A group of three polypyridyl complexes having a ligand CMIP=2-(2-Chloro-8-methylquinolin-3-yl)w-1H-Imidazo[4,5-f][1,10]phenanthroline, by changing the antracene ligands phen=1, 10-phenanthroline, bpy=2, 2′ bipyridine and dmb=4, 4-dimethyl-2, 2′- bipyridine and its Co(III) polypyridyl complexes[Co(phen)₂CMIP]³⁺(1), [Co(bpy)₂CMIP]³⁺(2), [Co(dmb)₂CMIP]³⁺(3) have been synthesized, fully characterized using different spectroscopic techniquesand confirmed the structures. The binding ability of Co(III) complexes towards CT–DNA was investigated by absorption, fluorescence and viscosity methods. The DNA binding constant of complex-1 showed the greatest intrinsic binding constant due to π-π stacking with DNA base pairs may exert some additional interactions such as hydrogen bonding with functional groups present on the edge of the DNA. The photoactivated cleavage of plasmid pBR322 DNA by complexes 1–3 was investigated and confirmed they cleave the pBR322 DNA in different forms. All the synthesized compounds were tested for antimicrobial activity by using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) organisms. The In-vitro cytotoxicity of these complexes was evaluated by MTT assay, among all complex 1 shows higher cytotoxicity than other complexes on HeLa cells. The induced apoptosis and cell cycle arrest of HeLa cells were investigated by flow cytometry for 24hrs. These new cobalt based complexes could be further developed as effectivemetalbased anticancer agents.