Synthesis, Molecular Docking, and antibacterial evaluation of Quinoline-Derived Ni(II), Cu(II) and Zn(II) complexes

We hereby report the synthesis of novel Ni(II), Cu(II) and Zn(II) complexes of (E)-2-(((7-chloro-2-hydroxyquinolin-3-yl)methylene)amino)-3-methylbutanoic acid ligand obtained by reacting 2,7-dichloroquinoline-3-carboaldehyde and amino acid, valine for antibacterial applications. The ligand and the metal complexes were characterized using FT-IR, UV–Vis, TGA/DTA, pXRD spectroscopic techniques and density functional theory (DFT) calculations. The Schiff base ligand was tridentate with ONO active binding sites as confirmed from its FT-IR spectral analysis. Disc diffusion method was used to assess the antibacterial potential of the Schiff base ligand and its metal complexes. The Schiff base ligand shows antibacterial activities of 8.33 ± 0.471 mm at concentration of 100 µg/ml and 9.33 ± 0.471 mm at concentration of 200 µg/ml against S. aureus. However, the copper complex exhibited zone of inhibition of 11.50 ± 0.408 mm at concentration of 100 µg/ml and 12.67 ± 0.471 mm at concentration of 200 µg/ml against S. aureus. This indicates that the copper complex has better antibacterial activity than the free Schiff base ligand. The overall result revealed the promising potential of the metal complexes for application as antibacterial agents. The DFT calculated absorption spectra agree with the corresponding experimental results. The molecular docking analyses also provided important insights on the interaction of the synthesized complexes with the target proteins.