Sabine Zitzer

Synthesis, crystal structure and spectroscopic properties of Y3O2Cl[SeO3]2 : Eu3+

Abstract The yttrium oxide chloride oxoselenate(IV) Y3O2Cl[SeO3]2, doped with Eu3+ at 3% mass percentage, can be obtained by common solid-state reactions from Y2O3, Eu2O3, YCl3 and SeO2, and crystallizes isostrucäturally with the analogous terbium(III) compound Tb3O2Cl[SeO3]2. The orthorhombic crystal structure (Pnma, a = 548.24(4), b = 1457.92(9), c = 1102.83(7) pm and Z = 4 for undoped yttrium samples) was identified by single-crystal X-ray diffraction data and the purity of the product was checked with powder XRD methods. The presence of isolated pyramidal [SeO3]2– units could be confirmed by Raman spectroscopy. The optical band gap was determined by diffuse reflectance spectroscopy (DRS) applying the Kubelka-Munk function. Fluorescence spectroscopy measurements revealed the prominent f → f-transitions for Eu3+-doped compounds in both the excitation and the emission spectra of Y3O2Cl[SeO3]2 : Eu3+.

Ein neues Selten-Erd-Metall(III)-Oxidchlorid-Oxotellurat(IV): Nd5O4Cl3[TeO3]2 / A New Rare Earth-Metal(III) Oxide Chloride Oxotellurate(IV): Nd5O4Cl3[TeO3]2

Pale violet, plate-like single crystals of the title compound, neodymium(III) oxide chloride oxotellurate( IV) Nd5O4Cl3[TeO3]2, can be obtained by the reaction of Nd2O3 with NdCl3 and TeO2 in equimolar ratios in evacuated silica ampoules within five days at 775 °C with an excess of CsCl added as fluxing agent. Nd5O4Cl3[TeO3]2 crystallizes in the monoclinic space group C2/m (no. 12) with the lattice parameters a = 1270.61(9), b = 562.70(4), c = 1008.97(8) pm, β = 90.784(3)°and Z = 2, and is thus isostructural to the lanthanoid(III) oxide halide oxoselenates(IV) Tb5O4Cl3[SeO3]2 and Gd5O4Br3[SeO3]2. The crystal structure exhibits three crystallographically different Nd3+ cations, of which (Nd1)3+ has a purely oxidic coordination sphere of eight oxide anions building up a square prism. (Nd2)3+ and (Nd3)3+ are both coordinated by oxide and chloride anions. The coordination polyhedron around (Nd2)3+ is a trigonal prism of oxide anions that is capped by one chloride anion to give a coordination number of seven. (Nd3)3+ resides in an eightfold coordination of five oxide and three chloride anions forming a square antiprism. All (O1)2− anions are surrounded tetrahedrally by Nd3+ cations as [ONd4]10+ units. These tetrahedra share common edges and vertices to generate two-dimensional infinite layers of the composition ∞2{[O4Nd5]7+}, which extend parallel to the (001) plane. The chloride anions (Cl1)−are connecting those slabs via Nd3-Cl1-Nd3 bridges along the [001] direction, while the (Cl2)− anions alternate with the Te4+ cations above and below the layers. The three-dimensional crystal structure of Nd5O4Cl3[TeO3]2 is completed by Te4+ cations, which are bonded to one (O2)2− and two (O3)2− anions to form ψ1-tetrahedra [TeO3]2− with a nonbinding, stereochemically active electron pair (“lone pair”) pointing into the free space between the chloride-decorated ∞2{[O4Nd5]7+} layers Graphical Abstract Ein neues Selten-Erd-Metall(III)-Oxidchlorid-Oxotellurat(IV): Nd5O4Cl3[TeO3]2 / A New Rare Earth-Metal(III) Oxide Chloride Oxotellurate(IV): Nd5O4Cl3[TeO3]2

Die Lanthanoid(III)-Oxid-Oxoselenate(IV) Ln2O[SeO3]2 (Ln=Sm–Tm)

Abstract Single crystals of compounds with the composition Ln2O[SeO3]2 (Ln=Sm–Tm) were synthesized by solid-state reactions of the lanthanoid sesquioxides (Ln2O3) with the corresponding tribromides (LnBr3) and selenium dioxide (SeO2) in a molar ratio of 2:1:2 in evacuated torch-sealed silica ampoules. For the terbium case, Tb4O7 and SeO2 have been reacted with elemental Tb in a molar ratio of 3:14:2. These lanthanoid(III) oxide oxoselenates(IV) all crystallize tetragonally with the space group P42/ncm and decreasing lattice parameters from the lighter to the heavier Ln3+ cations (from a=1077.03(8) pm and c=526.38(4) pm for Ln=Sm to a=1049.60(8) pm and c=516.04(4) pm for Ln=Tm) according to the lanthanide contraction. They show a three-dimensional network of condensed [LnO8]13− polyhedra with a channel structure, where all ψ1-tetrahedral [SeO3]2− units are coordinating with their O2− anions to square antiprisms [LnO8]13− and pointing with their non-bonding electron pairs into the empty channels, which propagate along [001]. As another characteristic feature of the crystal structure, [OLn4]10+ tetrahedra containing the non-selenium-bonded O2− anions are trans-edge-connected to form {[OLn4/2e]4+}∞1

Na2Y3Cl3[TeO3]4: Synthesis, Crystal Structure and Spectroscopic Properties of the Bulk Material and its Luminescent Eu3+-doped Samples

{}_\infty ^{\rm{1}}{\rm{\{ [O}}Ln_{4/2}^{\rm{e}}{{\rm{]}}^{{\rm{4}} + }}{\rm{\} }}

The new oxosilicate NaTbSi2O6: A comparison of its A- and D-type structure

chains, which run parallel to the lone-pair channels in [001] direction and build up a tetragonal rod-packing.

Das neue Neodym(III)‐Oxidchlorid‐Oxoselenat(IV) Nd7O5Cl3[SeO3]4

Colorless, platelet-shaped single crystals of Na2Y3Cl3[TeO3]4 were synthesized by a reaction of Y2O3 and TeO2 (molar ratio 3 : 8) in evacuated silica ampoules within five days at 775 °C with an excess of NaCl added as flux and reagent. The new quintenary compound crystallizes in the monoclinic space group C2/c with the lattice parameters a = 2380:69(14), b = 552:76(3), c = 1662:48(9) pm, β = 134:045(3)° and Z = 4. The crystal structure presents one of the rare oxotellurates(IV) containing isolated [TeO3]2− units, which could be verified by Raman spectroscopy. Doping with Eu3+ (3 mass-%) at the Y3+ sites in eightfold oxygen coordination leads to a strong orange-red luminescence of Na2Y3Cl3[TeO3]4:Eu3+ under UV excitation with a wavelength of λ = 254 nm. Beyond the electronic Eu3+ transitions of the 4 f 6 state, the fluorescence excitation spectrum shows an intense broad charge-transfer band resulting from both O2−→Eu3+ ligand-to-metal charge-transfer (LMCT) as well as electronic Eu3+ d→f and Te4+s→p transitions. The emission spectrum features the prominent f→f transitions of Eu3+-doped oxidic compounds. The optical band gaps of the undoped and doped samples were determined by diffuse reflectance spectroscopy revealing just minimal doping effects on the crystal structure. The optical band gaps could be assigned in the excitation spectrum in the charge-transfer broad-band region supporting the assumption of an inorganic antenna effect of the Te4+ cations. Graphical Abstract Na2Y3Cl3[TeO3]4: Synthesis, Crystal Structure and Spectroscopic Properties of the Bulk Material and its Luminescent Eu3+-doped Samples

Das erste Alkalimetall-Lanthanoid(III)-Iodid-Oxotellurat(IV): Na2Lu3I3[TeO3]4

Abstract Two different modifications of the composition NaTbSi2O6 were synthesized within the class of quaternary alkali-metal rare-earth metal(III) oxosilicates. Monoclinic NaTbSi2O6 (A-type structure: space group P21/c (no. 14); a = 542.57(4), b = 1376.54(9), c = 762.83(5) pm, β = 110.086(3)°, Vm = 80.557(9) cm3/mol, Z = 4) crystallizes isotypically with NaYSi2O6 und LiScSi2O6. In this ino-oxosilicate, the [SiO4]4– tetrahedra are vertex-shared and linked to form infinite zigzag chains ∞1{[SiO2/2vO2/1t]2–} along [001]. Both, the Na+ and the Tb3+ cations are coordinated by seven O2– anions each. The [TbO7]11– polyhedra get connected via trans-oriented edges to build up ∞1{[TbO4/2eO3/1t]7–} chains running along [001], which alternate with the ∞1{[SiO2/2vO2/1t]2–} chains. In contrast, triclinic NaTbSi2O6 with a novel D-type structure (space group: P-1 (no. 2), a = 549.41(4), b = 938.65(6), c = 972.30(7) pm, α = 117.263(2), β = 97.239(2), γ = 99.676(2)°, Vm = 85.798(9) cm3/mol, Z = 3) belongs to the cyclo-oxosilicates according to Na3Tb3[Si6O18] with Z = 1. The arrangement of the resulting corrugated six-membered [Si6O18]12– rings of vertex-shared [SiO4]4– tetrahedra is similar to a hexagonal closest packing parallel to (100). The two types of distorted [TbO6]9– octahedra are linked along [010] via common edges to form undulated infinite ∞1{[TbO4/2vO2/1t]5–} chains, which become alternatingly piled with the cyclo-[Si6O18]12– units and the incorporated Na+ cations along [010]. While the square-pyramidally coordinated (Na2)+ cations are situated between the isolated cyclo-oxohexasilicate anions, the sixfold coordinated (Na1)+ cations can be found inside the rings. They are therefore surrounded by the six bridging O2– anions of the cyclo-[Si6O18]12– units in a quasi-planar hexagonal coordination sphere.