (d, J= 5.2 Hz, 1H), 2.774 (t, J = 8 . 4 Hz, 4H), 1.649 (m, 4H), 1.380 (m, 4H), 1.311 (m, 8H), 0.881 (m, 6H). 3 "-Bromo-3,3 ""-didodecyl-2,2 ':5 '2 ":5 ",2 "':5 "',2 ""-pentathiophene (18) Magnesium (1.36 g, 56 mmol) and iodine (5 mg, 0.02 mmol) were brought to reflux in THF (60 mL), and 2-bromo-3-dodecylthiophene (9.29 g, 28 mmol) dissolved in THF (10 mL) was added dropwise by syringe. The green-brown mixture was heated at reflux for 2 h and allowed to cool. The Grignard solution was then added dropwise by cannula to a condenserfitted flask containing a solution of 5,3',5"-tribromo-2,2':5',2"-terthiophene (6.79 g, 14 mmol) and [PdCl (dppf)]-CH Cl (300 mg, 0.367 mmol) in Et 0/toluene (80 mL/60 mL). The yellow2  2  2  2  brown solution was stirred at reflux for 16 h, quenched with sat. aq NH4CI, and stirred for 1 h. The crude product was extracted with  CH2CI2,  washed with sat. aq NaHC03 once, then three  times with H 2 Q to give a bright orange solution that was condensed to give an orange-red liquid. The  crude product was run through a short silica gel plug with hexanes to remove 3-  dodecylthiophene side product and catalyst, and then purified by column chromatography on 27  silica gel using hexanes as eluent. The initial yellow band was a mixture of tetrathiophene side products. The second orange band was collected and the solvent removed to give 18 as a soft, waxy, bright orange solid. Yield: 7.61 g (66%). ' H N M R (200.1 M H z , CDC1 ): 8 7.37 (d, J = 3  5.4 Hz, 1H), 7.18 (d, J = 7 . 7 H z , 2H), 7.11 (d, .7=5.7 Hz, 1H), 7.07 (s, 1H), 7.06  (d,J=5.7Hz,  1H), 7.01 (d, J= 5.4 Hz, 1H).  4H),  6.93  (d, J= 7.8 Hz, 2H), 2.77 (m,  4H),  1.65 (m,  1.25 (m,  36H), 0.87 (t, J= 6.8 Hz, 6H). Anal. C 4H 9S Br requires C, 63.81; H , 7.18. found: C, 63.52; 4  5  5  H, 7.48%. 3,3 ""-Dihexyl-3 "-iodo-2,2 ':5',2":5 ",2 '":5 '"2 ""-pentathiophene (19) To a solution of 17 (316 mg, 0.478 mmol), Nal (71.6 mg, 0.956 mmol), and Cul (4.6 mg, 0.024 mmol) in xylenes/bis-2-methoxyethylether (10 mL/4 mL), 7V,A^-dimethylethylenediamine (0.005 mL, 4.2 mg, 0.048 mmol) was added.  A white precipitate formed and the resulting  mixture was heated to 165°C for 5 h. After cooling, a bright yellow organic layer and a green aqueous layer were formed with the addition of  CH2CI2  and  H2O.  The organic layer was  separated, washed three times with H 0 , dried with anhydrous M g S 0 and filtered. The solvent 2  4  was removed and the xylenes and bis-2-methoxyethylether were distilled off to leave an oily, crude product. Purification by column chromatography on silica gel using hexanes as eluent gave 19 as a soft, waxy, bright orange solid after removal of solvent. Yield: 0.325 g (96%). *H N M R (200.1 M H z , CDC1 ): 8 7.383 (d, J = 4.0 Hz, 1H), 7.184 (d, J = 5.2 Hz, 2H), 7.163 (s, 3  1H), 7.094 (dd, 7 = 5.2 Hz, J= 4.0 Hz, 2H), 7.012 (d, J= 4.0 Hz, 1H), 6.934 (d, J= 5.2 Hz, 2H), 2.799  (m, 4 H ) , 1.664 (m, 4 H ) , 1.338 (m, 12H), 0.895 (m, 6 H ) .  3,3""-Didodecyl-3 "-iodo-2,2 ' J ',2 ":5 "2 "':5 "',2 ""-pentathiophene (20) To a solution of 18 (7.61 g, 9.18 mmol) , Nal (2.75 g, 18.4 mmol), and Cul (87.5 mg, 0.459  mmol) in xylenes/bis-2-methoxyethylether (160 mL/40 mL), ^iV-dimethylethylene-  diamine (0.098 mL, 81 mg, 0.92 mmol) was added. A white precipitate formed and the resulting mixture was heated to 165°C for 16 h. After cooling, a dark yellow organic layer and a green aqueous layer were formed with the addition of  CH2CI2  and  separated, washed three times with H 2 O , dried with M g S 0  4  H2O.  The organic layer was  and filtered. The solvent was  removed and the xylenes and bis-2-methoxyethylether were distilled away to leave an oily crude product. Purification by column chromatography on silica gel using hexanes as eluent gave 20 as a soft, waxy bright orange solid after removal of solvent. Yield: 7.58 g  (94%).  !  H N M R (200.1  M H z , C D C l ) : 8 7.38 (d, J = 4.0 Hz, 1H), 7.19-7.16 (m, 2H), 7.16 (s, 1H), 7.11 ( d , J = 3 . 6 H z , 3  28  1H), 7.08 (d, J= 4.0 Hz, 1H), 7.01 (d, J = 3.8 Hz, 1H), 6.93 (d, J = 5.2 Hz, 2H), 2.77 (m, 4H), 1.65 (m, 4H), 1.25 (m, 36H), 0.87 (t, J = 6.6 Hz, 6H). Anal. C 4H 9S I requires C, 60.38; H , 4  5  5  6.79. found: C, 60.78; H, 6.88%. 3,3""-Dihexyl-3 "-diphenylphosphino-2,2 ':5 '2 ":5 "2 "':5 '"2 ""-pentathiophene (Phex T5) (21) 2  To a solution of 19 (325 mg, 0.458 mmol) and [Pd(OAc) ] (1.0 mg, 4.6 umol) in C H C N 2  3  (25 mL), distilled NEt (0.13 mL, 0.093 g, 0.92 mmol) and Ph PH (0.080 mL, 85 mg, 0.46 3  2  mmol) were added. The orange suspension darkened to greenish-brown with heating at reflux for 72 h and a dark oil was formed on the flask bottom. Solvent and volatiles were removed under reduced pressure and the crude product was extracted with CH C1 , washed with 1 M aq 2  2  K O H , 2 M aq HC1, then three times with H 0 . Removal of solvent left a dark, blackish oil. 2  Purification by column chromatography on silica gel using acetone-hexanes (5:95) as eluent resulted in elution of 21 as the third band. The isolated product was a bright orange viscous liquid after removal of solvent. Yield:  143 mg (41%).  31  P { ' H } N M R (162.0 MHz, CDC1 ): 3  8-23.0 (s). 3.3 ""-Didodecyl-3 "-diphenylphosphino-2,2 ':5 '2 ":5 "2 "':5 "'2 ""-pentathiophene  ( P D 0 2 T 5 ) (22)  To a solution of 20 (4.33 g, 4.95 mmol) and [Pd(OAc) ] (5 mg, 0.022 mmol) in C H C N 2  3  (250 mL), distilled NEt (1.4 mL, 1.0 g, 9.9 mmol) and Ph PH (0.86 mL, 0.92 g, 4.95 mmol) 3  2  were added. The orange suspension darkened to a greenish-brown with heating at reflux for 16 h and a black, gelatinous layer formed on the flask bottom. Solvent and volatiles were removed under reduced pressure and the crude product was extracted with CH C1 , washed with 1 M aq 2  2  K O H , 2 M aq HC1, then three times with H 0 . Removal of solvent left a brown oil. Purification 2  by column chromatography on silica gel using acetone-hexanes (5:95) as eluent resulted in elution of starting material 20, followed by 22 as an orange band, and an orange band containing the oxidized ligand eluted much later. The isolated product was a bright orange viscous liquid after removal of solvent. Yield: 4.29 g (93%). H N M R (200.1 M H z , CDC1 ): 5 7.37 (m, 10H, 5  3  phenyl), 7.15 (d, J= 5.2 Hz, 2H), 7.03 (d, .7=3.6 Hz, 1H), 7.01 (d, 7=4.0 Hz, 1H), 6.99 (d,J = 4.4 Hz, 1H), 6.96 (d, J= 3.8 Hz, 1H), 6.91 (d, J = 5.0 Hz, 2H), 6.63 (s, 1H), 2.73 (m, 4H), 1.61 (m, 4H), 1.25 (m, 36H), 0.87 (m, 6H).  31  P{'H} N M R (81.0 M H z , CDC1 ): 5 -23.5 (s). 3  Anal. C56H69S5P requires C, 72.05; H , 7.45. found: C, 71.65; H, 7.49%.  29  3,3 ,3  -lridodecyt-2,2 :5,2 :5 ,2 :5 ,2 :3 ,2  -hexathiophene (23)  Magnesium (0.37 g, 15 mmol) and iodine (3 mg, 0.01 mmol) were brought to reflux in THF (20 mL), and 2-bromo-3-dodecylthiophene (2.53 g, 7.64 mmol) dissolved in THF (5 mL) was added dropwise by syringe. The dark brown mixture was heated at reflux for 2 h and allowed to cool. The Grignard solution was then added dropwise by cannula to a condenserfitted flask containing a solution of 5,3',5"-tribromo-2,2':5',2"-terthiophene (1.10 g, 2.27 mmol) and [Ni(dppp)Cl ] (40 mg, 0.074 mmol) in Et 0/toluene (30 mL/20 mL) and the mixture 2  2  darkened from orange to red. After heating at reflux for 20 h, there was no change of the product mixture by T L C , and the reaction was quenched with sat. aq NH4CI, and stirred for 1 h. The crude product was extracted with CH C1 , washed with sat. aq NaHC03 once, then three times 2  2  with H 0 to give a dark red solution that was condensed to give a dark red liquid. Purification 2  by column chromatography on silica gel using hexanes as eluent resulted in the elution of six bands as follows:  3-dodecylthiophene (0.60 g, 31%), 5,3',5"-tribromo-2,2':5',2"-terthiophene  (0.26 g, 24%), mixed (3-substituted tetrathiophenes (0.22 g, 15%), mixed a,[3-substituted pentathiophenes (23 mg, 1.2%), 18 (21 mg, 1.1%), and 23 as orange-red solids. Yield: 0.51 g (23%). ' H N M R (300.1 MHz, CDC1 ): 5 7.32 (d, J= 4.8 Hz, 1H), 7.16 (d, J= 5.1 Hz, 1H), 7.14 3  ( d , J = 3 . 9 H z , 1H), 7.1 l(d, J=5.1 Hz, 1H), 7.05 (s, 1H), 7.02 (d,J=3.9 Hz, 1H), 6.98-6.92 (m, 4 H), 6.86 (d, J= 5.1 Hz, 1H), 2.77 (t, J= 1.1 Hz, 2H), 2.63 (t, J= 1.1 Hz, 2H), 2.40 (t, J= 7.5 Hz, 2H), 1.64 (m, 2H), 1.54 (m, 2H), 1.45 (m, 2H), [1.26 (m), 1.24 (m), 1.20 (m), 1.16 (m); 54 H], 0.87 (m, 9H). Anal. C o H S requires C, 72.09; H, 8.67. found: C, 72.10; H, 8.97%. 6  86  6  3,3""-Didodecyl-2,2 ':5',2":5 "2 "':5 "',2 ""-pentathiophene  (D02T5,  24)  A solution of 20 (300 mg, 0.343 mmol) in E t 0 (100 mL) was cooled to -20°C and 2  tt-BuLi (0.26 mL, 1.6 M in hexanes, 0.41 mmol) was added.  The yellow-orange solution  immediately changed color to dark orange. H 0 (0.10 mL, 5.55 mmol) was injected into the 2  solution and after 0.5 h and with slow warming, the solution turned yellow. The organic phase was washed three times with H 0 , dried with MgS04, filtered, and the solvent was removed to 2  leave a yellow residue. Purification by column chromatography on silica gel using hexanes as eluent gave 24 as a dark yellow powder after removal of solvent. Yield: 0.257 mg (100%). ' H N M R (400.1 M H z , CDCI3): 5 7.17 (d, J= 5.2 Hz, 2H), 7.11 (d,J= 3.6 Hz, 2H), 7.08 (s, 2H), 7.01 (d, J = 3.6 Hz, 2H), 6.93 (d, J = 5.2 Hz, 2H), 2.77 (t, J = 7.8 Hz, 4H), 1.64 (m, 4H),  30  1.37-1.25 (m, 36 H), 0.87 (t, J= 6.6 Hz, 6H). Anal. C 4H oS requires C, 70.53; H , 8.07. found: 4  6  5  C, 70.93; H , 8.27%. 5,5""-Dibromo-3,3""-didodecyl-3 "-iodo-2,2 ':5 '2 ":5 "2 "':5 "'2 ""-pentathiophene (25)  A solution of 20 (1.00 g, 1.14 mmol) and N B S (0.407 g, 2.28 mmol) were stirred in CHCI3/CH3COOH (100 mL/100 mL) at room temperature overnight. The solution was washed with H 2 O , 1 M aq NaOH, then three times with H2O, and the aqueous layer was extracted with The organic phases were dried with MgS04 and the solvent was removed. The crude  CH2CI2.  product was purified by column chromatography on silica gel using hexanes as eluent. The desired product eluted as the first band and was closely followed by a second band containing the monobrominated by-product. Removal of solvent gave 25 as bright orange solids. Yield: 0.982 mg (83%). *H N M R (400.1 MHz, CDCI3): 5 7.353 (d, J= 4.0 Hz, 1H), 7.150 (s, 1H), 7.081 (d, J= 4.0 Hz, 1H), 7.014 (d, J= 4.0 Hz, 1H), 6.946 (d, J= 4.0 Hz, 1H), 6.888 (s, 1H), 6.884 (s, 1H), 2.697 (t, J = 7.2 Hz, 4H), 1.598 (m, 4H), 1.333 (m, 4H), 1.236 (m, 32H), 0.855 (t, J = 6.8 Hz, 6H). Anal.  044^785^  requires C, 51.16; H , 5.56. found: C, 51.56; H , 5.59%.  3 "-Bromo-3,3 ""-didodecyl-5,5 ""-diiodo-2,2 ':5',2":5 ",2 '":5 '"2 ""-pentathiophene (26)  A  solution of 18 (353 mg, 0.426 mmol) and NIS (0.239 g, 1.06 mmol) in  CHCI3/CH3COOH (100 mL/100 mL) was stirred at room temperature for 16 h. A precipitate formed that was extracted with three times with H 2 O .  CH2CI2  and the solution was washed with  H2O,  1 M NaOH, then  After drying with M g S 0 4 and filtering, the solvent was removed.  A  portion of the crude material was lost when crystallization attempts in C H C l / E t O H solution 2  resulted in oxidation of some product.  2  Purification by column chromatography on silica gel  using acetone-hexanes (5:95) as eluent was successful, and the first band eluted contained the product as bright orange solids. Yield: 310mg(67%).  ' H N M R (400.1 MHz, CDC1 ): 5 7.346 3  (d, J= 4.0 Hz, 1H), 7.093 (d, J= 3.6 Hz, 1H), 7.065 (s, 3H), 7.000 (d, J= 4.0 Hz, 1H), 6.952 (d, J= 3.6 Hz, 1H), 2.708 (q, J = 8.0 Hz, 4H), 1.591 (m, 4H), 1.316 (m, 4H), 1.231 (m, 32 H), 0.852 (t, J= 6.8 Hz, 6H). Anal. C 4H57S I Br requires C, 48.93; H , 5.32. found: C, 49.21; H , 4  5  2  5.35%. 5,5 ""-Dihromo-3,3 ""-didodecyl-3 "diphenylphosphino-2,2 ':5',2":5 "2 '":5 '"2 ""-pentathiophene ( P B r D o T ) (27) 2  2  5  A suspension of 25 (800 mg, 0.826 mmol) and [Pd(OAc)2] (1.0 mg, 4.4 umol) was stirred in C H C N (60 mL), and distilled NEt (0.23 mL, 0.17 g, 1.7 mmol) and Ph PH (0.14 mL, 0.15 g, 3  3  2  31  0.826 mmol) were then injected into the flask. The orange suspension dissolved under reflux conditions and stirred for 20 h. Solvent and volatiles were removed under reduced pressure and the crude product was extracted with CH2CI2, washed with 1 M aq K O H , 2 M aq HC1, then three times with H2O.  Removal of solvent left an orange-brown oil.  Purification by column  chromatography on silica gel using acetone-hexanes (5:95) as eluent resulted in elution of starting material 25, followed by a side-product, then 27 as an orange band, and an orange band containing the phosphine oxide following.  The isolated product was a thick, yellow-orange  liquid after removal of solvent. Yield: 380 mg (42%). ' H N M R (400.1 MHz, CDCI3): 5 7.345 (m, 10H, phenyl), 7.105 (d, .7=3.6 Hz, 1H), 6.989 (d, .7=4.0 Hz, 1H), 6.923 (d, J = 3 . 6 H z , 1H), 6.889 (d, J = 3.6 Hz, 1H), 6.855 (s, 2H), 6.577 (s, 1H), 2.632 (m, 4H), 1.548 (m, 4H), 1.270 (m, 4H), 1.231 (s,32H), 0.851 (t, J= 6.6 Hz, 6H). -Bromo-3,3  31  P{'H} N M R (162.0 MHz, CDCI3): 5 -23.1 (s).  -aidodecyl-2,5 :2,2 :5 ,2 :5 ,2 :5 ,2  :5  ,2  -neptatniopnene (28)  A solution of 26 (50 mg, 0.046 mmol), CsF (63 mg, 0.46 mmol) and [Pd(PPh ) ] (2.3 3  4  umol, 5.4 mg) was stirred in THF (20 mL) at reflux, and a solution of 2-thienyl-l,3,2dioxaborinane (0.093 mmol, 15.6 mg) in THF (10 mL) was added to the mixture. After 2 h, the solution darkened from dark yellow to orange, and the solvent was removed. The product was purified by column chromatography on silica gel using acetone-hexanes (10:90) as eluent. The first band contained 26, the second band was a hexathiophene side-product, and the third band contained 28 as dark orange solids. Yield: 40.9 mg (89%). ' H N M R (400.1 MHz, CDC1 ): 3  8 7.381 (d,J= 3.9 Hz, 1H), 7.208 (d, J= 5.1 Hz, 2H), 7.158 (d, J= 3.6 Hz, 2H), 7.123 (d, J = 3.6 Hz, 1H), 7.083 (d, J= 3.9 Hz, 1H), 7.084 (s, 1H), 7.034 (d, J = 3.6 Hz, 1H), 7.009 (s, 2H), 7.007 (dd, J= 5.1 Hz, J= 3.6 Hz, 2H), 2.756 (m, 4H), 1.665 (m, 4H), 1.363 (m, 4H), 1.239 (m, 32H), 0.853 (t, J= 6.9 Hz, 6H).  2.3  Results  2.3.1 Synthesis The preparative routes used to obtain bis(phosphino)thiophene ligands P2T2 (9) and P2hex2T4 (11) are shown in Scheme 2-2. The quaterthiophene ligand 11 incorporates two hexyl 9  substituents to enhance solubility in organic solvents. Compound 10 is prepared by coupling 3-hexylthiophene to the a-brominated positions of 3,5,3',5'-tetrabromo-2,2'-bithiophene via palladium-catalyzed Kumada coupling.  17  Formation of the dianion at the (3-brominated positions 32  by addition of «-butyl lithium to 10, followed by quenching with chlorodiphenylphosphine, yields 11 as a bright yellow solid.  Scheme 2-2  P hex T (11) 2  2  4  As attempts to obtain crystals of 9 were not successful, (PO)2T (12) was prepared by 2  oxidation of 9 with hydrogen peroxide, and the X-ray crystal structure of this molecule was determined from a crystal grown from methylene chloride by Dr. O. Clot (Figure 2-2).  9  It was  observed that the sterically demanding phosphine oxide substituents force the thiophene rings to adopt close to a S-anti conformation in the solid state, with an interannular torsion angle (S-C-C-S) of 124.1(8)°.  33  (B)  (A)  Figure 2-2 (a) ORTEP view of (PO)2T2 (12). The hydrogen atoms are omitted for clarity and thermal ellipsoids are drawn at 50% probability, (b) ORTEP view down the C4-C5 axis illustrating the interannular torsion angle. Phenyl groups are omitted for clarity. Figure adapted from Ref.  (Phosphino)terthiophene ligands 13-15 were also prepared via lithiation with n-butyl lithium, followed by quenching with chlorodiphenylphosphine. The synthesis of PT3 (13) using this procedure (Scheme 2-3) yielded starting material, product, and a side-product.  During  purification by column chromatography, the three spots eluted at similar retention times; therefore, some product was lost due to discarded mixed fractions.  Some oxidation of the  product on the silica gel column may also have occurred, and the final yield was moderate at 28%.  Scheme 2-3 Br  Ph P, 2  l)«-BuLi,-15°C 28% 2) P h P C l , 2 5 ° C 2  3) HCl(aq)  PT (13) 3  34  Scheme 2-4 C,1 2H2 5 7  n  C.7H9  2eq iyMgEv  66%  2.5% [PdCl(dppf)] /7:8:6 THF-Et0-toluene 75°C 2  2  2 eq Nal 5% Cul 0.1 eq (NHMeCH )  2 2  1) 2eqNEt 10% [Pd(OAc)] 2) PhPH 2  C H Ph P 12  25  /4:1 xylenes-diglyme 165°C  2  2  // W v - | W s  2  94%  94%  /CH CN 85°C 3  PDo T 2  5  (22)  P-Brominated pentathiophenes 17 and 18 were synthesized via selective palladiumcatalyzed Kumada coupling of hexyl- or dodecylthiophene, respectively, to the a positions of 17  5,3',5"-tribromo-2,2':5',2"-terthiophene. could  not  be  prepared  by  The corresponding (phosphino)pentathiophene ligands  bromo-lithium  exchange  followed  by  addition  of  chlorodiphenylphosphine, due to low reactivity of the lithio-anion intermediate. An alternative •18  high temperature copper-catalyzed halogen exchange reaction  was used to form iodo-  substituted pentathiophenes 19 and 20 in high yield, and subsequent palladium-catalyzed crosscoupling with diphenylphosphine yielded Phex Ts (21) and PD02T5 (22). Shown in Scheme 19  2  2-4 is the three-step preparation of 22. Selective coupling at the a positions of 5,3',5"-tribromo2,2':5',2"-terthiophene with the dodecylthiophene Grignard reagent gave 18 in good yield (66%). The use of [PdCl2(dppf)] as a catalyst during the coupling step resulted in preferential reaction at 35  the a positions.  Alternatively, the use of [NiCbCdppp)] catalyst resulted in non-selective  dodecylthiophene substitution at all three brominated positions and yielded 23 as the major product (Scheme 2-4, bottom). In the case of the palladium-catalyzed coupling, 23 also formed if two equivalents of the Grignard reagent were exceeded, and careful stoichiometry must be maintained. The overall yield of 22 (87%) for the two-step process from 18 is an improvement over the yield for 13 (28%), and other reported yields for phosphinothiophenes prepared via lithiation and addition of chlorodiphenylphosphine. '  6 12  The compound Phex2Ts (21) and its  precursor compounds (17, 19) were prepared in small amounts and consumed for subsequent reactions; consequently, neither elemental analyses nor mass spectrometry were performed. However, the N M R data is analogous to that of the corresponding docecyl-pentathiophenes (18, 20, 22) and free of impurity peaks, so that one can be reasonably confident of the structures and purity of these compounds.  Scheme 2-5  1) 1.2 eq « - B u L i / E t 0 • 2) 16 eq H 0  P 12^25  Q H 2  2 5  2  2  Do T (24)  20  The soluble bis(dodecyl)pentathiophene  2  D02T5  5  (24) was prepared in quantitative yield by  exchange of 20 with n-butyl lithium followed by quenching with water (  Scheme 2-5). It was  observed that reaction of the anionic intermediate with water was slow.  The resulting dark  yellow powder is also easily oxidized, and is susceptible to reaction with oxygen in air. The a,a-dibrominated, P-iodinated pentathiophene 25 was prepared by a selective, room temperature reaction using iV-bromosuccinimide in chloroform/acetic acid solution (Scheme 2-6). Due to the higher reactivity of the iodo substituent relative to the bromo substituents towards palladium-catalyzed cross-coupling with diphenylphosphine, selective phosphine addition yielded the a-brominated P-(phosphino)pentathiophene ligand PBr Do T (27). 2  36  2  5  Scheme 2-6 C,,H 12 25  C,,H 12 25  n  n  2 eq NBS /1:1  20  C„H 12 25  -12 25  n  n  83%  CHCI3-CH3COOH  16 h, RT 1) 2eqNEt 10% [Pd(OAc)] 2) 1 eq PhPH 3  /CH CN 85°C 3  2  2  C H PhP 12  25  2  WJ  x  s  ~\JI  x  42%  P B r D o T (27) 2  The  p-brominated pentathiophene  18 was  iodinated at  2  the  5  a  positions with  AModosuccinimide to yield 26 (Scheme 2-7). The higher reactivity of the a-iodo substituents allowed subsequent selective reaction with 2-thienyl-l,3,2-dioxaborinane via Suzuki coupling under efficient, non-aqueous conditions to produce the heptathiophene 28 in high yield. 20  Compounds 27 and 28 were both found to be light- and oxygen-sensitive, and some decomposition may account for elemental analysis results that were not within the acceptable range (±0.4%) and are not reported here.  Identification relies on the ' H N M R spectra that  displayed peaks corresponding to the given structures (see Chapter 6, Figure 6-1 also) and are free from impurity peaks.  Scheme 2-7  37  2.3.2  Cyclic Voltammetry Oxidation potentials for ligands 9, 11, and 13-15 have been previously reported to be in  the range of 0.99-1.1 V vs. SCE (Table 2-1). ' Decreasing oxidation potential with extension of 6 9  thiophene chain length is generally observed, and incorporation of electron-donating methyl substituents also lowers oxidation potentials, as is observed for ligands 13-15. irreversible oxidation of triphenylphosphine  (PPI13)  The first,  was observed at a substantially higher  potential of 1.66 V vs. SCE by our experimental setup. Therefore, first oxidation potentials of the previously reported ligands are most likely thienyl-based. Excluding 1, oxidations of the ligands are higher in potential than those of the corresponding oligothiophenes, as shown in Table 2-1, and are irreversible. Thienyl reductions are too negative in potential to be observed experimentally. Table 2-1 Cyclic voltammetry data for P-phosphinothiophene ligands and derivatives, oligothiophenes, and triphenylphosphine Compound  Compound ±0.01 V vs. SCE  £l/2,ox  ±0.01 V v s . SCE  P T (9)  +1.10 '  Do T (24)  P hex T (11)  + 1.02 '  T  2  + 1.19  (PO) T (12)  >2  T  3  +0.98  T  4  +0.92  T  5  +0.65  2  2  2  2  2  4  2  b c  2  b c  PT (13)  1.30  PMeT (14)  1.18  PMe T (15)  1.05  PDo T (22)  +0.99 ,+1.37  3  3  2  2  3  5  M  W  5  b  a  e  PPh  M  +0.82,+1.07  3  6  e  6  + 1.66  b,f  b  Measurements carried out in CH C1 solution containing 0.1 M [(«-Bu)4N]PF6 supporting electrolyte. Veversible wave, E . Ref. Ref. Ref. C H C N solution. 2  c  2  9  d  6  e  p  21  f  3  Two irreversible oxidation waves, assigned as thienyl-based, were observed for the (phosphino)pentathiophene ligand 22. The first oxidation potential of 22 is lower than that of 13-15 due to an extended chain length. Compared to the corresponding pentathiophene 24, the thienyl-based oxidations of 22 are anodically shifted and irreversible due to diphenylphosphine substitution (Figure 2-3). Shown in Figure 2-4 is the correlation between the number of the thienyl rings and the oxidation potentials of all the P-phosphinothiophene ligands used and corresponding oligothiophenes. A general trend of decreasing oxidation potential with extension in chain length is observed. P-Phosphination generally increased oxidation potential, although diphosphination of bithiophene to give 9 resulted in a lower oxidation potential than that of T . 2  38  50 r 40 -  PDo T 2  5  (22)  30 -  <  20 -  c  fc 10 V  0 -10 -  0.6  0.8  1.0  1.4  1.2  1.6  Volts rv vs. SCE  Figure 2-3 Cyclic voltammetry of 22 and 24 in CH2CI2 at 4 * 1 0 " M concentrations, containing 1 M [(«-Bu)4N]PF6 supporting electrolyte, scan rate = 100 mV/s. 3  +PT (13)  -  1.2  1.1  3  " OT  3  - +P T (9) 2  w u GO  +PMeT (14)  2  2  +PMe T (15) 2  1.0 -  OT  >  3  +PhexT(ll) 2  2  +PDo T (22)  4  2  3  OT  0.9 h  5  4  ODo T (24) 2  0.8 -  5  0.7  OT 0.6  1  1  1  1  2  3  4  5  5  Number of Thienyl Rings Figure 2-4 Correlation between the oxidation potentials, Ei/2, , and the number of thienyl rings of the (3-phosphinothiophene ligands (+) and the corresponding oligothiophenes (O). A l l values are from the irreversible oxidation waves, E ,except that of 24. ox  p  39  2.3.3 Electronic Spectroscopy Table 2-2 Electronic spectroscopy data for P-phosphinothiophene ligands and derivatives, and oligothiophenes Compound  Absorption /nm [s /IVT'crn" ]  Emission X , /nm  3  X P2T2 (9)  1  m a x  252 (sh) (1.65 x 10 ) 4  b  max  -  c  P hex T (11)  254 (6.20 x 10 ), 3 40 (2.83 x 10 )  (PO) T (12)  254 (1.65 x 10 ), 2 86 (sh) (6.29 x 10 )  -  254 (3.42 x 10 ),.354 (1.77 x 10 )  420(sh), 442 (<> | = 0.0057)  2  2  4  4  2  4  -  c  4  2  PT (13)  3  4  3  4  d  454  PMeT (14)  254 (2.33 x 10 ), 362 (2.15 x 10 ) ' .  PMe T (15)  2 5 2 (3.42 x 10 ), 282 (sh) (2.57 x 10 ), 364 (3.63 x 10 )  457  2 5 0 (1.1 x 10 ), 374 (2.0 x 10 )  433, 450 (<> | = 0.055)  4  3  2  4  d  4  3  4  aPT (16)  4  d  4  3  PDo T (22)  4  e  251 (2.13 x 10 ), 340 (sh) (1.47 x l O ) , 406 (3.36 x l O )  499, 528 (<j) = 0.093)  5  252 (1.27 x 10 ),407 (3.27 x 10 )  487, 516 (4> = 0.16)  T  2  3 02 (4.10 x 10 )  -  T  3  3 5 5 (4.40 x 10 )  T  4  3 90 (4.66 x 10 )  5  416 (4.74 x lfj )  2  4  5  g  4  8  g  4  Do T (24) 2  T  4  4  4  f  4  4  4  g  409, 429 O = 0.056)  f  h  -  f  482, 514(<j) = 0.54)  f  h  "Measurements carried out in CH2CI2 solution. Degassed C H C N solution. Ref. Ref. Ref." Thienyl 71—>n* transition only, ref. Approximate quantum yields obtained by comparison to T . Ref. b  c  9  d  6  3  e  f  21  h  22  3  Absorption spectroscopy has been reported for ligands 9, 11, and 13-15 (Table 2-2). '  6 9  The bithiophene n—>n* transition of 12 shifts little compared to that of 9, despite the presence of electron-withdrawing phosphine oxide groups and an increase in the oxidation potential. The pentathiophene n—>n* transitions observed for 22 and 24 are red shifted compared with the terthiophene  n—»7T.*  transitions of ligands 13-15, as anticipated with extension in chain length.  Compared with T , the n—>n* transitions of both 22 and 24 are blue shifted by 10 nm. Shown in 5  Figure 2-5 is the correlation between the number of the thienyl rings and the absorption maxima. Generally, the n — t r a n s i t i o n energy decreases as the chain length increases.  It is also  observed that bis(phosphine) substitution substantially increases the n—>n* transition energy, while a lesser effect is observed with substitution of one phosphine. Phenyl 40  n—»7t*  transitions  are also expected and a shoulder at 340 nm is observed for 21 that could be the phenyl n—»rc* transition.  450 425 400  -  OT  375  Q 4  2  5  2  + aPT (16)  5  3  s 350  j  T O 5 Do T (24) PDo T (22)  PT (13)  + P hex T (ll)  3  2  2  4  325 -  250 -  OT  2  +P T (9) 2  i  2  i  3  4  5  Number of Thienyl Rings Figure 2-5 Correlation between ^ and the number of thienyl rings of representative phosphinothiophene ligands (+) and the corresponding oligothiophenes (O). > m a x  The  TX<—7i*  fluorescence emission spectrum of PT3 (13) is compared to that of T 3 and to  the emission of the a-(phosphino)terthiophene ligand aPT3 (16) (Figure 2-6). It is observed that attachment of the phosphine group at the a position for 16 red shifts the emission 21 nm, and has no effect on the intensity of the emission compared to T . 3  Ligand 13 displays n<— n*  fluorescence emission that is red shifted by 13 nm from that of T . However, the intensity is 3  greatly reduced to approximately one tenth that of T3. Ligand D02T5  PD02T5  (22) and pentathiophene  (24) display TC<—n* fluorescence emission that is red shifted by 5-17 nm from that of T , 5  and is also greatly reduced in emission intensity (Table 2-2).  41  0.4 o o o o o  0.3  c  3 O  <-> 0.1 0.0 350  400  450  500  550  600  650  700  X/nm  Figure 2-6 The T C < - K * fluorescence emission of (phosphino)terthiophene ligands 13 and 16, and T 3 . Absorbance at the excitation wavelength is set to 0.1.  2.4  Discussion P-Phosphinothiophene ligands with thienyl chain lengths of n = 2-4 (9,11,13-15) could be  prepared in moderate yields by reaction with «-butyl lithium followed by quenching with chlorodiphenylphosphine.  However, this procedure was not feasible for substitution of  pentathiophenes due to the formation of an unreactive intermediate anion, and a new route was attempted. Conversion of P-brominated pentathiophene derivatives 17-18 to the corresponding P-iodo derivatives 19-20 and efficient cross-coupling of the reactive iodo substituents with diphenylphosphine successfully yielded the P-(phosphino)pentathiophene ligands Phex T (21) 2  and  PD02T5  5  (22). The merits of this method are that it is efficient and is also not limited by the  number of anionic charges that the conjugated backbone can carry, so that the procedure could be applied to polythiophenes containing several P-iodo functionalized positions to yield conjugated polymers with multiple P-phosphine substituents. The reported X-ray crystal structure of the ligand oxide (PO) T (12) was used to 9  2  2  estimate the steric effect of adjacent diphenylphosphine groups attached to oligothiophenes (Figure 2-2). It is observed that there is a large interannular torsion angle (124.1(8)°) between the two thienyl rings in the crystal structure of 12, deviating substantially from the near-planar (-180°) torsion angles of solid state oligothiophenes ' -  42  and from the interannular torsion angle  calculated for the most stable conformation of T3 (147.6°).  A similar angle is likely present for  9 and for the central rings of 3 due to an analogous steric repulsion. The higher oxidation potential of P2hex2T (11) compared to T is consistent with expected twisting of the thienyl 4  4  chains. The lower oxidation potential of P T (9) compared to T 2  2  2  suggests less twisting or  donation of electron density from the lone pair of the phosphine group. It has been calculated that an oligothiophene H O M O is stabilized by interaction between the n system and an a phosphine, and the degree of lone pair character diminishes with an increase in oligothiophene length.  11  The irreversibility of the oxidation potentials of phosphinothiophene ligands could be  due to interaction of the oxidized thiophene chains with the phosphine group. The thienyl n—>n* transitions of bis(phosphine) ligands 9 and 11 are both blue-shifted by approximately 50 nm 26  relative to T and T , 2  4  respectively. The blue shifts are not likely to be due to an electronic  withdrawing effect since there is a negligible shift of n—±n* transition observed for P T 3 (13) (^max  =  354 nm),  12  which has one pendent phosphine attached, relative to T3 (355 nm).  26  Therefore, the steric effect of the bulky, adjacent phosphines twisting the thiophene chains out of conjugation is most likely shifting the n—>rt* transition. The transition of 9 is expected to be decreased in energy by electron donation from the phosphine lone pairs, but this contribution appears to be counteracted by chain twisting. This twisting of the thienyl backbone is interesting because the presence of metals could enhance the effect, and alter the conjugation pathway. The (3-(phosphino)terthiophene ligands P T (13), P M e T (14), and P M e T (15) display 3  3  2  3  anodic shifts of the irreversible oxidation potentials compared with T 3 , as does the P-(phosphino)pentathiophene 71—>7i*  ligand PDo2T (22) compared with D02T5 (24). 5  transition energies of 13 and 22 compared to  T3  The thienyl  and 24 are largely unaffected by  phosphine substitution, while the transitions of 14-15 are lower in energy due to methyl substitution. A combination of thienyl ring overlap and donation of electron density from the substituents is likely affecting the oxidation potentials and transition energies. Overall, results suggest that twisting of thiophene chains with addition of one diphenylphosphine group is not substantial. The 21 nm red shift observed for the  71 <— n*  fluorescence emission of C 1 P T 3 (16)  compared to T3 is consistent with a red shift in the absorption transition due to donation of a phosphine lone pair to the n conjugation." The  7t<— n* fluorescence  emission of 13 is 13 nm red  shifted from the emission of T3, though the absorption energy is equivalent. displays a relatively large Stokes shift.  Therefore, 13  This could indicate the transition has some n—>n*  character due to a lone pair lone pair contribution, and change in geometry from a more 43  pyramidal ground state to a planar excited state would result in the Stokes shift. It is also seen that while 01PT3 (16) does not show any difference in intensity compared with the P-substituted ligand  PT3  emission from  T3,  (13) is much weaker in intensity. The emission results of  D02T5  (24) indicate that the introduction of dodecyl chains decreases the intensity of emission compared to T , and p-(phosphino)pentathiophene 5  ligand  PD02T5  (22) displays a further  reduction in emission intensity compared to 24. It is probable that extra substituents placed at p positions reduce the thienyl-based emission intensity by the introduction of more degrees of freedom and the creation of more non-radiative relaxation pathways.  In the case of  constitutional isomers 13 and 16, simply the placement of the phosphine group at the p position rather than the a position reduces the intensity, and it is also possible that torsional oscillations facilitate more efficient non-radiative decay. Exploitation of the difference in reactivity between the bromo- and iodo-substituents towards phosphine cross-coupling and Suzuki reactions was demonstrated.  a,a,P-Halogenated  pentathiophene derivatives 25 and 26 were prepared for the purpose of developing a strategy to prepare long-chained multi-metallated oligothiophenes with  D02T5  as the repeat unit of the  thienyl backbone. The selective phosphine cross-coupling reaction of the central P-iodo position of 25 gave PBr2Do2T (27), which possesses two remaining bromo substituents at the terminal 5  a positions.  These brominated substituents  subsequent metal complexes.  could facilitate coupling reactions between  Alternatively, 26 contains a bromo-substituent at a central P  position and highly reactive iodo substituents at the a positions. The preparation of the Pbrominated heptathiophene 28 by Suzuki reaction in high yield demonstrated selective crosscoupling at the a positions. Syntheses carried out to prepare compounds 27 and 28 suggest possible reaction pathways that could be taken to prepare P-metallated polymers.  2.5  Conclusions The addition of two adjacent P-phosphine substituents alters thienyl structural and  electronic properties via steric and electronic interaction of the phosphine groups, while the addition of one P-phosphine substituent results in little conformational or electronic effect on the thiophene chains.  P-Phosphine substitution is shown to diminish thienyl n<-n* fluorescence  emission intensity compared with a-phosphine substitution.  The phosphine groups of the  P-bis(phosphino)thiophene ligands present sites where oligothiophene properties can be altered 44  via conformational change. The configuration of the p-phosphinothiophene ligands provides an opportunity for direct interaction of a phosphine-coordinated metal with the thiophene chain. Towards  the preparation  of ligands  of this  class,  a new synthetic  route  from  P-(bromo)oligothiophenes to P-phosphinothiophene ligands is demonstrated that is high-yielding and effective for preparation involving longer oligothiophenes.  Additionally, the reactivity  differences of the bromo- and iodo-substituents can be exploited to yield a-functionalized ligands or p-functionalized oligothiophenes. The P-phosphinothiophene ligands and derivatives thus prepared and characterized provide the foundation for a variety of metallated P phosphinothiophenes to be studied.  2.6 References (1)  Reddinger, J. L.; Reynolds, J. R. Chem. Mater. 1998, 10, 3-5.  (2)  Zhu, S. S.; Carroll, P. J.; Swager, T. M . J. Am. Chem. Soc. 1996, 118, 8713-8714.  (3)  Yam, V . W.-W.; L i , C.-K.; Chan, C.-L. Angew. Chem. Int. Ed. 1998, 37, 2857-2859.  (4)  Stott, T. L.; Wolf, M . O.; Patrick, B. O. Inorg. Chem. 2005, 44, 620-627.  (5)  Clot, O.; Wolf, M . O.; Patrick, B. O. J. Am. Chem. Soc. 2000, 122, 10456-10457.  (6)  Clot, O.; Wolf, M . O.; Patrick, B. O. J. Am. Chem. Soc. 2001, 123, 9963-9973.  (7)  Weinberger, D . A . ; Higgins, T. B.; Mirkin, C. A . ; Stern, C. L . ; Liable-Sands, L . ML; Rheingold, A. L. J. Am. Chem. Soc. 2001, 123, 2503-2516.  (8)  Rogers, C. W.; Wolf, M . O. Chem. Commun. 1999, 2297-2298.  (9)  Clot, O.; Akahori, Y . ; Moorlag, C ; Leznoff, D., B.; Wolf, M . , O.; Batchelor, R., J.; Patrick, B., O.; Ishii, M . Inorg. Chem. 2003, 42, 2704-2713.  (10)  Clot, O. n-Conjugated Materials Containing Transition Metals, Ph.D. Thesis; Department of Chemistry, University of British Columbia, Vancouver, Canada, 2001, 185 pp.  (11)  Stott, T. L.; Wolf, M . O . J . Phys. Chem. B 2004, 108, 18815-18819.  (12)  Clot, O.; Wolf, M . O.; Yap, G. P. A.; Patrick, B. O. J. Chem. Soc, Dalton Trans. 2000, 2729-2737.  (13)  Khor, E.; Ng, S. C ; L i , H. C ; Chai, S. Heterocycles 1991, 32, 1805-1812.  (14)  Kellogg, R. M . ; Schaap, A . P.; Harper, E. T.; Wynbert, H. J. Org. Chem. 1968, 33, 29022909.  (15)  Kobayashi, Y . ; Mizojiri, R.; Ikeda, E. J. Org. Chem. 1996, 61, 5391-5399.  (16)  Robbins, J. L . ; Edelstein, N . ; Spencer, B.; Smart, J. C. J. Am. Chem. Soc. 1982, 104, 1882-1893.  (17)  Nakanishi, H.; Sumi, N . ; Aso, Y.; Otsubo, T. J. Org. Chem. 1998, 63, 8632-8633. 45  Klapars, A.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 124, 14844-14845. Herd, O.; Hessler, A . ; Hingst, M . ; Tepper, M . ; Stelzer, O. J. Organomet. Chem. 1996, 522,69-76. Kirschbaum, T.; Azumi, R.; Mena-Osteritz, E.; Bauerle, P. New J. Chem. 1999, 23, 241250. Fichou, D. Handbook of Oligo- and Polythiophenes; Wiley-VCH: Weinheim, 1999. Becker, R. S.; de Melo, J. S.; Macanita, A . L . ; Elisei, F. J. Phys. Chem. 1996, 100, 18683-18695. Antolini, L.; Horowitz, G.; Kouki, F.; Gamier, F. Adv. Mater. 1998, 10, 382-385. Pelletier, M . ; Brisse, F. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1994, C50, 1942-1945. DiCesare, N . ; Belletete, M . ; Marrano, C ; Leclerc, M . ; Durocher, G. J. Phys. Chem. A 1998, 102, 5142-5149. Van Pham, C ; Burkhardt, A.; Shabana, R.; Cunningham, D. D.; Mark, H . B. J.; Zimmer, H. Phosphorus, Sulfur Silicon Relat. Elem. 1989, 46, 153-168.  46  CHAPTER 3 Synthesis and Characterization of Au(l) and Pd(ll) Complexes 3.1  Introduction One approach to alter the properties of conjugated oligo- or polythiophenes is to attach  pendent groups to the conjugated backbone. The attachment of metal groups to ^-conjugated backbones allows tuning of the electronic properties such as the colour, the electrochemical oxidation potential, or the conductivity. Pendent metal groups may electronically couple to an oligo- or polythiophene chain depending on proximity of the metal and the overlap of orbitals. Alternatively, metal coordination can change the conformation of the conjugated chain to modify the properties. P-Bis(phosphino)thiophenes that have two adjacent  P-phosphine substituents  can  coordinate one metal group in a bidentate fashion to form a seven membered ring, or coordinate two metal centers in a monodentate fashion. Complexes formed with these ligands have the potential to lock the conformation of a thiophene chain, or twist the chain due to the steric repulsion of two metal groups. As conjugation along a thienyl backbone is determined by the overlap between the n-orbitals of adjacent thiophene rings,  1  metallation that alters the  conjugation is also expected to modify electronic properties such as oxidation potential, absorption and emission wavelengths, and conductivity.  In order to probe the effect of  metallation on the structural and electronic properties, a collaborative project was carried out where model complexes were prepared with P-bis(phosphino)thiophene ligands P2T2 (9) andP hex T (11). 2  2  4  Chelated Pd(II) complexes 29 and 30 (Chart 3-1) were first prepared by Dr. O. Clot in this group.  2  The square planar Pd(II) center of these complexes is coordinated in a bidentate  fashion by both phosphine groups.  In order to complete the characterization of these  compounds, complex 30 was prepared and a crystal structure was obtained. Cyclic voltammetry and absorption spectroscopy experiments for 30 were carried out in order to establish consistent trends for the model complexes.  47  Chart 3-1  ci  ci  \  /  Pd  /\  Ph P 2  PPh  2  QH13  Pd(P hex T )Cl (30)  Pd(P T )Cl (29) 2  2  H13Q  2  2  2  Gold displays the property of aurophilicity, where closed-shell, d 3  one another to form weak bonds.  4  10  2  metals interact with  One example of a complex displaying aurophilicity is 31  (Chart 3-2). This complex can be used to sense potassium ions via emission resulting from Au-Au interactions.  4  In our group, cc-phosphinothiophenes have been used to prepare  Au(I)-thiophene metallocycles, such as 32.  5  Emissive states form due to gold-gold interactions  in the solid state, and the metallocycles fluoresce.  Chart 3-2  Au(I) complexes 33 and 34 were first prepared by collaborator Y . Akahori at Simon Fraser  University (Chart  3-3).  6  These  complexes 48  contain  two  gold  atoms  per  (3-bis(phosphino)thiophene ligand, and display Au-Au interactions in the solid state. For the purpose of further characterization of these compounds, complexes 33 and 34 were re-prepared, and cyclic voltammetry experiments were carried out. A l l of the results obtained for the Pd(II) and Au(I) complexes are reported, and their properties are compared to one another, to ligands P T (9) and P hex T (11), to the ligand oxide (PO) T (12), and to T and T (Chapter 2) in 2  2  2  2  4  2  2  2  4  order to establish structure/property relationships for these metal-oligothiophene hybrid materials.  Chart 3-3 ^Cl Ph P" ' A  ^ C l H C  U  2  1 3  ,>PPh  2  3.2  2  Ph P^  U  2  A /  (AuCl) P T (33) 2  6  >PPh  C H  2  6  13  (AuCl) P hex T (34)  2  2  2  2  4  Experimental  3.2.1 General Experimental Complex 29 was prepared by Y . Akahori. Complexes 30, 33 and 34 were prepared from 6  P2T2 (9) and P hex2T4 (11) according to previously reported procedures. Electronic absorption 6  2  spectra  were  obtained  in  CH C1 2  2  on  an  HP8452A  diode-array  spectrophotometer.  Electrochemical measurements were conducted on a Pine AFCBP1 bipotentiostat using a platinum disc working electrode, platinum coil wire counter electrode and a silver wire reference electrode. A n internal reference, either decamethylferrocene (-0.12 V vs. SCE) or ferrocene (0.41 V vs. SCE) was added to correct the measured potentials with respect to saturated calomel electrode (SCE).  7  The supporting electrolyte was 0.1 M [(n-Bu)4N]PF6 that was purified by  triple recrystallization from ethanol and dried at 90°C under vacuum for three days. CH C1 used 2  for cyclic voltammetry experiments was dried with C a H and distilled 2  49  2  3.2.2 X-ray Crystallographic Analysis Data for the X-ray crystallographic analysis of 30 was collected on a Rigaku/ADSC CCD diffractometer from crystals obtained by slow diffusion of hexanes over CH2CI2 solution. Crystal structure acquisition of 30 was completed by Dr. R. Batchelor at Simon Fraser University. Both hexyl groups are disordered, and the structure was modeled in two orientations, with the major disordered fragment refined anisotropically and the minor fragments refined isotropically.  Hydrogen atoms were placed in calculated positions.  Appendix 1 contains  crystallographic data for the crystal structure of 30. The cif file is available online.  3.3  6  Results  3.3.1 Synthesis and Crystallographic Studies  Scheme 3-1 CI - £ 1 ' PPh,  Pd  [PdCl ]  / \  2  • EtOH/MeCN H 0/HC1 50°C  Ph P  PPh  // w  2  2  2  Pd(P T )Cl (29) 2  2  2  [PdCl ] 2  »EtOH/MeCN H 0/HC1 50°C 2  C  P hex T (11) 2  2  6  H  H C  13  13  6  Pd(P hex T )Cl (30)  4  2  2  4  2  Ligands P T (9) and P h e x T (11) were chelated to a Pd(II) center to form complexes 2  2  2  2  4  29 and 30 that contain a metallocycle at the central rings of the T and T chains. The reaction 2  4  of [PdCl ] with 9 to yield the Pd(II) complex 29 as a bright yellow solid is shown in Scheme 2  50  3-1.  6  Complex 30 was prepared by the same method and purified by recrystallization from  CFbCb/hexanes solution. The orange, air-stable powder is soluble in polar solvents such as methylene chloride and chloroform.  Figure 3-1 ORTEP view of Pd(P2hex2T4)Cl2 (30). The hydrogen atoms are omitted for clarity and thermal ellipsoids are drawn at 50% probability.  Crystallographic analysis was carried out on a crystal of 30 hexanes/CH2Cl2 solution.  obtained  from  It is seen from the crystal structure data (Figure 3-1) that the  p-bis(phosphino)quaterthiophene ligand is chelated to one Pd(II) center via the two phosphine groups, forming a seven-membered ring with a P-Pd-P bite angle of 93.96(3)° (Table 3-1). The Pd(II) center in the solid state structure lies in a distorted square planar geometry with the cis chlorine atoms slightly raised above the P-Pd-P plane. Coordination of Pd(II) to 11 forces the thienyl sulfur atoms of the central bithiophene group to close to a syn conformation with an interannular torsion angle of 56.6(3)°. This angle is slightly higher than the interannular torsion angle that was observed for 29 at 51.1(2)°. Both angles are approximately the same magnitude 6  from planar as for the solid state structure of (PO)2T (12) at 124.1(8)°. A l l thienyl rings of 30 2  are oriented in an approximately syn fashion, with the sulfur atoms alternating above and below a 51  plane along the quaterthiophene chain. T4 is nearly planar in the solid state, while structural deviations are sometimes observed due to steric interactions between organic substituents. The 8  C8-C9 bond in 30 (1.452(4) A ) is shorter than either of the outer two interannular C-C bonds and  the interannular bonds lengths of T 4 , but is consistent with the interannular bond length in 29 (1.456(3) A ) .  6  Table 3-1 Selected interatomic distances (A) and angles (°) for PdtF^hexiT^Ch; (30) Bond length /A Pd,-P,  2.2490(9)  Pd,-Cl,  2.3426(9)  C4-C5  Pd,-P  2.2510(9)  Pd,-Cl  2.3342(9)  C8-C9  2  2  1.470(5)  C,2-C,  3  1.466(5)  1.452(4)  •  Bond Angle 1° P,-Pd,-P  93.96(3)  P -Pd,-Cli  169.06(4)  P,-Pd,-Cl,  86.04(3)  P -Pd,-Cl  90.40(3)  Pi-Pd,-Cl  170.38(4)  Pd,-P -C  10  113.77(10)  91.30(4)  Pd,-P,-C  7  118.23(10)  2  58.8(3)  S3"Cl -Cl3-  S -C8-C9-S3  56.6(3)  2  2  Cl,-Pd,-Cl  2  2  2  2  2  Torsion Angle 1° Si"C4-C5-S 2  2  •s  69.0(3)  4  The Au(I)-bithiophene complex 33 was synthesized via the reaction of P2T2 (9) with [AuCl(tht)] (tht = 2,3,4,5-tetrahydrothiophene) (Scheme 3-2).  6  Two solid state structures were  obtained by Y . Akahori; in both cases the Au(I) center binds to one phosphine and one chloride 6  in a nearly-linear geometry (Figure 3-2). The structure determined from crystals grown from CH C1 /Et 0 solution suggests a Au-Au interaction 2  2  2  metal atoms.  9,10  due to a distance of 3.3221(4) A between  The structure determined from crystals grown from CFbCVtoluene solution  appears as toluene adduct 33-tol and displays a greater Au-Au distance that does not suggest an interaction. In solution, only an averaged P{ H} N M R signal was observed for 33, and there 31  1  was no significant shift or decoalescence of the singlet in  CD2CI2  or in  CD2CI2/C7D8  from 183-  298 K . The average Au-P (-2.23 A ) and Au-Cl (-2.28 A ) bond lengths are comparable with those observed in substituted gold(I) triphenylphosphine chloride complexes (-2.23 and -2.29 A respectively).  11  The crystal structure of 33 displays the two thiophene rings oriented S-anti to  one other with an interannular torsion angle of 110.8(5)°, while for 33-tol, the torsion angle is 52  slightly larger, at 115.3(7)°. The ligand conformation of 33-tol is very similar to that of 33, despite the lack of a formal Au-Au bond (> 3.6 A).  Scheme 3-2  P hex T (11) 2  2  4  (AuCI) P hex T 2  2  2  4  (34)  Reaction of quaterthiophene ligand P2hex2T4 (11) with two equivalents of [AuCl(tht)] yielded red solids of 34 by an analogous procedure to that of 33 (Scheme 3-2). The solid-state structure of 34 is similar to that of 33, but with a quaterthiophene chain in the place of 6  bithiophene. The Au-Au bond length of 3.0879(7) A in 34 is shorter than that of 33, which may promote the observed decrease in the linearity of the Cl-Au-P angles of 34 (174.28(10)°, 176.87(12)°) compared to those of 33 (178.95(5)°) or 33-tol (179.14(6)°).  The interannular  torsion angles of the central, internal pair of rings of 34 are more twisted at 100.8(9)°, compared with both 33 (110.8(5)°) and (PO) T (12) (124.1(8)°) respectively, a consequence of the shorter 2  2  Au-Au bond. The central rings are approaching a 90° torsion angle; hence, minimal 7i-orbital overlap is expected. The sterically less hindered outer rings are only twisted by 28.5(12)° and 12.5(11)°, and are oriented close to an S-syn fashion with respect to one another.  3.3.2 Cyclic Voltammetry The cyclic voltammograms of 29 and 30 contain irreversible first oxidation waves at 1.67 V and 1.40 V , respectively, that are assigned as thienyl-based processes (Table 3-2). These oxidations occur significantly positive of ligands 9 and 11 (1.10, 1.02 V), and of T and T4 (1.19, 2  1.00 V), respectively. The oxidation potential of 30 is lower than that of 29 due to the longer oligothiophene chain length. Stabilization of the first thienyl oxidation of 30 also supports a second oxidation at 1.51 V (Figure 3-3a). When the working electrode was scanned repeatedly past the first oxidation waves in solutions of the 29 and 30, there was no evidence of film formation on the electrode surface.  Table 3-2 Cyclic voltammetry data of Pd(II)- and Au(I)-bis(phosphino)thiophene complexes Compound  +1.67 (P T b  2  2  Pd(P hex T )Cl (30) 2  2  4  2  4  +/0  2  >+2 ( P T  2  b  2  2  )  +1.40 (P hex T4 ), +1.59 (P hex T  2  (AuCl) P2hex T  +/0 2  b  (AuCl)2P T (33) 2  a  2 0  Pd(P T )Cl2 (29) 2  ±0.01 V vs. SCE  Ei/ , x  2  (34)  +/0 2  b  2  2  2+/+ 4  )  )  +1.49" (P hex2T4 ) +/0  2  Measurements carried out in C H 3 C N solution containing 0.1 M [(«-Bu)4N]PF6 supporting electrolyte, irreversible wave, E . p  54  14 Pd(P hex T )CI (30)  12  2  2  4  2  10  <  (b) -2 0.0  0.5  1.5 1.0 2.0 Volts /V vs SCE  -1  2.5  0.75  1.00 1.25 1.50 Volts FV vs SCE  1.75  2.00  Figure 3-3 Cyclic voltammograms of (a) Pd(II) complex 30 and (b) Au(I) complex 34 in CH2CI2 solution containing 1 M [(rc-Bu) N]PF6 supporting electrolyte, scan rate = 100 mV/s. Plot (a) also shows the Fc/Fc redox couple at 0.41 V vs. SCE. 4  +  7  Cyclic voltammetry of 33 indicates that the bithiophene oxidation potential is >2 V (Table 3-2) and is substantially shifted from the oxidation potentials of ligand 9 and T . 2  Complex 34 also displays an increase in oxidation potential compared to 11 and T . Au(I) 4  complexes 33 and 34 display more anodic oxidation potentials than Pd(II) complexes 29 and 30, which is likely due to an inductive, electron-withdrawing effect of the two complexed Au(I) groups. Repeat scans past the first oxidation wave for 34 showed no evidence of film formation on the electrode surface, though the oxidation wave is irreversible (Figure 3-3b). This result indicates that electropolymerization does not occur.  3.3.3 Electronic Spectroscopy Absorption spectra of 29 and 30 display multiple bands in the region of 258-451 nm. Complex 30 displays broad bands between 275-400 nm (Figure 3-4), which is the region of the Tt—>7i*  transition of P2hex T (11) (340 nm). A Cl—»Pd L M C T band is also expected at around 2  340 nm, " 12  14  4  and shoulders observed for complexes 29 and 30 at 354 nm and 340 nm,  respectively, could be attributed to this transition.  Absorption spectra of 30 in solvents of  different polarity (Figure 3-4) display a small shift for the weak, lowest energy absorption; however, the shift is within experimental error of the instrument (±1 nm), and the transition 55  cannot be confidently assigned as a charge transfer. The new transitions in the visible regions of 29 and 30 result in yellow and orange coloured complexes, respectively.  Table 3-3 Electronic spectroscopy data of Pd(II)- and Au(I)-bis(phosphino)thiophene complexes  Compound  3  A, P d ( P T ) C l (29) 2  2  5  5  P d ( P h e x T ) C h (30)  4  b  267 (2.06 x 10 ), 3 02 (1.68 x 10 ), 340 (sh)(1.42x 10 ), 451 (2.52 x 10 ) 4  4  2  1  max  258 (2.51 x 10 ), 280 (2.51 x 10 ), 354 (sh) (4.19x 10 ), 414 (sh) (9.22 x 10 )  2  3  2  Absorption /nm [e /IVr'cm" ]  4  4  3  ( A u C l ) P T (33) 2  2  239 (sh) (3.52 x 10 ) 4  2  (AuCl) P2hex T4 (34) 2  a  b  252 (2.88 x 10 ), 3 44 (1.66 x 10 ) 4  2  4  Measurements carried out in CH C1 solution. Ref. b  2  250  b  6  2  300  350  400  450  500  550  600  X/nm Figure 3-4 Absorption spectra of P d ( P h e x T ) C l displaying a shift in the low-energy band. 2  2  4  2  (30) in solvents of different polarity,  The bithiophene n—>TT* transition of 33 (Table 3-2) is blue shifted from the transition of P2T2 (9) (252 nm). While blue shifting suggests unfavorable thienyl 71-orbital overlap, it is unlikely that any Au-Au interactions persist in solution. In contrast, the quaterthiophene n—*n* transition of 34 is very close in energy to that observed for P hex2T (11). 2  56  4  3.4  Discussion The crystal structures of Pd(II) complexes 29 and 30 suggest an overall loss of Tt-orbital 6  overlap across the oligothiophene chains with metallation. The formation of the central Pd(II) metallocycles results in shorter interannular bond distances between the two central rings compared to T 4 .  However, interannular torsion angles of 51.1-56.6° for the locked  conformations  unfavorable  are  for  71-orbital  oligothiophene conformations in the solid-state.  overlap  compared  with  the  near-planar  The unfavorable torsion angles likely  counteract any enhanced conjugation due to shorter central bonds and overall conjugation across the central rings is likely to be poor. There are two factors that can contribute to the anodic shifts of 29 and 30 compared to the ligands and oligothiophenes: (a) the inductive effect of the metal and (b) a change in the interannular conjugation that results upon coordination. The interannular torsion angles of the complexes are unfavorable compared to oligothiophenes, but expected to be approximately the same distance from planarity compared to the corresponding ligands. Therefore, the electronwithdrawing effect of the PdCh group  15  is likely to be the more significant effect, resulting in  ~0.5 V anodic shifts of the oxidation potentials relative to both of the corresponding ligands. Compared to 29, increased n-orbital overlap across the quaterthiophene chain is expected for complex 30, in addition to electron donation from the P-hexyl chains, which likely supports the second, thiophene-based oxidation observed at 1.51 V . There are two possible reasons why complexes 29 and 30 do not electropolymerize. First, low conductivity of metal complexes that couple to form solids would deter film growth on the electrode surface, and it is likely that conductivity across even an extended 7T-conjugated backbone would be poor due to unfavorable rr-orbital overlap. Second, the bulky diphenylphosphine groups attached to the backbone may discourage interactions between chains to result in a non-conductive  film.  In contrast,  uncomplexed oligothiophene chains display near 180° coplanarity of the rings and rc-stacking solid lattices.  8  The broad bands that appear to be multiple transitions in the  TC—>-TC*  transition region of  the absorption spectra of 29 and 30 may be a consequence of the "locked" structure of the palladium complexes.  Complexation may limit free rotation of the oligothiophene rings in  solution and produce different conformations that do not easily interconvert. Bands observed are blue shifted overall from the expected n—>n* transition of T2 and T chains, as expected due to 4  less favorable n-orbital overlap in the locked conformation. Shoulders at 354 nm and 340 nm for 57  29 and 30, respectively, are in the expected region of the Cl—>Pd L M C T band reported for cis and trans PdCl2L2 (L=phosphine) complexes at -340 nm " and may correspond to this charge 12  14  transfer. Low-energy charge transfer bands are also observed that are weak and substantially red shifted from the reported region of the Cl—>Pd L M C T , and the origin of this transition is unknown. The extension of thiophene chain length appears to lower the energy of this band by 35 nm from 29 to 30. Due to multiple transitions occurring with Pd(II) metallation, yellow and orange coloured complexes are observed. The crystal structure of Au(I)-P-bis(phosphino)bithiophene complex 33 displays a weak Au-Au interaction at a separation of 3.3221(4) A , while the toluene adduct 33-tol demonstrates that an interruption of the interaction occurs easily via a weakly coordinating solvent. 31  single  6  The  1  P{ H} N M R peak observed in solution also suggests that the Au-Au interaction  observed for 33 can be easily disrupted by intermolecular forces. Fixing the conformation of the thiophene rings is a similar result of metal complexation as for the Pd(II) complexes discussed; however, in the case of the Au(I) complexes, the presence of two metals denies the chain the ability to align in an anti or syn planar arrangement and very unfavorable rc-orbital overlap is the result.  The eight-membered ring formed aligns the thienyl rings of 33 into a highly twisted  configuration with an interannular torsion angle of 110.8(5)°. Similar results are observed for the crystal structure of 34, although the Au-Au separation is shorter (3.0879(7) A ) , resulting in a 6  less planar torsion angle (100.8(9)°).  Crystal packing may be a factor promoting closer  proximity of the metal atoms, or the Au-Au interaction appears to be better stabilized when attached to an extended thiophene chain. Since the central interannular torsion angle is near 90°, the quaterthiophene chain can be considered as a pair of adjacent bithiophene units.  The  lengthened central interannular bond also suggests weak conjugation between the two central rings of 34.  The conformations that arise with Au(I) metallation contrast those of Pd(II)  metallation, where the C-C bond lengths between the central rings are decreased and rc-orbital overlap is less disrupted. In solution, the very anodic oxidation potential of 33 compared to 9 is most likely due to the loss of extended conjugation of the phosphine lone pairs combined with an electronwithdrawing inductive effect due to complexation of two Au(I) ions. Donation of phosphine lone pairs has been observed to more strongly affect the properties of short-chained phosphinothiophenes.  16  More unfavorable steric interaction of the bulkier Au(I) groups is also  possible. There is an anodic shift in the oxidation potential of 34 compared with 11, likely for 58  similar reasons though the shift is not as strong, reflecting that the phosphine lone pairs likely do not substantially affect conjugation of the quaterthiophene chain prior to complexation. Anodic shifts are not likely to be due to Au-Au interactions since these do not commonly occur in solution and are not indicated experimentally. Electropolymerization does not occur with repeat scans of the first oxidation wave of 34; it is likely that interannular twisting could occur in the solid state due to Au-Au interactions, and prevent any coupled materials from being sufficiently conductive to allow film growth.  The bulky substituents may also decrease conductivity  between chains. The bithiophene rc—>rc* transition of 33 is substantially blue-shifted from those of 9 and T . It is expected that twisting of the central rings is similar to that of 9, and the blue shift most 2  likely reflects removal of the phosphine lone-pairs from bithiophene Tt-conjugation. Complex 34 does not display a blue shift of the quaterthiophene  rc—>-7x* transition  compared to  11.  This result  again suggests that twisting is comparable to the ligand, and the phosphine lone pairs did not contribute significantly to the conjugation of 11.  3.5  Conclusions Binding metals to oligothiophenes via P-bis(phosphino)thiophene ligands results in  substantial effects on the electronic properties of the ^-conjugated system.  Changes in the  electronic properties that occur with Pd(II) or Au(I) complexation result from a combination of factors including changes in the interannular torsion angles, inductive electron-withdrawing effects of the metals, and charge transfers involving the complexed metal. The interannular torsion angles in the crystal structures of the complexes examined here are large relative to those typically observed in solid-state structures of oligothiophenes. The Pd(II) complexes display central interannular torsion angles between 51-57° that are similar in planarity to that observed for (PCO2T2 (12). The Au(I) complexes display torsion angles in the solid state that are very unfavorable for rc-orbital overlap, between 100-115°, that are most likely a consequence of AuAu  interactions. The choice of metal is therefore controlling the extent of n-orbital overlap. In solution, structures may be different from the solid state crystal structures, especially  for the Au(I) complexes that contain weak Au-Au bonds, and electronic spectroscopy and electrochemistry measurements are valid only for complexes in solution. Pd(II) complexation blue-shifts the thienyl rc—>-rc* transitions, likely producing multiple conformations, and also results in the appearance of charge-transfer bands. While Au(I) complexation of P T (9) blue 2  59  2  shifts the thiophene TC—>-TC* transition, likely due to the removal of the phosphine lone-pairs from conjugation, Au(I) complexation of P2hex2T4 (11) negligibly shifts the transition. The inductive effect due to the metals of all complexes is evident, as all first oxidation potentials are higher than those of the ligands. Oxidation potentials of the metal complexes are also mediated by chain-length.  Overall in solution, Au(I) complexation exerts less influence on the physical  properties than Pd(II) complexation that results in the formation of fixed metallocyclic structures. These complexes cannot be electrochemically coupled to produce polymers, likely due to lack of conductivity of solid films that are produced electrochemically. If extended chains of these model complexes are prepared by another method, it would be interesting to study the conductivity of the thiophene chains in fixed conformations resulting from metal complexation. The Au(I) complexes may especially be interesting as a potential conductive switch due the weak Au-Au interactions that may be formed and interrupted.  3.6  References  (1)  Bredas, J. L . ; Street, G. B.; Themans, B.; Andre, J. M . J. Chem. Phys. 1985, 83, 13231329.  (2)  Clot, O. K-Conjugated Materials Containing Transition Metals, Ph.D. Thesis; Department of Chemistry, University of British Columbia, Vancouver, Canada, 2001, 185 pp.  (3)  Bardaji, M . ; Laguna, A. J. Chem. Educ. 1999, 76, 201-203.  (4)  Yam, V . W.-W.; L i , C.-K.; Chan, C.-L. Angew. Chem. Int. Ed. 1998, 37, 2857-2859.  (5)  Stott, T. L.; Wolf, M . O.; Patrick, B. O. Inorg. Chem. 2005, 44, 620-627.  (6)  Clot, O.; Akahori, Y . ; Moorlag, C ; Leznoff, D., B . ; Wolf, M . , O.; Batchelor, R., J.; Patrick, B., O.; Ishii, M . Inorg. Chem. 2003, 42, 2704-2713.  (7)  Robbins, J. L . ; Edelstein, N . ; Spencer, B.; Smart, J. C. J. Am. Chem. Soc. 1982, 104, 1882-1893.  (8)  Lukevics, E.; Barbarella, G.; Arsenyan, P.; Belyakov, S.; Pudova, O. Chem. Heterocycl. Compd. 2000, 36, 630-662.  (9)  Pathaneni, S. S.; Desiraju, G. R. Inorg. Chem. 1993, 319-322.  (10)  Leznoff, D. B . ; Xue, B.-Y.; Batchelor, R. J.; Einstein, F. W. B.; Patrick, B. O. Inorg. Chem. 2001, 40, 6026-6034.  (11)  Leznoff, D. B . ; Rancurel, C ; Sutter, J.-P.; Rettig, S. J.; Pink, M . ; Paulsen, C ; Kahn, O. Inorg. Chem. 1999, 3593-3599.  (12)  Leung, K . H.; Szulbinski, W.; Phillips, D. L . Mol. Phys. 2000, 98, 1323-1330. 60  Trzeciak, A . M . ; Bartosz-Bechowski, H . ; Ciunik, Z.; Niesyty, K . ; Ziolkowski, J. J. Can. J. Chem. 2001, 79, 752-759. Verstuyft, A . W.; Redfield, D. A . ; Cary, L . W.; Nelson, J. H . Inorg. Chem. 1976, 75, 1128-1133. Corain, B.; Longato, B.; Favero, G.; Ajo, D.; Pilloni, G.; Russo, U . ; Kreissl, F. R. Inorg. Chim. Acta 1989, 157, 259-266. Stott, T. L.; Wolf, M . O. J. Phys. Chem. B 2004,108, 18815-18819.  61  CHAPTER 4 Synthesis and Characterization of P,S-Bound Ru(ll) Complexes 4.1  Introduction Direct bonding of metals to the backbone of thiophene chains can be employed to alter  the structural, chemical, and electronic properties of the conjugated material. Reported methods of  direct bonding to a thiophene backbone include metallation via thiophene,' 2 5  or via  6  incorporation of bipyridyl " or bithiazoyl groups.  Thiophenes can bond to transition metals by  various bonding modes, including ^'(S), r\ -, n - or r) -coordination, and metal-carbon bonding 2  4  5  7  that is most frequently at an a position (Chart 4-1).  C h a r t 4-1  V(S)  M-Cbond  Ru(II) has been reported to coordinate in an r\ (S) fashion to thiophenes; however, the l  bond is often weak.  Chelation of a metal to a thienyl ligand containing another group can  stabilize an r]'(S) bond. Examples of Ru(II) complexes coordinated by chelating thienyl ligands 8  9  are 35 and 36 that contain bis(thienyl)tetrazine and thienylbipyridine ligands, respectively (Chart 4-2). Bonding of metals to a thiophene via a M-C  bond may occur by the reaction of a  thiophene ring with metal complexes possessing vacant coordination sites, " 10  12  or by conversion  from V ( S ) coordinated complexes, as has been demonstrated for Re(II)- and Ru(II)-thienyl 62  complexes.  13,14  Scheme 4-1 shows an example of conversion from a Re(II) sulfur-bound  complex (37) to the carbon-bound complex (38). bonding mode (39) and an V(S)  14  Reversible switching between a M - C  coordination mode (40) via acid-base mediation has also been  reported for the Ru(II) complex depicted in Scheme 4-2.  Chart 4-2  37  63  15  The bis(bipyridine) Ru(II) group [Ru(bpy)2 ] exhibits electron and energy transfer processes.  16  Ru(bpy)3  and Ru(bpy)2L  2+  n  2+  complexes commonly display a Ru(d7i)->bpy(7i*)  metal-to-ligand charge transfer (MLCT) to generate a charge-separated state, which allows complexes of this type to be used as sensitizing dyes. A dye molecule adsorbed onto a large band gap, n-type semiconductor that is in contact with a reducing agent dissolved in an electrolyte solution comprises a dye-sensitized solar cell (DSSC), also called a Gratzel C e l l . ' 17  18  An example of a Gratzel cell is the system composed of the trimeric ruthenium dye complex RuL2(u-(CN)Ru(CN)L'2)2 (L = 2,2'-bipyridine-4,4'-dicarboxylic acid, L ' = 2,2'-bipyridine) deposited onto high surface-area titanium oxide and in contact with iodide/triiodide redox electrolyte (Figure 4-1).  19  The dye is excited with light to generate the charge-separated state,  and due to well-matched energies of the excited state and the Ti02 semiconductor, the excited electron is transferred to Ti02. Electrons are thus transferred to the negative electrode, and the dye is replenished of electrons by the redox couple to complete the circuit. The maximum conversion efficiency obtained to date for this system is 12%. semiconductor  dye  electrolyte  —  counterelectrode  •  e  Figure 4-1 Schematic representation of a Gratzel cell displaying the energy levels of the cell components and the electronic circuit with cell voltage A V that is created with light absorption of the ruthenium dye complex. Adapted from Ref. 19  The approach that is used here to promote direct coordination of a metal to a conjugated backbone is to covalently anchor the metal group via P-phosphinothiophene ligands. A n open site available on the metal is provided the opportunity of interacting with the thiophene chain. 64  Two open coordination sites are available for the Ru(bpy)2  group, allowing the possibility of  bonding to a P-phosphinothiophene ligand via phosphine-sulfur (P,S) or phosphine-carbon (P,C) bidentate bonding modes (Figure 4-2). Reversible switching between sulfur and carbon bonding modes as demonstrated in Scheme 4-2 could be used to alter polythiophene chain properties. By directly bonding the Ru(II) center to a polythiophene chain, favorable metal-thienyl orbital overlap could result in a charge-separated state due to the M L C T transition, and positive charges could be induced onto the conjugated backbone. The result can be thought of as a model for a molecular wire that conducts upon light absorption, or a light harvesting device. The proposed mechanism is similar to the Gratzel cell shown in that a dye molecule is attached to a substrate where conduction is induced. In the case of polythiophenes, conduction normally occurs with p-doping; therefore, electrons must be removed from the conjugated backbone.  A simple  schematic (Scheme 4-3) suggests the electron transfer process that could create positive charges, or holes, along an oligothiophene (T ) chain via a Ru(bpy) n  P,S bonding mode  2  sensitizing group.  P, C bonding mode  Figure 4-2 Two possible bidentate bonding modes of a P-phosphinothiophene chain attached to a Ru(bpy) group, P,S and P, C. 2+  2  Scheme 4-3  bpy TC*  Ru  dn  bpy  —j  T,n  TC  TC*  -—I  TC  65  Chart 4-3  RuPT -P,5'(41)  RuPMe T -P,5'(43)  RuPMeT -P,5(42)  3  2  3  3  Chart 4-4  ^  f  1(PF ) 6  l  C H 1 2  ;  Cl2H25  RuPhex T -.PS(44) ,  2  5  )  Ru(bpy)  2  RuPDo T -P,5'(45) 2  RuPBr Do T -,P S(46)  5  2  2  5  )  groups were coordinated via the phosphine and thienyl sulfur to  p-(phosphino)terthiophene ligands PT (13), PMeT (14), and PMe T (15) to yield Ru(II)-P S 3  3  2  3  (l  complexes 41-43 (Chart 4-3). p-(Phosphino)pentathiophene ligands Phex T (21), PDo T (22), 2  5  2  5  and PBr Do T (27) were used to prepare Ru(II)-.P,S complexes 44-46 (Chart 4-4). The effects 2  2  5  of the P,S bonding mode on the structural conformation of the thiophene chains, the thienyl redox potentials, and the thienyl rc—>rc* transitions were investigated. Density functional theory calculations were carried out for 41 to estimate the energies and localization of the HOMO and L U M O orbitals. Methyl substituents attached to the P-(phosphino)terthiophene ligands allow observation of the effect of electron-donating substituents on the conformational and electronic properties of the complexes. The electrochemical and spectroscopic properties of the Ru(bpy)  2+ 2  group bound to the p-phosphinothiophene ligands in the P,S bonding mode were also studied. Complexes 41-46 react with base, resulting in Ru(II) complexes where a thienyl carbon is bonded to the metal (P,C bonding). The characterization of these Ru(II)-P,C complexes is 66  discussed in Chapter 6. The Ru(II)-P,C complexes revert back to the P,S bonding mode by reaction with acid, and demonstrate an example of metal-thienyl bonding modes that are reversibly switchable.  4.2 4.2.1  Experimental General Experimental All reactions were performed using standard Schlenk techniques with dry solvents under  nitrogen. The synthesis and purification of ligands PT3 (13), PMeT3 (14), and PMe2T (15) 3  90  have been reported. Dr.  O. Clot.  All  21  The preparation of complex RuPTs-.P.S (41) was previously reported by other reagents were purchased from Aldrich or Strem Chemicals and were  1  *j 1  used as received. H and  P NMR  experiments were performed on either a Bruker AV-300 or a  Bruker AV-400 Spectrometer, and spectra were referenced to residual solvent ('H) or external 85%  H3PO4  ( P). Absorption spectra were obtained with a Cary 5000 in HPLC grade CH C1 . 31  2  Emission spectra were obtained with a Cary Eclipse in H P L C grade CH C1 or 2  2  CH3CN,  2  and  emission slits were set to 20 nm. Cyclic voltammetry experiments were carried out with a Pine AFCBP1 bipotentiostat using a platinum disk working electrode, platinum coil wire counter electrode, and a silver wire reference electrode.. Either decamethylferrocene (-0.12 vs. SCE) ferrocene (0.41 vs. SCE)  or  was used as an internal reference to calibrate the measured potentials  with respect to saturated calomel electrode (SCE).  The supporting electrolyte was 0.1 M  [(«-Bu)4N]PF6 that was purified by recrystallizing three times from ethanol and drying for three days at 90°C under vacuum. The lifetime measurement was carried out by Prof. C. Bohne at the University of Victoria by exciting the sample at 480 nm in 7 x 7 mm Suprasil cells at 20 ± 2°C with a Coherent Infinity OPO system. and  22  tunable laser, using the previously described laser flash photolysis  Deoxygenated samples were dissolved in C H C N to achieve absorbences between 0.3 3  0.5 (1 = 7 mm) at 480 nm. Emission decays were measured at fixed wavelengths, averaging  at least 5 kinetic traces, and emission spectra were obtained by collecting data at fixed wavelengths and averaging the values between set time windows after the laser pulse. The voltage of the photomultiplier used to detect the emission signal was kept constant throughout the collection of a spectrum.  67  4.2.2 Synthesis [Bis(2,2'-bipyridyl)(3 ~diphenylphosphino-5-methyl-2,2 ':5 '2 "-terthiophene-P,S)ruthenium(II)] [bis(hexafluorophosphate)] (RuPMeT -P,S) (42) 3  AgBF4  (230 mg, 1.15 mmol) was added to a deaerated solution of Ru(bpy) Cl2-2H 0 2  2  (300 mg, 0.576 mmol) in acetone (30 mL), stirred for 6 h, and filtered under nitrogen. To the red filtrate, PMeT3 (14) (272 mg, 0.610 mmol) was added and the mixture was heated to reflux for 18 h.  The resulting solution was concentrated to 10 mL and precipitated by addition to a  solution of N H P F (1.89 g, 11.6 mmol) in H 0 (100 mL). Recrystallization in ethanol-acetone 4  6  2  (9:1) gave 42 as bright yellow crystals. Yield: 0.340 g (51%). *H N M R (300.1 MHz, CO(CD ) : 3  2  5 9.13 (d, J= 5.7 Hz, 1H), 8.89 (d, J= 5.2 Hz, 1H), 8.78 (d, J= 8.2 Hz, 1H), 8.69 (d, J= 7.5 Hz, 1H), 8.68 (d, J = 8.1 Hz, 1H), 8.60 (d, J = 8.2 Hz, 1H), 8.28-8.22 (m, 3H), 8.09 (t, J = 8.0 Hz, 1H), 7.96 (d, J= 5.7 Hz, 1H), 7.83-7.81 (m, 1H), 7.69 (t, J = 6.9 Hz, 1H), 7.63-7.55 (m, 3H), 7.50 (d, J= 5.0 Hz, 2H), 7.45-7.32 (m, 6H), 7.22-7.16 (m, 3H), 708 (dd, J= 4.8 Hz, J= 3.9 Hz, 1H), 6.95-6.88 (m, 3H), 6.78-6.77 (m, 1H), 1.48 (s, 3H). CO(CD ) ): 3  2  5 28.5 (s), -143.0 (sep, J  P F  31  P { ' H } N M R (121.5 M H z ,  = 708 Hz, PF ). Anal. C 5H 5F N4S P Ru requires 6  4  3  12  3  3  C, 47.00; H , 3.07. found: C, 46.60; H , 3.05%. [Bis(2,2 -bipyridyl)(5,5 "-dimethyl-3 -diphenylphosphino-2,2 ':5 ',2 "-terthiophene-P,S) ruthenium(II)][bis(hexafluorophosphate)] (RuPM^T^-.P.S') (43) AgBF4  (406 mg, 2.38 mmol) was added to a deaerated solution of Ru(bpy) Cl2-2H20 2  (530 mg, 1.02 mmol) in acetone (50 mL), stirred for 18 h, and filtered under nitrogen. To the red filtrate, PMe2T (15) (497 mg, 1.08 mmol) was added and the mixture was heated to reflux for 3  24 h. The resulting solution was condensed to 10 mL and precipitated by addition to a solution of N H P F (1.89 g, 11.6 mmol) in H 0 (100 mL). Recrystallization in ethanol-acetone (9:1) 4  6  2  gave 43 as bright, yellow crystals. Yield: 0.624 g (52%).  !  H N M R (300.1 MHz, CO(CD ) ): 3  2  5 9.14 (d, J = 5.7 Hz, 1H), 8.84 (d, J = 5.0 Hz, 1H), 8.79 (d, J = 8.7 Hz, 1H), 8.69 (q, 2H), 8.61 (d, J = 8.4 Hz, 1H), 8.30-8.23 (m, 3H), 8.10 (t, J = 8.0 Hz, 1H), 7.98 (d, J = 5.4 Hz, 1H), 7.84-7.82 (m, 1H), 7.70 (t, J = 6.8 Hz, 1H), 7.63-7.49 (m, 4H), 7.46-7.35 (m, 5H), 7.23-7.17 (m, 3H), 7.12 (d, J = 3.3 Hz, 1H), 6.94-6.88 (m, 2H), 6.79-6.77 (m, 2H), 6.78 (s, 1H), 2.44 (s, 3H), 1.48 (s, 3H); P N M R (121.5 MHz, CO(CD ) ): 5 29.0 (s), -143.0 (sep, J 3 1  3  2  P¥  = 708 Hz,  PF ). Anal. C46H 7F N4S P Ru requires C, 47.47; H , 3.20; N , 4.81. found: C, 47.54; H , 3.38; 6  3  12  3  3  N , 4.47%.  68  [Bis (2,2 -bipyridyl)(3,3 ""-dihexyl-3 "-diphenylphosphino-2,2': 5'2": 5 "2 "': 5 '"2 ""pentathiophene-P,S)ruthenium(II)][bis(hexafluorophosphate)] (RuPhex T5-7 ,,S) (44) :,  2  AgBF4  (73 mg, 0.375 mmol) was added to a deaerated solution of R u ^ p y ^ C h ^ ^ O  (97 g, 0.186 mmol) in acetone (25 mL), stirred for 3 h and filtered under nitrogen. The resulting red filtrate was added to a suspension of Phex T (21) (143 mg, 0.187 mmol) in deaerated 2  5  acetone (25 mL) and the mixture was heated at reflux for 20 h. The resulting dark red solution was condensed to 10 mL, added dropwise by pipette into a solution of N H 4 P F 6 (15 g, 92 mmol) in H 0 (300 mL) and the resulting orange precipitate was recovered. 2  The precipitate was  dissolved in acetone, remaining solids were filtered off, and the solvent was removed. Recrystallization in ethanol-acetone (9:1) gave 44 as bright orange crystals. Yield:  150 mg  (55%). ' H N M R (400.1 M H z , CO(CD ) ): 8 9.25 (d, J= 5.6 Hz, 1H), 9.10 (d, J = 5.2 Hz, 1H), 3  2  8.71 (d,J = 8.0 Hz, 1H), 8.63 ( d , J = 8.0 Hz, 1H), 8.59 (d, J= 8.4 Hz, 1H), 8.56 (d, J= 8.8 Hz, 1H), 8.31 (dt, J= 1.2 Hz, J= 7.8 Hz, 1H), 8.25 (dt, J= 1.2 Hz, J= 7.8 Hz, 1H), 8.05 (dt, J = 1.2 Hz, .7=7.8 Hz, 1H), 7.98 (dt, J= 1.2 Hz, J= 8.0 Hz, 1H), 7.81 (d, J= 5.6 Hz, 1H), 7.75 (dt, J= 1.2 Hz, J = 6.8 Hz, 1H), 7.63 (d, J = 7.6 Hz, 1H), 7.61 (d, J = 8.8 Hz, 1H), 7.54 (t, J = 6.6 Hz, 1H), 7.49 (dd, J = 1.6 Hz, J = 7.2 Hz, 1H), 7.47 (d, J= 3.6 Hz, 1H), 7.42-7.38 (m, 5H, phenyl), 7.30 (dt, J = 1.2 Hz, J= 6.6 Hz, 1H), 7.27-7.22 (m, 3H), 7.18 (d, J= 5.2 Hz, 1H), 7.14 (d, J= 3.6 Hz, 1H), 7.07 (d, J= 3.2 Hz, 1H), 7.04 (d, J= 5.2 Hz, 1H), 7.02-6.95 (m, 4H), 6.74 (d, J = PH  5.2 Hz, 1H), 2.75 (t, J= 7.8 Hz, 2H), 2.22-2.06 (m, 2H), 1.61 (q, J = 7.2 Hz, 2H), 1.45  (m, 2H), 1.35-1.25 (m, 12 H), 0.86 (t, J= 6.8 Hz, 3H), 0.81 (t, J = 6.8 Hz, 3H). P{'H} N M R 31  (162.0 MHz, CO(CD ) ): 8 27.2 (s), -143.0 (sep, J 3  2  P F  = 708 Hz, PF ). 6  [Bis(2,2 -bipyridyl)(3,3 ""-didodecyl-3"-diphenylphosphino-2,2':5',2":5"2"':5"',2""pentathiophene-P,S)ruthenium(II)][bis(hexafluorophosphate)] (RuPDo2T5-/ ,5) (45) >  A g B F (1.79 g, 9.18 mmol) was added to a deaerated solution of Ru(bpy) Cl -2H 0 (2.39 4  2  2  2  g, 4.59 mmol) in acetone (150 mL), stirred for 3 h and filtered under nitrogen. The resulting red filtrate was added to a suspension of  P D 0 2 T 5 (22)  (4.29 g, 4.60 mmol) in deaerated acetone  (25 mL) and the mixture was heated at reflux for 20 h. The solution was condensed to 10 mL, added dropwise by pipette into a solution of N H 4 P F 6 (15 g, 92 mmol) in H 2 O (300 mL) and the resulting orange precipitate was recovered. The precipitate was dissolved in acetone, remaining solids were filtered off, and the solvent was removed. Recrystallization in ethanol-acetone (9:1) gave 45 as bright orange crystals. Yield: 3.44 g (46%). *H N M R (400.1 MHz, CO(CD ) ): 3  2  8 9.25 ( d , J = 6 . 0 H z , 1H), 9.09 (d, 7 = 5.6 Hz, 1H), 8.71 ( d , J = 7 . 6 H z , 1H), 8.63 ( d , J = 7 . 6 H z , 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.55 (d, J = 8.4 Hz, 1H), 8.31 (t, J = 8.0 Hz, 1H), 8.25 (t, J = 8.0 69  Hz, 1H), 8.05 (t,J= 7.8 Hz, 1H), 7.80 (t, J= 8.0 Hz, 1H), 7.81 (d, J= 5.6 Hz, 1H), 7.75 (t, J = 6.6 Hz, 1H), 7.64-7.60 (m, 2H), 7.55-7.48 (m, 2H), 7.46 (d, J = 4.0 Hz, 1H), 7.42-7.38 (m, 5H, phenyl), 7.30 (t, J= 6.8 Hz, 1H), 7.25-7.22 (m, 3H), 7.18 (d, J= 5.2 Hz, 1H), 7.14 (d, J= 4.0 Hz, 1H)„ 7.08 (d, J= 2.8 Hz, 1H), 7.04 (d, J= 4.8 Hz, 1H), 6.98-6.95 (m, 4H), 6.74 (d, J  PH  = 4.4 Hz,  1H), 2.75 (t, J = 7.8 Hz, 2H), 2.22-2.06 (m, 2H), 1.61 (q, J = 7.4 Hz, 2H), 1.45 (m, 2H), 1.28-1.25 (m, 36 H), 0.89-0.83 (m, 6H). -143.0 (sep, J  P F  31  P{'H} N M R (162.0 M H z , CO(CD ) ): 27.7 (s), 3  2  = 708 Hz, PF ). Anal. C 6H 5F N4S P Ru requires C, 55.77; H , 5.23; N , 3.42. 6  7  g  12  5  3  found: C, 55.38; H , 5.40; N , 3.31%. [Bis(2,2'-bipyridyl)(5,5""-dibromo-3,3""-didodecyl-3 "-diphenylphosphino2,2 ':5',2":5 "2 '":5 '"2 ""-pentathiophene-P,S)ruthenium(II)] [bis(hexafluorophosphate)] (RuPBr Do T -P,S) (46) 2  2  5  A g B F (99.9 mg, 0.513 mmol) was added to a deaerated solution of Ru(bpy)2Ci2-2H 0 4  2  (134 mg, 0.256 mmol) in acetone (150 mL), stirred for 3 h and filtered under nitrogen. The resulting red filtrate was added to a suspension of P B r D o T 2  5  (27) (280 mg, 0.257 mmol) in  deaerated acetone (25 mL) and the mixture was heated at reflux for 20 h. The solution was condensed to 10 mL, added dropwise by pipette into a.solution of NH4PF6 (15 g, 92 mmol) in H 0 (300 mL) and the resulting orange precipitate was recovered. The precipitate was dissolved 2  in acetone, remaining solids were filtered off, and the solvent was removed. Recrystallization in ethanol-acetone (9:1) gave 46 as pale orange crystals. (400.1 M H z , CO(CD ) ): 3  2  Yield:  110 mg (24%).  'H NMR  5 9.18 (d, J = 5.6 Hz, 1H), 9.12 (d, J = 5."6 Hz, 1H), 8.75 (d, J =  7.6 Hz, 1H), 8.64 (d, J = 8.0 Hz, 2H), 8.58 (d, J = 7.6 Hz, 1H), 8.33 (t, J = 7.6 Hz, 1H), 8.27 (t, J= 8.0 Hz, 1H), 8.09 (t, J = 7.6 Hz, 2H), 7.85 (d, J = 6.0 Hz, 1H), 7.74 (t, J = 6.6 Hz, 1H), 7.64-7.58 (m, 3H), 7.54 (d,J= 3.6 Hz, 1H), 7.51 (dd, J= 2.0 Hz, J = 7.6 Hz 1H), 7.43-7.38 (m, 5H, phenyl), 7.34 (t, J = 6.8 Hz, 1H), 7.22 (dt, J = 2.8 Hz, J= 7.6 Hz, 2H), 7.17 (d, J = 4.0 Hz, 2H), 7.14-7.12 (m, 1H), 7.13 (s, 1H), 7.04 (d, J = 4.0 Hz, 1H), 6.99 (d, 7=7.2 Hz, 1H), 6.96 (d, J= 7.2 Hz, 1H), 6.80 (s 1H), 2.72 (t, J = 7.8 Hz, 2H), 2.23-2.16 (m, 2H), 1.61 (q, J = 7.6 Hz, 2H), 1.48-1.38 (m, 2H), 1.28-1.26 (m, 36 H), 0.89-0.84 (m, 6H). CO(CD ) ): 27.1 (s), -143.0 (sep, J 3  2  P F  31  P { H } N M R (162.0 MHz, 1  = 708 Hz, PF ). Anal. C v e F f o F ^ N ^ P s B ^ R u requires 6  C, 50.86; H, 4.66; N , 3.12. found: C, 51.18; H, 4.64; N , 3.02%.  70  4.2.3 X-ray Crystallographic Analysis Suitable crystals of 41, 43, and 45 were obtained by slow diffusion of hexanes into acetone solution, and were mounted on a glass fiber. The data were collected at -100.0 ± 0.1 °C and the X-ray source in all cases was graphite monochromated M o - K a radiation. The structures were solved by direct methods and expanded using Fourier techniques. 23  24  A l l calculations were  performed using the teXsan  25  crystallographic software package of Molecular Structure  Corporation and S H E L X L - 9 7 .  26  Hydrogen atoms were placed in calculated positions. The  crystal structures were obtained and analysis carried out by Dr. B . Patrick at U B C . Data for 41 were collected to a maximum 29 of 55.7° on a Rigaku/ADSC C C D area detector in a series of two scans using 0.50° oscillations with 27.0 second exposures. Data were collected and processed using the d*TREK program.  27  The data were corrected for Lorentz and  polarization effects. The molecule crystallizes with one molecule of acetone in the asymmetric unit. One thiophene ring is disordered and was modeled in two orientations. The atoms of the minor fragment, as well as the disordered carbons of the major fragment were refined with isotropic thermal parameters. Hydrogen atoms were included in calculated positions. Data for 43 were collected to a maximum 29 of 55.8° on a Bruker X 8 diffractometer in a series of two scans using 0.50° oscillations with 12.0 second exposures. Data were collected using the Bruker S A I N T  28  software package and corrected for absorption effects using the multi-  scan technique ( S A D A B S ) . The data were corrected for Lorentz and polarization effects. The 29  molecule crystallizes with two molecules of acetone in the asymmetric unit. One PF6~ anion is disordered and was modeled in two orientations with relative populations of 0.88 and 0.12. The atoms of the minor fragment were refined isotropically, all other non-hydrogen atoms were refined anisotropically, and all hydrogen atoms were included in calculated positions. Data for 45 were collected to a maximum 29 of 53.5° on a Rigaku/ADSC C C D area detector in a series of two scans using 0.50° oscillations with 53.0 second exposures. Data were collected and processed using the d*TREK program. polarization effects.  27  The data were corrected for Lorentz and  The crystal used for analysis contained one [PFg] and one [BF4]~ -  counterion each. Both alkyl chains were disordered and were modeled in two orientations. In one case the disorder originates with the orientation of the thiophene rings, with 0.58 and 0.42 populations of the major and minor fragments. The second disordered alkyl chain was modeled with isotropic thermal parameters, to relative populations of 0.77 and 0.23 for the major and minor fragments. Hydrogen atoms were included in calculated positions. Appendix 1 contains  71  the crystallographic data for the crystal structures of 41, 43, and 45. C i f files are available online. '  30 31  4.2.4 Density Functional Theory Calculations Density functional theory calculations were carried out using the Gaussian 03 Package, and the B 3 L Y P ' 3 3  3 4  32  method was used to optimize the geometry. The 6-31 G* basis set was used  to model non-metallic atoms. A L A N L 2 D Z pseudopotential is used for inner shell calculations of the metal center, with the corresponding L A N L 4 basis set for the pseudopotential. To analyze the chemical bonding, natural bonding orbital (NBO) analysis was used. A l l calculations were carried out by Y . Zhang from the research group of Prof. A . Wang at U B C .  Gaussian View  software was used to generate depictions of the orbitals.  4.3  Results  4.3.1 Synthesis and Crystallographic Studies Ru(II)-(phosphino)terthiophene-.P,,S' complexes 41-43 were prepared by reaction of Ru(bpy)2Cl2 2H20 with AgBF4 and complexation with the appropriate ligand. The products -  were metathesized to the [PFe]~ salts and recrystallized in ethanol-acetone to give the air-stable complexes in good yield (Scheme 4-4).  Scheme 4-4  3) 20 eq NH PF 4  6  RuPT -/',5'(41) R = R' = H (79%) RuPMeT -/ ,5(42) R = Me, R' = H (51%) RuPMe T -/ ,5(43) R = R' = Me (52%) 3  J  3  5  2  72  3  (a)  (b)  Figure 4-3 (a) ORTEP view of RuPTa-P.S (41) (conformation A) and (b) ORTEP view of RuPMe T3-P,£' (43). Hydrogen atoms, counterions, and occluded solvents are omitted for clarity, and thermal ellipsoids are drawn at 50% probability. 2  Table 4-1 Selected interatomic distances (A) and angles (°) for 41 and 43 RuPT - P,5(41) 3  RuPMe T -^5(43)  J  2  Bond length /A  3  Bond length /A  Rui-Si  2.3640(8)  C33-C34  1.340(5)  Rui-Si  2.3621(6)  C 3-C  34  1.347(3)  Rui-Pi  2.3215(7)  C34-C35  1.426(5)  Rui-Pi  2.3397(6)  C34-C35  1.433(3)  S,-C 3  1.744(3)  C 5"C36  1.359(5)  S,-C  33  1.764(2)  C -C  1.3 5 6(3)  S,-C  1.751(3)  C 6"C37  1.452(4)  S,-C  36  1.750(2)  C36-C37  3  36  3  3  3  3 5  3 6  1.449(3)  Torsion Angle 1°  Torsion Angle 1° S1-C36-C37-S2  -147.02(19)  S1-C36-C37-S2  -150.71(12)  S2-C40-C41-S3  146.0(2)  S2-C40-C41-S3  165.48(12)  S2"C40-C4i-S3b  -41.3(5)  The solid-state structures of 41 and 43 were established by the X-ray crystallography of crystals grown from slow diffusion of hexanes into a solution of the complex in acetone. The structures of 41 and 43 are shown in Figure 4-3, and selected bond lengths and torsion angles are collected in Table 4-1. The (3-(phosphino)terthiophene ligands bind to Ru(II) in a P,S bonding mode, with the metal coordinated to the Si thiophene ring in an rj^S) fashion, resulting in the 73  formation in each case of a six-membered ring. We have observed this bonding mode previously in other ruthenium and palladium complexes. '  20 35  The Rui-Si bond lengths of 41 and 43 are  2.3640(8) A and 2.3621(6) A , which are shorter than the bond lengths observed for other hemilabile (2.390-2.397 A ) ' 1  3 6  and inert (2.380 A ) S-bound Ru(II)-thienyl complexes. The 9  plane of the bound thiophene is tilted from the Ru-S bond at angles of 58.3° (41) and 53.6° (43), which minimizes an unfavorable interaction between a sulfur lone pair occupying a n-orbital and the filled metal d  yz  orbital.  The sulfur atom is subsequently hybridized to an sp -type  hybridization, removing the lone pair with conjugation from the ring. This is indicated by and S i - C  36  S1-C33  bond lengths for 41 and 43 (> 1.744(3) A ) that approach C-S single bond lengths  38  and are elongated compared with calculated C-S bond lengths for T3 (1.7206 A and 1.7351 A respectively).  39  The  S1-C36-C37-S2  and  S2-C40-C41-S3  interannular torsion angles of 41 for  conformation A (147.02(19)°, 146.0(2)°) are close to those calculated for T 3 in solution (147.6°),  39  while the  S2-C4o-C4i-S3b  angle of conformation B (-41.3(5)°) is flipped into a syn  arrangement, but is twisted approximately the same amount from planarity. The corresponding angles of 43 (150.71(12)°, 165.48(12)°) indicate increased coplanarity and therefore greater rc-orbital overlap of adjacent thienyl rings compared to 41. In solid-state molecular structures containing aromatic rings, inter-ring separations of 3.3-3.8 A are indicative of molecular interactions due to 7i-stacking. '  40 41  There is evidence for  weak 7i-stacking interactions between the tilted Si thienyl and adjacent N i or N2 pyridyl rings of 41 (plane-to-plane distance between centroids = 3.708 A ) and 43 (3.675 A ) , and the N4 pyridyl and C21 phenyl rings of both 41 (3.777 A ) and 43 (3.580 A). These intramolecular 71-stacking interactions could promote the preferential crystallization of the diastereomers observed in the crystal structures of 41 and 43, in which the Si thienyl ring is tilted towards the N i or N2 pyridyl ring rather than towards the edge of the N 4 pyridyl ring, and likely enhances the stability of the complexes. Single peaks are observed in the P N M R spectra, also suggesting no evidence for 31  different complex diastereomers in solution.  Intermolecular 7x-stacking between rings is  observed for 43 but not for 41. The crystal structure of 43 (Figure 4-4) shows intermolecular Si and S3' thienyl rings that exhibit a plane-to-plane distance between centroids of 3.947 A , where closest distances between planes are within range of 71-stacking interactions (>3.583 A). Sulfur atoms of stacked rings are aligned anti to one another.  74  Figure 4-4 A portion of the unit cell of RuPMe T -P, S' (43) viewed normal to the 010 plane. Lines are drawn between thienyl groups that are stacked relative to one other. Hydrogen atoms, counterions, and occluded solvent have been removed for clarity, and thermal ellipsoids are drawn at 50% probability. 2  3  4  Ru(II)-(phosphino)pentathiophene-P,5' complexes 44-46 were prepared by a similar procedure as for 41-43 via reactions with the appropriate ligands (Scheme 4-5).  Repeated  crystallizations of 45 in ethanol containing minimal acetone provided brightly coloured, orange, needle-shaped crystals suitable for X-ray analysis. The crystal used to obtain the X-ray crystal structure of 45 (Figure 4-5) contained one [PF ]~ counterion and one [BF ]~ counterion per Ru(II) 6  4  complex. Compared to 41 and 43, the Ru-S bond of 45 is shorter (2.3578(14) A, Table 4-2), while the tilt angle between the plane of the thiophene ring and the Ru-S bond (58.4°) is similar. The S - C (1.762(6) A) bond is elongated by 0.028 A compared to the corresponding bonds of 2  5  the inner thiophene ring calculated for T (1.7342 A). 3  39  The interannular torsion angle between  the two bound thiophene rings (147.9(4)°) is very close to the corresponding torsion angle for 41 and expected torsion angles for T . ' 42  5  43  The disorder of the S and S rings of 45 is similar to the 4  disorder observed in the crystal structure of T ,  4 4  5  5  but may also be due to the long dodecyl chains.  Intramolecular TC-stacking for 45 is observed between the N pyridyl and C 4  4 5  phenyl rings  (3.520 A) and between the S thienyl and N i pyridyl rings (3.671 A), and similarly to 41 and 43, 2  there is a preference for the diastereomeric arrangement of the S thienyl ring as depicted. 2  Intermolecular re-stacking is not seen in the crystal structure, and is likely inhibited by the alignment of the dodecyl chains between the molecules that is observed.  75  Scheme 4-5 Ru(bpy) Cl -2H 0 + 2 AgBF 2  RuPhex T -P, S'(44) 2  5  1  2  2  RuPDo T -P,5 (45) 2  s  4  RuPBr Do T -/>,S (46) 2  2  5  Figure 4-5 X-ray crystal structure of RuPDo Ts-/ ,5' (45) (conformation B). Only the first carbon atoms of the dodecyl chains are shown, and the remaining carbon atoms of the chains, all hydrogen atoms and counterions are omitted for clarity. Thermal ellipsoids are shown at 50% probability. J,  2  76  Table 4-2 Selected interatomic distances (A) and angles (°) for RuPDo2T -/ ,S (45) ,  5  Bond length /A 2  2.3578(14)  S -C  8  1.745(6)  C -C  7  1.433(8)  Cg-C9  1.469(8)  Rui-Pj  2.3404(17)  C -C  6  1.358(8)  C -C  8  1.353(8)  S2-C5  1.762(6)  Ru,-S  2  5  6  7  Torsion Angle 1° S1-C4-C5-S2  32.0(6)  S3-Cl2"Cl3-S4b  177.1(4)  S2-C8-C9-S3  -147.9(4)  S4a-Cl6a-Cl7a-S5a  -24(3)  S3-C]2-Ci3-S4a  127.9(5)  S4b-Ci6b-Ci7b"S5b  50.2(19)  4.3.2 Density Functional Theory (DFT) Calculations DFT calculations were carried out for the simplest Ru(II)-(phosphino)terthiophene-.P >S' )  complex, RuPTs-P.iS' (41), in order to predict the frontier orbital energies of the complex in the gas phase. The DFT calculations predict that the H O M O is localized on the metal and the terthiophene rings, with a large contribution from the thiophene rings to create a mixed state (Figure 4-6). The H O M O is separated by ~1 eV from the HOMO-1, and the HOMO-1 shows only a contribution from a non-coordinated thiophene ring.  The HOMO-2 and the near-  degenerate HOMO-3 and HOMO-4 display a greater degree of metal character.  The near  degenerate L U M O and LUMO+1 are both centered primarily on the bipyridyl rings with a small contribution from the metal center. Bipyridine groups are expected to have a low-lying L U M O level that enable bipyridyl ligands to act as electron acceptor groups.  16  The LUMO+2 shows  localization of the orbital on the terthiophene rings and the metal center. According to the calculations, the lowest-energy transition from the H O M O to the L U M O is a R11/T3—»Ru/bpy charge-transfer  transition with an energy gap of 2.3783 eV.  The calculations predict a  surprisingly small extent of metal contribution to the H O M O , given that Ru(bpy)2L  n  complexes  generally exhibit a high-energy metal-based level, giving rise to a Ru—>bpy M L C T as the lowest energy transition. It is noted that the Ru-S bond length is predicted by DFT calculations to be 2.45 A , longer that in the crystal structure of 41 (2.3640(8) A ) and thus the calculations may be predicting less stabilization to the Ru(II) center from the thiophene rings via the Ru-S bond than is occurring.  Electronic spectra are also normally measured in solution, and the electronic  energy levels are altered by solvent effects that occur in solution.  77  LUMO+4 LUMO+3 LUMO+2  -7 LUMO+1 LUMO  -8  >» cn  I  -9  LU  HOMO -10  v t>  HOMO-1  -11  HOMO-2 HOMO-3/ HOMO-4  .3-3  Figure 4-6 Ordering of the calculated H O M O and L U M O energies of R u P T - P , 5 (41), and depictions of frontier orbitals. General orientation of 41 is shown at bottom. 3  78  Table 4-3 Calculated H O M O and L U M O energies for RuPT -P,.S (41) 3  Orbital  Energy /eV  Orbital  Energy /eV  HOMO  -9.6060  LUMO  -7.2277  HOMO-1  -10.740  LUMO+1  -7.1760  HOMO-2  -11.018  LUMO+2  -6.7893  HOMO-3  -11.081  LUMO+3  -6.3583  HOMO-4  -11.114  LUMO+4  -6.1507  4.3.3 Cyclic Voltammetry The cyclic voltammograms of 41-43 are displayed in Figure 4-7a. Oxidation of the complexes results in irreversible peaks at high potentials. Addition of electron-donating methyl substituents progressively lowers the first oxidation wave from 1.48 V (41) to 1.41 V (43) (Table 4-4). First oxidation peaks are assigned as oxidation of the Ru(II) center based on comparisons to calculations using ligand electrochemical parameters to predict the Ru(III/II) redox couple.  45  By this approach, it is assumed that all ligand contributions are additive. The expected redox potential  (E \ ) CA C  versus the normal hydrogen electrode (NHE) for Ru(II) complexes can be  determined by:  £calc(V) = I £  4.1  L  where EL is the ligand electrochemical parameter for each ligand attached to the Ru(II) center, each representing one sixth of a contribution. Based on the EL values for 2,2'-bipyridine (0.259), triphenylphosphine (0.39) and tetrahydrothiophene (0.30), i i a i c is 1.77 V vs. N H E , or 1.48 V vs. C  SCE. The calculated value is very close to the potentials of the first oxidation waves observed for 41-43, and are assigned as ruthenium-based. The only prominent thiophene-based oxidation wave observed for 43-45 is an irreversible shoulder at 1.69 V for 43. Oxidation of the terthiophene chains is expected to be significantly anodically shifted due to direct coordination to an electron deficient Ru(II) center, as is observed. New return waves observed on the first and subsequent scans of 41 and 42, observed as minor peaks at 1.14 V and 1.12 V , could be due to oxidative electropolymerization or dimerization at the terthienyl a positions, since a new return wave is not observed for methylcapped complex 43. The first bipyridyl reduction is irreversible for 41, which could indicate 79  interaction of the reduced bipyridyl group with the relatively electron-poor terthiophene group. Two reversible bipyridine reductions were observed at -1.24 and -1.46 V for 42 and 43; the reversibility is possibly due to stabilization of the reductions by donation of electron density or loss of reactivity at the a positions via methyl substitution. Thienyl-based reduction waves were observed at -1.79 and -1.81 V for 42 and 43, respectively, with a negative shift in potential upon addition of a second methyl substituent.  60 40  1  '  1  I  ; (a)  '  1  '  1  '  1  '  1  '  RuPT -P,5 (41) RuPMeT -P,5 (42) RuPMe T -P,5 (43)  1  '  3  ftS/ /jii  3  20  2  3  0 f  -20  ^  < c  QJ  fc  o  -40  1 1  1  1  1 1  1 I  60 '. (b)  t >  1  1  i i  |  |  i i  1  I  i i  1  |  i i  1  I  i i  RuPDo T -P S (45) 2  5  40 20 0 -20  i  .  i  1  -1.5  -1.0  .'  1  -40 -2.0  -0.5  0.0  0.5  1.0  1.5  2.0  Volts /V vs. SCE Figure 4-7 Cyclic voltammograms of (a) 41-43, and (b) 45 in C H C N solution at 4.0 x 10" M concentrations, containing 0.1 M [(«-Bu)4N]PF6 supporting electrolyte, scan rate = 100 mV/s. 3  3  Two irreversible oxidation waves were observed by cyclic voltammetry for 45. The first oxidation potential at 1.21 V is significantly lower than the ruthenium oxidation potentials in 41-43 and than the potential predicted using ligand electrochemical parameters. It is likely that the coordinating pentathiophene can no longer be approximated to tetrahydrothiophene.  The  first oxidation is still likely to be Ru(II)-based and the pentathiophene chain may be contributing 80  to stabilization of the charge, cathodically shifting the oxidation potential. There is a significant anodic shift of the thienyl-based oxidation wave of 45 (1.71 V ) from the first potentials of P D 0 2 T 5 (22) (0.99 V), and D o T 2  5  (24) (0.82 V), but is at a similar oxidation potential to that of  43, which is reasonable since the corresponding ligands values are also alike (Chapter 2). Reduction of 45 shows a bipyridyl reduction wave at -1.22 V that is slightly higher than for 42 and 43. The second quasi-reversible reduction of 45 (-1.36 V) is at a higher potential than would be expected for the second bipyridyl reduction compared to 42 and 43 and may be thienyl-based, as a pentathiophene group has a greater ability to accept an electron due to increased conjugation length.  A fast process, often characteristic of desorption from the  electrode surface, may explain the sharp return peak of the reduction wave.  Table 4-4 Cyclic voltammetry data of Ru(II)-phosphinothiophene-P,iS' complexes  Compound  3  £ i / , o x ± 0 . 0 1 V v s . SCE  £l/2,red±0.01 V V S . SCE  RuPT -P S'(41)  + 1.48 (Ru  IH/I1  )  -1.28 (bpy ")  RuPMeT -/ ,5(42)  + 1.44 (Ru  III/H  )  -1.24 (bpy -)  3  2  b  )1  b  J  3  b  0/  0/  -1.46 (bpy- ~) /2  -1.79 (PMeT + 1.41(sh) (Ru ) + 1.69(sh) ( P M e T b  RuPMe T -P,S(43) 2  3  III/H  )  -1.24 (bpy -) 0/  b  2  0/_ 3  +/0 3  )  -1.46 (bpy" ) /2_  -1.81 (PMe T ~) 0/  2  + 1.21 (Ru b  RuPDo T -P,5(45) 2  5  III/n  )  3  -1.22 (bpy -) 0/  + 1.71(sh) (PDo T b  2  +/0 5  )  -1.36(bpy- -) /2  Measurements carried out in C H C N solution containing 0.1 M [(«-Bu)4N]PF6 supporting electrolyte, irreversible wave, E . 3  p  4.3.4 Electronic Spectroscopy and Charge-Transfer Correlations The absorption spectra of the Ru(II)-.P, S' complexes 41-43 and 45 are shown in Figure l  4-8.  Bipyridyl n—»7T,* transitions occur between 280-282 nm (Table 4-5). Terthiophene n—>n*  transitions are observed as shoulders at -320 nm for 41-43. In comparison, the pentathiophene 7X—>7t*  transition is significantly red-shifted to 371 nm for 45. Phenyl  7t->7i*  transitions are also  expected and are likely obscured by other transitions for 41-43. The 323 nm shoulder observed for 45 is in a similar position to the. 340 nm transition observed for P D o T (22) and may 2  81  5  for 45 is in a similar position to the 340 nm transition observed for PDo T (22) and may 2  correspond to the phenyl transition. The  Ru(d7t)—>bpy(7T*)  5  M L C T transition shifts dramatically  with extension of the thiophene chain, from -400 nm for 41-43, resulting in the yellow colour of the complex solids, to 465 nm for 45, yielding orange solids (Figure 4-9).  5  i-  RuPT -P,5(41) RuPMeT -P,5(42) 3  4  °  • \ /1 3 y1  w  2  3  2  //  J  5  \\  1 / \\\  1h 1  300  Figure 4-8 solution.  2  A >WJ\  ~2 2  3  R„PMe T -P 5(43) RuPDo T -P,5 (45)  ,  1  ,  400  i  500 A,/nm  .  i  .  i  600  ,  700  800  Solution absorption spectra of Ru(II)-P,S' complexes 41-43 and 45 in  CH2CI2  Figure 4-9 Crystals of (a) R u P T ^ S (41) and (b) RuPDo T -F, S' (45), displaying the dramatic colour change with extension of the oligothiophene chain that is primarily due to shifting of the M L C T transition. 2  82  5  1  Table 4-5 Electronic spectroscopy data for Ru(II)-phosphinothiophene-.P,5' complexes Solution Absorption ^max /nm [e /IVT'cm" ]  Compound  Solid-State Absorption X /nm  3  1  RuPT -P,S  (41)  304,326,412  —  2 82 (3.91 x 10 ),3 20(sh) (1.97 x 10 ), 396 (1.89 x 10 )  308. 329, 422  —  2 82 (4.01 x 10 ), 3 20 (sh) (2.11 x io ), 404 (1.95 x 10 )  305, 331,430  —  2 80 (4.27 x 10 ), 323 (sh)  281,320 (sh), 377,464  4  RuPMeT -P,5 3  (42) 3  J  1  (43) RuPDozTs-P,^  (45)  A, x ma  4  4  4  RuPMe T - P, S  11  2 80 (3.79 x 10 ), 3 20 (sh) (1.83 x 10 ), 393 (1.80 x 10 ) 4  3  2  max  Emission /nm  4  4  4  4  4  (2.24 x i o ) , 371 (2.07 x l O ) , 465 (2.68 x l O ) 4  4  602 (x< 10ns)  c  4  Measurements carried out in CH2CI2 solution. determined from emission at 600 nm.  b  Degassed  CH3CN  solution.  c  Lifetime  Correlations can be made between electrochemical potentials and optical charge transfer energies for ruthenium bipyridine complexes.  46  The observed Ru—>bpy M L C T transition, E , is op  related to the positive energy difference between the Ru(III/II) and bpy(0/-l) redox couples, AE(redox), by:  E  op  - a A£"(redox) + const.  4.2  where a is usually close to unity, and the constant term collects all the solvent and reorganizational energies of the CT excited state. Figure 4-10 shows the linear correlation for all Ru(II)-i ,5 complexes, which gives: >  E  op  = 1.76 A£(redox) - 1.60  4.3  where sources of uncertainty are the irreversibility of the oxidations and that the oxidation value for 43 that is determined from a shoulder peak. The correlation suggests that M L C T transitions occur and that the first oxidation waves for 41-43 and 45 are ruthenium-based.  83  3.3  t*3  2.40  2.45  2.50  2.55  2.60  2.65  2.70  2.75  A£(redox) /eV  Figure 4-10 Linear fit of E  versus Ais(redox) for RufJI)-/ ,!? complexes 41-43 and 45. 3  op  Solid-state absorption spectra of 41-43 and 45 are also measured (Figure 4-11, Table 4-5). M L C T transitions red-shift 19-26 nm for 41-43 and 12 nm for 45 compared with solution spectra.  Thienyl 7c->rc* transitions red shift 6-10 nm, while the bipyridyl  TC-»TC*  transition  remains in the same position for 45, but red shifts ~20 nm for 41-43. Red shifts in the absorption spectra may be due to increased rc-orbital overlap due to stacking interactions in the crystal structures. Overall, smaller red shifts are observed for 8, and it is likely that the presence of the long dodecyl groups results in a disordered solid state upon drop casting.  R u P T ^ S (41) O  RuPMeT -P,5 (42)  ,C 03  3  RuPMe T -P,5 (43) 2  3  RuPDo T - P,5'(45) 2  5  J  N  O  2 300  400  500  600  700  800  K /nm  Figure 4-11 Solid state absorption spectra of Ru(II)-phosphinothiophene-P,5' complexes 41-43 and 45 drop-cast from solution in acetone. The primary M L C T transition is normalized to the same absorbance intensities for all spectra.  84  Complexation of Ru(bpy)2 fluorescence emission. The  groups to P-phosphinothiophenes quenches thienyl 7x<—rc*  Ru(d7i)<—bpy(7t*)  luminescence that is generally observed with  M L C T excitation for complexes containing the Ru(bpy)2 fragment is quenched for 41-43, 2+  possibly due to thermal population to a low-lying non-emissive Ru(II)-based energy level. Very weak luminescence from the M L C T state of 45, at 602 nm (approximate quantum yield of 0.01%), is shown in Figure 4-12. The luminescence lifetime of 45 was measured at 600 nm; however, the lifetime was shorter than the lower limit measurable with the instrumentation used. Thus, the lifetime of 45 is less than 10 ns. [Ru(bpy) ] 3  The short emission lifetime compared with  (T = 870 ns) and other [Ru(bpy)2(LL)J  complexes,  and the low quantum yield  support the conclusion that either significant thermal population of a low-lying, non-emissive metal-centered (MC) state is occurring, or vibrational relaxation pathways are competitive with emission from the M L C T state.  Figure 4-12 (a) Emission and excitation spectra of RuPDo2T5-.P, S' (45) in deaerated C H 3 C N solution. Solution abs = 0.1 at the excitation wavelength and the solvent spectra have been subtracted for clarity, (b) Emission spectra of RuPDo2T -P,5' (45) obtained at 12 ns, 37 ns, 90 ns and 143 ns average times after the incidence of the laser pulse. >  5  Very small amounts of a secondary product appear when the complexes are in solution for long periods of time, and more intense emission at -450 nm is observed at similar wavelengths and intensities to the emission of p-phosphinothiophenes. more rapidly in chlorinated solvents such as  CHCI3  or  CH2CI2  These products form  than in C H 3 C N or acetone. Since  the M L C T states are expected to be the lowest energy states of the metal complexes, the 5  appearance of higher-energy emission suggests that the ligand detaches from the metal. For 85  example, complex 45 displays a new luminescence band at 514 nm shortly after dissolution in C H 3 C N (Figure 4-13), and the excitation, emission spectra, and the higher intensity of this new emission matches that of PD02T5 (22) (Chapter 3). These secondary products appear to form in very small concentrations and are not easily observed by techniques other than emission measurements.  A new product does not appear to form for 45 at higher concentrations (~25 31  mM) since after 11 days in CO(CD3)2, new peaks were not observed in the  P N M R spectrum.  Similar results were seen for 41-43, though the secondary products form less rapidly.  31  P NMR  experiments showed that new products formed in solution disappeared completely with the addition of concentrated acid, to reform only the original Ru(II)-/ ,.S complexes. J  These  experiments suggest that there may be an equilibrium between the complexes and the unknown products.  The observation of emission due to a very minor amount of new product that is  forming illustrates how weakly 45 emits.  Figure 4-13 Emission spectra of R U P D 0 2 T 5 - P S (45) (a) at time = 0 h, and (b) at time = 0, 2.5,  and 22 h, showing the formation of new emission in C H 3 C N .  4.3.5 Reversible Molecular Switching Ru(II)-phosphinothiophene-P,S' complexes 41-46 dissolved in methanol react with NaOH base under reflux conditions. A color change from yellow (41-43) or orange (44-46) to dark brown or dark red, respectively, indicates the onset of a cyclometallation reaction. The bonding mode of the thiophene ring is converted, or switched, from coordination via a phosphine and a 86  thienyl sulfur (P,S) to bonding via a phosphine and a thienyl carbon to give Ru(II)phosphinothiophene-P, C complexes 47-52 (Chart 4-5).  Switching of the bonding mode,  essentially a deprotonation and cyclometallation reaction, does not proceed without heating. Complete reversion of Ru(II)-P,C complexes 47-52 to the Ru(II)-P,5 complexes occurs rapidly with the addition of HPF6 or HC1 at room temperature, concomitant with a color change from 31  deep brown-red to bright yellow-orange. Analysis of 47-52 by  P N M R spectroscopy after the  addition of acid indicated that this conversion occurred quantitatively with no side products. It was observed, as shown in Figure 4-14, that addition of HPF6 to Ru(II)-P,C complex 51 directly yields the pure Ru(II)-P,S complex 45. Shown in Scheme 4-6 is the general procedure for preparing the Ru(II)-P,C complexes and reversibly switching back to the Ru(II)-P,5' complexes. Detailed procedures and yields for the preparation of Ru(II)-P,C complexes 47-52, followed by characterization studies, are provided in Chapter 5.  C h a r t 4-5  Br  RuPT -.P,C(47) R = R' = H  RuPhex T -/ ,C(50) R = C H RuPMeT-.P,C (48) R = Me, R' = H RuPDo T -F,C(51) R = C, H RuPMe T -P,C(49) R = R'= Me 5  3  2  5  6  13  2  25  2  2  5  RuPBr Do T -P,C(52) 2  3  3  Scheme 4-6  1 M NaOH /MeOH 65°C 41-46  47-52  (P,S)  HPF or HC1 6  87  (P,C)  2  5  27.7 ppm  RuPDo T -P,S(45) 2  5  1 47.8 ppm  1 .  RuPDojT -P,C (51)  HPF  ,  6  27.7 ppm Product  50  -50  -100  -150  ppm  Figure 4-14 P N M R spectra of RuPDo T -P,S (45) and R U P D 0 2 T 5 - P , C (51). Addition of HPF6 (cone.) to a solution of 51 results in reversion to 45 (bottom) as observed by the reappearance of the peak at 5 27.7 and a dramatic color change from deep red to bright orange. 31  2  4.4  5  Discussion When the structural data of Ru(II)-7 5' complexes 41-43 and 45 are examined and :>  )  compared, the 0.011-0.043 A elongation of the S-C bond lengths of the bound thiophene rings relative to  T3  3 9  indicates that the sulfur atom is partially or fully removed from conjugation, as is  expected due to sp hybridization of a thienyl sulfur bound to a metal. Bond length changes of 3  the C-C bonds in the bound ring are <0.01 A ; therefore, complexation of a thienyl sulfur is not shown to interrupt conjugation across all of the rings. Despite structural constraints imposed by metal complexation, such as large tilt angles (53.7-58.4°) between Ru(II) and the bound thiophene, and intramolecular rc-stacking between the phenyl and thienyl rings, the torsion angles between the adjacent rings of 41 are close in value to that of T in solution (147.6°). 3  Complex 43 has a more coplanar conformation, which is expected as a result of electron donation by the methyl substituents.  The torsion angle between the bound rings of 45 is  equivalent to that of terthiophene, while the exterior rings align syn and anti and with multiple 88  conformations that are similar to T 5 .  These results suggest that oligothiophene chains are not  conformational^ affected by metallation with Ru(bpy)2 groups in the P,S bonding mode, and 2+  changes in properties observed with complexation are mainly electronic in nature. A decrease in electron density across the thiophene rings is indicated by a -35 nm blue shift of the thienyl n—>n* transitions of 41-43 and 45 compared to the terthiophene ligands 13-15 and pentathiophene ligand 22 (Chapter 2), and is likely due to a combination of 20  decreased electron density at the ring coordinated to a Ru(II) center and possibly near the complexed phosphine. Thienyl-based oxidation waves (>1.69 V) that are substantially higher in potential compared with ligands 13-15 (1.05-1.30 V )  2 0  or 22 (0.99 V) indicate removal of  electron density from the thiophene rings, which would contribute to larger thienyl n—>n* energy gaps, as observed by blue shifts in the absorption spectra. Complexation to Ru(II) also removes sufficient electron density to anodically shift the terthiophene-based reduction potentials of 42 and 43, indicated by the reversible third reduction waves observed at -1.79 V and -1.81 V , respectively (Table 4-4). The assignment of the third reduction potential as thiophene-based is in agreement with the DFT calculations of 41 predicting a thiophene-based LUMO+2. Cathodic shifts of the oxidation and reduction potentials reflect the change in electron density of the oligothiophene rings. P-Phosphinothiophenes directly bound to the Ru(II) center also interact with the orbitals of the attached Ru(bpy) vs. SCE),  16  2+ 2  group. Compared to the oxidation potential of [Ru(bpy)3] (1.01 V 2+  oxidation potentials are >0.40 V higher for the Ru(II)-P,5' complexes, as expected  from calculations with ligand electrochemical parameters,  45  and reflecting poorer electron  donation from a thienyl sulfur and phosphine compared to bipyridine rings. absorptions of 41-43 (452 nm).  16  between E  op  The M L C T  at 393-404 nm are -50 nm blue-shifted compared to [Ru(bpy)3]  2+  Despite blue-shifting of the transitions, observation of the expected correlation and A£(redox) for 41-43 suggest assignment of Ru—>bpy M L C T transitions. DFT  calculations for 41 predict a H O M O / L U M O gap of 2.38 eV that is lower in energy than the band edge of the M L C T transition observed (480 nm = 2.58 eV) and the difference between the first oxidation and reduction (2.76 eV). The electrochemical data is in agreement with the two, neardegenerate bipyridyl-based L U M O and LUMO+1 levels predicted by DFT calculations, while suggesting that the first oxidized level is primarily Ru(II)-based.  DFT calculations predict a  terthiophene-based H O M O , and the discrepancy may be due to a predicted Ru-S bond length that is longer than observed and also that calculations are carried out for the gas phase. DFT calculations do predict ruthenium/oligothiophene orbital mixing, and complex 45 displays 89  unexpected properties that may be due to orbital mixing, such as a stabilized (cathodically shifted) Ru(III/II) oxidation and an M L C T (465 nm) that is red shifted from that of [Ru(bpy) ] . 2+  3  Due to irreversibility of the first oxidation, it is difficult to definitively assign the oxidations via other experiments. 94-  94-  It is generally accepted that in Ru(bpy) L2 , Os(bpy)2L2 2  and related complexes,  absorption is primarily due to a singlet-based M L C T state and emission is from a triplet-based M L C T state, with spin-orbit coupling mixing the singlet and triplet states. " 5,47  It is observed  49  that Ru(II)-/ ,5 complexes 41-43 do not emit; therefore, the MLCT-based luminescence is J>  quenched. Quenching of the M L C T emission is observed in systems containing phosphines due to destabilization of the M L C T state without destabilization of a low- lying, M C state.  47,50  This  results in a low barrier for energy transfer to the non-emissive M C state and is major deactivation route at room temperature. Weak emission is observed at 602 nm for the Ru(II)pentathiophene-P.S complex 45 that is expected to have a stabilized M L C T * state according to the red-shifted transition energy; therefore, there may be a higher barrier to the M C state compared with 41-43. The observation of a substantially shorter lifetime (< 10 ns) for 45 than is normally observed for Ru(bpy) L 2  2+ n  complexes is in accordance with the presence of an  accessible non-emissive M C state; though, due to the possibility of mixing of the orbitals of Ru(II) and the pentathiophene chain, a modified M L C T excited state could also result in the shorter lifetime of the emission. It is evident that the C-H bond cleavage that occurs during the cyclometallation reaction involves the Ru(II) center. Formally, the cyclometallation reaction to a Ru(II)-/ , C complex is J>  deprotonation, and reversion to a Ru(II)-P,5 complex is protonation; however, oligothiophenes are not normally deprotonated  by NaOH.  Mo/Co catalysts are known to promote  dehydrosulfurization of thienyl rings, and activation of the C-H bonds of thienyl rings has been reported for Ru, Re, and Rh complexes.  '  13,14 51,52  In these studies, migration of a metal from  sulfur to carbon on the ring is observed, and the suggested mechanism of C-H activation via the formation of a r| -coordinated intermediate is supported. In the presence of base, the metal may 2  migrate to the inner C-C double bond in the Ru(II)-.P,S complexes, and the removal of electron density from the ring is expected to promote deprotonation, providing a site on the thienyl ring for carbon-metal bonding. A diagram of the proposed mechanism for reversible switching of the Ru(II)-(phosphino)terthiophene complexes is presented in Scheme 4-7.  90  Scheme 4-7  From the point of view of incorporating materials of this type into real devices, one can think of a molecular wire composed of polythiophene with one or more Ru(bpy)2 attached via the P,S bonding mode.  2+  groups  Crystalline and drop-cast solid state samples of the  Ru(II)-.P,S complexes display stability in air, and under U V and visible light, and intra- and intermolecular n-stacking of the bpy, phenyl, and thiophene rings may contribute towards complex stability. This characteristic is desirable for device fabrication. For use as a lightharvester, doping of polythiophene chains would have to be initiated by the Ru—>bpy M L C T , dependent on effective overlap of the Ru(II) and thienyl oxidation potentials.  The cyclic  voltammetry results, combined with the correlation studies, suggest that the Ru(II) oxidation potentials are lower than the thienyl oxidation potentials; therefore, an M L C T transition that effectively removes an electron from Ru(II) is not expected to p-dope the oligothiophene backbones. However, extension of the thienyl chains or addition of electron-rich groups could be used to overlap these potentials and promote doping.  Switching of the complexes to a  different bonding mode with different properties (Chapter 5) is interesting because this mechanism could be incorporated into a molecular device. If the conductivity of a molecular wire, doped via Ru(bpy)  2+ 2  excitation or other means, is altered via a change in metal  coordination, P,S to P, C molecular switching would provide a means to control current through a conjugated, organic system. 91  4.5  Conclusions Binding Ru(II) bis(bipyridyl) groups to P-phosphinothiophenes via a direct, metal-  thiophene P,S bonding mode affects the electrochemical and spectroscopic properties of oligothiophenes. In solution, the Ru(II)-/ ,5' complexes exhibit blue shifting of the thienyl J  TC—»TC*  transitions and anodic shifts in the thienyl oxidation potentials that are electronic inductive effects of the bound Ru(II) metal.  Direct metal-thiophene bonding to give the Ru(II)-7 ,5' :>  complexes does not result in unfavorable conformations of thienyl backbones and rc-orbital overlap appears unhindered from the solid-state structures obtained. The properties  of the Ru(bpy)  2+ 2  groups  are affected  by coordination of the  p-phosphinothiophene ligands and by the length of the thiophene chain. Coordination to the P-(phosphino)terthiophene ligands blue shifts the Ru drc->bpy rc* M L C T transition of 41-43 while the P-(phosphino)pentathiophene ligand of 45 stabilizes the Ru(II) center and red shifts the M L C T transition compared to [Ru(bpy)3J . MLCT-based emission is observed for 45; however, 2+  the observed emission is too weak for applications. Several factors encourage further investigation of these hybrid materials for molecular device applications. DFT calculations predict a mixed-orbital H O M O , though the lower Ru(II) oxidation  potential  compared  to the  thienyl oxidation potential  suggests that these  oligothiophenes would not be oxidatively doped via the M L C T transition. 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Organometallics 2001, 20, 1259-1275.  95  CHAPTER 5 Synthesis and Characterization of P,C-Bound Ru(ll) Complexes 5.1  Introduction Different modes of direct bonding of a metal to a thienyl backbone can be used to alter  the properties of oligo- or polythiophenes. In the previous chapter, the direct bonding of the Ru(II) bis(bipyridine) group to P-phosphinothiophene chains via a phosphine and a thienyl sulfur atom, to yield P,S-bound Ru(II)-phosphinothiophene complexes, was discussed.  These  Ru(II)-/ ,5' complexes could be converted to a P,C bonding mode where a thienyl carbon is J,  bonded to Ru(II). The P,C-bound Ru(II)-phosphinothiophene complexes 47-52 (Chart 5-1) that are described in this chapter are formed from the corresponding Ru(II)-/ ,5 complexes 41-46, and J  can be switched back to the .PS-bound complexes with the addition of acid, as was described in Chapter 4.  Chart 5-1  R RuPT -P,C(47) R=R'=H RuPMeT -P,C(48) R=Me, R-H RuPhex T -/ ,C(50) R = C H, RuPDo T -P,C(51) R = C H RuPMe T -P,C(49) R=R'=Me 3  C12H25  >  2  3  2  3  2  5  5  6  3  12  25  RuPBr Do T -P,C(52) 2  2  5  Compared to the Ru(II)-.P,S complexes, the Ru(II)-P,C complexes lack a proton and a [PF6]~  counterion, and carry a +1 rather than a +2 charge on the complex.  The  P-phosphinothiophene ligands are formally -1 charged anions, and are therefore electron rich ligands. Greater electron density of oligothiophene chains contributes to higher energies of the n orbitals and could result in orbital overlap with the d7i orbital of the Ru(II) center. Scheme 5-1 96  shows the expected shifts of the  T (7i) n  and Ru(d7i) orbital levels that would occur with  conversion from a complex comprised of a less electron-rich oligothiophene to a complex with a more electron-rich oligothiophene.  Increased electron donation to Ru(II) via the Ru-C bond  would also be expected to result in a higher energy  Ru(d7t)  orbital, as depicted. The ideal system  for light harvesting applications (Scheme 5-1, right side), would result in the higher in energy than the due to the  Ru(d7i)  Ru(d7i)—>bpy(n*)  T (7x) n  level shifting  level, so that electron transfer could occur between these levels  M L C T transition. A change in bonding mode from the P,S to the  P,C bonding mode could result in shifts of the orbital levels as depicted due to binding an electron rich (3-phosphinothiophene ligand, and this possibility is investigated by spectroscopic studies of the model complexes.  Scheme 5-1 bpy n*  —  bpy  L  7i*  —  _  Switch Bonding Mode  Ru  dn T„  71  P,C  P,S  The characterization of Ru(II)-/ , C complexes 47-52 is similar to that completed for the J  Ru(II)-/ 5' complexes, and the physical properties of the complexes in the two different bonding J>  )  modes can be compared. Density functional theory calculations were carried out for complex 47, predicting the energies and localization of the frontier orbitals. Changes in alignment of the thienyl rings in the solid state structures, thienyl redox potentials, and thienyl n—>n* transitions are observed.  Also, the effect that the change in bonding mode from P,S to P,C has on the  M L C T absorption and emission is studied. In contrast to the Ru(II)-/ ,5' complexes, the Ru(II)J  P, C complexes exhibit cathodically shifted and reversible oxidation potentials that enable a more 97  complete study of the electronic states of the complexes via electron paramagnetic resonance spectroscopy and spectroelectrochemistry techniques.  5.2 5.2.1  Experimental General Experimental All reactions were performed using standard Schlenk techniques with dry solvents under  nitrogen. The preparation of Ru(II)-P,5 complexes 41-46 was described in Chapter 4. A l l other reagents were purchased from Aldrich or Strem Chemicals and were used as received. ' H and 31  P N M R experiments were performed on either a Bruker AV-300 or a Bruker AV-400  Spectrometer, and spectra were referenced to residual solvent ('H) or external 85% H3PO4 ( P). 31  Absorption spectra were obtained with a Cary 5000 in H P L C grade were obtained with a Cary Eclipse in HPLC grade  CH2CI2  CH2CI2.  Emission spectra  or C H 3 C N , and emission slits were set  to 20 nm for measurements on metal complexes. Cyclic voltammetry experiments were carried out on a Pine AFCBP1 bipotentiostat using a platinum disk working electrode, platinum coil wire counter electrode, and a silver wire reference electrode. Either decamethylferrocene (-0.12 vs. SCE) or ferrocene (0.41 vs. SCE) was used as an internal reference to calibrate the measured potentials with respect to saturated calomel electrode (SCE).  The supporting electrolyte was  0.1 M [(«-Bu)4N]PF6 that was purified by recrystallizing three times from ethanol and drying for three days at 90°C under vacuum. The lifetime measurement was carried out by Prof. C. Bohne at the University of Victoria by exciting the sample at 480 nm in 7 x 7 mm Suprasil cells at 20 ± 2 °C with a Coherent Infinity OPO tunable laser, using the previously described laser flash photolysis system. Deoxygenated samples were dissolved in acetonitrile to achieve absorbances 1  between 0.3 and 0.5 (1 = 7 mm) at 480 nm.  Emission decays were measured at fixed  wavelengths, averaging at least 5 kinetic traces, and emission spectra were obtained by collecting data at fixed wavelengths and averaging the values between set time windows after the laser pulse. The voltage on the photomultiplier used to detect the emission signal was kept constant throughout the collection of a spectrum. Electron paramagnetic resonance experiments were carried out in deaerated acetonitrile solution on a Bruker System ESP 300 equipped with a Bruker ER035M gaussmeter and an HP 5350B microwave counter, and experiments were conducted by Dr. B. Sarkar in the research group of Prof. W. Kaim at the University of Stuttgart, Germany.  The magnetic field was provided by a superconducting magnet (Cryogenics  Consultant), which generates fields up to 12 T. 98  Spectroelectrochemical experiments were  performed in deaerated acetonitrile that was distilled prior to use, with 0.1 M [(«-Bu)4N]PF6 supporting electrolyte that was recrystallized twice from methanol/ethanol solution and dried at 100°C under vacuum for several days. Optical measurements were conducted in a thin-layer spectrochemical cell under semi-infinite diffusion conditions using a reflective platinum 2  electrode and an optical fiber detector, a platinum sheet as the counter electrode, and a Ag/AgCl wire as the reference electrode with a film thickness of 0.5 mm to give a path length of 1.0 mm. Spectroelectrochemical measurements were conducted by the author in the research group of Prof. P. Bauerle at the University of Ulm, Germany.  5.2.2 Synthesis [Bis(2,2 -bipyridyl)(3 -diphenylphosphino- 2,2':5',2''-terthiopheno-P,C)ruthenium(II)] [hexafluorophosphate] (RuPT -P,C) (47) 3  NaOH (1.2 g, 30 mmol) was dissolved in deaerated M e O H (30 mL) to give a 1.0 M solution. RuPT^-P.S (41) (0.10 g, 0.088 mmol) was dissolved into the solution and stirred at reflux for 18 h. A color change from yellow to dark brown was observed. The solution was then cooled to room temperature, concentrated to 10 mL, and added dropwise by pipette into a solution of NH4PF6 (0.28 g, 1.76 mmol) in H 0 (15 mL) to form a brownish-black precipitate. 2  The precipitate was isolated by filtration, washed with water (10 mL), then ether (15 mL), and recrystallized in EtOH-acetone (9:1) to give 47 as black, shiny crystals. Yield: 43.3 g (50%). ' H N M R (300.1 M H z , CO(CD ) ): 8 8.87 (d, J= 5.7 Hz, 1H), 8.57 (d, J= 8.1 Hz, 1H), 8.51 (d, 3  2  J= 8.1 Hz, 1H), 8.47-8.42 (m, 3H), 8.07 (dd, J = 8.0 Hz, J = 1.9 Hz, 1H), 7.98-7.85 (m, 3H), 7.77-7.64 (m, 4H), 7.52-7.39 (m, 5H), 7.36 (dd, 7 = 4.8 Hz, J= 1.3 Hz, 1H), 7.26 (td, J = 6.8 Hz, 1.4 Hz, 1H), 7.18 (dd, J= 3.9 Hz, J= 1.3 Hz, 1H), 7.12 (td, J= 7.2 Hz, J= 1.4 Hz, 1H),  J=  7.06-7.02 (m, 2H); 6.93-6.89 (m, 3H), 6.65 (d, J= 2.7 Hz, 1H), 6.52-6.47 (m, 2H), 6.38 (d, J = 8.1 Hz, 1H). PF ). 6  31  P { H } N M R (121.5 MHz, CO(CD ) ): 8 46.7 (s), -143.0 (sep, J ]  X  3  2  ??  = 708 Hz,  Anal C44H F N S P Ru-C H60 requires C 53.86; H , 3.65; N , 5.35. found: C, 53.89; 32  6  4  3  2  3  H, 3.41; N , 5.34%. [Bis(2,2 -bipyridyl)(3 -diphenylphosphino-5-methyl-2,2':5 '2 "-terthiopheno-P, C)ruthenium(II)] [hexafluorophosphate] (RuPMeT -P, Q (48) 3  NaOH (0.72 g, 18 mmol) was dissolved in deaerated M e O H (18 mL) to give a 1.0 M solution. RuPMeTs-PS (42) (0.600 g, 0.521 mmol) was dissolved into the solution and stirred at reflux for 18 h. A color change from yellow to dark brown was observed. The solution was 99  then cooled to room temperature, concentrated to 10 mL, and added dropwise by pipette into a solution of N H 4 P F 6 (1.70 g, 10.4 mmol) in  H2O  (90 mL) to form a brownish-black precipitate.  The precipitate was isolated by filtration, washed with water (10 mL), then ether (15 mL), and recrystallized in EtOH-acetone (9:1) to give 48 as black, shiny crystals. Yield: 0.376 g (72%). ' H N M R (400.1 M H z , CO(CD ) ): 8 8.85 (m, 1H), 8.56-8.49 (m, 2H), 8.42-8.38 (m, 3H), 8.03 3  2  (m, 1H), 7.92 (m, 2H), 7.83 (m, 2H), 7.6-7.61 (m, 3H), 7.41 (m, 5H), 7.32 (m, 1H), 7.24 (m, 1H), 7.12 (m, 2H), 7.02 (m, 1H), 6.89 (m, 3H), 6.61 (m, 1H), 6.49 (m, 2H), 6.06 (m, 1H), 2.16 (s, 3H).  31  P { ' H } N M R (162.0 MHz, CO(CD ) ): 5 44.9 (s), -143.0 (sep, J 3  2  P F  = 708 Hz, PF ). 6  Anal. C 9H 4F N4S P Ru requires C, 53.83; H, 3.41. found: C, 54.04; H , 3.49%. 4  3  6  3  2  [Bis(2,2 -bipyridyl)(5,5 "-dimethyl-3 -diphenylphosphino-2,2 ':5 '2 "-terthiophene-P,C) ruthenium (II)J [hexafluorophosphate] (RuPMe T3-.P, Q (49) 2  NaOH (0.716 g, 0.0179 mmol) was dissolved in deaerated M e O H (18 mL) to give a 1.0 M solution. RuPMe2T3-P,5' (43) (0.55 g, 0.47 mmol) was dissolved into the solution and stirred at reflux for 18 h. A color change from yellow to dark brown was observed. The solution was then cooled to room temperature, concentrated to 10 mL, and added dropwise by pipette into a solution of  NH4PF6  (1.54 g, 9.4 mmol) in H 0 (80 mL) to form a brownish-black precipitate. 2  The precipitate was isolated by filtration, washed with water (10 mL), then ether (15 mL), and recrystallized in EtOH-acetone (9:1) to give 49 as black, shiny crystals. Yield: 0.468 g (85%). ' H N M R (300.1 MHz, CO(CD ) ): 5 8.85 (d,J= 5.7 Hz, 1H), 8.57 (d, J= 7.8 Hz, 1H), 8.52 (d, 3  2  J= 8.1 Hz, 1H), 8.44-8.37 9m, 3H), 8.05 (dd, J = 8.0 Hz, J= 1.5 Hz, 1H), 7.96-7.84 (m, 4H), 7.70-7.62 (m, 3H), 7.47-7.38 (m, 4H), 7.27-7.10 (m, 4H), 6.93-6.88 (m, 3H), 6.70 (dd, J = 3.3 Hz, J= 1.3 Hz, 1H), 6.51-6.46 (m, 3H), 6.07 ( d , J = 1.3 Hz, 1H), 6.52-6.47 (m, 2H), 6.38 (d, J = 8.1 Hz, 1H), 2.42 (s, 3H), 2.15 (s, 3H).  31  P{'H} N M R (121.5 M H z , CO(CD ) ): 8 46.5 (s), 3  2  -143.0 (sep, ' j p = 708 Hz, PF ). Anal. C 6 H F N S P R u - C H 0 requires C, 54.69; H , 3.93; F  6  4  36  6  4  3  2  3  6  N , 5.21. found: C, 54.96; H, 3.60; N , 5.22%. [Bis(2,2 -bipyridyl)(3,3 ""-dihexyl-3 "-diphenylphosphino-2,2 ':5 '2 ":5 "2 "': 5 '"2 ""pentathiopheno-P,C)ruthenium(II)J [hexafluorophosphate] (RuPhex Ts-.P,C) (50) 2  To a deaerated solution of NaOH (1.2 g, 0.030 mol) dissolved in MeOH (30 mL), RuPhex T5-P,5' (44) (150 mg, 0.103 mmol) was added and the solution was heated to reflux. 2  After 1 h, the solution turned from orange to a deep red. After 16 h stirring at reflux, the burgundy-red solution was condensed to 150 mL and added dropwise by pipette into a solution  100  of N H 4 P F 6 (600 mg, 3.46 mmol) in H 2 O (50 mL) and stirred 1 h to give a red-black precipitate. Recrystallization from EtOH gave 50 as a very dark, red powder. Yield: 61.2 mg (45%). ' H N M R (400.1 M H z , CO(CD ) ): 5 8.90 (d, J= 5.6 Hz, 1H), 8.63 (d, J= 8.0 Hz, 1H), 8.57 (d, J = 3  2  8.0 Hz, 1H), 8.47 ( t , / = 1.6 Hz, 3H), 8.11 (t, .7= 7.6 Hz, 1H), 7.98 (t, .7=6.8 Hz, 2H), 7.94-7.90 (m, 2H), 7.74 ( t , J = 8.4 Hz, 2H), 7.67 (m, 1H), 7.50-7.42 (m, 5H), 7.38 (d, J = 5.2 Hz, 1H), 7.32 (t, .7=5.2 Hz, 1H), 7.20 (d, .7= 4.8 Hz, 2H), 7.14 (m, 1H), 7.10 (d, .7= 4.0 Hz, 1H), 7.03 (d, J = 5.6 Hz, 1H), 6.98-6.92 (m, 3H), 6.87 (d, J = 5.2 Hz, 1H), 6.72 (d, J = 2.4 Hz, 1H), 6.53 (t, J = 8.0 Hz, 2H), 6.44 (s, 1H), 2.77 (m, 2H), 2.45 (m, 2H), 1.63 (q, J = 7.2 Hz, 4H), 1.42-1.20 (m, 12 H), 0.86 (t, J = 6.6 Hz, 6H). P{'H} N M R (162.0 M H z , CO(CD ) ): d 45.6 (s), -143.0 (sep, 31  3  J  P F  2  = 708 Hz, PF ). 6  [Bis(2,2 -bipyridyl)(3,3 ""-didodecyl-3 "-diphenylphosphino-2,2 ':5 ',2 ":5 "2 "': 5 '"2 ""pentathiopheno-P,C)ruthenium(II)] [hexafluorophosphate] (RuPDo T5-P,C) (51) 2  To a deaerated solution of NaOH (12 g, 0.30 mol) dissolved in MeOH (300 mL), RuPDo T -7 ,5'"(45) (1.00 g, 0.611 mmol) was added and the solution was heated to reflux. ,  2  5  After 1 h, the solution turned from orange to a deep red. After 16 h stirring at reflux, the burgundy-red solution was condensed to 150 mL and added dropwise by pipette into a solution of  (3.00 g, 17.3 mmol) in H 0 (200 mL) and stirred 1 h to give a red-black precipitate.  NH4PF6  2  Recrystallization from EtOH gave 51 as a very dark, red powder. Yield: 410 mg (45%). ' H N M R (400.1 M H z , CO(CD ) ): 5 8.89 (d, J= 5.2 Hz, 1H), 8.63 (d, J= 8.0 Hz, 1H), 8.56 (d, J = 3  2  1.6 Hz, 1H), 8.48-8.44 (m, 3H), 8.12-8.08 (m, 1H), 8.00-7.89 (m, 4H), 7.77-7.72 (m, 2H), 7.66 (m, 1H), 7.50-7.43 (m, 5H), 7.37 (d, .7= 5.2 Hz, 1H), 7.31 (t, .7= 6.0 Hz, 1H), 7.19-7.13 (m, 3H), 7.06 (d, J = 4.0 Hz, 1H), 7.03 (d, J= 4.8 Hz, 1H), 6.98-6.92 (m, 3H), 6.86 (d, J = 5.2 Hz, 1H), 6.72 (d, J= 2.4 Hz, 1H), 6.54 (t, J= 8.0 Hz, 2H), 6.44 (s, 1H), 2.77 (m, 2H), 2.45 (m, 2H), 1.63 (m, 2H), 1.44 (m, 2H), 1.26 (m, 36 H), 0.84 (m, 6H). P{'H} N M R (162.0 MHz, CO(CD ) ): 31  3  5 44.8 (s), -143.0 (sep, J  PF  2  = 708 Hz, PF ). Anal. C 6 H F N S P R u requires C, 60.98; H, 5.66; 6  7  84  6  4  5  2  N , 3.74. found: C, 61.29; H , 5.78; N , 4.00%. [Bis(2,2 -bipyridyl)(5,5""-dibromo-3,3 ""-didodecyl-3 "-diphenylphosphino2,2': 5',2":5 "2 '":5 '"2 ""-pentathiopheno-P,C)ruthenium(II)J [hexafluorophosphate] (RuPBr Do T -P,Q(52) 2  2  5  To a deaerated solution of NaOH (1.2 g, 0.030 mol) dissolved in MeOH (30 mL), RuPBr Do T5-P,5' (46) (50 mg, 0.029 mmol) was added and the solution was heated to reflux. 2  2  After 16 h stirring at reflux, the dark-red solution was condensed to 15 mL and added dropwise 101  by pipette into a solution of N H 4 P F 6 (6.00 mg, 3.46 mmol) in H 2 O (50 mL) and stirred 1 h to give a red-black precipitate. Recrystallization from EtOH-acetone (99:1) gave 52 as a dark, redpurple crystals. Yield: 35.7 mg (75%). ' H N M R (400.1 M H z , CO(CD ) ): 8 8.88 (d, J = 3  2  5.2 Hz, 1H), 8.64 (d, J= 8.4 Hz, 1H), 8.58 (d, J= 7.2 Hz, 1H), 8.49-8.45 (m, 3H), 8.12 (t, J = 6.8 Hz, 1H), 7.98 (m, 2H), 7.93-7.89 (m, 2H), 7.74 (t, J = 8.4 Hz, 3H), 7.52-7.43 (m, 5H), 7.32 (d, J= 6.8 Hz, 1H), 7.20 (d,J= 4.0 Hz, 1H), 7.15-7.09 (m, 2H), 7.10 (s, 1H), 6.99-6.92 (m, 3H), 6.94 (s, 1H), 6.75 (m, 1H), 6.55-6.51 (m, 2H), 6.40 (s, 1H), 2.74 (m, 2H), 2.45 (m, 2H), 1.62 (m, 2H), 1.45 (m, 2H), 1.26 (m, 36 H), 0.84 (m, 6H). 8 46.6 (s), -143.0 (sep, J  P F  3I  P { ' H } N M R (162.0 MHz, CO(CD ) ): 3  2  = 708 Hz, PF ). Anal. CyeH^FeNjSsPaB^Ru requires C, 55.37; 6  H, 5.01; N , 3.40. found: C, 56.78; H, 4.99; N , 3.28%.  5.2.3 X-ray Crystallographic Analysis Suitable crystals of 47 and 49 were obtained by slow diffusion of hexanes into acetone solution, and were mounted on a glass fiber. The data were collected at -100.0 ± 0.1 °C and the X-ray source in all cases was graphite monochromated M o - K a radiation. The structures were solved by direct methods and expanded using Fourier techniques. 3  4  Hydrogen atoms were  placed in calculated positions. The crystal structures were obtained and analysis carried out by Dr. B. Patrick at U B C . Data for 47 were collected to a maximum 29 of 55.7° on a Rigaku/ADSC C C D area detector in a series of two scans using 0.50° oscillations with 47.0 second exposures. Data were collected and processed using the d*TREK program, and corrected for Lorentz and polarization 5  effects.  The molecule crystallized with one molecule of acetone in the asymmetric unit.  Hydrogen atoms were included in calculated positions. A l l calculations were performed using the teXsan crystallographic software package of Molecular Structure Corporation. 6  Data for 49 were collected to a maximum 29 of 58.1° on a Bruker X8 diffractometer in a series of two scans using 0.50° oscillations with 12.0 second exposures using the Bruker SAINT  7  software package. Data were corrected for absorption effects using the multi-scan technique (SADABS ) and corrected for Lorentz and polarization effects. One [PF6]~ anion is disordered 8  and was modeled in two orientations with relative populations of 0.85 and 0.15. The atoms of the minor fragment were refined isotropically, all other non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included in calculated positions. A l l refinements were  102  performed using the S H E L X L - 9 7 crystallographic software package. Appendix 1 contains the 9  crystallographic data for the crystal structures of 47 and 49. C i f files are available online. '  10 11  5.2.4 Density Functional Theory Calculations Density functional theory calculations were carried out using the Gaussian 03 Package, and the B 3 L Y P ' 1 3  1 4  12  method is used to optimize the geometry. The 6-31 G* basis set was used to  model non-metallic atoms. A L A N L 2 D Z pseudopotential is used for inner shell calculations of the metal center, with the corresponding L A N L 4 basis set for the pseudopotential. To analyze the chemical bonding, N B O analysis was used. A l l calculations were carried out by Y. Zhang of the Prof. A . Wang research group at UBC.  Gaussian View software was used to generate  depictions of the orbitals.  5.3  Results  5.3.1 Synthesis and Crystallographic Studies The Ru(II)-(phosphino)terthiophene-P,C complexes 47-49 were prepared by reaction of the corresponding Ru(II)-P,5' complexes 41-43 with NaOH dissolved in methanol, and heating at reflux for 18 hours (Scheme 5-2). Yields (50-85%) were higher in methanol solution than for reactions in CH3CN/H2O solution (10-50%).  A color change from yellow to dark brown  indicated the onset of the reaction, which occurred within one hour of stirring reflux conditions in basic solution. Analysis of crude samples of the Ru(II)-P,C complexes indicated the presence of some oxidized ligand that was removed by recrystallization of the products. The solid-state structures of 47 and 49 (Figure 5-1, Table 5-1) were established by X-ray crystallography from crystals grown by slow diffusion of hexanes into a solution of the complex in acetone. Ru(II) is directly bonded to a thienyl carbon to yield cyclometallated complexes in the P, C bonding mode, with the bound thiophene ring tilted very little from plane the Ru-C bond at angles of 7.3° for 47 and 8.6° for 49. This more planar conformation allows back donation from a Ru(drt) orbital to the terthiophene  TC*  orbital, and the 15  RU1-C35  bond lengths (2.076(3) A  and 2.095(2) A ) are longer than the calculated double bond length in Ru=CH  + 2  (1.88 A ) ,  1 6  but  shorter than Ru-C single bonds reported for ruthenium bound to alkyl ligands (~2.22 A ) , ' 1 7  1 8  indicating that the bond possesses some double bond character. A n antibonding interaction is also indicated by elongated thienyl C-C double bonds, primarily the  C35-C36  bond lengths of 47  and 49 that are elongated by 0.044 A and 0.040 A , respectively, compared to the corresponding 103  bond lengths of RuPT -P,S (41) and RuPMe T -P,S (43) (Chapter 4). The S i - C 6 - C 7 - S torsion 3  2  3  3  3  2  angles of 47 (-10.7(7)°) and 49 (-19.7(3)°) show that the bound thienyl rings of the Ru(II)-P,C complexes are more coplanar compared to those of the P.iS-bound complexes. Intramolecular Ti-stacking ' is observed between the adjacent N 4 pyridyl and C-21 phenyl rings of 47 based on 19 20  inter-ring separations of 3.510 A , while the corresponding distance for 49 is 3.901 A . Intermolecular thienyl rings in the crystal structures of 47 and 49 are separated by > 4 A .  Scheme 5-2  R u P T - / , C ( 4 7 ) R = R' = H (50%) R u P M e T - P , C ( 4 8 ) R = Me, R' = H (72%) R u P M e T - P , C ( 4 9 ) R = R' = Me (85%)  R u P T - P , S (41) R = R' = H RuPMeT-j-.P.S (42) R = Me, R' = H R u P M e T - . P , S (43) R = R' = Me  5  3  3  2  3  2  3  3  Scheme 5-3  RuPhex T -P,5(44) 2  5  M e  Q  2  R u P B r 2 D o T - P , S (46) 2  5  65°C 18 h  Ru(II)-(phosphino)pentathiophene-P,C Ru(II)-P,5  complexes  44-46  by , the'  C (50)  (45%) (45%)  2  •  s  R u P D o T - P , C (51)  RuPhex T -.P,  U  RuPDo T -P,5(45)  2  5  RuPBr2Do T -P, 2  complexes same  5  50-52  procedure  5  C (52) (75%)  were  synthesized  as  for  the  from Ru(II)-  (phosphino)terthiophene-P,C complexes (Scheme 5-3). Crystals of RuPDo T -P,C (51) suitable 2  5  for X-ray analysis could not be obtained, possibly due to disorder of the pentathiophene chain or the dodecyl substituents combined with a reduced positive charge and number of counterions compared to RuPDo Ts-P,5 (45). RuPhex2Ts-P,C (50), containing shorter hexyl substituents, 2  was expected to give crystals that exhibit less disorder and greater crystallinity compared to 51, 104  and was prepared for the purpose of obtaining a crystal structure. Recrystallizations carried out using ethanol, methanol, acetone, hexanes, and mixtures thereof did not yield crystals of 50 suitable for X-ray analysis, and often an oily precipitate was obtained.  Figure 5-1 (a) ORTEP view of RuPT -P, C (47) and (b) ORTEP view of RuPMe T -P,C (49). Hydrogen atoms, counterions, and occluded solvents are omitted for clarity, and thermal ellipsoids are drawn at 50% probability. 3  2  3  Table 5-1 Selected interatomic distances (A) and angles (°) for 47 and 49 RuPT -P, C (47)  RuPMe T -PC(49) 2  3  Bond length /A  Bond length /A  2.076(3)  C -C 4  1.350(4)  Ru,-C  Rui-P,  2.2737(7)  C 4-C 5  1.431(4)  S,-C  33  1.719(3)  C 5"C 6  S,-C  36  1.747(3)  C 6"C 7  Ru,-C  35  3  33  3  3  3  3  3  3  3  2.095(2)  C -C 4  1.370(4)  Rui-P,  2.2954(7)  C 4-C 5  1.450(3)  1.394(4)  Si-C  33  1.734(3)  C 5"C 6  1.398(3)  1.445(4)  Sl"C 6  1.758(2)  C 6"C 7  1.448(4)  35  3  3 3  3  3  3  3  3  3  3  Torsion Angle 1°  Torsion Angle 1° Si-C 6"C 7-S2  -10.7(3)  Sl"C 6-C -S2  -19.7(3)  S2-C40-C4l-S  161.6(2)  S -C40"C4i -s  16.0(3)  3  3  3  3  2  105  37  3  5.3.2 Density Functional Theory (DFT) Calculations DFT calculations were carried out on RuPT -.P, C (47) for comparison to the calculations 3  done for R u P T ^ ^ S (41). Calculations of the localization and energies of the frontier orbitals of the gas phase 1+ charged complex (Table 5-2, Figure 5-2) predict that the H O M O is localized on both the Ru(II) metal and the terthiophene rings, with a larger contribution from the metal than was predicted for 41 (Figure 5-2). Similarly to 41, the H O M O is separated by ~1 eV from the HOMO-1, though for the .P,C-bound complex the HOMO-1 is also composed of mixed metalterthiophene orbitals.  The nearly degenerate L U M O and LUMO+1 are centered on the  bipyridine rings and the metal center. Bipyridine ligands are expected to possess a low-lying L U M O level that enable them to act as charge transfer acceptors.  21  The LUMO+2 also primarily  displays localization on the bipyridine rings. As the (phosphino)terthiopheno ligand is formally -1 charged and electron rich, the terthiophene n* acceptor levels are higher compared with 41. The calculations predict a lowest-energy terthiophene/Ru—»Ru/bpy charge-transfer transition from the H O M O to the L U M O of 2.1062 eV in energy. A Ru->bpy M L C T is expected for Ru(bpy)2L  n  2+  complexes, which corresponds to the predicted HOMO—>LUMO transition, with  additional contribution from the n orbitals of the terthiophene group.  Table 5-2  Calculated H O M O and L U M O energies for R u P T - P , C (47) 3  Orbital  E n e r g y /eV  Orbital  Energy /eV  HOMO  -6.6935  LUMO  -4.5873  HOMO-1  -7.5493  LUMO+1  -4.5272  HOMO-2  -7.7488  LUMO+2  -3.7835  HOMO-3  -8.0484  LUMO+3  -3.7835  HOMO-4  -8.1107  LUMO+4  -3.4913  106  Figure 5-2 (a) Ordering of the calculated HOMO and L U M O energies of RuPT -/ ,C(47), and depictions of the frontier orbitals. General orientation of 47 is shown at bottom. >  3  107  5.3.3 Cyclic Voltammetry The cyclic voltammograms of 47-49 (Figure 5-3) display R u  III/n  oxidations (0.49-0.57 V),  terthienyl oxidations (0.96-1.11 V) and two bipyridyl reductions (-1.53 to -1.55 V , -1.78 V). Assignments of the ruthenium oxidation potentials can be made based on ligand electrochemical parameters (EC).  22  Due to the absence of a ligand parameter for a carbon-bound thiophene or II  TO  /TTT  similar aromatic ring, the known Ru calculate the expected oxidation potential  oxidation potential of 53 (i^aic),  (Chart 5-2) was used to  using E values to correct for the measured L  oxidation potential. Complex 53 possesses similar bonds to the Ru(II)-P C complexes, with the )  metal center bound via a carbon atom to a phenyl ligand and to two bipyridyl ligands, while the sixth coordination is to a pyridyl ring rather than to a phosphine. Using the known oxidation potential of 53 (0.464 V vs. SCE), the estimated oxidation potential is of 47 is: £  where one E  L  c a  ic  (V) = 0.464 - 0.259 + 0.39 = 0.60  value for 2,2'-bipyridine (0.259) is subtracted  5.1  and the E  L  value for  triphenylphosphine (0.39) is added to give 0.60 V vs. SCE. This value is very close to the first oxidation potential of the P,C Ru(II) complex 47 (0.57 V ) that is assigned to be Ru(II)-based. The oxidation potentials of 48 and 49 are lower in value due to the attachment of the electron donating methyl substituents.  C h a r t 5-2  53  108  I  -2.0  ,  I  .  -1.5  I  .  I  -1.0  .  -0.5  I  0.0  .  I  0.5  .  I  1.0  .  I  1.5  Volts / V vs. S C E  Figure 5-3 Cyclic voltammograms of (a) 47-49, and (b) 51 in C H C N solution at 4.0 x 10" M concentrations, containing 0.1 M [(«-Bu)4N]PF6 supporting electrolyte, scan rate = 100 mV/s. 3  3  Table 5-3 Cyclic voltammetry data of Ru(II)-phosphinothiophene-P,C complexes  Compound RuPT -/>,C(47) 3  £i/2,ox ±0.01  V vs.  -1.53 (bpy ") -1.78 (bpy ")  +0.51 (Ru ) + 1.04(PMeT ")  -1.54 (bpy '") -1.78(bpy- -)  +0.49 (Ru ) +0.96 (PMe T ")  -1.55(bpy -) -1.78 (bpy ")  +0.49 (PDo T ~) +0.80 (Ru ) + 1.46 ( P D o T )  -1.52(bpy -) -1.83 (bpy ")"  m/  07  72  3  J  3  )  III/n  0/  3  RuPMe T P,C(49) 2  3j  III/H  0/  2  RuPDo T -P,C(51) 2  5  £l/2,red±0.01 V V S . SCE  +0.57 (Ru ") + 1.11 (PT ~) 0/  RuPMeT -/ C(48)  SCE  3  0/  2  3  5  III/H  0  /2  0/  72  0/  72  +/0  2  5  Measurements carried out in C H C N solution containing 0.1 M [(/?-Bu) N]PF6 supporting electrolyte. 3  4  109  Assignments of all oxidation and reduction potentials (Table 5-1) are substantiated by the addition of two methyl substituents to the terthiophene rings having a greater effect on the thienyl oxidation potentials (0.15 V decrease) than on the ruthenium oxidation potentials (0.08 V decrease), and almost no effect on bipyridyl reduction potentials. Conversion to the P,C bonding mode from the Ru^I)-/ ,.!) complexes cathodically shifts the ruthenium-based oxidations and 5  terthienyl oxidations ~(-0.9 V) and <(-0.6 V), respectively, while the bipyridyl reductions are less affected. The thienyl oxidations of the Ru(ll)-P,C complexes are also cathodically shifted from those of the corresponding ligands 13-15 (1.05-1.30 V ) , reflecting how the terthiophene chains are electron rich. It is noted that formally, oxidation of the P-phosphinothiopheno ligands are from a -1 to neutral state. DFT calculations are in agreement with the assignment of both reductions as bipyridyl-based, while predicting a mixed Ru/terthiophene H O M O rather than a Ru(II)-based level. Conversion from Ru(II)- ,iS' complex 45 to Ru(II)-P,C complex 51 significantly lowers D  J  both oxidation potentials from 1.21 and 1.46 V ; to 0.49 and 0.80 V . Compared to the Ru(II)terthiophene-P, C complexes, the first and second oxidations of 45 are close in value, which could indicate nearly degenerate oxidation levels. The assignments of the oxidations of 45 are reversed compared with the terthiophene complexes (Table 5-3), with the first oxidation assigned as thienyl-based, and the second oxidation assigned as Ru(II)-based. The reasoning for these assignments is provided in sections 6.3.4 and 6.3.5 and in the Discussion.  The first,  thienyl-based oxidation potential of 45 is significantly lower than those of P D 0 2 T 5 (22) (0.99 V) and  D02T5  (24) (0.82 V ) , which can be attributed to the formal negative charge on the bound  ligand.  5.3.4 Electron Paramagnetic Resonance Electron paramagnetic resonance (EPR) experiments were carried out in order to definitively assign whether the metal or the ligand is oxidized with the first oxidation couple. The reversibility and stability of the oxidized species of the Ru(II)-.P,C complexes facilitate measurement of EPR spectra of the first oxidation products.  Due to the short spin-lattice  relaxation times often observed with transition metal radicals, a metal-based signal usually cannot be observed at 298 K ;  2 4  therefore, measurements were also taken of samples frozen at 110  K following oxidation. Due to spin-orbit coupling of transition metals within the crystal field,  110  three signals at gi, g , and g are observed along the different axes for samples in frozen 2  3  matrices. The anisotropy of the g factor is characterized by:  Ag = gi - g  5.1  3  where gi and g are replaced by g i and g\\ values for samples that only generate two peaks. 3  Generally, a larger metal contribution results in a broader signal and a larger Ag value. Hyperfine coupling constants are rarely distinguished for ruthenium complexes of this type except at very low temperature (<5 K ) . It was observed for complex 47 at 298 K (Figure 5-4a) that the very weak, broad signal expected for a metal-based radical was seen only when the sample was oxidized to the extent that a second oxidation species was also observed at g = 1.9880.  This species is identified as a  ligand-based radical due to its narrow peak width, although the peak is still broad compared to that expected for a free organic ligand. The ligand is therefore thought to be still complexed to the metal, since the relaxation behavior of slower-relaxing paramagnetic centers is influenced by proximity to a fast-relaxing metal center.  When the temperature is lowered to 110 K , the  24  ruthenium-based signal of 47 can be more easily observed, though the second oxidation species is still seen. The Ag value observed for the metal-based signal of 47 (0.2505) indicates metal character, but is smaller than for completely metal-based R u tensor reported for polycrystalline Ru(bpy) (2.64, 1.14), giving a Ag value of 1.40.  3+ 3  III/n  oxidation. For example, the g  diluted in diamagnetic powder at 77 K is (gi, g||) =  25  The methyl substituted complex 48 displays a broad, metal-based signal at 298 K , and three peaks at 110 K , with a Ag value of 0.1892. Both a signal at room temperature and a decreasing Ag value indicate that the radical is more ligand-based than for 47. The dimethylated complex 49 also exhibits a signal at room temperature, and only two peaks, g i and g||, can be distinguished at 110 K with an even lower Ag value of 0.0918. It is evident that the oxidized species exhibit a loss of metal character from 47 to 49; however, the anisotropy observed at low temperature indicate that all oxidations are essentially metal-based and are in agreement with the electrochemical assignments for the Ru(II)-(phosphino)terthiophene-P,C complexes.  Ill  3000 3100 3200 3300 3400 3500 3600 3700 3800 B/mT  3000 3100 3200 3300 3400 3500 3600 3700 3800 B/mT  3000 3100 3200 3300 3400 3500 3600 3700 3800 B/mT  Figure 5-4 E P R spectra at room temperature (RT = 298 K ) and low temperature (110 K) of the first oxidized species of (a) R U P T P , C (47), (b) RuPMeT -P, C (48), and R u M e P T - P , C (49). 3  3 J  1.12  2  3  The EPR result for 51 contrasts those for 47-49. The spectra of 51 at 298 K and 110 K are very similar; single peaks are observed that do not display the anisotropy at low temperature that is characteristic for metal complexes (Figure 5-5). These spectra are shown with the EPR spectrum of the corresponding pentathiophene  D02T5  (16) that displays a very narrow signal  characteristic of a hydrocarbon radical. Since a metal-based radical is not observed, it is most likely that oxidation of 51 is pentathiophene-based and the broad signal is due to metal attachment decreasing the relaxation time. Detachment of a pentathiophene species from the metal is not indicated, as a very narrow signal would be observed similar to that of 16. Based on the EPR spectra of 51, the assignment of a thienyl-based first oxidation species by cyclic voltammetry is supported.  (a) J g = 1.9653 '  3100  3200  3300  3400  3500  3600  3700  3800  B/mT Figure 5-5 EPR spectra of the first oxidized species of (a) D 0 2 T 5 (24) (Chapter 2) at room temperature (298 K), and (b) RuDo PTs-.P, C (51) at room temperature (298 K ) and low temperature (110 K). 2  5.3.5 Optical Spectroscopy and Charge-Transfer Correlations Conversion from Ru(II)-(phosphino)terthiophene-/ ,S' complexes 41-43 to the Ru(lT)-P,C J>  complexes 47-49 alters the absorption spectra with an accompanying color change of the solution from bright yellow to deep brown (Figure 5-6), and the complexes appear black in the solid state (Figure 5-7a). The terthiophene n—>n* transitions red shift ~30 nm and the bipyridyl 113  71—>7T*  transitions red shift -15 nm compared to the Ru(II)-.P,S complexes.  transitions are likely obscured by more intense transitions.  Phenyl  K—>K*  The Ru(d7t)—»bpy(7T*) M L C T  transitions red shift 56-63 nm and weak transitions assigned as "spin-forbidden" M L C T transitions " are observed as shoulders at 617-633 nm, accounting for the very dark colour of 26  30  the complexes. Compared to the corresponding terthiophene ligands (Table 3.2, Chapter 3), terthiophene 71—transitions are only -10 nm blue-shifted.  300  400  500  600  700  800  X /nm  Figure 5-6 solution.  Solution absorption spectra of Ru(H)-P,C complexes 47-49 and 51 in CH C1 2  2  (a)  Figure 5-7 (a) R u P T - P , C (47) crystals and (b) RuPDo T -P, C (51) powder, displaying the very dark colours of the complexes due to their broad absorption range. 3  2  114  5  Electronic spectroscopy data for Ru(II)-phosphinothiophene-.P, C complexes  T a b l e 5-4  Compound  Solution Absorption A. ax /nm [e /IVr'cm" ]  Solid-State Absorption ^ x /nm  3  1  m a  m  295 (4.63 x 10 ), 347 (2.00 x 10 ), 456 (1.84 617 (sh)(2.25 x 10 )  RuPT -P,C  A, x ma  754 (x = 22 ± 2 ns)  295 (4.72 x 10 ), 3 5 0 (1.91 x if) ), 459 (2.03 x 10 ), 628 (sh) (2.20 x 10 )  304, 368 (sh), 475, 635 (sh)  763  295 (4.64 x 10 ), 351 (1.97 x 10 ), 460 (2.07 633 (sh) (2.10 x 10 )  301,364 (sh), 473, 630 (sh)  772  4  (47)  0  315,375 (sh), 482, 635 (sh)  4  3  Emission /nm  x  10 ), 4  c  3  RuPMeT -P,C  4  3  4  (48)  4  3  RuPMe T -P,C 2  4  3  4  (49)  x  10 ), 4  3  295 (5.24 x 10 ), 3 60 (2.63 x 10 ), 380 (sh)  306, 400 (sh), 507, 627 (sh)  4  RUPD02T5-PC  4  (51)  (2.59  x l O ) , 485 (3.15 4  x  10 ), 4  615 (sh)(2.62 x 10 ) 3  Measurements carried out in CH2CI2 solution. determined from emission at 750 nm.  b  Degassed C H 3 C N solution.  c  Lifetime  Switching the bonding mode from Ru(II)-(phosphino)pentathiophene-P,5' complex 45 to the P,C-bound complex 51 does not affect the optical transitions as strongly as for the terthiophene complexes. Still, there is a dramatic colour change in solution from orange to dark red, and complex 51 is a very dark red powder in the solid state (Figure 5-7b).  While the  bipyridyl rc—>Tt* transition and the charge transfer band red shift 15 nm and 20 nm, respectively, the pentathiophene n—>n* transition shifts from 371 nm for 45 to a broad peak at 360 nm with a shoulder at 380 nm for 51. The two transitions observed could correspond to conformations of the pentathiophene chain that are unable to interconvert rapidly in solution due to the constrained nature of the bonding to ruthenium. This is supported by the observation that the polarity of the solvent affects the relative intensities of these peaks; the peak at 360 nm is more intense in CH2CI2,  while the peak at 380 nm is prominent in C H 3 C N . Calculations have been reported  predicting that the ground state of pentathiophene is twisted while the excited state is planar (quinoidal); therefore, multiple ground state conformations would result in different rc—nr.* transition energies.  31  The weak transition observed as a shoulder at 615 nm is assigned as a  spin-forbidden M L C T transition and the charge transfer band at 485 nm is significantly more intense than the M L C T bands of the terthiophene complexes.  115  2.76  (a)  2.72  P,CRuPMeT (48)  2.720 - (b)  P,CRuPT (47)  41  3  2.715  3  2.68 / ,CRuPMe T (49)"  R = 0.99639 SD = 0.00148  J  2  3  > PJ  >  2.64  PJ  •2.705 2.700 .  2.60 2.56  2.710  » X  2.695 -/+ 49  iiP,CRuPDo T (51) 2  48  5  l  1  ,  1  ,  1  l  .  l  .  i  2.04 2.05 2.06 2.07 2.08 2.09 2.10 AE /eV  1.98 2.00 2.02 2.04 2.06 2.08 2.10 AE /eV  Figure 5-8 (a) Plot of the primary CT optical transition (E ) versus the difference in potential between the first oxidation potentials and first reduction potential (AE) for all Ru(II)-P,C complexes, and (b) the linear fit for the Ru(II)-(phosphino)terthiophene-/ ,C complexes. op  J  For bis(bipyridine) ruthenium(II) complexes, a correlation can be made between the observed Ru->bpy M L C T transition, E , and the difference between the Ru(III/II) and bpy(0/-l) op  redox couples, Afi'(redox).  32  Figure 5-8 shows a linear correlation for the Ru(II)-  (phosphino)terfhiophene-P, C complexes; however, pentathiophene complex 51 deviates significantly from this linear correlation. The linear fit for 47-49 gives:  E  op  = 0.38 zl£(redox) + 1.92  5.2  where the slope (a) is 0.38 and the constant term (1.92) collects all of the solvent and reorganizational energies of the excited state. While the fit is good, a deviates from unity, which is the value usually observed for [Ru(bpy)2L ] n  2+  complexes.  Correlations of this type are  generally valid when charge transfer occurs by a very similar process for complexes in a series, and i f the oxidation is metal-based and the reduction is bipyridyl-based. Since 51 does not correlate well with the Ru(II)-phosphinoterthiophene complexes, it is likely that the charge transfer occurs by a different process. In addition, it is not expected that 51 should correlate, since the EPR results indicated that the first oxidation of the complex is not metal-based, but thienyl-based.  116  The solid-state absorption spectra of Ru(II)-P, C complexes 47-49 and 51 (Figure 5-9) display red shifts of the bipyridyl n—>n* (9-20 nm), M L C T (13-26 nm), and thienyl rc—»rc* transitions (13-28 nm) compared to solution spectra that could be due to intramolecular stacking interactions such as are observed in the crystal structures of 47 and 49. Broader bands are observed that may be due to different conformers of the oligothiophene chains in the solid state, and/or vibrational fine structure.  Solid state absorption spectra of Ru(II)-P C complexes 47-49 and 51 drop-cast from solution in acetone. The primary CT transition is normalized to the same absorbance intensities for all spectra.  Figure 5-9  )  The Ru(II)-P, C complexes exhibit changes in the luminescence spectra compared to the Ru(II)-/ ,5' complexes that are likely related to shifting energies of the emitting states. Ru(II),  (phosphino)terthiophene-P, C complexes 47-49 show emission bands at 754-772 nm that are just red shifted of the spin-forbidden transitions, and are likely from the same low-lying M L C T level. Approximate quantum yields of the emission are -0.001%, and the intensity of the emission decreases with the addition of methyl substituents (Figure 5-10a). The emission lifetime of 47 was determined to be 22 ± 2 ns, though a very short-lived (< 10 ns) species was also observed below 620 nm that is likely due to the formation of a more emissive decomposition product (Figure 5-10b). The Ru(II)-(phosphino)pentathiophene-P,C complex 51 does not display any observable emission, which could indicate increased deactivation of the excited state via vibrational pathways.  Both the decrease in the emission intensity of 48-49 and the lack of 117  emission for 51 could be due to more vibrational relaxation modes that are introduced with methyl and dodecyl substitution of the oligothiophene chains. As was observed for the ^ ( I I ) - ^ , ^ complexes, small amounts of secondary products formed in solutions of the Ru(II)-P,C complexes.  These products formed more rapidly in  chlorinated solvents and at low concentration and exhibited more intense emission at wavelengths similar to those of the ligands, suggesting that the ligand detaches from the metal. 31  P N M R spectrum of complex 51 displayed a small peak at 5 41.2 after 1 hour in  The  CO(CD3)2, and multiple minor peaks were formed after 24 hours. Similar results were observed for 47-49, though the secondary products formed less rapidly. The addition of concentrated acid to all Ru(II)-P,C complexes resulted in conversion of all species to the corresponding, pure Ru(II)-P,5' complexes, as observed by peaks in the P N M R spectra. 31  6|  RuPT -P,C(47)  5  RuPMeT -P,C(48)  1  (a)  3  RuPMe T -P,C(49) 2  £  3  Jc  2|  >  3  i  • * • °  •  3  A 4J  •  1  1  -  CO  i  (b)  14 ns 62 ns 113 ns 137 ns •  • •  C w  1  • ••  01 "  400  •  A  A  o  5 i  600  700 X /nm  £  0  600  A  A  fj  .  A  • • •  A A  A  ^  •  A A  A  A A A  0 640 Q  • •  0  i  O  i  .  i  680 720 X /nm  0 0 B 1  760  Figure 5-10 (a) Emission and excitation spectra of 47 (A, = 456 nm, A, = 748 nm), 48 (A, = 459 nm, A, = 751 nm), and 49 (A, = 460 nm, A. - 761 nm) in deaerated C H 3 C N . Solution abs = 0.1 at the excitation wavelength and the solvent spectra have been subtracted for clarity, (b) Emission spectra of 47 obtained at 14 ns, 62 ns, 113 ns and 137 ns average times after the incidence of the laser pulse. ex  era  5.3.6  ex  em  ex  em  Spectroelectrochemistry Spectroelectrochemistry experiments were carried out to probe the origin of the charge  transfer (CT) bands of the Ru(lT)-P,C complexes, and to further characterize the oxidized species. A requirement for spectroelectrochemistry experiments is that the oxidized species be stable, as was demonstrated by cyclic voltammetry experiments. The complexes were oxidized 118  at progressively higher oxidation potentials to generate the first oxidation species, and the resulting absorption spectra in the visible/NIR region were measured. It was observed that the oxidized complexes were stable and displayed reversibility to oxidation over the duration of an experiment, generally six hours. The effect of oxidation on the CT band of each complex, as well as the formation of new bands, was observed. Figure 5-11 displays the spectra of complex 49 that was oxidized in the region of the first oxidation potential (0.49 V), where the spectrum of neutral 49 was subtracted from each spectrum to display the difference spectra. Oxidation between 300-600 mV resulted in bleaching of the M L C T band at 466 nm, and the formation of a strong absorption band at 577 nm and two broad bands of lesser intensity at 663 nm and 1329 nm.  I  I  I  400  600  I  I  I  800  I  1000 X /nm  I  I  1200  I  1  L  1400  Figure 5-11 Difference spectra of 49 in deaerated C H 3 C N solution with 0.1 M [(rc-Bu)4N]PF6 supporting electrolyte. The solution was oxidized at progressively higher oxidation potentials every 25 mV and the spectrum of neutral 49 was subtracted.  The Ru(II)-(phosphino)terthiophene-.P,C complexes 47 and 48 displayed very similar results to 49, with bleaching of the M L C T band and simultaneous formation of new bands (Figure 5-11). The EPR results allow assignment of the oxidations as metal-based; therefore, the spectra are compared to the spectroelectrochemistry data of [Ru(bpy)3] and related complexes. 3+  With oxidation, [Ru(bpy) ] 3  displays a weak band at 675 nm and bleaching of the M L C T band  (453 nm), while for [Ru(X2-bpy)3J complexes and mixed-bpy complexes, new bands can form 3+  119  in the range between 640-800 nm. '  These bands are assigned as L M C T transitions from a  bipyridine group to Ru(III) that increases in intensity i f the bipyridyl group is electron rich (such as for substituted bipyridine rings) or with decreasing value of Ru(III/II) redox potential.  33  L M C T transitions if this type could account for the bands observed at 632-663 nm, and the bands are fairly intense compared to those reported, which can be attributed to the low Ru(III/II) redox values.  Table 5-5 Spectroelectrochemistry data for P,C Ru(II)-phosphinothiophene complexes and related oligothiophenes Oxidized Species  Absorption A.  P,CRuPT (47 )  + 3  max  Oxidized Species  3  /nm  Absorption A,  max  /nm  558, 632, 1326  54  +  572,880  b  562,646,1332  55  +  620, 939  c  +  P,CRuPMeT (48 )  + 3  +  P,CRuPMe T (49 ) 2  Do T  577, 663, 1329  + 3  2  (24 )  +  +  5  (673, 1291), 728 d  a  +  PCRuPDo T (51 ) 2  679, 940, 1405  + 5  56  +  725, 1240  c  +  Measurements carried out in deaerated C H C N solution with 0.1 M [(rc-Bu)4N]PF6 supporting electrolyte. Ref . Ref . Peaks due to formation of dimer. 3  b  35  c  36  d  Chart 5-3  56  120  The  intense, high-energy transitions (558-577 nm) and the low-energy transitions  (1326-1332 nm) of 47-49 are not observed for [Ru(bpy)3]  or for related complexes, indicating a  role of the attached terthiophenes in the oxidation of these complexes. Spectroelectrochemical studies of the oxidized species of terthiophenes 54  and 55  (Chart 5-3) show the formation of  intense bands at -600 nm and weaker bands at -900 nm. The intense transitions are similar in position and intensity to the transitions observed for 47-49. There may be a general equilibrium for the Ru(II)-(phosphino)terthiophene-/ , C complexes between charge localization on the Ru(II) J  center, and on the terthiophene chain (Scheme 5-4), resulting in the presence of both oxidation features in the spectra. Note that oxidation of a phosphinothiophene group formally results in a neutral ligand. If the terthiophene 7i-orbitals and the Ru(II) drt-orbitals (HOMO) are close in energy, charge transfer from the terthiophene chain to Ru(III) could occur for the oxidized species. The band edge of the low-energy transitions (1600 nm = 0.775 eV) is similar to the energy difference between the R u  and PMe T3 ~ redox couples (-0.5 eV) seen by cyclic  I1I/n  0/  n  voltammetry, and it is expected that an optical transition would be greater in energy to overcome solvent and reorganizational energies.  Scheme 5-4  Ru -PMe T 3+  n  The  3  spectroelectrochemical spectra  -  *~ Ru -PMe T 2+  n  for the  3  n = 0-2  Ru(II)-(phosphino)pentathiophene-P,C  complex 51 also show bleaching of the charge-transfer band at 497 nm and the formation of intense and weak bands at 679 and 1405 nm, respectively, that are red shifted from the transitions observed for 47-49 (Figure 5-12). The band at 940 nm is substantially shifted from the 632-663 nm bands of 47-49, and does not indicate a Ru(III)—»bpy L M C T . The spectrum of the oxidized species of D 0 2 T 5 (16) displays bands that shift with increasing oxidation, suggesting that the 728 nm transition is the oxidized species, while the 673 and 1291 nm bands that form are due to a 2+ charged dimer that is expected to form for oxidized oligothiophenes. 56  36  Pentamer  (Chart 5-3) displays bands at 725 and 1240 nm when oxidized. The first transitions of 1 6  +  and 56 are similar to those of 51 , and it can be speculated from the expected ordering of the +  +  energy levels that the transitions of 51 at 940 nm and 1405 nm could be due to bpy—>PDo2Ts +  121  and Ru(II)-»PDo2T charge transfers, respectively. If the band edge of the low-energy transition 5  of 5 1 is taken as 1800 nm by extrapolation of the spectrum, the energy (0.689 eV) is similar to +  the energy difference between the R u  II1/n  and PMe T3 " redox couples (0.31 eV), as will be 0/  n  further discussed.  Figure 5-12 Difference spectra of (a) complex 51 and (b) pentathiophene 24 (Chapter 2) in deaerated C H C N solution with 0.1 M [(«-Bu)4N]PF supporting electrolyte. The solution was oxidized at progressively higher oxidation potentials every 25 mV and the spectrum of neutral 51 was subtracted. 3  5.4  6  Discussion The P,C bonding mode of complexes 47-52 resulted in a planar conformation of the  bound ring that would allow back-donation from the Ru(II) d TC* antibonding orbital of the bound thiophene ring.  15  orbital into the unoccupied  yz  Since sp hybridization at the bound 2  carbon does not allow significant deviation from a trigonal planar arrangement, tilt angles of the bound rings of 47 and 49 are only 9-10°, and loss of conjugation around the bound thiophene rings can be inferred by 0.033-0.042 A elongation of the C35-C36 bonds compared to Ru(II)-P,5' complexes 41 and 43 (Chapter 4). While some disruption of conjugation is a consequence of the P,C bonding mode, marked increases in coplanarity of the terthiophene rings compared to the Ru(II)-P,5' complexes are also observed.  The interannular torsion angles between the bound  rings of 47 (10.7(3)°) and 49 (19.7(3)°) are closer to planar compared with those calculated for T3 (147.6°).  37  These results indicate that the conformations of the oligothiophene chains are twisted  by metallation with Ru(bpy) groups in the P C bonding mode. 2+  122  Compared to the Ru(II)-(phosphino)terthiophene-P, S' complexes, P,C-bound complexes l  47-49 are electron-rich, as reflected by thienyl oxidation potentials that are decreased by > 0.7 V ,  to yield oxidations at 1.11-0.96 V that are quasi-reversible. The terthiophene rings oxidize at higher potentials than the Ru(II) center, which is a different  result than the mixed  metal/terfhiophene H O M O state predicted by the DFT calculations for RuPT3-P,C (47), but is in agreement with the metal-based EPR spectra observed for the oxidized species of 47-49. The P,C bonding mode evidently stabilizes the ruthenium center to approximately the same extent as for the complexed terthiophene ligands. In contrast, the Ru(II)-(phosphino)pentathiophene-7 ,C J  complex 51 displays a reversible first oxidation at 0.49 V that is thienyl-based, as confirmed by the EPR data, and close in potential to the R u  II/in  oxidation. The cathodic shift of the thienyl  oxidation is presumed to be due to extension of the thiophene chain and possibly the electrondonating alkyl chains, to result in pentathiophene- and metal-based orbitals that are close in energy and approximate the relative orbital energies shown in Scheme 5-1. The increased electron density and coplanarity of the terthiophene rings of 47-49 compared to the Ru(II)-/' 5' complexes results in -30 nm red shifts of the terthiophene n—>n* )  transitions and are at similar wavelengths as those of the corresponding ligands (Chapter 3). The two pentathiophene n—MI* transitions at 360 and 380 nm that are observed for 51 are not significantly removed from the transition for RuPDo2T - P,S (45) (371 nm). Pentathiophenes do 5  J  not normally show conformational structure in solution, but it has been observed at low temperature, and the P,C bonding mode may result in a barrier to interconversion between two 31  conformers. Interconversion between two conformers would still be relatively fast since only single peaks are observed by  31  P N M R spectroscopy and cyclic voltammetry at room  temperature. Switching the bonding mode from P,S to P,C modifies the properties of the bound Ru(bpy)  2+  group. The ruthenium-based oxidation potentials of terthiophene complexes 47-49  decrease 0.72-0.92 V , reflecting an increase in electron donation from a thienyl carbon to the Ru(II) center compared to a thienyl sulfur. Oxidation potentials of this range have been observed for other cyclometallated Ru complexes. '  38 39  The effect of switching the bonding mode on the  bipyridyl reduction potentials is not substantial. The difference in energy (AE) between first ruthenium-based oxidations and the first bipyridyl reduction is known to correlate to the M L C T transitions (E ) of [Ru(bpy)3J and related complexes. '  32 40  2+  op  For the terthiophene complexes  47-49, conversion to the P,C bonding mode contracts the A E values and red shifts the M L C T  transitions 56-63 nm to also result in lower values for E . Since the energies obtained from the o p  123  electrochemical and optical measurements correlate, this is further corroboration that Ru—»bpy M L C T transitions occur. The AE and E  o p  values of 51 do not correlate with 47-49 and the  charge transfer is thought to be by a different process which is not surprising considering that the first oxidation is not assigned as the R u " redox couple. in/  Mixing of nearly degenerate  pentathiophene- and Ru(II)-based orbitals could also result in a M L C T transition that cannot be compared to pure metal to ligand based transitions. The low energy bands observed for all P,C bound complexes are assigned as transitions to a low-lying state that is mostly triplet in character. Transition to a low-lying "forbidden" level is observed as a relatively strong transition in osmium polypyridine complexes ")f> A") A"X  orbit coupling, ' ' and as a much weaker transition for the [Ru(bpy)3]  ' due to spin  9A 9ft  complex " and some  9Q "30  94-  [Ru(bpy)2(LL)]  94-  29,30 41  complexes. '  This transition, due to its very weak intensity, is often covered  by superimposed, allowed M L C T transitions that are much stronger in intensity. In the P,C bonding mode, these transitions occur at long wavelengths to form a broad shoulder extending to 700 nm so that the combined spectra cover the visible range, similarly to Ru(bpy)2L2 complexes that have been synthesized as black absorbers for possible applications in photovoltaic cells. '  44 45  The anionic character of the cyclometallated (phosphino)oligothiophene ligands stabilizes the excited states by electron donation to Ru to shift the bands, a trend that has been observed in 111  Ru/Os polypyridine complexes. '  30 41  The overall effect of stabilizing the Ru " excited state, a 1  reduction in the M L C T absorption energy, is equivalent to incorporating a bpy-type acceptor ligand.  46  9+  In Ru(bpy)2L2 -type complexes, while absorption is primarily to a singlet-based M L C T state, emission is from a triplet-based M L C T state, with spin-orbit coupling mixing the singlet and triplet states. ' ' '  29 41 47 48  Ru(II)-P,C complexes 47-49 display very weak luminescence that  approaches the near infrared region (754-772 nm). These singlet-based M L C T states should be low enough in energy to create a barrier to a low-lying metal centered (MC) level, and the formation of a more electron-rich complex has been observed to promote luminescence in another Ru(bpy)2L2 switchable system. 2+  49  However, very low intensity emission was observed,  and could be due to competing non-radiative relaxation that increases with increasing vibrational modes introduced by the addition of alkyl substituents to the ligands.  The short 22 ± 2 ns  lifetime observed for the emission of 47 is in agreement with the presence of competing deactivation pathways, while the decreasing intensity from 47 to 49 is also in accordance with the energy gap law. ' 50  51  A n alternative explanation for the very weak, or lack of, luminescence  observed for all of the Ru(II)-P, C complexes is that the M L C T excited state is being quenched 124  by electron transfer from the oligothiophene to the Ru(III) center that is formed by light absorption, or is partially quenched by derealization of positive charge onto the thienyl chains i f orbital overlap is favorable.  When the emission spectra are compared to those of the  corresponding Ru(II)-/ ,5' complexes, the (phosphino)terthiophene complexes exhibit P,S-OF¥, J  P . C - O N emission, while the (phosphino)pentathiophene complex exhibits P,S-ON, P , C - O F F emission.  7K  #3  ~f.7K  0>2  Figure 5-13 Proposed energy-level diagram and transitions, Ti and T2, for T , where energy levels O1-O3 represent the highest fully occupied, singly-occupied and unoccupied antibonding MO's, respectively. Adapted from reference . n  3  The results of the spectroelectrochemistry studies can be used to further characterize the oxidized states of the Ru(II)-P,C complexes, and suggest the ordering of the energy levels for these metal-thiophene complexes. Bleaching of the M L C T transitions is observed with the initial oxidation of all complexes, so it can be inferred in each case that M L C T transitions involve the species that is oxidized first. Interestingly, all spectroelectrochemical spectra suggest oxidation of the oligothiophene chains, including the (phosphino)terthiophene complexes that display metal-based radicals by EPR spectroscopy. Excluding dimer formation, which is not expected to occur for the Ru(II) complexes, oligothiophene chains are expected to undergo two possible transitions: the first transition (Ti) is from a singly occupied molecular orbital (SOMO) to an empty antibonding M O , and a lower-energy transition (T2) is expected from the highest fully occupied M O to the SOMO (Figure 5-13). match those at 557-577 nm for  47 -49 , +  +  36  The higher-energy T i transitions of Tj  +  chains  while the Ti transition observed for Ts chains is similar +  125  in energy to the transition at 649 nm 51 . The lower-energy T transitions could be obscured in +  2  the measured spectra, or weak in intensity. The oxidized Ru-(phosphino)terthiophene-/ , C complexes 47 -49 also display transitions >  +  +  (632-663 nm) characteristic of metal-based bpy—»Ru(III) L M C T transitions, ' and low-energy 33 34  bands that may be PMe T3—^Ru(III) L M C T transitions. The oxidized (phosphino)pentathiophene n  complex 51 does not display a transition in this region, consistent with the pentathiophene chain +  as the first species oxidized. If the highest occupied level of 51 is expected to be the singly +  occupied molecular orbital (SOMO) of the PD02T5 ligand, then the proposed M O diagram for the complex, including orbital overlap with the Ru(II) centre, is as depicted in Figure 5-14. The highest-energy transition (T'i = 1.55 eV, as estimated from the band edge) would correspond to a transition from the SOMO-based *D to the empty n antibonding M O O 4 . T' (1.13 eV) is 3  2  tentatively assigned as a transition from the occupied n M O <Di to <I>, which is higher in energy 3  from that observed for 56 . +  36  T'3 (0.69 eV) could correspond to a transition from the  Ru(II)-based orbital 0 to the closely spaced 0 . 2  3  PDO T (TC*) 2  7FT  5  <]>4  T',  PDO T (TC)  A  SOMO  1  2  5  7K <E>3  T'  3  Ru(dTt)  T' PDo T (:-) 2  5  +  2  0>i  +  Figure 5-14 Proposed molecular orbital diagram for 51 and transitions T ' i , T ' and T'3, with energy levels O1-O4. +  2  126  When the data is taken as a whole, it is interesting to consider that the ordering of the Ru(II) and PD02T5 energy levels can be controlled by the type of coordination mode, and extension of the oligothiophene chain. Due to evidence that with a Ru(bpy)2 -based M L C T transition, positive charges could be introduced into the thienyl backbone complex 51, use of extended complexes of this type as a photoconducting molecular wire as depicted in Figure 5-15 can be visualized. Further investigation into the formation of a charge-separated state with light absorption could be carried out by observing the excited state lifetime via transient absorption spectroscopy. The stability in air and under U V and visible light of crystalline and drop-cast solid-state samples of the Ru(II) P,C complexes encourages further studies of this class of complexes for real applications.  Complexes containing longer oligothiophene chains or  polythiophene would likely improve the processibility and flexibility of materials of this type.  /  Figure 5-15 Representation of Ru(II)-phosphino(pentathiophene)-P,C complex 51 as a lightharvesting molecular wire. The M L C T transition results in charge separation and p-doping of the oligothiophene chain, so that the chain can conduct current.  5.5 Conclusions Binding Ru(II) bis(bipyridyl) groups to P-phosphinothiophenes via the P,C bonding mode results in very different electrochemical and spectroscopic properties compared to the Ru(II)-P,5' complexes.  Due to a combination of a more electron rich system and increased  planarity of the oligothiophene chains with P,C bonding, red shifts are observed for the thienyl TC—>u*  transitions, resulting in transition energies very close to those of the ligands, and the  thienyl oxidations are cathodically. shifted to potentials lower in value to those of the  127  corresponding ligands. Hence, direct metal-thiophene bonding in the P,C bonding mode does not hinder 71-orbital overlap, as is supported by the solid-state structures obtained. Interaction of the Ru(bpy)2 groups with the P-(phosphino)oligothiophene ligands in the 2+  P,C bonding mode results in low-energy M L C T transitions and a broad absorption region, a desirable characteristic of potential light-harvesting materials. Extension of the oligothiophene chain length is shown to result in a reordering of the energy levels, as is inferred from the results of cyclic voltammetry, EPR, optical spectroscopy, and spectroelectrochemistry  experiments.  MLCT-based emission observed is very weak and is considered to be essentially quenched. Complex applications.  51 exhibits the  most promising characteristics  for molecular device  In contrast to the Ru(II)-P,5' complexes, the P.C-bound complex 51 displays a  thienyl-based first oxidation, which could allow oxidative doping of a pentathiophene chain concurrent with Ru—>bpy M L C T transition. The solid state stability of the complexes encourage their investigation as molecular conducting materials. 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J. / . Phys. Chem. 1983, 87, 952-957.  130  CHAPTER 6 Preliminary Polymerization Studies 6.1  Introduction Polynuclear metallated polythiophenes are expected to exhibit properties different from  those of mononuclear metallated oligothiophenes, since the interaction between metal centers and the conjugated backbone could be enhanced by multiple points of contact with metal centers. Also of interest to study are the interactions between metal centers that could occur across a rc-conjugated thiophene chain acting as a molecular wire. Electronic interactions between metal centers can be used to probe the distance the electronic modification can be "sensed" along a conjugated molecule. " 1  4  Since the Ru(II)-phosphinothiophene complexes that have been  described displayed properties very different from those of oligothiophenes, it is of interest to observe the properties of the polynuclear Ru(II)-phosphinothiophenes. Therefore, multinuclear metallated counterparts of the Ru(II)-phosphinothiophene-P,5' or Ru(II)-phosphinothiophene-.P, C complexes that incorporate Ru(bpy)  2+ 2  groups were targeted for study. These systems should  also be good candidates for studying metal-metal interactions across rc-conjugated chains, due to strong interactions between the bound metal group and the conjugated backbones. There are two general methods for preparing polynuclear metallated oligo- or polythiophenes. Most commonly, ligands are prepared with multiple points for metallation along the thiophene chains, ' and this approach allows the coordination of different metals. A n 5 6  alternative route is the coupling of mononuclear complexes via functionalities on a thienyl ligand, which has the advantage of better controlling the composition of the polymeric product, though successful coupling is highly dependant on the reactivity of the metal center during the polymerization reaction.  Reported methods of polymerization of Ru(II) complexes via  functionalized ligands include Ni(0)-catalyzed homocoupling, ' Stille coupling, and Suzuki coupling.  9  Both routes towards metallated polymers are investigated for this project and preliminary polymerization reactions have been performed.  In Chapter 2, compound 26 (Chart 6-1) was  described that is functionalized with iodo substituents at both a positions and with a bromo substituent at one central (3 position. These iodo substituents exhibit higher reactivity than the bromo substituent, as was demonstrated by a Suzuki cross-coupling reaction of 26 to yield the 131  (3-bromo functionalized heptamer  28 (Chapter 2).  The preparation  of P-brominated  polythiophene chains via Suzuki cross-coupling reactions of 26 with a thiophene diboronic ester to give poly-26T (Chart 6-2) was attempted. In this case, the thiophene ring of the diboronic ester functions as a bridging group. The desired polymer poly-26T incorporates alkyl chains and unsubstituted p positions that could bind to an open site of a complexed metal.  Chart 6-1  The second route investigated uses Ru(II) complexes as building blocks. Polymerization of the P,5-bound complex was first attempted via Ni(0)-catalyzed homocoupling of the a,a-dibrominated Ru(II) complex 46. This polymerization procedure is the most direct of those reported and does not require cross-coupling with a bridging group; successful coupling of 46 would yield poly-46 (Chart 6-2). As both monomers, 26 and 46, are not symmetric, polymers 132  would not be regioregular as depicted, but all possible coupling orientations would occur for both polymerization routes: head-to-head (HH), head-to-tail (HT) and tail-to-tail (TT).  6.2  Experimental  6.2.1 General Experimental Reactions were performed using standard Schlenk techniques with dry solvents under nitrogen unless otherwise specified. Procedures to prepare 26 and RuPBr2Do2T -P,S' (46) have 5  been described in previous chapters.  [NiBr2(PPh3)2]  catalyst,  10  activated zinc dust,  10  and  2-thienyl-l,3,2-dioxaborinane were prepared by published procedures. A l l other reagents were 11  purchased from Aldrich or Strem Chemicals.  ' H and  31  P { H } N M R experiments were 1  performed on either a Bruker AV-300 or Bruker AV-400 spectrometer, and spectra were referenced to residual solvent ('H) or external 85%  H3PO4  ( P). Microanalyses (C, H , N) and 31  mass spectrometry experiments were performed at U B C by M . Lakha and M . Lapowa, respectively.  6.2.2 Polymerization Reactions Suzuki coupling, 1:1 ratio: Poly-3 "-bromo-3,3 ""-didodecyl-2,2':5'2":5 "2 "':5 '"2 "":5 ""2 ""'hexathiophene (poly-26T) A solution of 26 (1.00 g, 0.926 mmol), CsF (647 mg, 4.26 mmol) and [Pd(PPh ) ] 3  4  (53.2 mg, 0.046 mmol) was stirred in THF (30 mL) at reflux, and a solution of 2,5-bis(l,3,2dioxaborolan-2-yl)-thiophene (233 mg, 0.926 mmol) in THF (10 mL) was added to the mixture. After 16 h, the solution had darkened from dark yellow to a red-purple suspension.  CH2CI2  was  added and purple-green solids were filtered off. The solvent was removed to give an orange-red residue.  The crude product was run through a chromatographic column using silica gel and  CH2Cl2-hexanes as eluent. Starting material was recovered (245 mg, 25%) followed by multiple fractions that varied in colour between orange and dark red but were not isolated in significant amounts. Suzuki coupling, excess diboronic ester: Poly-3 "-bromo-3,3 ""-didodecyl-2,2':5 '2 ":5 "2"': 5 '"2 "":5 ""2 '""-hexathiophene (poly-26T) A solution of 26 (1.00 g, 0.926 mmol), CsF (1.21 g, 7.95 mmol) and [Pd(PPh ) ] 3  4  (1.00 mg, 0.087 mmol) was stirred in THF (30 mL) at reflux, and a solution of 2,5-bis(l,3,2133  dioxaborolan-2-yl)-thiophene (436 mg, 1.74 mmol) in THF (10 mL) was added to the mixture. After 24 h, the solution had darkened from dark yellow to a dark red mixture. The solvent was removed to give red-purple solids that were transferred to a Soxhlet finger. Soxhlet extraction was carried out by successive extractions.with EtOH, hexanes,  CH2CI2,  and C H C I 3 . Dark orange  solids (0.236 g) were collected from the hexanes fraction, dark red solids (0.197 g) were collected from the C H 2 C I 2 fraction, and shiny greenish crystals that had a strong odour and are likely catalyst by-product were then collected from the CHCI3 fraction, leaving no remaining solids in the Soxhlet finger. The crude product of the  CH2CI2  fraction displayed evidence of  containing coupled oligothiophenes by H N M R and mass spectroscopy. !  Estimated yield  (monomer M W = 908): 0.197 g (23%). ' H N M R (400.1 M H z , CDCI3): 5 (broad peaks) 7.358 (m, 1H), 7.199 (m, 1H), 7.145 (m, 1H), 7.095 (m, 1H), 7.066 (m, 2H), 7.034 (s, 1H), 6.996 (m, 2H), 2.750 (m, 4H), 1.664 (m, 4H), 1.390 (m, 4H), 1.240 (m, 32H), 0.853 (m, 6H). Nickel-catalyzed cross-coupling, 2 h reaction: Poly-[Bis(2,2 -bipyridyl)(3,3 ""-didodecyl-3 "diphenylphosphino-2,2 ':5 '2 ":5 "2 '":5 '"2'"'' -pentathiophene-P\S)ruthenium(II)]  [bis(hexafluorophosphate)] (poly-46) [NiBr (PPh ) ] (4.3 mg, 8.9 umol), zinc dust (5.6 mg, 0.086 mmol) and NMe I (11.6 mg, 2  3  2  4  0.0576 mmol) was stirred for 1 h under nitrogen in THF (10 mL) at 50°C.  46 (50.0 mg,  0.0288 mmol) dissolved in THF (10 mL) was added and the mixture was stirred for 2 h at 50°C. The solution changed colour from orange to orange-brown.  The solution was cooled and  condensed to 10 mL, and added dropwise by pipette into a solution of N H 4 P F 6 (3.00 g, 18.0 mmol) in H 2 O (60 mL) to form a dark orange precipitate.  The suspension was filtered and  washed with H 2 O , then dissolved in acetone and the green catalyst and zinc were filtered off. The red filtrate was collected and removed of solvent. The solids were recrystallized from EtOH to give a dark orange precipitate. -143.0 (sep, J  P F  31  P { ' H } N M R (162.0 M H z , CO(CD ) ): 5 27.1 (s), 28.1 (s), 3  2  = 708 Hz, PF ). 6  Nickel-catalyzed cross-coupling, 16 h reaction: Poly-[Bis(2,2 -bipyridyl)(3,3 ""-didodecyl-3 "diphenylphosphino-2,2 ':5',2":5 "2 "':5 '",2 ""-pentathiophene-P,S)ruthenium(II)]  [bis(hexafluorophosphate)] (poly-46) [NiBr (PPh ) ] (21.5 mg, 44.7 umol), zinc dust (28.0 mg, 0.428 mmol) and 2  3  2  NBU4I  (53.2 mg, 0.144 mmol) was stirred for 2 h under nitrogen in THF (10 mL) at 50°C, and the mixture changed from light amber to dark brown in colour. 46 (50 mg, 0.144 mmol) dissolved in THF (10 mL) was added and the mixture was stirred for 16 h at 50°C. The solution was cooled 134  and condensed to 10 mL, and added dropwise by pipette into a solution of NH4PF6 (3.00 g, 18.0 mmol) in H 2 O (60 mL) to form a dark red precipitate. The suspension was filtered, and the dark red precipitate (86 mg) was recovered and dried.  31  P{'H} N M R (162.0 MHz, CO(CD ) ): 8 3  45.42 (s), 44.65 (s, minor peak), 44.32 (s, minor peak), -143.0 (sep, J  P F  2  = 708 Hz, PF ). The 6  dark red precipitate was dissolved in acetone, catalyst and zinc solids were filtered off, and the solvent was removed and the resulting orange-red solids (53 mg) were dried. Multiple peaks were observed by P { ' H } N M R (162.0 MHz) in CO(CD ) solution between 45.4-20.0 ppm and 31  3  2  a signal at -143.0 (sep, JPF = 708 Hz) due to [PFe]~ (see Results section).  6.3  Results  6.3.1 Coupling of (3-Halogenated Oligothiophenes Palladium catalyzed Suzuki cross-coupling of 26 with the diboronic ester 2,5-bis(l,3,2dioxaborolan-2-yl)-thiophene was carried out via non-aqueous conditions using CsF as the activating base, as shown in Scheme 6-1. Reaction in a 1:1 ratio of 26 to the diboronic ester resulted in the recovery of significant starting material (25%).  Therefore, the reaction was  repeated with approximately a 1:2 ratio of 26 to the diboronic ester, and a colour change to a dark red colour indicated the formation of longer oligo- or polythiophene chains. Due to the possibility of chains of varying length, a Soxhlet extraction was carried out to separate the fractions. Soluble salts were extracted with MeOH, and any remaining starting materials, short oligomers and silicon grease were subsequently extracted with hexanes. Dark red solids were then extracted with CH C1 , and the amount recovered was estimated to correspond to a yield of 2  2  23% if all ends of the starting materials have reacted to form a polymer chain.  Scheme 6-1 1) 10 eq CsF 0.05 eq Pd (PPh ) THF  3 4  26  poly-26T  Reflux 2 h  135  — |  7.40  7.30  7.20  7.10  7.00  i  i  .  ppm  Figure 6-1 ' H N M R spectra of the aromatic region of (a) heptathiophene 28 and (b) the coupled products of the Suzuki cross-coupling reaction of 26 and thiophene (T), to give poly-26T.  The ' r i N M R spectrum of the dark red solids recovered displayed broad peaks that are characteristic of oligomeric or polymeric thiophene chains (Figure 6-lb), at very different positions from those of the spectrum of 26 that does not display any peaks between S 7.346-7.093. In fact, the coupled product displays peaks that are very similar in chemical shift and relative integration to those of the p-brominated heptamer 28 (Figure 6-la), suggesting that thienyl coupling has occurred at the a-iodinated positions.  136  Chart 6-3  T = 82 —I n n n n  = = = =  1 2 3 4  M = 906/908 2 M = 1812/1814/1816 3 M = 2718/2720/2722/2724 4 M = 3624/3626/3628/3630/3632  0B -  127  B E = 85  0  1771.1  1818.1  2082.1  1999.2 1900.1 | 1982.1  I  1089. 2727.0 2644.0 [ 1253  2163.  2910.0 |  2807.9/2807.9  II  2990.9  3739.7 3656.6 1 3820.5  0 .10 J  m /z  Figure 6-2 M A L D I - T O F mass spectrum of poly-26T, 700-4000 m/z region.  The results of mass spectroscopy indicate that long oligothiophene chains are present in the cross-coupled product. Chart 6-3 displays the expected mass corresponding to 1-4 monomer units of coupled materials, as well as the mass of end groups that may be present. The spectrum displayed in Figure 6-2 shows four clusters of peaks that appear to correspond generally to the masses of 1 -4 pentamer units. The main peak at 1171 is not the expected mass for the starting material, and may be a fragmentation product. Peaks listed in Table 6-1 can be assigned to 137  specific oligothiophenes, though as thiophene (T) and the boronic ester (BE) have similar masses, the boronic esters listed could also be represented by boronic ester-terminated oligothiophenes. The peak at m/z = 2727 is most likely due to a boronic ester-terminated chain of seventeen thiophene rings. While all peaks cannot be assigned, they are generally spaced by m/z = 82, indicating the fragmentation of thiophene units.  Table 6-1 Peaks corresponding to coupled oligomers in the mass spectrum of poly-26T. Peak  m/z  2M(1816) + 2  1818.1  2M(1816) + T + 2  1900.1  3M (2724) - T + 2  2644.0  3M (2723) - T + BE + 1  2727.0  3M (2724) + T + 2  2807.9  Oligothiophene  6.3.2 Coupling of Ru(ll)-Complexes Ni(0)-catalyzed homocoupling was attempted for the T^S-bound Ru(II) complex 46 that incorporates two bromo substituents at the a positions of the pentathiophene ligand (Scheme 12  6-2).  The reaction also requires the presence of zinc dust and an alkylammonium iodide.  Initially, the coupling reaction was carried out for only 2 h at 50°C, as per the reported procedure, and the solution darkened upon addition of the Ru(II) complex. However, mainly starting material was recovered from the reaction products.  By P N M R spectroscopy, the 3 1  starting material, with a peak at 5 27.1, was shown to be the major product recovered, but a minor peak at 8 28.1 ppm was also observed (Figure 6-3a). 138  Scheme 6-2  27.1  (a)  28.1  28.5 — 1  1  28.0  27.5  —  27.0 , 1  .,  1  1  50 ppm  i  i  i  i  1  ,  -100  -50  0  —  J. 1  f  -150  28.0  (b) 45.4  33.8 ,32.3  20.0  I' I 27 4  ' i ""i 45 40  y 1" " i" "r " 1" 35 30 25 20  1 1 1 1  '  I  50 ppm  r  -i  i  ,  p 0  1  "i  ~1~  -50  1  -100  r  •150  Figure 6-3 P N M R (162.0 MHz) spectra in CO(CD ) of products of Ni(0) coupling reaction of 46 at50°C (a) 2 h, (b) 16 h. 31  3  2  The coupling reaction was then attempted for a 16 h reaction time, and using greater equivalents of catalyst, zinc, and alkylammonium iodide than shown in Scheme 6-2 (~5 times 139  excess). 3 1  Orange-red solids were recovered that did not contain the starting material 46 by  P N M R spectroscopy; however, many peaks were observed in the spectrum, and most were  removed from the range of chemical shifts expected for a polymerized product (Figure 6-3b). The peak at 5 20.0 suggests the presence of oxidized ligand, and the peak at 8 45.4 could indicate a cyclometallated product. While the major peak at 8 28.0 is near the chemical shift of 46, the peak is not broadened, as would be expected for a polymer. A small, broad peak is present upfield of the peak at 5 27.4; however, this product would comprise a very small amount of the crude product.  6.4  Discussion As the palladium-catalyzed Suzuki cross-coupling of 26 to give 28 had been successful  (Chapter 3), the same non-aqueous conditions were attempted to yield poIy-26T. A 1:1 ratio of 26 to the diboronic ester was not sufficient for all of the starting material to react. When a ratio close to 1:2 was used, all of the starting material was reacted, and broad peaks in the H N M R ]  spectrum signaled that long oligomers may have formed. Mass spectrometry also suggests the formation of coupled pentamer chains, linked by thiophene bridging units. One uncertainty is that the central P-brominated position may also couple, and C experiments could be carried out 1 3  to determine substitution along the thienyl backbone. Ni(0)-catalyzed homocoupling of ruthenium complexes was first attempted, as it is a simple procedure requiring only a dihalogenated substrate, and has been reported to be effective for the coupling of brominated aromatic ligands of Ru(II) complexes to yield dinuclear complexes. '  7 13  Suzuki coupling reactions were not attempted for the .PS-bound complex 46 due  to the possibility of conversion to the P,C bonding more during reaction in the presence of base. The multiple peaks observed by P N M R spectroscopy after coupling for 16 hours indicate that 31  ligand oxide and a variety of metallated products have formed, and only a small broad peak is present that could indicate polymerized product. The intensities of the peaks observed are very small compared to those of the PF6~ anion, suggesting further that many products are formed in small amounts. The main disadvantage of a polymerization route from 46 to make poly-46 is that the metal center can react and this is most likely occurring for the Ni(0)-catalyzed coupling reactions. The formation of a peak at 45.4 ppm by P N M R spectroscopy suggests that a Ru-C 31  bound complex is formed. Neither reaction, for a shorter and longer reaction duration, indicated the majority formation of a polymerized product, since a strong, broadened peak was not 140  observed. Other coupling reactions of metal complexes should be attempted.  The P,C-bound  Ru(II) complex 52 could provide a better substrate for Suzuki cross-coupling that has proven to be effective for oligothiophenes, since this complex should not be sensitive to reaction with base.  6.5  Conclusions The preliminary results of the polymerization reactions performed to date indicate that  Suzuki cross-coupling of p-brominated pentathiophene  chains that are iodinated at the  a positions is a viable route towards the preparation of a multi-functionalized ligand, and subsequently, polynuclear metallated polymers. While the polymerization of Ru(II) complexes has been attempted without success, other coupling reactions such as Suzuki cross-coupling should be attempted, possibly using the P, C-bound complexes. Both polymerization routes have the inherent disadvantage that the monomers are non-symmetrical and the structure of a resulting metallated polymer cannot be controlled.  6.6  References  (1)  Stott, T. L.; Wolf, M . O. Coord Chem. Rev. 2003, 246, 89-101.  (2)  Pappenfus, T. M . ; Mann, K . R. Inorg. Chem. 2001, 40, 6301-6307.  (3)  Laye, R. H.; Couchman, S. M . ; Ward, M . D. Inorg. Chem. 2001, 40, 4089-4092.  (4)  Cameron, C. G.; Pickup, P. G. J. Am. Chem. Soc. 1999, 121, 11773-11779.  (5)  Constable, E. C ; Rees, D. G. F. Polyhedron 1998, 77, 3281-3289.  (6)  Collin, J. P.; Laine, P.; Launay, J. P.; Sauvage, J. P.; Sour, A . Chem. Commun. 1993, 434-435.  (7)  Griffiths, P. M . ; Loiseau, F.; Puntoriero, F.; Serroni, S.; Campagna, S. Chem. Commun. 2000, 2297-2298.  (8)  Trouillet, L.; De Nicola, A.; Guillerez, S. Chem. Mater. 2000, 72, 1611-1621.  (9)  Chodorowski-Kimmes, S.; Beley, M . ; Collin, J.-P.; Sauvage, J.-P. Tetrahedron Lett. 1996, 37, 2963-2966.  (10)  Iyoda, M . ; Otsuka, H.; Sato, K.; Nisato, N . ; Oda, M . Bull. Chem. Soc. Jap. 1990, 63, 8087.  (11)  Kobayashi, Y . ; Mizojiri, R.; Ikeda, E. J. Org. Chem. 1996, 61, 5391-5399.  (12)  Johansson, K . O.; Lotoski, J. A . ; Tong, C. C ; Hanan, G. S. Chem. Commun. 2000, 819820.  (13)  Fanni, S.; D i Pietro, C ; Serroni, S.; Campagna, S.; Vos, J. G. Inorg. Chem. Commun. 2000, 3, 42-44. 141  CHAPTER 7 Conclusions and Future Directions 7.1  Conclusions This thesis describes the synthesis and study of P-phosphinothiophene ligands and  derivatives, and Au(I)-, Pd(II)-, and Ru(II)-phosphinothiophene complexes. Modifications of the structural, chemical, and electronic properties of the ligands and the new metal-oligothiophene hybrid materials prepared were observed. This section summarizes the results of this study, and gives conclusions based on the overall data obtained, with reference to the initial goals. Mono- and bisubstituted P-phosphinothiophenes of n = 2-5 thiophene rings were used as coordinating groups to anchor metals to oligothiophene chains.  Two adjacent P-phosphine  substituents alter the structural and electronic properties of the oligothiophene backbones, while one P-phosphine substituent exerts little influence. The mediation of electronic properties by extension of thienyl chain-length is also observed. P-Bis(phosphino)thiophene ligands present binding sites where oligothiophene properties can be altered via metallation, which is seen with Pd(II) or Au(I) complexation. Strong conformational effects are observed in the solid state complexes as unfavorable interannular torsion angles, where the choice of metal controls the extent of Ti-orbital overlap.  Au-Au bonding does not likely persist in solution, but Au(I)  complexes could be used to "switch" conductivity using the weak Au-Au interactions.  The  H O M O - L U M O gaps are increased for both complexation types via inductive electronwithdrawing effects, and additionally by the fixed metallocyclic conformations of the Pd(II) complexes.  Pd(II) complexation also introduces L M C T charge transfers and metal-based  transitions. Overall, metal complexation with P-bis(phosphino)thiophene generally discourages 7x-orbital overlap across the organic chain, but the introduction of "switchable" bonds such as Au-Au interactions may prove useful to mediate conjugation. Mono-substituted P-phosphinothiophene ligands provide anchored metals an opportunity to directly interact with oligothiophene chains. New P-(phosphino)pentathiophene ligands were prepared by selective substitutions of a,P-functionalized derivatives that display a narrow H O M O / L U M O gap. Binding bis(bipyridine) Ru(II) groups to P-phosphinothiophenes via direct, metal-sulfur (P,S) and metal-P-carbon (P,C) thienyl bonding modes affect the structural and 142  electronic properties of oligothiophenes, and reversible switching between the P,S and P,C bonding modes is mediated by Ru(II)-promoted acid-base chemistry.  Thienyl backbone  conformations appear favorable from the solid-state structures of both bonding modes, and comparatively, the P,C bonding mode displays increased planarity. The Ru(II)-/ ,5' complexes J  exhibit decreased conjugation via electronic inductive effects of the bound Ru(II) metal, while the electron rich oligothiophene moieties of the Ru(II)-.P,C complexes are equivalent electronically to the corresponding (3-phosphinothiophenes.  The bound bis(bipyridine) Ru(II)  group exhibits M L C T absorption and emission transitions that are affected by the bonding mode and thienyl chain length. Destabilization of the Ru(II) center in the P,S bonding mode increases the energy of M L C T transitions compared to the P,C bonding mode that displays low-energy M L C T transitions and a broad absorption region. MLCT-based emission is largely quenched due to |3-phosphinothiophene complexation in both binding modes. Investigation of the oxidized states of Ru(II)-P,C complexes suggested that for the Ru(II)-(phosphino)/je«tathiophene-.P,C complex, the charge mainly resides on the thienyl chain, in contrast to the shorter-oligothiophene Ru(II)-P,C complexes and the Ru(II)-P,5 complexes where the charge primarily resides on the metal. These results demonstrate that oligothiophene chain length and bonding mode result in a reordering of the energy levels. DFT calculations of Ru(II)-/ ,5' and the Ru(II)-P,C complexes >  also predicted a mixed metal-thienyl HOMO.  The MLCT-based absorption transition of this  pentathiophene complex could induce oxidative doping of the rc-conjugated chain, to create a light-harvesting material. The reversibly switchable P,S and P,C bonding modes that mediate conjugation along oligothiophene chains could also find applications as molecular electronic switches. Polymerization reactions towards the preparation of polynuclear polymers have also been attempted, but pure products have not yet been-isolated. Other coupling reactions should be attempted, possibly using the Ru(II)-P, C complexes or new, symmetrical monomers. In conclusion, this thesis has addressed many of the goals initially set for the study. Metal-oligothiophene-hybrid materials have been prepared with attached metal groups that interact with the conjugated chain. Direct metal-oligothiophene (Type II) bonding is found to more strongly alter the properties and display more favorable rc-orbital overlap compared to metals attached in pendent positions to oligothiophene chains (Type I).  Structure-property  relationships have been established relating chain-length, metal-type and the mode of bonding to the electronic properties.  It was intended that this project would be extended to include the  synthesis and characterization of metal-polythiophene complexes, but this goal has not yet been attained.  Finally, possible applications as molecular electronic wires or switches or as light 143  harvesting materials have been suggested by the electronic properties observed for the metaloligothiophene materials, though the practicality of these applications require further evaluation.  7.2 Suggestions  for Future  Work  Several projects found within this thesis could be developed further, and new studies could also stem from this work. The p-bis(phosphino)pentafhiophene ligands that were prepared demonstrated a high-yielding new synthetic route suitable for the synthesis of extended P-phosphinothiophenes and multi-substituted P-phosphinothiophene polymers. The preparation of these new ligands could result in materials with improved conductive properties.  The  Au(I)-bis(phosphino)thiophene complexes displayed aurophilicity that could be potentially 1  useful to mediate conjugation, and these materials could be further evaluated in the solid state by absorption and emission spectroscopy. Decreased Ti-orbital overlap is expected when Au-Au bonds are present, and these interactions can also be identified by Au(I)-based luminescence. Electropolymerized Au(I)-oligothiophene materials would be of interest, and modification of the oligothiophene backbone structure via chain extension or the variation of substituents to promote coupled product is worth pursuing. Studies of the P,S and P,C-bound bis(bipyridine) Ru(II)-phosphinothiophene complexes have provided the most interesting results in this thesis, and these compounds are rich with possibilities for future work. P,C Ru(II) complexes would be interesting to study further, due to their reversible oxidation potentials that enable good characterization of the oxidized species. It is desirable to determine i f a long-lived charge-separated state is formed with excitation of the complexes, which would enable light-harvesting applications. Transients created by excitation could be characterized by their lifetimes and absorption spectra using laser flash photolysis techniques, and these studies are already underway.  Localization of charge on the  oligothiophene chain was observed only for the Ru(II)-(phosphino)pentathiophene-P,C complex, suggesting that a further extended oligothiophene chain would be of interest. Complexes with oligothiophenes of n > 5 chain length could be prepared that may show an improvement in metal-thienyl orbital overlap. Potential materials applications could be evaluated by preparing devices where a Ru(II)-oligothiophene material is drop-cast or spin-coated onto an electrode surface, with contacts deposited on the surface of the film. Photocurrent would be monitored, corresponding to the creation of charge carriers in the material.  144  The investigation of these hybrid materials could also be extended to incorporate Os, as the bis(bipyridine) Os(II) group displays similar charge transfer properties to the bis(bipyridine) Ru(II) group. " Differences in electronic properties for Os(II) complexes include higher energy metal-centered d-orbitals that are less likely to quench MLCT-based emission, a lower O s  III/n  oxidation potential, and increased spin-orbit coupling that can result in more intense transitions to forbidden states.  6  Since the Os"  1711  oxidation potential is lower than that of R u  11I/n  , it is  unlikely that the H O M O would overlap with that of oligo- or polythiophene chains. However, hybrid materials could be potentially used as emitters in organic light emitting diode (OLED) devices if excitons formed along thiophene chains match the M L C T excited state energy. There would be less likelihood in Os(II)-phosphinothiophene systems of emission quenching by low-lying d-orbitals, as was observed for the Ru(II)-phosphinothiophene complexes. Towards the preparation of polynuclear metallated oligo- or polythiophenes, a new route using a symmetric monomer unit is suggested that would result in regioregular materials. Given the results of the coupling reactions that were carried out here, the synthesis of functionalized polythiophene chains followed by metallation is suggested as the most viable route.  The  challenge for designing a symmetric monomer unit is to ensure that there is an unsubstituted thiophene ring next to each phosphine-substituted ring, so that metal-P-carbon bonding can take place. Alkyl groups should also be incorporated to ensure solubility of the resulting oligomers or polymers. It is suggested that a P,P-dibromo-ct,a-diiodobithiophene could be cross-coupled via Suzuki coupling with a thiophene boronic ester to give a bifunctionalized quaterthiophene 7  (Scheme 7-1), or coupled with the bithiophene diboronic ester shown to yield a functionalized polythiophene chain with symmetric quaterthiophene repeating units (Scheme 7-2). The chains would be made soluble in organic solvents by adding two alkyl groups to the central bithiophene units that should arrange anti to one another so rc-orbital overlap is not disrupted. The alkyl groups also block the 3-positions of the starting material so that halogen addition reactions at the desired positions can be more easily performed.  P-Brominated polythiophenes thus prepared  could be subsequently phosphinated and metallated via procedures that have been described to yield complexes such as the Ru-P,C complexes depicted in Chart 7-1. The binuclear complex could be used to model interactions between metals across a rc-conjugated chain, and the properties could then be compared to the polynuclear metal-polythiophene hybrid material.  145  Scheme 7-1  3) Reflux  Scheme 7-2  1) 10 eq CsF 0.05 eq Pd (PPh ) THF  3 4  R  Br,  R  Br  3) Reflux  C h a r t 7-1  Binuclear Metal-Oligothiophene Hybrid Material  Polynuclear Metal-Polythioph Hybrid Material  146  7.3  References  (1)  Bardaji, M . ; Laguna, A. J. Chem. Educ. 1999,76, 201-203.  (2)  Yam, V . W.-W.; L i , C.-K.; Chan, C.-L. Angew. Chem. Int. Ed. 1998, 37, 2857-2859.  (3)  Mamo, A . ; Juris, A.; Calogero, G.; Campagna, S. Chem. Commun. 1996, 1225-1226.  (4)  Mamo, A.; Stefio, I.; Poggi, A.; Tringali, C ; D i Pietro, C ; Campagna, S. New J. Chem. 1997, 21, 1173-1185.  (5)  Caspar, J. V.; Meyer, T. J. Inorg. Chem. 1983, 22, 2444-2453.  (6)  Kalyanasundaram, K . Photochemistry of Polypyridine and Porphyrin Complexes; Academic Press: London, 1992.  (7)  Kirschbaum, T.; Azumi, R.; Mena-Osteritz, E.; Bauerle, P. New J. Chem. 1999, 23, 241250.  (8)  Stott, T. L.; Wolf, M . O. Coord. Chem. Rev. 2003, 246, 89-101.  147  Appendix 1 Crystal Structure Data Table Al-1 Selected crystal structure data for Pd(P2hex2T4)Cl2 (30) Formula  C52H 2P S Cl2Pd  V/A  MW  1044.48  pcalc/g C m  Crystal System  triclinic  Z  Space Group  P\  H (Mo-Ka)/mm  a/A  13.6973(8)  Pcaic/g cm"  1.418  blA  13.7726(9)  R \ wR [/>3o(/)]  0.041,0.082  clA  14.2939(8)  i?, , w^  0.073, 0.089  a/°  73.154(8)  v/A  2445.6(3)  p/°  76.805(9)  Reflections Collected /Unique (Rj„t)  22238/9992 (0.059)  y/O  73.740(9)  GOF  0.93  T/K  173(1)  5  R = S I |F | - |F | | /E|F |. 0  C  0  b  2  2445.6(3)  3  4  1.418  3  2 _1  3  b  x  2  a  b 2  (all data)  3  Rw = {S[w(F - F^^/StwfFo ) ]} " 2  2  0  148  2  1  76  Table A l - 2 Selected Crystal Structure Data for 41, 43, and 45 RuPT -P S(41)  RuPMe T3-/ ,5(43)  R u P D o ^ s - P . S (45)  Formula  C47H39F, 2N4P3S3ORU  C46H37F, 2N4P3S3RU  C 6H8 Fi2N S.5P3Ru  MW  1194.00  1280.11  1578.65  T/K  173(1)  173(1)  173(1)  Crystal System  triclinic  monoclinic  triclinic  Space G r o u p  P\  P2,/a  P\  a/A  10.9127(4)  16.122(2)  12.858(1)  blk  11.2475(4)  15.480(2)  14.6776(9)  elk  20.5749(4)  2.026(3)  20.115(1)  a/°  74.704(6)  90.0  77.793(7)  p7°  76.606(7)  95.67  89.283(7)  y/O  91.102(8)  90.0  87.576(8)  2361.0(2)  5470(1)  3706.9(4)  1.679  1.554  1.41  2  2  2  65.7  57.4  47  22282/9749 (0.046)  192904/12954 (0.057)  32178/14467 (0.053)  [/>2CT(7)J  0.041,0.100  0.032, 0.085  0.074, 0.165  (all data)  0.059,0.106  0.048, 0.091  0.134,0.216  0.99  1.05  1.02  3  v/k  3  Pcalc/g C m "  3  z p. ( M o - K c O / m m "  1  Reflections Collected/ Unique ( R ) int  R\ x  wR  b 2  Ri , wR a  b 2  GOF  J  )1  2  'R, = Z | |F | - |F | 1 /S|F |. w R = {S[w(F -F ) ]/Z[w(F ) ]}' b  0  C  0  2  2  0  2  2  c  149  2  0  2  /2  7  5  4  Table A l - 3 Selected Crystal Structure Data for 47 and 49 .  RuPT -/>,C(47)  RuPMe T -/ ,C(49)  Formula  C 7H38F N40P RuS3  C 6H N F P S Ru  MW  1064.00  1017.98  T/K  173(1)  173(1)  Crystal System  triclinic  triclinic  J  3  4  Space Group  6  2  4  2  P\  36  3  4  6  2  3  P\  a/A  10.1989(3)  9.939(1)  b/A  14.9169(5)  11.999(2)  clA  15.2939(3)  19.528(3)  a/°  77.207(5)  73.361(5)  B/°  79.517(5)  77.896(5)  y/O  88.763(6)  88.836(5)  2230.7(1)  2179.8(5)  1.560  1.551  2  2  63  64.2  Reflections Collected/ Unique (R ,)  20959/9173 (0.045)  60575/11290 (0.053)  Ri\ wR  0.034, 0.040 [/>3a(/)]  0.037, 0.088 [/>2a(7)]  / f , , w / ? ( a l l data)  0.063, 0.090  0.063, 0.107  GOF  1.00  1.06  v/A  3  Pcalc/g " l i "  3  Z /<Mo-Ka)/mm  _1  in  b 2  a  b  2  l  R, = S I |F | - |F | | /Z|F |. w R = {Z[w(F - F ) ]/Z[w(F ) ]} ' b  0  C  0  2  2  0  2  c  150  2  2  0  2  !  

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