Structurally characterized mononuclear isostructural Ni(II), Cu(II) and Zn (II) complexes as a functional model for phenoxazinone synthase activity

Three new mononuclear complexes of the type [M(L)(2)](ClO4)(2), with Ni(II) (1), Cu(II) (2) and Zn(II) (3) ions, have been synthesized and structurally characterized, using the N,N,O donor Schiff base ligand 2-[(phenyl-pyridine-2-yl-methylene)-amino]-ethanol]. An X-ray diffraction study reveals identical crystallization patterns for each of the complexes, in the monoclinic crystal system with the C2/c space group. Interestingly, the synthesized complexes are isostructural in nature. The complexes showed biomimetic phenoxazinone synthase-like activity for the aerial oxidation of o-aminophenol to phenoxazine-2-one, separately in methanol (MeOH) and acetonitrile (ACN) solutions. For each of the complexes, the turnover numbers were found to be higher in MeOH than in ACN. The highest catalytic activity between among the three complexes was found to be for complex 2. (C) 2019 Elsevier Ltd. All rights reserved.