Photoinduced ligand exchange, excited state charge transfer, photoisomerization, and sensitization of 1O2 production represent important reactions initiated by light with potential applications that include photochemotherapy (PCT) and solar energy conversion. Transition metal complexes possessing nitriles in the coordination sphere exhibit high quantum yield of ligand exchange in coordinating solvents, such that irradiation of these complexes results in the formation of covalent adducts between the metal and Lewis basic sites on biomolecules. These systems represent a new class of potential PCT agents because their mode of action differs significantly from those currently in use, which rely on the production of reactive oxygen species. The presentation will focus on new strategies to tune the electronic structure and steric bulk of ligands to enhance photoinduced ligand dissociation. Ultrafast time-resolved studies will be presented which show the unprecedented population of two reactive states in single molecules, such that two pathways useful for PCT can be accessed simultaneously. In addition, these complexes are also able to deliver caged drugs when irradiated with visible light. Strategies will be presented to improve the yields of the various excited state pathways possible in these multiple-action complexes. The application of these complexes to problems in solar energy conversion for the photocatalytic production of H2 will be discussed.

Control of excited states of transition metal complexes: Optimizing multiple excited state pathways

249th National Meeting (2015)

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