Photoinduced Electron Transfer Reactions of Ruthenium(II) Phenanthroline Complexes with Dimethylaniline in Aqueous and Micellar Media

Four [Ru(NN) 3 ] 2+ complexes (NN = polypyridine) with ligands of varying hydrophobicity with different charges +2, 0 and −4 were synthesized. The photophysics and photoinduced electron transfer reactions of these Ru(II)-complexes with dimethylaniline (DMA) as the quencher have been studied in aqueous medium and ionic and non-ionic micellar medium. The extent of binding of the complexes with the surfactant interface is evident from the calculated binding constant values (K). Dimethylaniline (DMA) being a neutral quencher, the hydrophobic and electrostatic interactions competing with one another and their combined effect with the surfactants were reported by observing the quenching rate constant (k q ) values. The formation of anilinium cation radical in transient absorption spectrum confirms the excited state electron transfer reactions of ruthenium(II) complexes with dimethylaniline. The calculated rate constant values (k q ) are in good agreement with the experimental k q values giving quantitative evidence for the bimolecular reductive quenching rate constant for the complexes with DMA. Pseudophase ion exchange model is successfully applied to analyse the quenching data.