Micellar effect on the photophysics of heteroleptic ruthenium(II)-phenanthrolinedisulfonato complexes.

Luminescent heteroleptic ruthenium(II) complexes of type RuLn X(3-n) [L = 1,10-phenanthroline (phen), X = 4,7 diphenyl phenanthroline disulfonate, (dpsphen) n = 0,1,2,3] were synthesized and their photophysical properties investigated in homogeneous and cationic (CTAB), anionic (SDS) and nonionic (Triton X-100) micelles. The luminescent quantum yield and lifetime of the complexes were found to increase in the presence of micellar media and on the introduction of a disulfonate ligand into the coordination sphere. Both electrostatic and hydrophobic interactions play an important role in the micellar media. Thus, by changing the nature of the ligands and the medium, we were able to tune the photophysical properties of Ru(II) complexes.

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.