Models for enzyme–substrate adduct of non-heme iron-containing enzymes, synthesis and characterization

Mononuclear iron(III) complexes of (HNEt3)[FeLNEC(TBC)], (HNEt3)[FeLNEB(TBC)] and (HNEt3)[FeLNEM(TBC)] as new models for enzyme–substrate adducts of catechol dioxygenases have been prepared and characterized, where H2LNEC, H2LNEB and H2LNEM are amine bis(phenolate) ligands with chlorine, bromine and methyl substituted phenol groups and TBC is a tetrabromo catecholate dianion. These complexes were characterized by IR, UV–vis, elemental analysis and magnetic measurements. X-ray structure analysis of complexes has revealed that the iron(III) core in the model compounds is a distorted octahedral coordination sphere and surrounded by two phenolate oxygen atoms, two amine nitrogens and two oxygen atoms of TBC. UV–vis spectroscopy exhibits two intense absorption bands in the range of 450–650 nm in dichloromethane. These bands are assigned to the catecholate and ligand to Fe(III) charge-transfer bands. The electrochemical features of the adduct complexes were investigated in dichloromethane solution by employing cyclic voltammetry (CV).