title: Chemical and structural evolution in the Th-SeO3(2-)/SeO4(2-) system: from simple selenites to cluster-based selenate compounds.
abstract: While extensive success has been gained in the structural chemistry of the U-Se system, the synthesis and characterization of Th-based Se structures are widely unexplored. Here, four new Th-Se compounds, α-Th(SeO3)2, β-Th(SeO3)2, Th(Se2O5)2, and Th3O2(OH)2(SeO4)3, have been obtained from mild hydrothermal or low-temperature (180-220 °C) flux conditions and were subsequently structurally and spectroscopically characterized. The crystal structures of α-Th(SeO3)2 and β-Th(SeO3)2 are based on ThO8 and SeO3 polyhedra, respectively, featuring a three-dimensional (3D) network with selenite anions filling in the Th channels along the a axis. Th(Se2O5)2 is a 3D framework composed of isolated ThO8 polyhedra interconnected by [Se2O5](2-) dimers. Th3O2(OH)2(SeO4)3 is also a 3D framework constructed by octahedral hexathorium clusters [Th6(μ3-O)4(μ3-OH)4](12+), which are interlinked by selenate groups SeO4(2-). The positions of the vibrational modes associated with both Se(IV)O3(2-) and Se(VI)O4(2-) units, respectively, were determined for four compounds, and the Raman spectra of α- and β-Th(SeO3)2 are compared and discussed in detail.
authors.affiliation: Institute of Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH , 52428 Jülich, Germany.
authors.forename: Bin
authors.initials: B
authors.lastname: Xiao
authors.forename: Eike
authors.initials: E
authors.lastname: Langer
authors.forename: Jakob
authors.initials: J
authors.lastname: Dellen
authors.forename: Hartmut
authors.initials: H
authors.lastname: Schlenz
authors.forename: Dirk
authors.initials: D
authors.lastname: Bosbach
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Suleimanov
authors.forename: Evgeny V
authors.initials: EV
authors.lastname: Alekseev