We present here the syntheses of a mononuclear Cu-II complex and two polynuclear Cu-II-Ni-II complexes of the azenyl ligand, 4-(pyridin-2-ylazenyl)resorcinol (HL; 1). The reaction of HL (1) and copper(II) perchlorate with KCN gave a mononuclear complex [CuL(CN)] (4). Using 4, one pentanuclear complex, [{CuL(NC)}(4)Ni](ClO4)(2) (5) and one trinuclear complex, [{CuL(CN)}(2)NiL]ClO4 (6), were prepared and characterized by elemental analyses, magnetic susceptibility, molar conductance, IR, and thermal analysis. Stoichiometric and spectral results of the mononuclear Cu-II complex indicated that the metal/ligand/CN ratio was 1 : 1 : 1, and the ligand behaved as a tridentate ligand forming neutral metal chelates through the pyridinyl and azenyl N-, and resorcinol O-atom. The interaction between the compounds (the ligand 1, its Ni-II and Cu-II complexes without CN, i.e., 2 and 3, and its complexes with CN, 4-6) and DNA has also been investigated by agarose gel electrophoresis. The pentanuclear Cu4Ni complex (5) with H2O2 as a co-oxidant exhibited the strongest DNA-cleaving activity.