Oxidant dependent oxidation of copper bound catecholate: Catecholase versus catechol dioxygenase activity

Abstract

A series of new mixed ligand copper complexes CuII(PBI)(O2Ncat) (1) (PBI=2-(2-pyridyl)-benzimidazole), CuII(DMPBI)(O2Ncat) (2) (DMPBI=5,6-dimethyl-2-(2-pyridyl)-benzimidazole), CuII(PBO)(O2Ncat) (3) (PBO=2-(2-pyridyl)-benzoxazole), CuII(PBT)(O2Ncat) (4) (PBT=2-(2-pyridyl)-benzothiazole), and Cu(TBA)(O2Ncat) (5) (TBA=4-(1H-1,3-benzodiazol-2-yl)-1,3-thiazole) have been synthesized by classic organic, bioinorganic methods. The complexes have been found to mimic catechol oxidase and catechol dioxygenase activity depending on the oxidant used. Triplet state dioxygen activates the complex leading to intradiol cleavage product, 2-nitromuconic acid while sterically more demanding tert-butyl hydroperoxide (TBHP) oxidizes the 4-nitrocatechol (4-O2NcatH2) ligand into 4-nitrobenzoquinone. We have also found that the electron density on the copper center significantly increase the reactivity toward the oxidant used.