Photosensitized electron transfer and charge separation have been demonstrated by steady-state and nanosecond laser flash photolysis in the presence of redox active surfactant aggregates prepared from CH2=C(CH3)COC(CH2)11(C 5H4N+)2CH3,Br -,I- (RMV2+). Tris(2,2′-bipyridine)ruthenium chloride (Ru(bpy)3 2+) has been used as a sensitizer. Forward electron transfer from excited Ru(bpy)3 2+ to RMV2+ aggregates has been shown to be faster than that from Ru(bpy)3 2+ to methylviologen (MV2+) in homogeneous solutions. Conversely, the undesirable back-reaction between the reduced electron acceptor RMV+· and the oxidized sensitizer Ru(bpy)3 3+ has been found to be considerably retarded compared to the reaction between MV+· and Ru(bpy)3 2+. Further, unlike MV+·, RMV+· decayed by a two-step process. These results have been rationalized in terms of a mechanism which requires most of the photosensitized forward electron transfer to occur on the surface of RMV2+ aggregates. Subsequently, some of the oxidized sensitizer escapes the potential field of RMV2+ and charge recombination is retarded by electrostatic repulsions between the positively charged aggregates and Ru(bpy)3 3+.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry