A New Dinuclear Copper(II)-Hydrazone Complex: Synthesis, Crystal Structure and Antibacterial Activity

Increasing microbial resistance has become a threatening situation for humanity. Therefore, new active antimicrobial compounds are needed to be synthesized. Copper complexes, one of these types of biologically active compounds, appear as compounds with a wide range of biological uses. Many scientific investigations have shown that copper complexes have antibacterial, antimalarial, anti-inflammatory, and anticancer activities. In this study, a new bis-copper(II) complex based on a hydrazone ligand (Ligand A) was designed, synthesized, and evaluated as an antimicrobial agent. The characterization of copper(II) complex was mainly done with single crystal X-ray diffraction and other spectroscopic techniques (FT-IR and Elemental Analysis). In order to determine the chemical structure and vibrational properties, theoretical calculations were carried out. Vibrational wavenumbers and HOMO-LUMO energy gap of copper(II) complex were investigated using the DFT/ B3LYP method, LanL2DZ basis set. The agreement between experimental and theoretical results were observed. Information about local and global chemical activity, the electrophilic and nucleophilic nature of copper(II) complex were theoretically obtained. The ligand and its copper(II) complex were investigated for their antibacterial effects against Gram (+) and Gram (-) bacteria. The results show that copper(II) complex was more effective in reducing cell viability of Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus epidermidis than free hydrazone ligand, whereas it was not effective towards Gram (-) forms. Copper(II) complex displayed the highest antimicrobial activity against Staphylococcus aureus ATCC 25923 and S. epidermidis CECT 4183. The results suggested that the designed metal complex can be a good alternative to similar complex systems as an antimicrobial agent. Besides, there are not many studies in the literature on the antibacterial activities of the copper(II) complex and its ligand. For this reason, the study will contribute to the literature.