Pyrazole bridged binuclear transition metal complexes: Synthesis, characterization, antimicrobial activity and DNA binding/cleavage studies

A new ligand system having pyrazolato endogenous bridging component and N4S2 donating sites is synthesized by the condensation of 3,5-dichloroformyl-1H-pyrazole with phenylthiosemicarbazide. Both ligand and its binuclear CoII, NiII, CuII and ZnII complexes are characterized by the spectral and analytical methods. All the complexes were found to be binuclear monomeric in nature with octahedral geometry and nonelectrolytes. Electrochemical activity is observed only for the CuII complex in the applied potential range. Ligand and complexes were screened for antimicrobial activity and made to interact with Escherichia coli DNA to investigate the binding/cleaving ability by absorption, hydrodynamic, thermal denaturation and electrophoresis studies. The copper complex exhibited higher inhibition against a gram negative bacterium, E. coli and shown good intercalating ability with E. coli DNA.

► Pyrazole based complexes act as good antibacterial agents and DNA intercalators.
► The intercalating interaction with DNA of Escherichia coli caused a change its conformation.
► The ligand acts as hexadentate tribasic chelate with N4S2 donating sites.
► All complexes are binuclear in nature with octahedral geometry.