Copper(II) and nickel(II) complexes with N′-[(Z)-phenyl(pyridin-2-yl)methylidene]acetohydrazide: Synthesis, crystal structures, DFT calculations and antioxidant effects

Abstract

Two mononuclear copper(II) and nickel(II) complexes viz., [Cu(HL)(L)]NO3·2H2O 1 and [Ni(L)(Neocup)]ClO4·MeOH 2 (where HL/L−=N′-[(Z)-phenyl(pyridin-2-yl)methylidene]acetohydrazide) complexes were synthesized and characterized by routine physiochemical techniques. Both complexes were structurally characterized using single crystal X-ray diffraction studies and belonging to space group P21/n for 1 and P1¯ for 2 respectively. Complex 1 has hexacoordinated geometry with 1:2 metals to ligand ratio whereas complex 2 has pentacoordinated with two ligand and Schiff base and neocuproine donors sites. The room temperature EPR spectrum of 1 shows two S=1/2 signals due to the elongated axial symmetry. Time dependent DFT calculations on the optimized structure of 1 and 2 in DMSO solvent allowed for the assignment of specific electronic transitions in the UV–Vis spectrum. The highest occupied molecular orbital (HOMO) was noted to consist of 55% Cu-d and 100% Ni-d character identified as the dx2–y2 orbital. In addition, antioxidant activity showed that both complexes exhibited significant scavenging effect against super oxide anion from radicals.