Characteristics of multidentate schiff base ligand and its complexes using cyclic voltammetry, fluorescence, antimicrobial behavior and DFT-calculations

The electrochemical behavior of a series of the metal complexes [Fe(III), Ni(II), Ru(III),Pd(II) and Hf(IV)]derived from the Schiff base ligand(E)-5-((phenyl(-pyridin-2-yl) methylene) amino) pyrimidine-2,4(1H, 3H)‑dione(H₂L) which was previously prepared from condensation of 5-aminouracil and 2-benzoylpyridine was studied by using cyclic voltammetric technique. The Schiff base ligand H₂L and its metal complexes exhibited quasi- reversible oxidation- reduction with three electron transfer and it was suggested that their reactions on the platinum surface electrode are not purely diffusion controlled but also under adsorption control. The redox reactive sites of the H₂L and its complexes were located via the geometry optimization and frequency calculations using density functional theory (DFT) at the B3LYP/LanL2DZ level of theory. In addition, the Schiff base ligand and its metal complexes exhibit fluorescent properties. The antimicrobial activity of the Schiff base ligand H₂L and its metal complexes was tested against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus(, Gram-negative bacteria (E. coli and Pseudomonas aeruginosa) and fungal strain (Aspergillus niger) by using agar well-diffusion method. The microbial testes of the ligand (H₂L) and its metal complexes exhibited good inhibition efficiency to prevent growth of bacteria.