Seven coordinated cobalt(II) complexes with 2,6-diacetylpyridine bis(4-acylhydrazone) ligands: Synthesis, characterization, DNA-binding and nuclease activity

A new series of pentadentate 2,6-diacetylpyridine bis(4-acylhydrazone)s (H2L1 and H2L2) based seven-coordinated cobalt(II) complexes, [Co(L-n)X-2] (n = 1 and X = DMF for (1); n = 2 and X = H2O for (2)); [Co(H2Ln)Y-2] (n = 1 or 2; Y = N-3 or NCS ), has been synthesized and characterized by using spectroscopic techniques. Single crystal X-ray study of [Co(L-1)(DMF)(2)] (1) complex exhibits pentagonal-bipyramidal coordination geometry where the pentadentate N3O2 ligand in the equatorial plane of the bipyramid and two dimethylformamide molecules in the axial area. Interaction of the cobalt(II) complexes with CT DNA has been investigated by absorption titration method and viscosity measurements which reveal that the cobalt(II) complexes could bind with CT DNA through intercalation. Cleavage activity of the complexes (1) and (2) with pBR 322 plasmid DNA was evaluated by agarose gel electrophoresis demonstrating that the ability of the complexes to cleave the pBR 322 plasmid DNA via oxidative pathway, possibly due to the involvement of a diffusible hydroxyl radical mechanism in presence and absence of an oxidative agent. The nuclease activity of the Co(II) complexes has strong dependence on the concentration of complex and reaction time, both in presence and absence of hydrogen peroxide. (C) 2015 Elsevier B.V. All rights reserved.