Studies on heterocyclic anchored Cu(II) complexes with ONO pincer type donor ligand as an efficient biomimetic and anticorrosion agent

Abstract

Four complexes of the composition [Cu(ASBINH) (H2O)],(1), [Cu(ASBINH)imdz],(2), [Cu(ASBINH)py],(3) and [Cu(ASBINH)2],(4) have been synthesized. These complexes are novel due to the presence of newly synthesized ONO tridentate pincer type ligand, anchored with imidazole/pyridine as a co-ligand. The structure of ligand ASBINH and complexes 1–4 has been discussed in the light of molar conductance, magnetic susceptibility, electronic spectra, FT-IR, 1H-NMR, 13C-NMR, ESI-MS, TGA and EPR analysis. The structure of compounds has been satisfactorily modelled by density functional theory calculations. The FT-IR data have suggested the presence of diazo and azomethine group in the ligand and the ligand is coordinated with metal through azomethine-N and phenolic-O. 1H-NMR and 13C-NMR of ligand exhibit correlation coefficient of 0.964 and 0.990 respectively. EPR spectrum of complex 1 at RT and LNT suggests a distorted square-planar geometry around Cu(II). Solvent effects on the keto-enol equilibria of ligand ASBINH were observed using electronic spectra. The ligand was in keto-enol tautomeric equilibrium in polar and non-polar solvents. The μeff values for the complexes fall at ∼1.72 BM which rules out the possibility of any M-M interaction in the structural unit of the complexes. The synthesized complexes display efficiency in the disproportionation reactions of hydrogen peroxide. Moreover, imidazole anchored complex 2 shows excellent catalytic activities for the disproportionation of H2O2. The kinetics of the catalase-like activity was investigated and data was applied to Lineweaver Burk plot, which reveals Michaelis Menten behaviour of complexes. The corrosion inhibition performance of ligand and complexes on mild steel in 1 M HCl solution was studied by weight loss measurement method.