A LASER FLASH-PHOTOLYSIS STUDY OF MAGNETIC-FIELD EFFECTS IN PHOTOINDUCED ELECTRON-TRANSFER BETWEEN RU (BPY) 3(2+) AND N,N'-DIMETHYLVIOLOGEN IN MICELLAR SOLUTIONS

The kinetics of electron transfer between photoexcited Ru(bpy)3(2+) and N,N'-dimethylviologen (MV2+) have been studied by means of laser flash photolysis in sodium dodecyl sulfate (SDS) and sodium laurate (SL) micelles. The decay of photoexcited Ru(bpy)3(2+) follows first-order kinetics with k(obs) almost-equal-to 10(6)-10(7) s-1, and dependences of k(obs) versus surfactant and quencher concentrations were obtained. Analysis of the data showed that the quenching is mainly intramicellar. Although SDS solutions show no escape of the radicals MV+ and Ru(bpy)3(3+) from the micelles, for solutions of SL micelles an escape value phi-es almost-equal-to 0.08 was determined. The dependences of phi-es on the concentration of SL and SDS show a drop in the vicinity of the cmc. Radical MV+ is not incorporated into the SL micelles. An increase of phi-es in the SL micelles up to 20-25% was observed under application of an external magnetic field (B = 0.2-0.47 T) during steady-state irradiation and laser flash photolysis studies. The magnetic field effect is mainly described according to a hyperfine coupling mechanism. Geminate recombination kinetics of the pair 3[MV+, Ru(bpy)3(3+)] was observed in both SDS and SL micelles. Pertinent kinetic analyses were made and the requirements for geminate recombination kinetics observations were discussed.