Investigation of 1O2 generation by water-soluble α-diimine complexes of platinum(II) and palladium(II) with 3,4-dihydroxybenzoic acid as photosensitizers

✍ Scribed by Victor Anbalagan; T.S. Srivastava

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 609 KB
• Volume: 66
• Category: Article
• ISSN: 1010-6030
• DOI: 10.1016/1010-6030(92)80007-i

✦ Synopsis

Eight complexes with the formula [M(N-N)(DHBA)] (where MS Pd(I1) or Pt(II), N-N is 2,2'-bipyridine (BPY), 2,2'-biquinoline (BIQ), l,lO-phenanthroline (PHEN), 4,7-diphenyll,lO-phenanthroline (DPP) and DHBA is 3,4_dihydroxybenzoic acid dianion) were found to photosensitize the oxidation of 2,2,6,6-tetramethyl4-piperidinol (NH) in N,N-dimethylformamide (DMF) to the nitroxide radical. This photo-oxidation reaction involves singlet molecular oxygen ('0,) as an intermediate and its presence was confirmed by quenching studies using bis(diethyldithiocarbamato)nickel(II), a well known '02 quencher. The ability of these complexes to photosensitize the above photo-oxidation reaction follows the order, [Pt(PHEN)(DHBA)] -Hz0 > [Pt(DPP)(DHBA)] -Hz0 > [Pt(BIQ)(DHBA)] > [Pd(PHEN)-(DHBA)] > [Pt(BPY)(DHBA)] > [Pd(DPP)(DHBA)] > [Pd(BPY)(DHBA)] .CHsOH > [Pd(BIQ)(DHBA)].

This order depends on the metal ion, the nature of the a-diimine ligand and the geometry of the metal complex.