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.