Synthesis, DNA binding properties and antibacterial activity of lanthanide complexes with 2-benzoylpyridine isonicotinoylhydrazone

Abstract

Lanthanide(III) complexes of general formula [Ln(BPINH)₂(NO₃)](NO₃)₂ (where, Ln = La, Ce, Pr, Nd, Sm, and BPINH = 2-benzoylpyridine isonicotinoylhydrazone) have been synthesized under mild reaction conditions with excellent yields. The structure of BPINH is determined using single crystal X-ray diffraction studies. The lanthanide complexes have been characterized by elemental analysis, molar conductance and various spectral techniques such as FT-IR, UV-vis, IR and ¹H-NMR spectroscopies. Electrolytic nature of complexes is investigated by conductivity studies. The spectral data suggest that the ligand acts as a neutral tridentate NNO-donor system. Electrochemical behaviour of metal complexes is investigated by using cyclic voltammetry. The complexes undergo quasi-reversible one-electron reduction. Absorption titration studies reveal that these complexes are avid binders (K_b = 10⁵) to calf-thymus DNA. The antibacterial activities of the ligand and its lanthanide complexes have been screened in vitro against, Bacillus subtilis (MTCC-441) and Staphylococcus aurous (MTCC-3160) which are gram positive and Salmonella typhi (MTCC-735) and Escherichia coli (MTCC-1652) which are gram negative organisms. It has been observed the lanthanide complexes show more pronounced activity than the ligand (BPINH).