American Chemical Society
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How are Centrosymmetric and Noncentrosymmetric Structures Achieved in Uranyl Borates?

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posted on 2010-03-15, 00:00 authored by Shuao Wang, Evgeny V. Alekseev, Jared T. Stritzinger, Wulf Depmeier, Thomas E. Albrecht-Schmitt
Four uranyl borates, UO2B2O4 (UBO-1), α-(UO2)2[B9O14(OH)4] (UBO-2), β-(UO2)2[B9O14(OH)4] (UBO-3), and (UO2)2[B13O20(OH)3]·1.25H2O (UBO-4), have been prepared from boric acid fluxes at 190 °C. UBO-3 and UBO-4 are centrosymmetric, whereas UBO-1 and UBO-2 are noncentrosymmetric (chiral and polar). These uranyl borates possess layered structures constructed from UO8 hexagonal bipyramids, BO3 triangles, and BO4 tetrahedra. In the case of UBO-4, clusters of BO3 triangles link the layers together to form open slabs with a thickness of almost 2 nm. The ability of uranyl borates to use very similar layers to yield both centrosymmetric and noncentrosymmetric layers is detailed in this work.