Reactivity of the charge transfer excited state of sodium decatungstate at the nanosecond time scale

Abstract

Previous studies have put into evidence the key role of a charge transfer excited state, noted X, in the primary steps of laser photolysis of sodium decatungstate solutions. In this work, we report a thorough study of the reactivity of the X transient towards different organic and inorganic substrates in acetonitrile and in water. The bimolecular reaction between X and the substrates is shown to occur on the nanosecond time-scale, either by H atom or electron transfer, and leads to the formation of the reduced form Y of decatungstate.We find that H atom transfer reactions are ruled by Z–H (Z=C, N, O) binding energies and lead to Y formation quantum yields that may reach the X formation quantum yield, whereas electron transfer reactions are ruled by the substrates' oxidation potential (Marcus reorganisation energy λ=1.0–1.3 eV for aromatics in acetonitrile) and lead to Y formation quantum yields similar to that obtained in the pure solvent.