MICELLAR EFFECT ON THE PHOTOINDUCED ELECTRON-TRANSFER REACTIONS OF RUTHENIUM(II)-POLYPYRIDYL COMPLEXES WITH PHENOLATE IONS - EFFECT OF CETYLTRIMETHYLAMMONIUM CHLORIDE

Although the emission spectra and excited-state lifetime of Ru(bpy)(3) (2+) (bpy = 2,2'-bipyridine), Ru(dmbpy)(3)(2+) (dmbpy = 4,4'dimethyl-2 ,2'-bipyridine) and Ru(phen)(3)(2+) (phen = 1,10-phenanthroline) are l ittle affected by the addition of the cationic surfactant cetyltrimeth ylammonium chloride (CTAC), an appreciable shift in lambda(max)(em), e mission in tensity and emission lifetime are observed for Ru(dtbpy)(3) (2+) (dtbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) and Ru(dpphen)(3)(2) (dpphen = 4,7-diphenyl-1,10-phenanthroline). These results point out the importance of hydrophobic interactions over the coulombic repulsi on thereby bringing the ruthenium(II) complexes close to the cationic micelles. The rate of luminescence quenching of five Ru-(NN)(3)(2+) c omplexes, with alkyl-substituted phenolate ions in the presence of CTA C, follows different trends depending on the nature of the ligand in R u(NN)(3)(2+) as well as the quencher. The micellar inhibition is expla ined by considering ArO- being strongly associated with CTAC leaving R u(NN)(3)(2+) in the aqueous phase. The micellar catalysis at high [CTA C] with Ru(dtbpy)(3)(2+) and Ru(dpphen)(3)(2+) may be due to the opera tion of predominant hydrophobic interaction over the electrostatic rep ulsion.