title: Octanuclear oxothiomolybdate(v) rings: structure and ionic-conducting properties.
abstract: A family of alkali salts of octanuclear oxothiomolybdate rings has been synthesized by crystallization of the [Mo(8)S(8)O(8)(OH)(8)[HMO(5)(H(2)O)]](3-) (noted HMo(8)M(3-); M=Mo, W) and [Mo(8)S(8)O(8)(OH)(8)(C(2)O(4))](2-) (noted Mo(8)ox(2-)) anions in an aqueous solution of ACl (A=Li, Na, K, Rb). Single-crystal X-ray diffraction experiments have been performed showing that the alkali salts exhibit a similar three-dimensional structure. Disordered alkali ions form columns to which the anionic rings are anchored. Ionic-conductivity measurements on pressed pellets have revealed two different behaviors. The lithium salts of HMo(8)M(3-) (M=Mo, W) are moderately good proton conductors at room temperature (sigma=10(-5) S cm(-1)) and the profile of conductivity as a function of relative humidity shows that the conductivity is due to surface-proton motion (particle-hydrate-type mechanism). On the other hand, the lithium salt of Mo(8)ox(2-) competes with the best crystalline lithium conductors at room temperature (sigma=10(-3) S cm(-1)), and (7)Li NMR experiments confirm the mobility of the lithium ions along the one-dimensional channels of this material.
authors.affiliation: Institut Lavoisier, IREM, Université de Versailles Saint-Quentin, 45 Avenue des Etats-Unis, UMR 8637, 78035 Versailles Cedex, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: du Peloux
authors.forename: Anne
authors.initials: A
authors.lastname: Dolbecq
authors.forename: Philippe
authors.initials: P
authors.lastname: Barboux
authors.forename: Guillaume
authors.initials: G
authors.lastname: Laurent
authors.forename: Jérôme
authors.initials: J
authors.lastname: Marrot
authors.forename: Francis
authors.initials: F
authors.lastname: Sécheresse