Synthesis and characterization of novel chelation-free Zn(II)-azole complexes: Evaluation of antibacterial, antioxidant, and DNA binding activity

Abstract

Here, we have synthesized novel chelation-free Zn(II)-complexes (1-3) [ZnCl₂L₂] of monodentate ligands with L= 2-isopropylimidazole (L1), 2-methylbenzimidazole (L2), and 2-methylbenzoxazole (L3) and evaluated their antibacterial, antioxidant and DNA binding activities. The chelation-free properties of these coordination complexes were confirmed by UV-Vis spectroscopy, ¹H-NMR spectroscopy, single X-ray crystallography, and elemental analysis. Complexes 1-3 exhibited substantial antibacterial activity against all antibiotic susceptible bacteria within a concentration range of 100-200 µg/ml while free ligands L1 and L2 exhibited weak antibacterial activity considerably concentration above 200 µg/ml. Also, both complexes 2 and 3 were twice more active against methicillin-resistant staphylococcus aureus (MRSA) than complex 1. Furthermore, we found that complexes 1-3 showed DNA binding activity with E. coli plasmid DNA (pDNA) and calf thymus DNA (CT-DNA), which may be a plausible mechanism for their antibacterial activity. We also investigated the antioxidant activity of complexes 1-3 and found that complex 2 exhibited potential antioxidant activity compared to complexes 1 and 3. All these results suggest that the chelation-free Zn(II)-complexes can be the future candidates for more advanced biological studies.