Two zinc(II) and cadmium(II) complexes based on the V-shaped ligand 2,6-bis(2-benzimidazolyl)pyridine: Synthesis, crystal structure, DNA-binding properties and antioxidant activities

Two zinc(II) and cadmium(II) complexes based on a V-shaped ligand 2,6-bis(2-benzimidazolyl)pyridine (bbp) have been synthesized and characterized by elemental analysis, molar conductivities, IR, UV–Vis spectra and X-ray single crystal diffraction. Zn(II) and Cd(II) ions are six-coordinated in the structures of [Zn(bbp)2](pic)2·2DMF (1) and [Cd(bbp)2](pic)2·2DMF (2) (pic = picrate), and forming a distorted octahedron. The DNA-binding properties of the complexes were investigated by spectrophotometric methods and viscosity measurements. The experimental results suggest the complexes bind to DNA in an intercalation mode, and DNA-binding affinity of the Zn(II) complex is stronger than that of the Cd(II) complex owning to the different V-shaped angle (αV). Antioxidant assay in vitro shows that both two complexes possess significant hydroxyl radical scavenging activity, and the Zn(II) complex also reveal potent superoxide radical scavenging activity.