The effect of salts on the rate constants for quenching of luminescence oftris(2,2 '-bipyridyl)ruthenium(II) complexes and on dissociation constantsof radical-ion pairs

Rate constants for luminescence quenching of tris(2,2'-bipyridyl) ruthenium (II) complexes (Ru(bpy)(3)(2+)) by sulfite ions and the ionic form of 1-bro mo-2-naphthol (-OArBr) and the yields of free radical ions from radical-ion pairs (gamma) are measured as functions of the salt concentration in an aq ueous solution. It is reliably established that upon addition of inorganic salts (NaClO4, Na2SO4, Na2SO3, KBr) to the system, the yield of radical ion s reduces with increasing salt concentration in both cases. However, the ab solute yields gamma of radical ions from (Ru(bpy)(3)(+)... SO3.-) and (Ru(b py)(3)(+)...(OArBr)-O-.) radical-ion pairs and their dependences on salt co ncentration differ dramatically. The commonly accepted model allowing for v ariation in the diffusion rate of the reagents and formation of ion pairs u pon addition of salts fails to account for the results obtained. Alternativ e models are also considered.