Photoactivated DNA cleavage and anticancer activity of oxovanadium(IV) complexes of curcumin

Oxovanadium(IV) complexes [VO(Fc-pic)(acac)](ClO4) (1), [VO(Fc-pic)(cur)](ClO4) (2), [VO(Ph-pic)(acac)](ClO4) (3) and [VO(Ph-pic)(cur)](ClO4) (4), where Fc-pic and Ph-pic are ferrocenylmethyl-bis-(2-pyridylmethylamine) (in 1, 2) and bis-(2-pyridylmethyl)benzylamine (in 3, 4), respectively, acac is acetylacetonate anion (in 1, 3) and cur is curcumin anion (in 2, 4) were prepared, characterized and their photo-induced DNA cleavage and anticancer activity studied. The crystal structure of 1 as its PF6− salt (1a) shows the presence of a VO2+ moiety in VO3N3 coordination geometry. The complexes show a d–d band at ∼790 nm in DMF and display V(IV)/V(III) redox couple near −1.45 V vs. SCE in DMF-0.1 M TBAP. The complexes are avid binders to calf thymus DNA. Complex 2 efficiently photo-cleaves plasmid DNA in near-IR light of 785 nm forming OH radicals. The curcumin complexes show photocytotoxicity in HeLa cancer cells in visible light of 400–700 nm with significant cellular uptake within 4 h of incubation time.