A V-shaped ligand Bis(2-benzimidazolymethyl)amine (bba) and its nickel(II) picrate (pic) complex, with composition [Ni(bba)2](pic)2·3MeOH, have been synthesized and characterized on the basis of elemental analyses, molar conductivities, IR spectra, and UV/vis measurements. In the complex, the Ni(II) ion is six-coordinated with a N2O4 ligand set, resulting in a distorted octahedron coordination geometry. In addition, the DNA-binding properties of the Ni(II) complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The experimental results suggest that the nickel(II) complex binds to DNA by partial intercalation binding mode. 1. Introduction Binding studies of small molecules to DNA are very important in the development of DNA molecular probes and new therapeutic reagents [1]. Transition metal complexes have attracted considerable attention as catalytic systems for use in the oxidation of organic compounds [2], probes in electron-transfer reactions involving metalloproteins [3], and intercalators with DNA [4]. Numerous biological experiments have demonstrated that DNA is the primary intracellular target of anticancer drugs; interaction between small molecules and DNA can cause damage in cancer cells, blocking the division and resulting in cell death [5–7]. Since the benzimidazole unit is the key-building block for a variety of compounds which have crucial roles in the functions of biologically important molecules, there is a constant and growing interest over the past few years for the synthesis and biological studies of benzimidazole derivatives [8–10]. Since the characterization of urease as a nickel enzyme in 1975, the knowledge of the role of nickel in bioinorganic chemistry has been rapidly expanding [11]. The interaction of Ni(II) complexes with DNA appears to be mainly dependent on the structure of the ligand exhibiting intercalative behavior [12–14]. In this context, we synthesized and characterized a novel Ni(II) complex. Moreover, we describe the interaction of the novel Ni(II) complex with DNA using electronic absorption and fluorescence spectroscopy and viscosity measurements. 2. Experimental 2.1. Materials and Methods Calf thymus DNA (CT-DNA) and Ethidium bromide (EB) were purchased from Sigma Chemicals Co. (USA). All chemicals used were of analytical grade. All the experiments involving interaction of the ligand and the complexes with CT-DNA were carried out in doubly distilled water buffer containing 5？mM Tris and 50？mM NaCl and adjusted to pH 7.2 with hydrochloric acid. A solution of CT-DNA gave a
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