INTERLIGAND ELECTRON-TRANSFER AND TRANSITION-STATE DYNAMICS IN RU(II)TRISBIPYRIDINE

The interligand electron transfer (ILET) dynamics in the excited metal-to-ligand charge transfer state of Ru(II)trisbipyridine have been studied using picosecond time-resolved absorption polarization spectroscopy. The ILET dynamics have been studied in several solvents with widely varying relaxation times, and over the temperature range of -85-degrees-C to room temperature. The solvents studied include acetonitrile, propanol, ethylene glycol, and glycerol. The results show that ILET is relatively fast in acetonitrile (approximately 47 ps), slower and nonexponential in propanol and ethylene glycol (approximately 30-200 ps), and fast in glycerol (approximately 30 ps). The glycerol results are roughly temperature independent. These results can be understood in terms of a model in which photoexcitation places the system near the ILET transition state and solvent relaxation competes with ILET in the nascent distribution. Following solvent relaxation a slower, steady state (probably transition state theory) rate is obtained.