Photocytotoxic oxovanadium(IV) complexes of ferrocenyl-terpyridine and acetylacetonate derivatives

•Oxovanadium(IV) complexes are photocytotoxic in cancer cells in visible light.•DCFDA assay shows photo-generation of ROS by the complexes in HeLa cells.•Better uptake of the complexes is observed for MCF-7 than HeLa cancer cells.•Apoptotic cell death on light exposure is evidenced from the Hoechst staining.•The oxovanadium(IV) complexes show DNA binding and photocleavage activity.

Oxovanadium(IV) complexes [VO(Fc-tpy)(acac)](ClO4) (1), [VO(Fc-tpy)(nap-acac)](ClO4) (2), [VO(Fc-tpy)(py-acac)](ClO4) (3) and [VO(Ph-tpy)(py-acac)](ClO4) (4) of 4ʹ-ferrocenyl-2,2ʹ:6ʹ,2ʺ-terpyridine (Fc-tpy) and 4ʹ-phenyl-2,2ʹ:6ʹ,2ʺ-terpyridine (Ph-tpy) having monoanionic acetylacetonate (acac), naphthylacetylacetonate (nap-acac) or pyrenylacetylacetonate (py-acac) ligand were prepared, characterized and their photocytotoxicity in visible light studied. The ferrocenyl complexes 1–3 showed an intense charge transfer band near 585 nm in DMF and displayed Fc+/Fc and V(IV)/V(III) redox couples near 0.66 V and −0.95 V vs. SCE in DMF-0.1 M TBAP. The complexes as avid binders to calf thymus DNA showed significant photocleavage of plasmid DNA in green light (568 nm) forming OH radicals. The complexes that are photocytotoxic in HeLa and MCF-7 cancer cells in visible light (400–700 nm) with low dark toxicity remain nontoxic in normal fibroblast 3T3 cells. ICP-MS and fluorescence microscopic studies show significant cellular uptake of the complexes. Photo-irradiation of the complexes causes apoptotic cell death by ROS as evidenced from the DCFDA assay.

Graphical abstractFerrocenyl-terpyridine oxovanadium(IV) acetylacetonates having pendant fluorophores are remarkably photocytotoxic in HeLa and MCF-7 cancer cells with less toxicity for normal 3T3 fibroblast cell. The apoptotic cell death involves photo-generated ROS.Figure optionsDownload full-size imageDownload as PowerPoint slide