Synthesis, Spectral Characterization, Antimicrobial Screening and DNA Binding, Cleavage Studies of Transition Metal Complexes of Heterocyclic Ligand Derived from 4-aminoantipyrine and 2-Mercaptobenzimdazole

A new Mannich base 4-((2-mercapto-1H-benzoimidazol-1-yl)methylamino)-1,5-dimethyl-2- phenyl-1H-pyrazol-3(2H)-one was synthesized from 2-Mercapto benzimidazole, formaldehyde and 4-aminoantipyrine. Further the new ligand was made to react with metal(II) chlorides to obtain the metal complexes[ Cu(II), Ni(II), Co(II) and Zn(II) complexes]. The structure of the complexes has been investigated by using elemental analysis, IR, UV-ViS, ¹H NMR, ¹³C NMR, EPR, Mass spectra, magnetic susceptibility and conductivity measurements. The elemental analysis and spectral studies indicate octahedral geometry for all the complexes. The electrochemical property of the ligand and its metal complexes has been studied by cyclic voltammetry. Biological screening of the ligand and metal(II) complexes have been carried on Streptococci, Staphylococcus aureus, Pseudomonas, Klebsilla Pneumoniae, Chromo bacterium, Candida albicans by the well diffusion method which indicate that the metal(II) complexes possess higher activity than the free ligand. The binding properties of metal complexes with DNA were investigated by viscosity measurements. Detailed analysis reveals that the metal complexes intercalate into the DNA base stack as intercalators. The DNA cleavage ability of all the complexes was examined on calf thymus (CT-DNA) plasmids using gel electrophoresis experiment in presence of H₂O₂. From the results it is concluded that all the complexes cleave DNA.