| Abstract
| - Excitation of Ru(deeb)(bpy)22+, bis(2,2‘-bipyridine)(2,2‘-bipyridine-4,4‘-diethylester)ruthenium(II) hexafluorophosphate, bound to nanocrystalline TiO2 thin films and immersed in an acetonitrile bath at 25 °Cunder an argon atmosphere, results in the formation of a species, the transient spectral characteristicsfor which are, consistent with a metal-to-ligand charge transfer, MLCT, excited state. The spectrum decaysby kinetics that are inconsistent with a simple first-order process. Modeling of the data as a function ofirradiance has been accomplished assuming parallel unimolecular and bimolecular excited-state deactivationprocesses. The quantum yield for excited-state formation depends on the excitation irradiance, consistentwith triplet−triplet annihilation processes that occur with k ≥ 1 × 108 s-1.
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