Photoinduced ligand exchange, excited state charge transfer, photoisomerization, and sensitization of 1O2 production represent the important reactions with potential applications that include photodynamic therapy (PDT), solar energy conversion, and molecular switches.  Complexes of Ru(II) and Rh2(II,II) possessing nitriles in the coordination sphere exhibit high quantum yield of ligand exchange in coordinating solvents. In the presence of DNA, irradiation of these complexes results in the formation of covalent adducts between the metal and the polyanion. The toxicity of these complexes increases significantly upon irradiation with visible light, and mechanistic studies show that compounds are able to enter cells and inhibit DNA replication. The potential application of these complexes for PDT will be discussed.  At a fundamental level, the dynamics of photoinduced ligand exchange have been investigated using ultrafast spectroscopy.Overall, these systems represent a new class of potential PDT agents whose mode of aciton differs significantly from those currently in use.

Control of excited states of transition metal complexes for applications in biology

243rd National Meeting (2012)

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