A series of neutral hexacoordinated nickel(II) complexes of formula [Ni^II (L)X₂] (where L = 3,4-bis(2-pyridylmethylthio)toluene with tetradentate N₂S₂ donor set and X = chloride (1), azide (2), cyanate (3) and isothiocyanate anion (4)) have been synthesized and isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods along with detailed structural characterization of 1,2 and 3 by single crystal X-ray diffraction analyses. The structural study showed that the nickel(II) ion has a distorted octahedral geometry being chelated by the tetradentate N₂S₂ ligand and bound to cis- located choride or pseudohalide anions. In dimethylformamide solution the complexes showed quasi-reversible Ni^II/Ni^III redox couples in cyclic voltammograms with E_1/2 values of +0.723, +0.749, +0.768 and +0.868 V for 1, 2, 3 and 4, respectively. The study of interaction of the complexes with calf thymus DNA, bovine serum albumin (BSA) and human serum albumin (HSA) using spectroscopic and physicochemical tools clearly indicates that the complexes interact with DNA via groove binding mode.