Synthesis, characterization and investigation of photophysical and biological properties of Cu(II) and Zn(II) complexes of benzimidazole ligands

In this work, two benzimidazole ligands (L-1 and L-2) containing a central pyridine ring that have two alkylated (pentyl for L-1 and hexyl for L-2) benzimidazole units at the second and sixth positions were synthesized. Mononuclear Cu(II) and Zn(II) complexes with the general formulae of [ML(X)(2)] (where M: Cu(II) or Zn(II), L: L-1 or L-2 and X: NO3- or NCS-) were synthesized, and their structures were characterized by the spectroscopic and analytical methods. Moreover, Cu(II) complexes [CuL1(Bipy)](ClO4)(2) and [CuL2(Bipy)](ClO4)(2) (where Bipy: 2,2 '-bipyridine) were also prepared. The solid structures of complexes [CuL1(NCS)(2), [CuL1(Bipy)](ClO4)(2) and [CuL2(NO3)(EtOH)]NO3 were determined by single crystal X-ray diffraction studies. The DNA binding properties of the ligands and their metal complexes were investigated by the spectrophotometric titrations. The compounds showed considerable DNA binding affinities. The structural variations and coordination geometry around the metal centre were found to affect the binding properties.