Aspects of Artificial Photosynthesis. Photosensitized Electron Transfer and Charge Separation in Redox Active Surfactant Aggregates

Article abstract of DOI:10.1021/j100242a040

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)COO(CH2)11(C5H4N⁺)2CH3, Br^-, I^- (RMV²⁺).Tris(2,2'-bipyridine)ruthenium chloride (Ru(bpy)3²⁺) has been used as a sensitizer.Forward electron transfer from excited Ru(bpy)3²⁺ to RMV²⁺ aggregates has been shown to be faster than that from Ru(bpy)3²⁺ to methylviologen (MV²⁺) in homogeneous solutions.Conversely, the undesirable back-reactionbetween the reduced electron acceptor RMV⁺. and the oxidized sensitizer Ru(bpy)3³⁺ has been found to be considerably retarded compared to the reaction between MV⁺. and Ru(bpy)3²⁺.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 repulsion between the positively charged aggregates and Ru(bpy)3³⁺.