Quenching of excited tris(2,2'-bipyridine)ruthenium(II) by metal 1,2-dithiolene complexes

Abstract

The quenching of excited Ru(bpy)/sub 3//sup 2 +/ by MS/sub 4/C/sub 4/(C/sub 6/H/sub 5/)/sub 4/ and MS/sub 4/C/sub 4/(CN)/sub 4//sup 2 -/ (M = Ni, Pt) has been studied in CH/sub 3/CN and DMF. The dynamic quenching rate constants, which are nearly diffusion controlled, have been analyzed in terms of diffusional parameters and unimolecular quenching constants. The unimolecular quenching constants for the MS/sub 4/C/sub 4/(CN)/sub 4//sup 2 -/ quenchers are lower by 2 orders of magnitude than those for the MS/sub 4/C/sub 4/(C/sub 6/H/sub 5/)/sub 4/ quenchers, and this effect has been attributed to a different degree of adiabaticity. The quenching mechanism has been investigated by using sacrificial scavengers for oxidized or reduced (Ru(bpy)/sub 3//sup 2 +/. Evidence for oxidative quenching by the MS/sub 4/C/sub 4/(C/sub 6/H/sub 5/)/sub 4/ complexes was obtained. For the MS/sub 4/C/sub 4/(CN)/sub 4//sup 2 -/ quenchers, either energy transfer or reductive electron transfer followed by very efficient cage recombination is a possible quenching mechanism. 48 references, 4 figures, 2 tables.