Co(III) and Ni(II) complexes of an anthracene appended aroyl hydrazone: Synthesis, crystal structures, DNA binding and catecholase activity

The Co(III) and Ni(II) complexes [Co(L2)2(bpy)]Cl (1) and [Ni(L2)2(phen)] (2) (where L2 is a monoanionic bidentate hydrazone ligand and bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been synthesized and characterized by infra-red, UV–Vis, ESI-MS spectroscopies and elemental analyses. Complexes 1 and 2 were structurally characterized by single crystal X-ray diffraction. Structural analysis reveals a distorted octahedral coordination environment around the metal center with an MN4O2 chromophore [M = Co(III) and Ni(II)], with the hydrazone ligand acting as a monoanionic bidentate N,O-donor. Binding of complexes 1 and 2 with calf thymus DNA (CT-DNA) was investigated by UV–Vis absorption, fluorescence spectroscopy and viscosity measurements. Complex 1 shows excellent catecholase mimicking activity with 3,5-di-tert-butylcatechol (3,5-DTBCH2) as the substrate. Kinetic measurements suggest the rate of catechol oxidation follows saturation kinetics with respect to the substrate and the kcat value was found to be quite high, with a value of 1.00 × 105 h−1.

Octahedral Co(III) and Ni(II) complexes containing two bidentate hydrazone ligands have been synthesized. The binding of the complexes with calf thymus DNA (CT-DNA) were investigated. The Co(III) complex possesses significant catecholase activity and the catalytic efficiency is among the highest known for Co(III) model complexes.Figure optionsDownload as PowerPoint slide