Synthesis, structural characterization, antimicrobial, antioxidant and DNA binding studies of some novel homo-binuclear Schiff base metal (II) complexes

A novel bi-nucleating Schiff base ligand, 6,6'-(((1E,1'E)-thiophene-2,5-diylbis (methaneylylidene))bis (azaneylylidene))bis (3,4-dimethylaniline), and five binuclear M (II) complexes were synthesized. The bi-nucleating Schiff base ligand and its metal complexes were characterized using various physicochemical techniques, e.g. elemental analyses, spectroscopic methods, conductivity and magnetic moment measurements. The low molar conductance of the complexes in dimethylsulfoxide shows their non-electrolytic nature. The antibacterial activities were screened against pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Pseudomonas putida and Bacillus subtilis). The antifungal activity was screened against Aspergillus niger, Aspergillus flavus and Rhizoctonia bataicola. The antimicrobial activity data showed that the metal complexes are more potent than the parent Schiff base ligand against microorganisms. The antioxidant activities of the synthesized compounds were investigated through scavenging activity against 2,2-diphenyl-2-picrylhydrazyl, superoxide anion, hydroxyl and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radicals. The complexes have superior radical scavenging activity than the free ligand and the scavenging effects of the Cu (II) complex are stronger than those of the other complexes. DNA binding studies were performed using electronic spectroscopy, fluorometric competition studies and viscosity measurements. The data indicated that there is a marked enhancement in biocidal activity of the ligand under similar experimental conditions because of coordination with metal ions.