Biomimetic catalytic activities of copper (II) ferrocenecarboxylate complexes with nitrogen based ligands as catechol oxidase and phenoxazinone synthase and for oxidative coupling of 2,6-dimethylphenol

Abstract

Biomimetic catalytic activities of copper (II) ferrocenecarboxylate complexes with nitrogen based ligands as catechol oxidase and phenoxazinone synthase and for oxidative coupling of 2,6-dimethylphenol

A.Latif Abuhijleh Chemistry Department, Birzeit University, P.O.Box14, West Bank, Palestine. E-Mail: latif@birzeit.edu

Copper is one of the most important metals ,beside Fe and Zn, present in several metalloenzymes and is involved in a large number of biological functions including enzyme-catalyzed reactions [1]. Binary and ternary copper carboxylate complexes have been used as biomimetic of copper containing enzymes. As part of our ongoing research on the study of biomimetic activities of copper (II) carboxylate complexes with biologically important nitrogen based ligands, we report here the results of our studies on the synthesis and oxidase catalytic activities of copper(II) complexes of ferrocenecarboxylate with nitrogen donor ligands pyrazole and 1,2-dimethylimidazole. The complexes, bis(ferrocenecarboxylato) tetrakis(pyrazole) copper(II) (1) and cis-bis (ferrocenecarboxylato) bis(1,2-dimethylimidazole) copper(II) (2) have been prepared from the reaction of tetrakis(ferrocenecarboxylato) bis(tetrahydrofuran) dicopper(II) and the appropriate base. Based on the spectral results for complex (1), the Cu(II) ion is coordinated in the plan with four nitrogen atoms of pyrazoles and the axial sites are occupied by oxygen atoms from two ferrocenecarboxylato groups to yield Cu[N]sub4+ O[sub]2 chromophore. We had previously determined crystal structure of complex (2) by X-ray crystallography. In this complex the copper ion is in a cis- square-planar environment consisting of two imidazole nitrogen atoms and a carboxylate oxygen atom from each ferrocenecarboxylato ligand . The second oxygen atoms of the carboxylate functionalities are involved in weak interactions with the copper ion in the axial positions. The biomimetic catalytic oxidase activities of complexes 1 and 2 toward the aerobic oxidations of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butyl-o-benzoquinone (3,5-DTBQ) (catecholase activity), and o-aminophenol (OAP) to o-amino-3H-phenoxazine-3-one (APX) (phenoxazinone synthase activity) have been studied and the results will be presented. In addition, the results of the catalytic activities of these complexes for C-O polymerization or C-C dimerization coupling of 2,6-dimethylphenol (DMP) will be presented

[1] S.E. Allen, R.R.Walvoord, R. Padilla-Salinas, and M.C.Kozlowski, Chem.Rev. 2013 ,113, 6214