Synthesis, crystal structure, electrochemical and anti-corrosion studies of Schiff base derived from o-toluidine and o-chlorobenzaldehyde

Abstract

In this report, a Schiff base, E-N-(2-chlorobenzylidiene)-2-methylaniline, has been synthesized and characterized using Elemental analysis, MS, FTIR, and NMR (1H and 13C) spectroscopic techniques. The structure of the compound was determined by single crystal X-ray diffraction studies. The structure showed a disorder, as if ‘inverted’, around a point between the carbon and nitrogen bridge atoms in a 0.68:0.32 ratio. The methyl and chloride swap positions of the opposite phenyl rings, as well as bridging carbon and nitrogen. The solid state molecular geometry has been compared with the theoretical data obtained using density functional theory (DFT). The ELUMO–HOMO, dipole moments, chemical potential, absolute electronegativity and hardness of the compound were studied by DFT. The corrosion inhibition study of the Schiff base was investigated for mild steel in 1 M HCl medium using electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy) methods. The results showed that the compound exhibited appreciable inhibition efficiency at higher concentration with potentiodynamic polarization studies revealing a mixed-type inhibitor of predominantly anodic type. Scanning electron micrographs (SEM) and EDX studies revealed the film-forming ability of the ligand on the mild steel surface. Some quantum chemical parameters calculated correlate well with the experimental results. Based on the theoretical and experimental results obtained, the enhanced corrosion inhibition efficiency could be ascribed to the presence of the azomethine and the aromatic rings characteristic of the Schiff base.