Spectroscopic studies, structural characterization and electrochemical studies of two cobalt (III) complexes with tridentate hydrazone Schiff base ligands: Evaluation of antibacterial activities, DNA-binding, BSA interaction and molecular docking

Co(III) complexes of tridentate Schiff base ligands derived from N-(2-hydroxybenzylideneamino)benzamide (H2L1) and 2-(2-hydroxybenzylidene)hydrazine-1-carboxamide (H2L2) were synthesized and characterized using IR, Raman, H-1-NMR and UV-Vis spectroscopies. X-ray single crystal structures of complexes 1 and 2 have also been determined, and it was indicated that these Co(III) complexes are in a distorted octahedral geometry. The cyclic voltammetry (CV) of the complexes indicates an irreversible redox behavior for both complexes 1 and 2. The antibacterial effects of the synthesized compounds have been tested by minimum inhibitory concentration and minimum bactericidal concentration methods, which suggested that the metal complexes exhibit better antibacterial effects than the ligands against Gram-positive bacteria. The effects of the drug (drug=ligands and complexes) on bovine serum albumin (BSA) were examined using circular dichroism (CD) spectropolarimetry, and it was revealed that the BSA (BSA, as a carrier protein) secondary structure changed in the presence of the drug. Interaction of the drug with calf-thymus DNA (CT-DNA) was investigated by UV-Vis absorption, fluorescence emission, CV and CD spectroscopy. Binding constants were determined using UV-Vis absorption. The results indicated that the studied Schiff bases bind to DNA, with the hyperchromic effect and non-intercalative mode in which the metal complexes are more effective than ligands. Furthermore, molecular docking simulation was used to obtain the energetic and binding sites for the interaction of the complexes with Mycobacterium tuberculosis enoyl-acyl carrier protein reductase (InhA), and results showed that complex 1 has more binding energy.