Abstract
A new rubidium uranyl silicate, Rb2(UO2)2O(Si3O8) (1), was obtained using high-temperature approach from the melt in silica tubes. Its crystal structure was solved by direct methods: hexagonal, P6/m, a = 27.7992(7), c = 7.2346(2) Å, V = 4841.8(3) Å3, R1 = 0.033. The structure of 1 represents a new structure type with unprecedented topology not observed before among U(VI) oxides and oxysalts. It is comprised of layers with large voids derived from the U3O8 structure formed exclusively by pentagonal UrO5 bipyramids. The low-occupied Rb sites are located in the interlayer space. The SiO4 silicate tetrahedra in the structure of 1 share vertices to form rolled [Si6O16]8− chains. The nanotubules [(UO2)(Si6O16)]6− penetrate through both U3O8-derived layers and Rb interlayer. These tubules are attached to the U3O8 derived sheets via uranyl-uranyl interactions and edge-sharing between silicate tetrahedra and UrO5 bipyramids.
Acknowledgments
Technical support by the X-Ray Diffraction and Geomodel Resource Centers of Saint-Petersburg State University is gratefully acknowledged.
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Research ethics: Not applicable.
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Author contributions: The authors have accepted responsibility for the entire content of this manuscript and approved its submission.
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Competing interests: The authors state no conflict of interest.
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Research funding: This work was financially supported by the Russian Science Foundation through the grant 23-27-00153 (E.V.N. and Y.G.T.).
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Data availability: The raw data can be obtained on request from the corresponding author.
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