2021 Synthesis, Characterization and Antibacterial Activity of Schiff Base, 4-Chloro-2-{(E)-[(4-Fluorophenyl)Imino]Methyl}Phenol and Its Transition Metal (II) Complexes

Abstract

The mortality rate in the world continues to increase due to severe challenge of multidrug resistance in treating a host of bacterial infections. Therefore, an effort to develop new antibacterial agents with novel mechanisms of action, higher activity and improved selectivity to address and counter this antibiotic resistance is important. This will avert significant threats posed to human and animal survival. Schiff base transition metal (II) complexes have exhibited great promise with regard to structural modification of existing drugs and reversing bacterial resistance. In this study, new Mn (II), Co (II), Ni (II), Cu (II) and Zn (II) complexes of the Schiff base ligand, L, 4-chloro-2-{(E)-[(4-fluorophenyl)imino]methyl}phenol derived from 5-chlorosalicylaldehyde and 4-fluoroaniline were synthesized. The ligand and the complexes obtained were characterized by Fourier-Transform Infrared, Ultraviolet-visible, and Nuclear Magnetic Resonance Spectroscopy. The elemental analysis data showed that the metal com¬plexes formed had the general formulae [ML2(H2O)2], where M = Mn (II), Co (II), Ni (II), Cu (II) and Zn (II). The spectroscopic data showed that “O” and “N” donor atoms of the Schiff base ligand participated in coordination to the transition metal (II) ions. An octahedral geometry was thus proposed for these complexes. Molar conductance studies on the complexes indicated they were non-electro¬lytic in nature. The Schiff base ligand and its transition metal (II) complexes were tested in vitro to evaluate their antibacterial activity against Gram negative bacteria (Escherichia coli and Pseudomonas ae¬ruginosa) and Gram positive bacteria (Bacillus subtilis and Staphylococcus typhi) using the disc diffusion method. The evaluation results revealed that the transition metal (II) complexes exhibited higher anti¬bacterial activity than the free Schiff base ligand against the same bacterial strain. The increased activity of the complexes might be due to partial sharing of the positive charge of metal ion with the donor groups of the Schiff base ligand.