Choosing a good linker to link electron donor(s) and acceptor(s) is a key issue in designing artificial photosynthetic systems. Work to be presented is focused on a series of [Ru(bpy)32+] compounds linked to 1-3 Pd2+ by oligo(aminoethylglycine) for use in photocatalytically dimerizing a-methylstyrene. We previously reported a series of [Ru(bpy)3]2+ complexes derivatized with aminoethylglycine (aeg) with pendant bipyridine (bpy) ligands. Coordination of Cu2+ to bpy forms desired [Ru(bpy)3]2+ �hairpin� loop and results in up to 98% excited state quenching. We take one step further by the introduction of a different metal center (Pd2+) that is able to perform chemical work. This is the first example using the aeg chain between a photosensitizer and a reaction center. The products have faster reaction rates and better selectivity than conjugated linkers described in the literature. We also compares the catalytic efficiency when linking [Ru(bpy)32+] with 1, 2 and 3 Pd2+ centers and find Ru-3(Pd)3 has the lowest catalytic activity because of lower chemistry stability. Further investigation is conducted to understand the excited state quenching mechanism. Solvent study of Ru-Pd catalysts shows a negative trend of the nonradiative decay rate vs. Pekar factor, which indicates an electron transfer process. Variable temperature study, which shows a large reorganization energy (>1 eV), with experiments using added sacrificial electron donor together indicate an electron transfer process from [Ru(bpy)3]2+ to Pd2+. Our system is a good model for studying soft linkages between photosensitizers and reaction centers that can be further applied to other reactions.

Aminoethylglycine-linked Ru-Pd complexes photocatalytically dimerize a-methylstyrene

246th National Meeting (2013)

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