KINETICS OF NITROXYL RADICAL OXIDATION BY RU(BPY)(3)(3-DOPED TIN DIOXIDE COLLOIDAL PARTICLES() FOLLOWING PHOTOSENSITIZATION OF ANTIMONY)

Uncharged, water-soluble nitroxyl free radicals are shown by laser fla sh photolysis to be effective reductants of the Ru(bpy)(3)(3+) (bpy = 2,2'-bipyridine) that is produced via photosensitization at the surfac es of colloidal semiconductor particles composed of antimony-doped tin dioxide. The bimolecular rate constant for the reduction of Ru(bpy)(3 )(3+) by the 3-carbamoyl-PROXYL radical in the colloidal suspension, ( 4.9 +/- 0.2) x 10(8) M(-1) s(-1), is about one-third of the rate const ant for the corresponding reaction in homogeneous aqueous solution, (1 .4 +/- 0.1) x 10(9) M(-1) s(-1). The high quantum efficiency for produ ction of Ru(bpy)(3)(3+), 0.93 +/- 0.01, together with the fact that th e oxidized nitroxyl radicals are widely used as oxidants in organic sy ntheses, makes such systems of interest for effecting photocatalytic o xidation reactions.