Homo- and heteroleptic 3-methylbenzoates of zinc(II) ion based on N-donor heterocycles; structure, DNA binding and pharmacological evaluation

Abstract

Herein, one homoleptic (C1) and three heteroleptic zinc(II) carboxylates (C2-C4) were synthesized by using 3-methylbenzoic acid (HL) as primary ligand and N- donor heterocycles, i.e., 2,2′-bipyridine (C2), 1,10-phenanthroline (C3) and 2,9-dimethyl-1,10-phenanthroline (C4) as hetero-ligands. The complexes were characterized by multiple techniques that include (1H and 13C) nuclear magnetic resonance (NMR), Fourier Transform infrared (FTIR) spectroscopy and single crystal X-ray diffraction (XRD) analysis. The FTIR spectra of complexes suggested different coordination modes of the carboxylate ligand around the metal center. The single crystal XRD analysis confirmed dinuclear (C2 and C3) complexes having five coordinated zinc centers with distorted square pyramidal geometry, whereas in the mononuclear complex C4, the tetra-coordinated zinc(II) has a distorted tetrahedral geometry that can also be regarded as five coordinated if the bonding of oxygen (O4) lying at the margined distance of Zn-O bond is to be considered. The SS-DNA interaction study has shown enhanced DNA binding affinity for the heteroleptic complexes C2-C4 compared to the free ligand acid HL and homoleptic complex C1. The in vitro antibacterial and antifungal study validated the chelation theory and overtone’s concept. The enzyme inhibition study data revealed a concentration dependent inhibition of the alkaline phosphatase by the synthesized complexes.