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Femtosecond Transient Absorption Anisotropy Study on [Ru(bpy) 3 ] 2+ and [Ru(bpy)(py) 4 ] 2+ . Ultrafast Interligand Randomization of the MLCT State

2005; American Chemical Society; Volume: 109; Issue: 21 Linguagem: Inglês

10.1021/jp0509212

1520-5215

Staffan Wallin, Jan Davidsson, Judit Modin, Leif Hammarström,

Electron Spin Resonance Studies

It is known that the relaxed excited state of [Ru(bpy)3]2+ is best described as a metal to ligand charge transfer (MLCT) state having one formally reduced bipyridine and two neutral. Previous reports have suggested [Malone, R. et al. J. Chem. Phys. 1991, 95, 8970] that the electron "hops" from ligand to ligand in the MLCT state with a time constant of about 50 ps in acetonitrile. However, we have done transient absorption anisotropy measurements indicating that already after one picosecond the molecule has no memory of which bipyridine was initially photoselected, which suggests an ultrafast interligand randomization of the MLCT state.