Photoinduced intra-molecular electron transfer in aniline-containing Ru(II) polypyridine complexes

Abstract

The photoinduced intra-molecular electron transfer in three aniline-containing Ru(II) polypyridine complexes, [Ru(bpy) 2(bpy-bmam)](PF 6) 2 ( 2), Ru(dcbpy)(bpy-bmam)(NCS) 2 ( 3), and Ru(dcbpy)(bpy-mam)(NCS) 2 ( 4) (bpy-bmam=4,4′-bis( N-methyl-anilinomethyl)-2,2′-bipyridine, bpy-mam=4-methyl-4′-( N-methyl-anilinomethyl)-2,2′-bipyridine, dcbpy=4,4′-dicarboxyl-2,2′-bipyridine, bpy=2,2′-bipyridine), was investigated using steady-state and time-resolved absorption and emission spectra, and photoinduced inter-molecular electron transfer between [Ru(bpy) 2(dmbpy)](PF 6) 2 ( 1) (dmbpy=4,4′-dimethyl-2,2′-bipyridine) and N, N-dimethylaniline was also studied for comparison. While inter-molecular reductive quenching of 1’s emission by aniline was less efficient, nearly half emission was quenched intra-molecularly in 2. Upon photoinduced electron injection onto the conduction band of TiO 2 from 3 or 4 anchored on the TiO 2 surface, intra-molecular electron transfer from aniline moiety to Ru(III) orbital occurred rapidly with rate constants of 3.4×10 7 and 2.6×10 7 s −1, respectively, restricting the interfacial recombination of injected electrons with Ru(III) and as a result improving the photoelectrochemical behavior of 3 or 4 when used in dye-sensitized nanocrystalline semiconductor solar cells.