Synthesis and characterization of an iron(III) complex of glycine derivative of bis(phenol)amine ligand in relevance to catechol dioxygenase active site

A glycine derivative of bis(phenol)amine ligand (HL(Gly)) was synthesized and characterized by (1)H NMR and IR spectroscopies. The iron(III) complex (L(Gly)Fe) of this ligand was synthesized and characterized by IR, UV-Vis, X-ray and magnetic susceptibility studies. X-ray analysis reveals that in L(Gly)Fe the iron(III) center has a distorted trigonal bipyramidal coordination sphere and is surrounded by an amine nitrogen, a carboxylate and two phenolate oxygen atoms. The mentioned carboxylate group acts as mu-bridging ligand for iron centers of neighbor complexes. The variable-temperature magnetic susceptibility indicates that L(Gly)Fe is the paramagnetic high spin iron(III) complex. It has been shown that electrochemical oxidation of this complex is ligand-centered due to the oxidation of phenolate to the phenoxyl radicals. The L(Gly)Fe complex also undergoes an electrochemical metal-centered reduction of ferric to ferrous ion. The oxygenation of 3,5-di-tert-butyl-catechol, with L(Gly)Fe in the presence of dioxygen was investigated. (C) 2011 Elsevier Ltd. All rights reserved.