Sensibilisierte Photolyse von Bis(dimethylglyoximato)cobalt(III)-Komplexen mit axial koordiniertem Azid bzw. Thiophenolat als photochemischen Opferliganden

Abstract

Sensitized Photolysis of Bis(dimethylglyoximato)cobalt(III) Complexes with Axially Coordinated Azide or Thiophenolate as Photochemical Sacrificial Ligands The photolysis of [N3Co(dmg)2pyr] 1a and [PhSCo(dmg)2pyr] 1b (dmg = dimethylglyoxime, pyr = pyridine) is sensitized by both [Ru(bpy)3]Cl22 (bpy = 2,2′-bipyridine) and Michler's thioketone 3 (4,4′-bis(dimethyl-amino)-thiobenzophenone). Quenching of 2 by the cobalt(III) chelates 1a and 1b was studied by luminescence spectroscopy. The quenching rate constants calculated are in the order of magnitude of kq ≅ 106 mol−1 s−1. Polychromatic irradiation (> 250 nm) of 1b and 3 in the presence of thiophenole (PhSH) leads to hydrogen evolution, whereas long-wavelength (546 nm) irradiation does not. The results of these sensitization experiments support strongly a mechanism of catalyzed photolysis of PhSH as proposed earlier.