Cobalt(II) complexes of a benzimidazole functionalized tridented nitrogen-donor iminopyridine ligand: Synthesis, characterization and phenoxazinone synthase activity studies

Abstract

In the present report, a nitrogen-donor benzimidazole functionalized imine based tridentate ligand: 2-(1H-benzo[d]imidazol-2-yl)-N-(1-(pyridin-2-yl)ethylidene)aniline (HL) and its cobalt(II) complex (1) have been synthesized in good yield. The ligand HL is unstable

cyclizes via a C-N bond formation reaction to result a new compound D. The cobalt complex 1 has been characterized by using various physicochemical characterization techniques as well as single crystal X-ray structure determination. The electronic structure of the complex 1 was studied by cyclic voltammetry, UV-Vis spectroscopy and DFT calculations. The complex (1) is an active catalyst for phenoxazinone synthase activity in methanol medium under aerobic condition. The oxidation of 2-aminophenol (OAPH) to 2-aminophenoxazine-3-one (APX) follows a saturation rate kinetics with the formation of a catalyst-substrate adduct. Mechanism of the reaction was studied by ESI-MS and EPR spectroscopy that showed indeed a catalyst-substrate adduct formation during the reaction. A sharp EPR signal at g = 2.006 indicates generation of an organic radical during the oxidation reaction. The catalyst is found to be quite active with a turnover number (Kcat) of 52.5 h-1. © 2018 Scientific Publishers. All rights reserved.