Synthesis, Spectral Investigation, DFT, Antibacterial, Antifungal and Molecular Docking Studies of Ni(II), Zn(II), Cd(II) Complexes of Tetradentate Schiff-Base Ligand

By refluxing 4-nitro-o-phenylenediamine and 5-nitro salicylaldehyde, a new Schiff base ligand was synthesized. By reacting the appropriate precursor with the tetradentate Schiff base ligand, three nitro-substituted nickel(II), zinc(II) and cadmium(II) complexes were synthesized. UV-Visible, FTIR and 1H NMR spectral investigations were used to characterize the ligand. Molar conductance, LC-MS, UV-visible and FTIR spectrum analysis were used to characterize the synthesized metal(II) complexes. The ligand and metal(II) complexes were also tested for antibacterial activity. DFT simulations were performed at the B3LYP/6-311G (d,p) and LanL2dz levels of theory were utilized to study the geometry of the Schiff base ligand and the metal(II) complexes. In addition, the molecular orbital occupancy of HOMO and LUMO, as well as the molecular electrostatic potential (MEP), were computed. Molecular docking investigation were conducted utilizing the active sites of the E. coli FabH-CoA complex (PDB ID: 1HNJ) receptor in order to detect the interactions between metal(II) complexes and define their likely binding locations.