Photodynamic Therapy (PDT) has emerged as an alternative to conventional treatments for dermatological and endoscopically-accessible cancers.  The mechanism of current PDT agents relies on the generation of singlet oxygen in the tissue to induce cell death, a situation that limits their use to non-hypoxic tumors. Di-rhodium metal-based PDT agents, however, can act independently of oxygen, due to the generation of a photoactive species that can covalently bind to or cleave DNA upon irradiation with light.  Research in our laboratories has revealed that the cytotoxicity of di-rhodium compounds with certain chelating diimine ligands is significantly enhanced when irradiated with visible light. It has also been documented that irradiation of partially solvated dirhodium carboxylate complexes with visible light (400-700 nm) for 30 min induces exchange of two equatorial CH3CN ligands with H2O with a 34-fold enhancement in cytotoxicity over the controls performed in the dark. The design as well as photochemical and biological properties of new generations of di-rhodium compounds are being explored in an effort to tune the energy of the photo-active state in both the �electron acceptor� and the �monodentate leaving group� type partial paddlewheel compounds. Extrapolation of the current goals for di-rhodium compounds to di-rhenium, di-ruthenium and di-iridium is also being undertaken with the objective of preparing compounds of similar structures is of great interest, since studies of the heavier congeners have been very limited or non-existent in the literature.

Dinuclear metal-metal bonded   compounds as new PDT agents

243rd National Meeting (2012)

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