Browsing by Author "Zimmer, Frank C."

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    The first members of the monoclinic lanthanoid(III) fluoride oxoarsenate(III) series Ln2F2[As2O5] (Ln=La - Nd and Sm)
    (2025) Locke, Ralf J. C.; Zimmer, Frank C.; Schleid, Thomas
    In synthesis experiments for the preparation of Ln5F3[AsO3]4 representatives in evacuated glassy silica ampoules at temperatures of maximum 825 °C, surprisingly compounds with the composition Ln2F2[As2O5] could be obtained and subsequently also reproduced on target. The new Ln2F2[As2O5] representatives with Ln = La - Nd and Sm crystallize needle‐shaped in the monoclinic space group P21/c with lattice parameters ranging from a = 793.24(5) pm, b = 1346.39(9) pm, c = 1359.41(9) pm and β = 106.932(3)° for La2F2[As2O5] to a = 769.11(5) pm, b = 1307.50(9) pm, c = 1328.74(9) pm and β = 106.819(3)° for Sm2F2[As2O5] with Z = 8. Their crystal structure can be broken down into two parts consisting of infinite [Ln2F2]4+ and discrete [As2O5]4− units. Three distinct kinds of fluoride anions are trigonally planar surrounded by lanthanoid cations and another one carries even a fourth of them in their coordination sphere with a secondary contact resulting in a distorted tetrahedron. These [FLn3]8+ and [FLn3+1]11+ building blocks share common corners and edges creating strands {[F2Ln2]4+}, which propagate along [100]. The four different As3+ lone‐pair cations form ψ1‐tetrahedra [AsO3]3− with three oxygen atoms and are conversurally linked pairwisely creating dinuclear pyroanionic [As2O5]4− units. These [As2O5]4− groups arrange themselves alternatingly along [100] with their lone pairs pointing into central empty channels. The {[F2Ln2]4+} strands are linked to the [As2O5]4− units via four distinguishable Ln3+ cations providing them coordination numbers of eight and nine. Raman spectroscopy confirmed that no (OH)− groups resulting from the synthesis were present apt to replace part of the F− and the stoichiometry Ln2F2[As2O5] was verified using WDXS elemental analyses.
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    Y5F3[AsO3]4 and Y5Cl3[AsO3]4 : two non-isostructural yttrium halide oxoarsenates(III) and their potential as hosts for luminescent Eu3+- and Tb3+-doping
    (2025) Locke, Ralf J. C.; Mikuta, Martina; Ledderboge, Florian; Zimmer, Frank C.; Höppe, Henning A.; Schleid, Thomas
    Y5F3[AsO3]4 crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network 3∞{[Y5F3]12+} and the remaining part consists of ψ1-tetrahedral [AsO3]3- units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y5Cl3[AsO3]4 crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9) pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)° for Z = 4. Condensation of [(Y1,2)O8]13- polyhedra via four common edges each leads to fluorite-like 2∞ {[(Y1,2)Oe8/2]5-} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)3+ cations with their Cl- ligands on the one hand and the As3+ cations with their lone-pairs of electrons on the other, which also form within [AsO3]3- anions lone-pair channels along [010]. Both colorless compounds can be obtained by solid-state reactions from corresponding mixtures of the binaries (Y2O3, As2O3 and YX3 with X = F and Cl) at elevated temperatures of 825 °C, most advantageously under halide-flux assistance (CsBr for Y5F3[AsO3]4 and ZnCl2 for Y5Cl3[AsO3]4). By replacing a few percent of YX3 with EuX3 or TbX3, Eu3+- or Tb3+-doped samples are accessible, which show red or green luminescence upon excitation with ultraviolet radiation.