Structural, spectroscopic, and biological properties of an asymmetric Cu (II) Schiff-base complex: Synthesis, DNA/BSA interactions, and antimicrobial potential with experimental and computational insights

A copper (II) complex with the asymmetric bidentate Schiff-base ligand (E)-2-(((4-chlorophenyl) imino) methyl) phenol was synthesized and characterized using FTIR and UV–VIS spectroscopy. Photoluminescence studies were conducted on both the copper (II) complex and the free ligand. XRD analysis revealed the copper (II) complex crystallizes in the monoclinic system, space group P21/c. The complex structure was optimized using DFT calculations with B3LYP/6-31G+(d,p) and Lanl2dz basis sets, with QTAIM and NBO analyses confirming complex formation. The energy gap of the copper (II) complex was determined to be 3.701 eV (alpha state) and 2.764 eV (beta state). MEP analysis of the optimized structure indicated a hydrophobic environment around the nitrogen atom, with the molecule exhibiting overall hydrophobicity. The chlorine atoms were identified as potential nucleophilic sites. The antimicrobial efficacy of a Schiff base copper (II) complex was evaluated against selected pathogenic bacteria (B. subtilis, B. megaterum, K. pneumoniae, E. coli) and the fungus Candida albicans. Among these C. albicans for complex showed larger zones (11–15.5 mm) at higher concentrations such as 2 and 2.5 mg/mL. Molecular docking studies suggested strong binding affinity between the complex and the target protein, this was further supported by obtained root means square deviations, root means square fluctuations, radius of gyration and hydrogen bond values during simulations. The binding free energy between BSA and the copper (II) complex was calculated as −8.7 kcal/mol, indicating significant interaction. However, only weak van der Waals interactions were observed between the complex and DNA. Toxicity studies revealed the copper (II) complex had minimal irritant effects on ocular and cutaneous tissues, with a low lethal dose. In comparison, Tricresyl phosphate showed moderate to severe ocular irritancy and modest cutaneous irritancy.