Creation of New Chemistry for Energy Conversion from pH gradients

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Aqua-Ru-quinone complexes, [Ru(trpy)(Q)(OH_2)]^<2+>, dissociate proton to give[Ru(trpy)(Q)(OH^-)]^+ with anionic hydroxy group or [Ru(trpy)(SQ)(HO^-)]+ with hydroxy radical, that is produced by intramolecular electron transfer from hydroxy anion to quinone. Dissociation of hydroxy proton of [Ru(trpy)(Q)(OH^-)]^+ also intramolecula electron transfer from the resultant oxy1 dianion ot quinone. We have successfully isolated [Ru(trpy)(SQ)(O^-)]^0 and determinined the molecular structure of the first Ru-oxo complex with oxyl radical. The fact that Ru-O bound distance of the oxyl radicla complexes is close to that of Ru-OH_2 bond indicates that the multi-bond character is not so high in the Ru-O bond. The Ru-oxo complex with oxyl radicla has essentially no ability to oxidize organic compounds, but one-electron oxidized form of the complex abstract hydrogen atoms of cyclic diens. Compared with monomeric Ru-oxo complexes, dinuclear Ru-oxo one showed high reactivity for hydrogen abstraction of cyclic dienes upon two electron oxidation of the complex. Moreover, the dinuclear complex showed high catalytic ability for four-electron oxidation of water, and the turnover number of dioxygen was 35000 based on the complex. Thus, we succeeded energy conversion from pH gradients to electricity, and also oxidation of not only organic compounds but also water by using unique redox behavior of aqua-Ru-dioxolene complexes.