Photoinduced electron-transfer reactions of micelle-forming surfactant ruthenium(II) bipyridyl derivatives

Abstract

A series of surfactant ruthenium(II) bipyridyl derivatives have been prepared having either one or two long alkyl chains on a single bipyridine. The critical micelle concentrations of the chloride salts of the complexes were determined using surface tensiometry, and aggregaton numbers were obtained from static light-scattering measurements. In addition, photophysical properties of the complexes were examined as a function of the degree of aggregation. The emission maximum for complexes of the type [(bpy)₂ Ru(L-L]²⁺ L-L = surfactant bipyridine, exhibits a bathochromic shift of ca. 15 nm upon micellization. Luminescence quenching of one complex, [(bpy)₂Ru(MC17)²⁺(MC17 = 4-methyl-4′-heptadecyl-2-2′-bipyridine), with methyl viologen (MV²⁺) was examined as a function of the surfactant complex concentration by both static and dynamic luminescence measurements. Quenching of micellized complex was found to be at least a factor of 20 slower than quenching of the free surfactant complex. The photoreduction of Mv²⁺ by the complex in the presence of a sacrificial electron donor, EDTA, was also examined as a function of the concentration of [(bpy₂Ru(MC17)]²⁺. Quantum yields for MV²⁺ photoreduction were determined and compared with values obtained using [Ru(bpy)₃]²⁺ under similar conditions.