Rekis T, Schönleber A, van Smaalen S. On the puzzling case of sodium saccharinate 1.875-hydrate: structure description in (3+1)-dimensional superspace.
ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2020;
76:18-27. [PMID:
32831236 PMCID:
PMC8788847 DOI:
10.1107/s2052520619014938]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 11/05/2019] [Indexed: 06/11/2023]
Abstract
The structure of sodium saccharinate 1.875-hydrate is presented in three- and (3+1)-dimensional space. The present model is more accurate than previously published superstructures, due to an excellent data set collected up to a high resolution of 0.89 Å-1. The present study confirms the unusual complexity of the structure comprising a very large primitive unit cell with Z' = 16. A much smaller degree of correlated disorder of parts of the unit cell is found than is present in the previously published models. As a result of pseudo-symmetry, the structure can be described in a higher-dimensional space. The X-ray diffraction data clearly indicate a (3+1)-dimensional periodic structure with stronger main reflections and weaker superstructure reflections. Furthermore, the structure is established as being commensurate. The structure description in superspace results in a four times smaller unit cell with an additional base centring of the lattice, resulting in an eightfold substructure (Z' = 2) of the 3D superstructure. Therefore, such a superspace approach is desirable to work out this high-Z' structure. The displacement and occupational modulation of the saccharinate anions have been studied, as well as their conformational variation along the fourth dimension.
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