pH and Micellar Effects on the Quenching of Tris(2,2′-bipyridine)Ruthenium(II) Luminescence by 1-Alkyl-4,4′ -bipyridinium : Evidence of Deep Embedment of the Quencher Cations in Sodium Dodecyl Sulfate Micelle

Abstract

The effects of pH and sodium dodecyl sulfate (SDS) micelle on the quenching of Ru(bpy)32+ luminescnce by N-alkyl-4,4′-bipyridinium ions (RBPY+ : R=methyl, octyl, dodecyl, benzyl) were investigated. In the absence of SDS, the quenching rate at pH 2 is similar to that of the corresponding methylalkyl viologens and much greater than that in pH 8 solution due to greater reducibility of the protonated form of RBPY+ (HRBPY2+). The quenching rate at pH 2 is strongly enhanced by the presence of SDS, while that at basic pH is greatly retarded. These observations are explained by deep embedment of RBPY+ into the hydrophobic hydrocarbon region of the micelle, whereas Ru(bpy)32+ and HRBPY2+ locate in the Stern layer of the micelle.