Polarity and Chirality in Uranyl Borates: Insights into Understanding the Vitrification of Nuclear Waste and the Development of Nonlinear Optical Materials.

Wang, S. A., Alekseev, E. V., Ling, J., Liu, G. K., Depmeier, W. and Albrecht-Schmitt, T. E. (2010) Polarity and Chirality in Uranyl Borates: Insights into Understanding the Vitrification of Nuclear Waste and the Development of Nonlinear Optical Materials. Chemistry of Materials, 22 (6). pp. 2155-2163. DOI 10.1021/cm9037796.

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Abstract

Four new sodium uranyl borates, alpha-Na[(UO(2))(2)B(10)O(15)(OH)(5)] (NaUBO-1), beta-Na[(UO(2))2B(10)O(15)-(OH)(5)] (NaUBO-2), Na[(UO(2))(2) B(10)O(15)(OH)(5)]center dot 3H(2)O (NaUBO-3), and Na[UO(2))B(6)O(10)(OH)]center dot 2H(2)O (NaUBO-4), and four new thallium uranyl borates, alpha-Tl(2)[(UO(2))(2)B(11)O(18)(OH)(3)] (TIUBO-1), beta-Tl(2)[(UO(2))(2)B(11)O(18)(OH)(3)] (TIUBO-2), Tl[(UO(2))(2)B(10)O(16)(OH)(3)] (TIUBO-3), and Tl(2)[(UO(2))(2)B(11)O(19)-OH)] (TIUBO-4), have been prepared via the reaction of sodium nitrate or thallium nitrate, uranyl nitrate, and excess boric acid at 190 degrees C. These compounds share a common structural motif consisting of a linear uranyl, UO(2)(2+), cation surrounded by BO(3) triangles and BO(4) tetrahedra to create a UO(8) hexagonal bipyramidal environment around uranium. The borate anions bridge between uranlyl units to create sheets. Additional BO(3) triangles extend from the polyborate layers and are directed approximately perpendicular to the sheets. In some compounds, these units can link the layers togethher to yield three-dimensional networks with large pores to house the Na(+) or Tl(+) cations and water molecules. The structures are all noncentrosymmetric and are either polar or chiral. While the uranyl borate layers are noncentrosymmetric in and of themselves, there is also twisting of thhe interlayer BO(3) groups to reduce thhe interlayer spacing, producing helical features in some structures. Na[(UO(2))B(6)O(10)(OH)]center dot 2H(2)O and beta-Tl(2)[(UO(2))(2)B(11)O(18)(OH)(3)], which can be obtained as pure phases, display second-harmonic generation of 532 nm light from 1064 nm light.

Document Type: Article
Keywords: bond-valence parameters one-dimensional uranyl structural-characterization crystal-chemistry hydrothermal preparation plutonium compound boric-acid iodates uranium rb
Research affiliation: Kiel University
Refereed: Yes
Date Deposited: 22 Dec 2011 05:48
Last Modified: 28 Mar 2018 10:18
URI: https://oceanrep.geomar.de/id/eprint/15724

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