Visible light driven photodegradation of methylene blue with two reduced Schiff base complexes of zinc(II): Exploration of their phosphatase mimicking ability

Abstract

Two dinuclear zinc(II) complexes, [(SCN)Zn(L)(μ1,3-OAc)Zn(DMSO)] (1) and [(dca)Zn(L)(μ1,3-OAc)Zn(DMSO)] (2), {H2L = 2,2′-[(2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)]bis[6-ethoxy-phenol]and dca = dicyanamide} have been synthesized and characterized. X-ray crystallographic analyses have confirmed their structures. Both the complexes have shown excellent phosphatase mimicking activity {kcat ~ 266 h−1 for complex 1 and 204 h−1 for complex 2 at 298 K}, evaluated spectrophotometrically by monitoring the increase in absorbance at ~425 nm, indicating the gradual release of 4-nitrophenolate by the hydrolysis of 4-nitrophenylphosphate ester with time, when 4-NPP (disodium 4-nitrophenylphosphatehexahydrate) has been used as substrate. Both complexes have also been found to be efficient photocatalyst for the degradation of methylene blue (MB). The degradation efficiency reaches to ~90% (for both complexes) using 15 mg of catalyst in 100 mL 20 mg/L MB solution within 35 min.