Formation and photodestruction of dual dipole-bound anion (H(2)O)(6){e(-)}CH(3)NO(2).

A new type of dipole-bound anion composed of water and nitromethane (CH(3)NO(2)) is formed via the incorporation of CH(3)NO(2) into argon-solvated water hexamer anions, (H(2)O)(6) (-)Ar(m). The reaction proceeds as an Ar-mediated process such that an effective energy dissipation through sequential Ar evaporation gives rise to the formation of [CH(3)NO(2)(H(2)O)(6)](-). Photoelectron spectroscopy is employed to probe the electronic properties of the [CH(3)NO(2)(H(2)O)(6)](-) anion, which reveals that the dipole-bound nature of (H(2)O)(6) (-) remains almost intact in the product anion; the vertical detachment energy of [CH(3)NO(2)(H(2)O)(6)](-) is determined to be 0.65+/-0.02 eV. This spectroscopic finding, together with other suggestive evidences, allows us to refer to [CH(3)NO(2)(H(2)O)(6)](-) as a dual dipole-bound anion described as (H(2)O)(6){e(-)}CH(3)NO(2), where the diffuse excess electron interacts with both the (H(2)O)(6) and CH(3)NO(2) moieties via the electron-dipole interactions. The photodestruction of (H(2)O)(6){e(-)}CH(3)NO(2) at 2134 nm (0.58 eV) occurs with a competition between electron detachment and fragmentation. The latter leads exclusively to the formation of CH(3)NO(2) (-)(H(2)O)(3), indicating that the dual dipole-bound anion serves as a precursor to the hydrated valence anion of CH(3)NO(2).

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