Synthesis and structural investigation of o-Vanillin scaffold Schiff base metal complexes: Biomolecular interaction and molecular docking studies

Schiff base metal complexes such as VNPV (VO(IV)), VNPCo (Co(II)), VNPNi (Ni(II)), VNPCu (Cu(II)) and VNPZn (Zn(II)) have been synthesised by using the ligand (VNP) which was prepared by the condensation reaction of o-Vanillin and N-phenyl-o-phenylenediamine. Elemental analysis, UV–visible, FT-IR, ESI-MS, ESR, 1H NMR, XRD, SEM and Cyclic Voltammogram methods were used to evaluate the above metal complexes. The metal center in the complexes is four coordinated by using the tetradentate N2O2 donar Schiff base ligand to form square pyramidal geometry for VO(IV) metal complex and square planar geometry for other metal complexes. The disc well-diffusion method was used on agar plate to assess the in vitro antibacterial activities of the ligand and its metal complexes against bacteria such B. amyloliquefaciens, B. cereus, B. subtilis, S. epidermidis and S. aureus. From the results demonstrate that the metal complexes of the ligand exhibit better antibacterial behaviour on S. aureus bacteria than the other bacterial strains. The antioxidant studies were carried by DPPH free radical scavenging assay method and from the results it is found that the VNPCu complex has better antioxidant activity than the ligand and other metal complexes. Additionally, the spectral techniques like UV–visible absorption, fluorescence and molecular docking methods were used to examine the interactions between the ligand and metal complexes with biomolecules (DNA and BSA). The CT-DNA cleavage activities of metal complexes with CT DNA were examined by gelelectrophoretic method. From the results, the VNPCu complex has only cleave the DNA molecules than the other metal complexes. According to the results of the investigations, the metal complex VNPCu exhibits better interaction with the biomolecules than the free ligand and other metal complexes.