Four new ruthenium(ii) complexes [Ru(bpy)2(NHPIP)](ClO4)2 (Ru-1), [Ru(phen)2(NHPIP)](ClO4)2 (Ru-2), [Ru(bpy)2(AHPIP)](ClO4)2 (Ru-3), and [Ru(phen)2(AHPIP)](ClO4)2 (Ru-4) (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline; NHPIP = 2-(3-nitro-4-hydroxylphenyl)imidazo[4,5-f][1,10]phenanthroline; AHPIP = 2-(3-amino-4-hydroxylphenyl)imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized by elemental analysis, electrospray mass spectrometry, and 1H NMR spectroscopy. The cytotoxicity in vitro of these complexes against BEL-7402, HeLa, MG-63, and MCF-7 cells was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. Ru-4 shows the highest cytotoxic activity towards the selected cell lines among the four complexes. The morphological apoptosis was assayed by an acridine orange/ethidium bromide staining method, and the percentages of necrotic and apoptotic cells were determined by flow cytometry. The cellular uptake and the cell cycle arrest in BEL-7402 cell was investigated. The results showed these complexes inhibit the proliferation of BEL-7402 cells at G0/G1 phase arrest. The detection of mitochondrial membrane potentials using the fluorescence probe JC-1 (5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolcarbocyanine iodide) exhibited that the mitochondrial membrane potentials decrease. Upon irradiation, these complexes can effectively cleave pBR322 DNA.