Synthesis and characterization of an iron(III) complex of an ethylenediamine derivative of an aminophenol ligand in relevance to catechol dioxygenase active site

Abstract

An ethylene diamine derivative of a bis(phenol)diamine ligand (H2L) was synthesized via the Mannich reaction and subsequent ring cleavage of the produced imidazoline ring (H2LIm), and then it was characterized by 1H NMR and IR spectroscopies and CHN analysis. The iron(III) complex (FeLCl) of this ligand was synthesized and characterized by IR, UV–Vis, X-ray and magnetic susceptibility studies. X-ray analysis reveals that in FeLCl the iron(III) center has a distorted square pyramidal coordination sphere and is surrounded by a chlorine atom, two amine nitrogen and two phenolate oxygen atoms of the ligand. Variable-temperature magnetic susceptibility measurements indicate that FeLCl is a paramagnetic high spin iron(III) complex. It shows weak antiferromagnetic interactions through NH⋯Cl intermolecular interactions. The ligand-centered electrochemical oxidation of this complex, due to the oxidation of phenolate group to phenoxyl radicals, as well as the electrochemical metal-centered reduction of the ferric ion to the ferrous ion were investigated. In addition, the efficient cleavage by oxygenation of 3,5-di-tert-butyl-catechol with FeLCl in the presence of dioxygen was observed.