title: Solvent-dependent molecular structure of ionic species directly measured by ultrafast x-ray solution scattering.
abstract: Ionic species often play important roles in chemical reactions occurring in water and other solvents, but it has been elusive to determine the solvent-dependent molecular structure with atomic resolution. The triiodide ion has a molecular structure that sensitively changes depending on the type of solvent and its symmetry can be broken by strong solute-solvent interaction. Here, by applying pump-probe x-ray solution scattering, we characterize the exact molecular structure of I(3)(-) ion in water, methanol, and acetonitrile with subangstrom accuracy. The data reveal that I(3)(-) ion has an asymmetric and bent structure in water. In contrast, the ion keeps its symmetry in acetonitrile, while the symmetry breaking occurs to a lesser extent in methanol than in water. The symmetry breaking of I(3)(-) ion is reproduced by density functional theory calculations using 34 explicit water molecules, confirming that the origin of the symmetry breaking is the hydrogen-bonding interaction between the solute and solvent molecules.
authors.affiliation: Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, Republic of Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Kim
authors.forename: Jae Hyuk
authors.initials: JH
authors.lastname: Lee
authors.forename: Joonghan
authors.initials: J
authors.lastname: Kim
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Nozawa
authors.forename: Tokushi
authors.initials: T
authors.lastname: Sato
authors.forename: Ayana
authors.initials: A
authors.lastname: Tomita
authors.forename: Kouhei
authors.initials: K
authors.lastname: Ichiyanagi
authors.forename: Hosung
authors.initials: H
authors.lastname: Ki
authors.forename: Jeongho
authors.initials: J
authors.lastname: Kim
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Adachi
authors.forename: Hyotcherl
authors.initials: H
authors.lastname: Ihee
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D000838:Anions / Q000737:chemistry; D007454:Iodides / Q000737:chemistry*; D007455:Iodine / Q000097:blood; D000432:Methanol / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D000097:Acetonitriles; D000838:Anions; D007454:Iodides; D012997:Solvents; D014867:Water; D007455:Iodine; D000432:Methanol; C032159:acetonitrile