Terpyridyl oxovanadium(IV) complexes for DNA crosslinking and mito-targeted photocytotoxicity

Oxovanadium(IV) complexes [VO(L-1/L-2)Cl-2](n+) (1,2) of (anthracenyl)terpyridine (An-tpy as L-1 in 1, n = 0) and triphenylphosphonium-appended (anthracenyl)terpyridine (An-tpy-TPP+ as L-2 in 2, n = 1) were synthesized, characterized and their DNA crosslinking ability, photocytotoxicity in visible light and cellular localization in cancer cells studied. The bromide derivative of 2, viz. [VO(An-tpy-TPP)Br-2]Br (3) is structurally characterized. The structure showed trans disposition of two halides in the coordination sphere and the TPP+ unit is a pendant to the terpyridyl ligand. The DNA melting and comet assay studies on the complexes suggest the formation of DNA crosslinks. Complexes 1 and 2 displayed similar to 10 fold increase in cytotoxicity on exposure to visible light (400-700 nm) when compared to those in dark in HeLa and MCF-7 cells. FACScan (Fluorescence Associated Cell Sorter Scan) analysis showed cellular apoptosis when treated with the complex in visible light in comparison to their dark controls. Fluorescence microscopic studies using complex 2 revealed its mitochondrial localization within the cancer cells.