title: Hydride ions in oxide hosts hidden by hydroxide ions.
abstract: The true oxidation state of formally 'H(-)' ions incorporated in an oxide host is frequently discussed in connection with chemical shifts of (1)H nuclear magnetic resonance spectroscopy, as they can exhibit values typically attributed to H(+). Here we systematically investigate the link between geometrical structure and chemical shift of H(-) ions in an oxide host, mayenite, with a combination of experimental and ab initio approaches, in an attempt to resolve this issue. We demonstrate that the electron density near the hydrogen nucleus in an OH(-) ion (formally H(+) state) exceeds that in an H(-) ion. This behaviour is the opposite to that expected from formal valences. We deduce a relationship between the chemical shift of H(-) and the distance from the H(-) ion to the coordinating electropositive cation. This relationship is pivotal for resolving H(-) species that are masked by various states of H(+) ions.
authors.affiliation: 1] Center for Secure Materials, Materials and Structures Laboratory, Tokyo Institute of Technology, R3-34, 4259 Nagatsuta, Yokohama 226-8503, Japan [2] †Present address: Department of Applied Chemistry, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Katsuro
authors.initials: K
authors.lastname: Hayashi
authors.affiliation: 1] Department of Physics and Astronomy, University College London, London WC1E 6BT, UK [2] †Present address: Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Peter V
authors.initials: PV
authors.lastname: Sushko
authors.affiliation: Department of New Business Development, Asahi Kasei Corporation, 1-105 Kanda-Jinbocho, Tokyo 101-8101, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hashimoto
authors.affiliation: Department of Physics and Astronomy, University College London, London WC1E 6BT, UK.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Shluger
authors.affiliation: Frontier Research Center, Tokyo Institute of Technology, S2-13, 4259 Nagatsuta, Yokohama 226-8503, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Hosono