Synthesis, Characterization, DFT Analysis, Biological Evaluation, and Molecular Docking of Schiff Base Derived from Isatin–Isoniazid and Its Metal (II) Complexes

A series of octahedral Zn(II), Cu(II), Ni(II), and Co(II) complexes have been synthesized with ONO donor Schiff base ligand N'-(6-chloro-2-oxoindolin-3-ylidene)nicotinohydrazide (3) derived from the reaction of 6-chloro isatin (1) and isoniazid (2). The chemical structures of the compounds were elucidated by spectral and physicochemical techniques. The spectral data reveal the octahedral geometry for all the metal (II) complexes. The compounds were screened for their antibacterial and antifungal activity; all the metal (II) complexes exhibited enhanced activity. The Cu(II) and Co(II) complexes displayed equipotent anti-TB activity when evaluated with standard Ciprofloxacin. Furthermore, the Ni(II) and Co(II) complexes showed excellent antioxidant activity compared to the standard drug. Density Functional Theory (DFT) estimations for ligand (3) at the DFT/B3LYP level via 6-31 G++ (d, p) replicate the structure and geometry. Finally, HOMO and LUMO analysis was used for the charge transfer interface of the structure. The Cu(II), Ni(II), and Co(II) complexes exhibited good docking properties in molecular docking studies against Cytochrome c Peroxidase (2 x 08).