Photoactive platinum compounds: synthesis, characterization and interaction with biomolecules.

A series of cationic Pt(IV) complexes was synthesized, starting from Pt(II) precursors bearing modified terpyridine ligands. Selected complexes were studied in a photoreaction with light at λ = 365 nm and we found them to be light-sensitive, both in organic solvent and in aqueous buffer. The product of this photoreaction was a reduced Pt(II) compound that, in the case of [Pt(OCOCH3)2Cl(phterpy)][CF3SO3], was found to be the Pt(II) precursor [PtCl(phterpy)][CF3SO3], as proved by UV-Vis studies and by proton NMR. The electrochemical behavior of the Pt(IV) complexes revealed an irreversible reduction process that was attributed to the couple Pt(IV) → Pt(II). The binding ability of [PtCl(phterpy)][CF3SO3] toward DNA was assessed with spectrophotometric titrations and resulted to be non-intercalative. The cytotoxic potency against of selected compounds against human ovarian cancer cells A2780, either sensitive or resistant to cisplatin, was found to be minor than cisplatin. However, [Pt(OCOCH3)2Cl(phterpy)][CF3SO3] proved to be a photocytotoxic agent, because its IC50 was potentiated after irradiation with UV light at 365 nm. Finally, the interaction with model proteins and single stranded DNA has been explored. High-resolution mass spectrometry studies revealed that the Pt(IV) behave as prodrugs, being able to bind to biological targets only when irradiated