Synthesis, characterization and biological activities of Co(II), Cu(II), Zn(II), and Cd(II) metal complexes of 1,10 phenanthroline based Schiff base

Abstract A Schiff base ligand prepared from amino acid (L-Histidine) and salicylaldehyde (L1), 1,10 phenanthroline (L2) and its transition metal complexes of general formula [ML1L2] (where M = Co(II), Cu(II), Zn(II), and Cd(II)) has been synthesized and tested for in vitro antimicrobial study against harmful bacterial strains Escherichia coli (gram negative bacteria), Bacillus subtilis, Staphylococcus aureus (gram positive bacteria), and fungal organisms Aspergillus flavus, Rhizophus stolonifer and Mucor ellipsoideus respectively via agar-well diffusion technique. The larvicidal activity of the complexes was tested against Culex quinquefasciatus mosquito. The synthesized complexes exhibited excellent antioxidant properties both by DPPH and Hydrogen peroxide assays. Analytical and spectroscopic techniques such as UV-Visible, FTIR, SEM, NMR, and HRMS were used to characterize the produced Schiff base metal complexes. TGA-DTA analysis was used to investigate the thermal stability of the complexes. The redox characteristics of the complexes were examined using cyclic voltammetry. Cd(II) complex shows the maximum zone of inhibition values 20 mm and 21 mm for S. aureus, and M. ellipsoideus, respectively. Among the synthesized complexes, Cd(II) complex showed highest antimicrobial, larvicidal activity and very good antioxidant property.