Synthesis, spectroscopic and electrochemical studies of N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine and its Cu(II) complex: DNA cleavage and generation of superoxide anion

A novel tetradentate Cu(II) complex of the type, [CuL](NO(3))(2) was synthesized by the interaction of Schiff base ligand, N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine, L obtained by the condensation of thiophene-2-carboxaldehyde and 1,8-diaminonaphthalene. The formation of Schiff base ligand, L and its Cu(II) complex was confirmed on the basis of results of elemental analyses, mass, FT-IR, (1)H and (13)C{(1)H} NMR spectral studies. UV-Vis, EPR and magnetic susceptibility data support a square planar environment around Cu(II) ion. However, molar conductance values confirmed 1:2 electrolytic nature for the Cu(II) complex. The electrochemical studies of Cu(II) complex was carried out by using cyclic voltammetry which revealed the complex to exhibit quasi reversible process. The biological activity of Cu(II) complex such as ability to bind DNA and DNA cleavage were studied where the Cu(II) complex was shown to cause considerable DNA cleavage and also generated reactive oxygen species such as superoxide anion. Since it is known that various anticancer drugs act through induction of oxidative stress that is mediated by reactive oxygen species, our results suggest a putative role of Cu(II) complex similar to various anticancer drugs.