Mixed-ligand complexes of platinum(II) and palladium(II) with 1,10-phenanthroline and aromatic chelating ligands containing OH of SH groups as photosensitizers for the generation of 1O 2

Abstract

[M(phen)(XX)] complexes (where M is Pd II or Pt II), phen is 1,10-phenanthroline and XX is a dianion of catechol (CAT), 4 tert-butylcatechol (BCAT), 3,4-dimercaptotoluene (DMT) or thiosalicylic acid (TSA) photosensitize the photo-oxidation of 2,2,6,6,-tetramethyl-4-piperidinol in a molecular-oxygen-saturated solution of dimethylformamide (DMF) when irradiated with light of wavelent 300 – 800 nm. This photo-oxidation reaction involves singlet molecular oxygen ( 1O 2) as an intermediate. The presence of 1O 2 is demonstrated by quenching with bis(di- n-butyldithiocarbomato)-nickel(II) or 10%waterDMF. The ralative efficiency of the various complexes is as follows: [Pd(phen)(BCAT)] > [Pt(phen)(BCAT)] > [Pd-(phen)(CAT)] > [Pt(phen)(CAT ] > [Pd(phen)(TSA)] > [Pd(phen)(DMT)]. This order depends on the net ligand field of the mixed ligands attached to palladium(II) and platinum(II) in these complexes.