Antimicrobial activities and docking studies of new Schiff base ligand and its Cu(II), Zn(II) and Ni (II) Complexes: Synthesis and Characterization

Abstract

New Schiff base ligand (E)-2-(((7-chloro-2-hydroxyquinolin-3-yl) methylene) amino)-3-phenylpropanoic acid was synthesized using 2,7-dichloroquinoline-3-carboaldehyde and Phenylanine in ethanol. Using new ligand Copper, Zinc and Nickel complexes were also synthesized and characterized using FTIR, UV–Vis, 1H NMR, 13C NMR, TGA-DTA, and pXRD spectroscopic techniques. From its FTIR spectra, the synthesized Schiff base ligand was verified to be a tridentate ligand containing ONO active binding sites. To evaluate the Schiff base and its metal complexes' antibacterial properties, the disc diffusion method was employed. The antibacterial activity the ligand at a concentration of 100 µg/ml against B. cereus, S. aureus, E. coli, and S. typhi were found to be 10.00 ± 0.41, 6.05 ± 0.21, 8.00 ± 0.408, and 7.17 ± 0.236, respectively, whereas its antifungal activity against C. albinas was found to be 11.25 ± 0.204. Zinc complex showed antibacterial activities against B. cereus (9.33 ± 0.62), S. aureus (12.08 ± 0.42), E. coli (9.50 ± 0.40), S. typhi (6.75 ± 0.20), C. albinas (10.33 ± 0.24) at a concentration of 100 µg/ml whereas the nickel complex exhibited a bit lower activities against B. cereus (6.05 ± 0.22), S. aureus (6.58 ± 0.11), E. coli (6.08 ± 0.11), S. typhi (6.50 ± 0.22), C. albinas (7.50 ± 0.25) at a concentration of 100 µg/ml. On the other hand, the copper complex showed relatively highest antibacterial activity against B. cereus (18.67 ± 0.41), S. aureus (25.05 ± 0.41), E. coli (21.08 ± 0.31), S. typhi (22.05 ± 0.07), and the antifungal activity against C. albinas was 24.08 ± 0.43 than the other two complexes and the ligand. The overall results showed that the copper complex was found to have good antibacterial and antifungal activities. This is mostly caused by its small crystalline size (29.7 nm), which was inferred from the pXRD results.