Synthesis and characterization of Cu(II), Co(II) and Ni(II) complexes of a benzohydrazone derivative: Spectroscopic, DFT, antipathogenic and DNA binding studies

Abstract

Co(II), Ni(II) and Cu(II) complexes of a benzohydrazone derivative, obtained by the reaction of dehydroacetic acid and benzohydrazide, have been synthesized and characterized by conventional spectroscopic techniques, elemental analyses, magnetic susceptibility and conductivity methods, and screened for antibacterial, DNA binding and cleavage properties. Spectroscopic, magnetic and elemental analyses indicated a square planar and a tetrahedral geometries with formula, [M(L)2], for the Ni(II) and Co(II) complexes, respectively, while a tetrahedral geometry of formula, [ML(H2O)2]·CH3COO−, was adopted for the Cu(II) complex. The Ni and Co complexes were non-electrolytes with molar conductance within the range of 11.46–14.01 Ω−1cm2mol−1, while the copper complex was a 1:1 electrolyte in DMSO with a value of 55.11 Ω−1cm2mol−1. The copper complex had the highest antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA by agarose gel electrophoresis in the presence and absence of peroxide oxidant (H2O2) and free radical scavenger (DMSO), indicated no activity for the ligand, and a moderate activity for the complexes, with the copper complex cleaving more efficiently in the presence of H2O2. Upon evaluating the complexes for antimicrobial and A-DNA activities using molecular docking technique the copper complex was found to be most effective against Gram-positive (S. aureus) bacteria. [CuL(H2O)2]+ showed good interaction with hydrogen bonding with the major-groove (C2.G13 base pair) of A-DNA. Density functional theory (DFT) calculations of structural and electronic properties of complexes revealed that [CuL(H2O)2]+ had a smaller HOMO-LUMO gap, suggesting a higher tendency to donate electrons to electron accepting species of biological targets.