Synthesis, crystal structure, theoretical investigation and catalytic activity study of mononuclear nickel(II) complex.

Abstract

A mononuclear square planar complex of [Ni(o-val)2]·2H2O (NiL2) (where o-val is o-vanillin anion) has been synthesized by reacting nickel(II) chloride hexahydrate with o-vanillin followed by characterization of the complex by UV–Vis and FT-IR spectroscopic techniques and single-crystal X-ray diffraction analysis technique. Theoretically calculated IR frequencies well matched with the experimental data in solid state. HOMO–LUMO energy of the complex has been calculated in gas phase as well as in solvent phase (MeOH, EtOH and DMF) to predict the kinetic stability of the complex. Presence of H-bonding interaction within the complex with lattice water molecule was supported by Hirshfeld surface analysis, and the calculated H-bonding energy was found to be 7.5368 kJ/mol. Complex NiL2 (L = o-val) was found to be active for catalysing the oxidation of 3,5-DTBCH2 to 3,5-DTBQ under aerobic condition in methanol solvent with turnover number (kcat) 230 h‒1. Phenoxazinone synthase activity of the complex NiL2 was also investigated using 2-aminophenol as a model substrate in methanol medium, and the kcatvalue was found to be 45 h‒1.