A Photo‐Caged Platinum(II) Complex That Increases Cytotoxicity upon Light Activation

A novel platinum(II) photocaged complex called [Pt(cage)] has been prepared and characterized by X‐ray crystallography. The complex contains a photolabile nitrophenyl group incorporated into the backbone of a tetradentate ligand that contains two pyridyl and two amide nitrogen donor sites. The intact complex is unreactive toward ligand‐exchange reactions until activation with UV light cleaves the ligand backbone, releasing a Pt II complex that more readily exchanges its ligands, as verified by reaction with a methionine‐containing peptide. [Pt(cage)] is non‐toxic to MCF‐7 cells in the dark, whereas brief UV exposure induces cell death of human breast cancer MCF‐7 cells at a level approaching that of cisplatin. By using light to alter the coordination chemistry around the metal center, [Pt(cage)] represents a new strategy for potentially delivering metal‐based drugs in a site and time specific manner.