Synthesis and properties of gold(I) and Ruthenium(II) complexes of beta-substituted oligothiophenes

• Main Author: Kuchison, Angela Maria
• Language: English
• Published: University of British Columbia 2011
• Online Access: http://hdl.handle.net/2429/31566

Oligothiophenes functionalized in the beta-position with ethynyl and aryl phosphine groups (57 – 59) are reported. Compounds 57 and 59 are used as bridging ligands with Au(I) (80 – 82, 93 – 95), while compounds 57 and 58 are used as tridentate ligands with Ru(II) (104 – 112). The optical and electronic properties of these compounds were studied with absorption and emission spectroscopy, transient absorption spectroscopy, X-ray crystallography, and electrochemistry. The lowest energy absorption bands and emission bands were found to be sensitive to the substituent and conjugation. The lowest energy pi-based absorption band in complex 80 was blue-shifted, while complexes 93 – 95 and 104 – 112 caused a bathochromic shift in the comparable band. Complexes 80, 93 and 94 showed ligand based emission at 295 K, complex 95 at temperatures <185 K, and complexes 104 – 112 were nonemissive. Complex 109 showed a transient absorption at 475 nm with a liftetime of ~100 ns. Grinding a solid state sample elicited changes in absorption and emission of powders of 57 and 80. Grinding powdered 57 caused a temporary emission and absorption band hypsochromically shifted from the unground material, whereas grinding 80 caused a bathochromic shift of the absorption bands and strong emission. These results were attributed to changes in conformation of the terthiophene backbone. Crystal structures of 80, 81, 93 – 95, 105, 109 and 110 gave insight into the ligand binding and conjugation along the terthiophene backbone. Sterically bulky substituents increased the torsion angle between adjacent thienyl units in 57 relative to 59; 80 and 82 relative to 57; and 93 and 94 relative to 59. Solid state structures of complexes 80, 81, and 93 – 95 showed the ligand bridged two Au(I) centres, while structures of 105, 109 and 110 showed 57 binding as a tridentate ligand. The cyclic voltammograms of 57 – 59, 93 – 95, and 104 – 112 were obtained. Compounds 59 and 93 – 95 electrochemically polymerize. Complex 95 and poly-95 have Au(I/II) oxidation waves. Complexes 104 – 110 and 112 also have metal-based oxidation waves. The Ru(II/III) oxidation waves of 104 – 110 were used to determine the ligand electrochemical parameter of 57. === Science, Faculty of === Chemistry, Department of === Graduate