Antibacterial efficacy, spectroscopic, and redox profiling of a cu(II)-sulphadimidine Schiff base complex through DFT computational analysis

Abstract

Schiff bases, with their stable coordination to transition metals, are widely explored in catalysis and biomedical research. This study reports the synthesis and characterization of a Cu(II) complex derived from a Schiff base ligand formed by condensation of 4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulfonamide and 2-hydroxybenzaldehyde. The complex was synthesized by refluxing the Schiff base with Cu(II) chloride in ethanol and characterized using elemental analysis, FT-IR, UV-Vis, 1H-NMR, HRMS, and magnetic susceptibility measurements. Spectroscopic data indicated coordination through the azomethine nitrogen and phenolic oxygen donor atoms, while electronic spectral and magnetic data supported a square-planar Cu(II) environment. The Cu(II) complex exhibited moderate antibacterial activity against Escherichia coli at 100 ppm, with an inhibition zone exceeding 10mm, whereas the free Schiff base showed lower activity. Electrochemical measurements over −2.5 to +2.5 V at a scan rate of 0.1 V s⁻¹ revealed a metal-centered reductive response attributable to the Cu(II)/Cu(I) couple. Molecular docking showed binding affinities of −7.7 and −11.1 kcal mol⁻¹ toward 6LUP and 1EVE, respectively. DFT calculations gave a HOMO-LUMO gap of 0.71 – 0.72 eV, providing insight into the electronic properties of the complex. KEY WORDS: Schiff base, Density functional theory, Molecular electrostatic potential, ADMET, Antibacterial activity Bull. Chem. Soc. Ethiop. 2026, 40(12), 2639-2653.                                                            DOI: https://dx.doi.org/10.4314/bcse.v40i12.10