Oxidative cyclization and synthesis of benzoxazole derivatives and hydrolytic phosphatase activity studies on dinuclear diphenoxo-bridged zinc(II)complexes

Abstract

Diphenoxo bridged dinuclear zinc complexes, [Zn2(Phimp)2(Cl)2] (1) (PhimpH = (E)-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Zn2(Me-Phimp)2(Cl)2] (2) (Me-PhimpH = (E)-4-methyl-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), [Zn2(OMe-Phimp)2(Cl)2] (3) (OMe-PhimpH = (E)-4-methoxy-2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)phenol), were synthesized and spectroscopically characterized. The molecular structure of 2 was determined using X-ray crystallography. DFT and TD-DFT calculations were performed to optimize the molecular geometry, interpret the spectroscopic results and investigate the contribution of the ligands to the redox properties of the complexes. Phenoxyl radical complexes were generated in solution via chemical oxidation using ceric ammonium nitrate (CAN) and the redox properties were examined through cyclic voltammetric measurements. The hydrolysis of para-nitrophenylphosphate (PNPP) by all the dinuclear zinc complexes was investigated to mimic phosphatase activity. Catalytic oxidative cyclization by these complexes and synthesis of benzoxazole derivatives was investigated.