Synthesis, Spectral Studies, Corrosion Inhibition Potential, Density Functional Theory Calculations and Molecular Docking Simulation of CU(II) Complexes having Pentadentate Schiff Base Ligand

Abstract

A pentadentate Schiff base ligand and its binuclear copper(II) complexes were synthesized from 2,6-diformyl-4-methylphenol and                                4-nitro-o-phenylenediamine in a 1:2 molar ratio. The ligand, with N₂O₃ donor sites, coordinates with two Cu(II) ions after phenolic deprotonation. Structural characterization by ¹H NMR, ¹³C NMR, IR, UV–Vis, ESR, and conductivity measurements confirmed non-electrolytic behavior in DMF and supported a square planar geometry for the Cu(II) centers. Corrosion inhibition studies on mild steel in 0.1 N HNO₃ at 298 K showed high efficiency, attributed to adsorption of the compounds and formation of a protective barrier layer. Density functional theory calculations, including electrostatic potential mapping, HOMO–LUMO energy gap analysis, and Mulliken charges, were consistent with experimental observations. Molecular docking with the human estrogen receptor and breast cancer-associated protein (PDB ID: 5GIX) revealed favourable binding interactions, indicating potential biological activity of the Cu(II) complexes.