A uranium(IV) silicate has been synthesized under high-temperature, high-pressure hydrothermal conditions. The structure consists of unbranched dreier single layers with the composition [Si(2)O(5)] that are connected by UO(6) octahedra to form a 3D framework with 7-ring channels where the Cs(+) cations are located. Each UO(6) octahedron spans four neighboring dreier single chains and, therefore, introduces a high degree of corrugation in the silicate layers. The U 4f X-ray photoelectron spectroscopy spectrum was measured to confirm the valence state of the uranium. A comparison of related metal silicate structures is made. After the synthesis of this compound, all members in the family of uranium silicates and germanates with oxidation states of uranium from 4+ to 6+ have been observed.
A new uranyl silicate, K2Ca4[(UO2)(Si2O7)2], with a 1D chain structure has been synthesized from a solution of mixed alkali- and alkaline-earth-metal cations under hydrothermal conditions at 550 °C and 1400 bar and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. It crystallizes in the triclinic space group P1̅ (No. 2) with a = 6.6354(2) Å, b = 6.6791(2) Å, c = 9.6987(3) Å, α = 98.324(2)°, β = 93.624(2)°, γ = 112.310(2)°, and Z = 1. Its crystal structure consists of a 1D chain of uranyl disilicate formed of corner-sharing UO6 tetragonal bipyramids and Si2O7 double groups. The adjacent chains are separated by K(+) and Ca(2+) cations. It is the first example of uranyl silicate with a 1D chain structure.
A mixed-valence uranium(IV,VI) germanate has been synthesized under high-temperature, high-pressure hydrothermal conditions. The structure contains discrete U(IV)O(6) octahedra and U(VI)O(6) tetragonal bipyramids, which are connected by three-membered single-ring Ge(3)O(9)(6-) anions to form a three-dimensional framework with 9-ring channels. The U 4f X-ray photoelectron spectroscopy spectrum was measured to identify the valence states of the uranium.
Five new uranyl arsenates, Na14[(UO2)5(AsO4)8]·2H2O (1), K6[(UO2)5O5(AsO4)2] (2a), K4[(UO2)3O2(AsO4)2] (2b), Rb4[(UO2)3O2(AsO4)2] (3), and Cs6[(UO2)5O2(AsO4)4] (4), were synthesized by high-temperature, high-pressure hydrothermal reactions at about 560 °C and 1440 bar and were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and photoluminescence spectroscopy. Crystal data for compound 1: triclinic, P1, a = 7.0005(3) Å, b = 12.1324(4) Å, c = 13.7428(5) Å, α = 64.175(2)°, β = 89.092(2)°, γ = 85.548(2)°, V = 1047.26(7) Å(3), Z = 1, R1 = 0.0185; compound 2a: monoclinic, P2₁/c, a = 6.8615(3) Å, b = 24.702(1) Å, c = 7.1269(3) Å, β = 98.749(2)°, V = 1193.89(9) Å(3), Z = 2, R1 = 0.0225; compound 2b: monoclinic, P2₁/c, a = 6.7852(3) Å, b = 17.3640(8) Å, c = 7.1151(3) Å, β = 98.801(3)°, V = 828.42(6) Å(3), Z = 2, R1 = 0.0269; compound 3: monoclinic, P2₁/m, a = 6.9783(3) Å, b = 17.4513(8) Å, c = 7.0867(3) Å, β = 90.808(3)°, V = 862.94(7) Å(3), Z = 2, R1 = 0.0269; compound 4: triclinic, P1, a = 7.7628(3) Å, b = 9.3324(4) Å, c = 11.9336(4) Å, α = 75.611(2)°, β = 73.136(2)°, γ = 86.329(2)°, V = 801.37(5) Å(3), Z = 1, R1 = 0.0336. The five compounds have layer structures consisting of uranyl square, pentagonal, and hexagonal bipyramids as well as AsO4 tetrahedra. Compound 1 contains chains of discrete uranyl square and pentagonal bipyramids, 2a contains three-polyhedron-wide ribbons of edge- and corner-sharing uranyl square and pentagonal bipyramids, 2b and 3 contain dimers of edge-shairing pentagonal bipyramids that share edges with hexagonal bipyramids to form chains, and 4 contains one-polyhedron-wide zigzag chains of edge-sharing uranyl polyhedra. The double sheet structure of 1 is new, but the chain topology has been observed in an organically templated uranyl sulfate. Compound 2b is a new geometrical isomer of the phosphuranylite group. The sheet anion topologies of 2a and 4 can be obtained by splitting the β-U3O8-type sheet into complex chains and connecting the chains by arsenates.
A new uranium(VI) silicate, Cs(2)UO(2)Si(10)O(22), has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction, luminescence, and solid state NMR spectroscopy. It crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 12.2506(4) Å, b = 8.0518(3) Å, c = 23.3796(8) Å, β = 90.011(2)°, and Z = 4. Its structure consists of silicate double layers in the ab plane which are connected by UO(6) tetragonal bipyramids via four equatorial oxygen atoms to form a 3D framework with nine-ring channels parallel to the b axis where the Cs(+) cations are located. The photoluminescence emission spectrum at room temperature consists of one broad structured band which is typical of uranyl. The (29)Si MAS NMR spectrum is consistent with the crystal structure as determined from X-ray diffraction, and the resonances in the spectrum are assigned. A comparison of related uranyl silicate structures is made.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.