Seven-coordinated cobalt(II) complexes with 2,6-diacetylpyridine bis(4-hydroxybenzoylhydrazone): synthesis, characterisation, DNA binding and cleavage properties

Synthesis and characterisation of three seven-coordinated cobalt(II) complexes of 2,6-diacetylpyridine bis(4-hydroxybenzoylhydrazone) (H4L) ligand, [Co(H2L)(H2O)(2)] (1), [Co(H4L)(N-3)(2)] (2) and [Co(H4L)(NCS)(2)] (3) are described. The structures of the complexes were characterised by elemental analysis, IR, UV-vis and magnetic susceptibility measurement. The molecular structure of the [Co(H4L)(NCS)(2)] (3) was also determined by X-ray crystallography. Single crystal X-ray revealed that the Co(II) complex (3) has a pentagonal-bipyramidal coordination geometry, with pentadentate N3O2 ligand in the equatorial plane of the bipyramid and two isothiocyanato groups in the axial area. Interaction of the cobalt(II) complexes with CT-DNA was investigated by absorption titration method and viscosity measurements. Cleavage activity of the complexes with pBR 322 plasmid DNA was evaluated by agarose gel electrophoresis in presence and absence of an oxidative agent, and the mechanism of DNA cleavage was investigated. The results suggest that the cobalt(II) complexes bind effectively and they exhibit nuclease activity, which has strong dependence on the concentration of complex and reaction time, both in presence and absence of hydrogen peroxide.