The DNA binding ability of the novel complexes [Fe(L2)2L1] (PF6)2 [Complex (1)] and [Zn(L2)2L1] (PF6)2 [Complex (2)] containing bioactive mixed ligand of the type L1=2-hydroxy-4- methyl-1,8-naphthyridine and L2 =1,10-phenanthroline were synthesized and structurally characterized by elemental analysis, IR and 1H NMR spectral studies. The intrinsic binding constant Kb has been estimated at room temperature. The binding constant of 1.8 x 104 M-1 for complex (1) and 2.1 x 104 M-1 for complex (2) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2, respectively, as obtained from absorption spectra indicate that the complexes intercalate between the base pairs of the CT-DNA tightly. The oxidative cleavage activity of the complexes (1) and (2) were studied by using gel electrophoresis and the results show that complexes have potent nuclease activity.