A new series of Ni(II) and Zn(II) complexes were synthesized from bidentate isomeric pyridyl tetrazole ligands such as 2-(1-vinyl-1H-tetrazol-5-yl)pyridine (L1), N,N-dimethyl-3-(5-(pyridin-2-yl)-1H-tetrazol-1-yl)propan-1-amine(L2), 2-(2-vinyl-2H-tetrazol-5-yl)pyridine(L3), N,N-dimethyl-3-(5-(pyridin-2-yl)-2H-tetrazol-2-yl)propan-1-amine (L4). All the complexes were characterized by the elemental analysis, molar conductance, FTIR, UV–vis and magnetic studies. The conductance and spectroscopic data suggested that, the ligands act as monobasic bidentate ligands and form octahedral complexes with general formula [M(L1−4)2Cl2], (M = Ni(II) and Zn(II)). In addition metal complexes displayed good antioxidant and moderate nematicidal activities. The cytotoxicity of ligands and their metal complexes have been evaluated by MTT assay. The DNA cleavage activity of the metal complexes was performed using agarose gel electrophoresis in the presence and absence of oxidant H2O2. All metal complexes showed significant nuclease activity in the presence of H2O2.