TEMPO-mediated aerobic oxidation of alcohols using copper(II) complex of bis(phenol) di-amine ligand as biomimetic model for Galactose oxidase enzyme

Abstract

Mononuclear copper complexes of four-dentate N2O2 bis(phenol) diamine ligands (H2LNEX X: C and OB in which C and OB are chloro and tert-butyl-methoxy substituents on phenol groups) have been synthesized and characterized by IR, UV–Vis, single crystal X-ray diffraction, magnetic susceptibility studies and cyclic voltammetry techniques. The CuLNEX complexes show the square pyramid geometry of the coordination sphere with the copper centers surrounded by two nitrogen and oxygen atoms from the coordinating ligand and an axially bound water molecule. The effective magnetic moments of 1.7 and 1.8BM confirm a monomer complex with copper(II) center. Electrochemical oxidation of these complexes yielded the corresponding Cu(II)-phenoxyl radical species. In addition, CuLNEX complexes, have shown efficient catalytic activities for TEMPO-mediated oxidation of a set of alcohols to the corresponding aldehydes in the presence of molecular oxygen as oxidant at room temperature.