Synthesis, Characterization, and Electrochemical Properties of Bis(2-benzimidazolylmethyl-6-sulfonate)amine-based zinc(II), copper(II), and oxidovanadium(IV) Complexes: SOD Scavenging, DNA binding, and Anticancer Activities

The synthesis of a tridentate ligand, bis(2-benzimidazolylmethyl-6-sulfonate)amine H(2)SBz is described together with its zinc(II), copper(II), and oxidovanadium(IV) complexes [SBz-M(H2O)(2)] (M = Zn2+ 1, Cu2+ 2, and VO2+ 3). The ligand and its metal complexes 1-3 were characterized based on elemental analysis, conductivity measurements, spectral, and magnetic studies. The magnetic and spectroscopic data indicate a square pyramidal geometry is proposed for all complexes. The redox properties of the ligand and its complexes 1-3 were extensively investigated by using cyclic voltammetry. Complexes 1 and 2 exhibited quasi-reversible single electron transfer process. Whereas in complex 3, only one electron oxidation peak was observed at + 0.72 V, which is due to the oxidation of V-IV to V-V. The SOD-like activity of complexes 2 and 3 has been investigated and showed that both complexes possess the capability to dismutase the superoxide anion generated in nitrobluetetrazolium/superoxide system. The electrochemical DNA binding studies by using oxidovanadium(IV) complex 3 was investigated and showed that the modified electrode with DNA causes the peak potentials, E-pc, and E-pa shifted to more positive values. This may be attributed to diffusion of the metal complex bound to the large, slowly diffusing DNA molecule and the resulted peak current due the equilibrium of free and DNA-bound oxidovanadium(IV) complex to the electrode surface. Complexes 2 and 3 were also assessed for their cancer chemotherapeutic potential towards colon cancer cell line (Caco-2) and showed that these complexes have the potential to act as an effective anticancer drug with IC50 values of 4.0 and 2.5 mu M for complexes 2 and 3, respectively