Synthesis and computational studies of novel cobalt(II) and oxovanadium(IV) complexes of quinoline carbaldehyde derivative ligand for antibacterial and antioxidant applications

Abstract

Novel metal complexes [Co(HL)2(H2O)2)] (1) and [VO(HL)2] (2) were synthesized using 2-((2-hydroxyethyl)amino)quinoline-3-carbaldehyde, ligand in 1:2 metal–ligand ratio in methanolic solution. The compounds were characterized with 1HNMR, 13CNMR, UV–Visible spectroscopy, fluorescence spectroscopy, FTIR Spectroscopy; powder X-Ray Diffraction, Scanning Electron Microscopy – Energy Dispersive X-Ray Spectroscopy, Mass Spectroscopy and thermogravimetric analysis. The FTIR spectral data showed that the ligand is bidentate that bound to metal ions through the nitrogen of amine (NH) and the deprotonated hydroxyl group (OH). The powder XRD and SEM results indicate that both the complexes showed polycrystalline nature. The formation constants of the complexes were determined spectroscopically and the values are 2.05 × 106 and 6.29 × 105 for Co(II) and V(IV) complexes respectively). Both metal complexes are stable at the specified temperatures, and the thermodynamic parameters indicated that the reactions are spontaneous with exothermic nature of metal-ligand interactions. Antibacterial activities of the complexes were evaluated with disk diffusion and agar dilution method. The Co(II) complex showed recognizable bacterial activity, against Pseudomonas aeruginosa with mean inhibition zone of 20.65 ± 0.18, with minimum inhibitory concentration (MIC) values of 3.25 µg/mL. Additionally, the antioxidant activity of the complexes were also determined in vitro using 1,1-diphenyl-2-picryl hydrazyl, in which Co(II) complex showed higher antioxidant activities with half maximal inhibitory concentrations IC50 of 9.15 µg/ml. The results of binding mode of these compounds against receptors Escherichia coli, Pseudomonas aeruginosa and Streptococcus pyogenes were in good agreement with the in vitro biological activity results.