DNA photocleavage and anticancer activity of terpyridine copper(II) complexes having phenanthroline bases

Copper(II) complexes [Cu(ph-tpy)(B)](ClO4) (1–3), where ph-tpy is (4′-phenyl)-2,2′:6′,2″-terpyridine and B is N,N-donor phenanthroline base, viz. 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and characterized from analytical and spectral data. Complex 1, characterized by X-ray crystallography, shows a distorted square-pyramidal (4 + 1) CuN5 coordination geometry having the tridentate ph-tpy ligand at the basal plane and bidentate phen bound to the axial-equatorial sites. The complexes display a d–d band near 650 nm in aqueous DMF. The complexes are avid binders to calf thymus DNA giving the binding order: 3 (dppz) > 2 (dpq) > 1 (phen). The dpq and dppz complexes show photo-induced DNA cleavage activity in red light via photo-redox pathway forming hydroxyl radicals. The cytotoxicity of the dppz complex 3 was studied by MTT assay in HeLa cancer cells. The IC50 values are 3.7 and 12.4 μM in visible light of 400–700 nm and dark, respectively.

Terpyridine copper(II) complexes [Cu(ph-tpy)(B)](ClO4)2 of phenanthroline bases (B) are intercalative binders to DNA. The dipyridoquinoxaline and dipyridophenazine complexes show DNA photocleavage activity in red light via HO pathway. The dipyridophenazine complex shows cytotoxicity in HeLa cells giving IC50 values of 3.7 and 12.4 μM in visible light and dark, respectively.Figure optionsDownload as PowerPoint slide