SENSITIZED PHOTOLYSIS OF BIS(DIMETHYLGLYO XIMATO)COBALT(III) COMPLEXES WITH AXIALLY COORDINATED AZIDE OR THIOPHENOLATE AS PHOTOCHEMICAL SACRIFICIAL LIGANDS

The photolysis of [N3Co(dmg)(2)pyr] la and [PhSCo(dmg)(2)pyr] 1b (dmg= dimethylglyoxime, pyr=pyridine) is sensitized by both [Ru(bpy)(3)]C-2 2 (bpy=2,2'-bipyridine) and Michler's thioketone 3 (4,4'-bis(dimethyl- amino)thiobenzophenone). Quenching of 2 by the cobalt(III) chelates la and Ib was studied by luminescence spectroscopy. The quenching rate c onstants calculated are in the order of magnitude of k(q) congruent to 10(6) mol(-1) s(-1). Polychromatic irradiation (>250 nm) of Ib and 3 in the presence of thiophenole (PhSH) leads to hydrogen evolution, whe reas long-wavelength (546 nm) irradiation does not. The results of the se sensitization experiments support strongly a mechanism of catalyzed photolysis of PhSH as proposed earlier.