Synthesis and DNA interaction studies of Ni(II), Cu(II) and Co(II) complexes with a polyamine ligand containing homopiperazine; X-ray crystal structure of Cu(II) complex

Macroayclic complexes of Ni(II), Cu(II) and Co(II) were synthesized via the reaction of 1,4-bis(o-aminobenzyl)-1,4-diazacycloheptane (L) with the respective metal salts. The polyamine ligand and the corresponding complexes were characterized by mass spectrometry, elemental analysis and FT-IR and for [CuL](ClO4)2(2), by a single crystal X-ray structural analysis which revealed the copper was in a square planar environment. The interaction of the ligand and its complexes with calf thymus DNA (ct-DNA) at pH 7.4 was investigated by UV–Vis, competitive fluorescence spectroscopic methods and dynamic viscosity measurements. These results of these experiments supported intercalative mode of binding. The competitive fluorescence studies in the presence of methylene blue (MB) as an intercalator probe showed that the ligand and its complexes were able to release MB from DNA helix. Viscosity measurements were in good agreement with the results of the competitive fluorescence, indicating that all compounds are intercalating species.