Mixed-Ligand Palladium(II) and Platinum(II) Complexes—Photosensitizers of 1O2 Production and Chemical Quenchers of 1O2

Abstract

Abstract [M(nn)(dhn)] (where M is Pd(II) or Pt(II), nn is 2,2′-bipyridine, 1,10-phenanthroline, 2,2′-biquinoline, or 4,7-diphenyl-1,10-phenanthroline, and dhn is dianion of 2,3-naphthalenediol) photooxidizes the 2,2,6,6-tetramethyl-4-piperidinol in N,N dimethylformamide via 1O2 when irradiated with light of wave-lengths of 420 to 800 nm in presence of molecular oxygen. The presence of 1O2 as an intermediate is confirmed by quenching studies using bis(dibutyldithiocarbamato)nickel(II) and 20% water in DMF. The relative efficiency of 1O2 production sensitized by the above complexes depends on nature of metal, ligand, and geometry of the complexes. However, [Pd(bpy)(dmt)] and [Pd(phen)(dmt)] undergo photooxidation via 1O2 when sensitized by hematoporphyrin IX and its metal derivatives on photolysis under similar conditions. The relative efficiency of 1O2 production depends on the nature of metal in porphyrin.