Synthesis, crystal structure, spectral characterization and antimicrobial activity of Zn(II) and Ni(II) compounds with the Schiff base ligand 3, 5-dichlorosalicylaldehyde o-phenylenediamine

Abstract

Two novel compounds namely Zn(L1)(H2O) 1 and Ni(L1) 2 (L1 = 3, 5-dichlorosalicylaldehyde o-phenylenediamine) were synthesized by the slow evaporation method of aqueous solution at room temperature. The structure of the ligand L1 was optimized using DFT, and it was demonstrated that the potential coordination sites between the calculated metal ions and the ligand structure were consistent with the experimental results. X-ray single-crystal diffraction analysis indicated that compounds 1-2 formed 2D supramolecular layer structures through π···π stacking or hydrogen bonding interactions. Hirshfeld surface analysis revealed that Cl…H interactions were the predominant interactions in compounds 1-2. Furthermore, the energy framework analysis indicated that dispersion energy played a dominant role in the energy composition of these compounds. The results of antibacterial experiments for Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA) indicated compound 1 was a potential antibacterial agent for MRSA (inhibition zone: 15 mm). The ion release capacity of compounds 1-2 was evaluated by ion release experiments, resulting in the release of Zn(II) ions (24.81 µg/mL after 4 days) and Ni(II) ions (14.40 µg/mL after 4 days). Molecular docking analysis revealed the interaction modes of compounds 1-2 with UDP-N-acetylenolpyruvoylglucosamine reductase (MurB) and dihydrofolate reductase (DHFR) in bacteria, which involved hydrophobic, stacking, hydrogen bonding, and halogen bonding interactions. Potential antibacterial mechanisms of compounds 1-2 were proposed.