Synthesis, characterization and spectroscopic studies of nickel (II) complexes with some tridentate ONN donor Schiff bases and their electrocatalytic application for oxidation of methanol

Some tridentate Schiff base ligands (L1-L5) and their nickel complexes [NiL(PR3)]; (where L1 = N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L2 = 3-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L3 = 5-Bromo-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L4 = 5-nitro - N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L5 = 5-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile) were synthesized and characterized by IR, UV-Vis, 1H NMR spectroscopy. The geometry of [NiL2 (PPh3)] and [NiL5 (PPh3)] were determined by X-ray crystallography. Density theoretical calculations were performed to optimize the structures of the ligands and complexes, and their IR spectra using density functional theory (DFT). The time-dependent density functional theory (TD-DFT) was employed to calculate the absorption spectra of the structures. Also, nickel complexes were electrochemically dispersed on multi-walled carbon nanotubes (MWCNTs) and their electrocatalytic properties for oxidation of methanol have been studied by cyclic voltammetry.99