Synthesis, structural elucidation, DFT, and antimicrobial evaluation of novel Cu(II)-hydrazone Schiff base complexes

Abstract

Herein, we report the synthesis, characterization, antimicrobial evaluation, and density functional theory (DFT) analysis of two hydrazone Schiff bases (L1 and L2) and their homoleptic and heteroleptic copper(II) complexes (Cu(L1)2, Cu(L2)2, and CuL1L2). The compounds were successfully characterized via Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis), and nuclear magnetic resonance (NMR) spectroscopies, as well as melting point determination, conductivity and magnetic susceptibility measurements, mass spectrometry, thermogravimetry, and X-ray crystallography. Antimicrobial activity was evaluated against some bacteria and fungi using the agar diffusion method. DFT analysis was performed with a hybrid functional, B3LYP, and Def2TZVP basis set. NMR and FTIR spectra confirmed ligand formation and coordination of the metal through imine and carbonyl groups. A single crystal was obtained only for L1 after several attempts. Conductivity data, UV-visible spectra, and magnetic moment values of the complexes were all in favor of the square planar geometry. All the synthesized compounds displayed satisfactory antimicrobial potency, with L2 and CuL1L2 showing superior activity against Pseudomonas flurescens and Candida albican, compared to the standard drug (Chloramphenicol). The DFT results not only corroborated the experimental findings but also provided valuable insights into the mechanism of action of the synthesized compounds. KEY WORDS: Antimicrobial resistance, DFT, Homoleptic and heteroleptic copper(II) complexes, Hydrazone Schiff base, p-toluic acid hydrazide Bull. Chem. Soc. Ethiop. 2026, 40(10), 2097-2114.                                  DOI:  https://dx.doi.org/10.4314/bcse.v40i10.4