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Published July 17, 2001 | Supplemental Material
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Synthesis, Structure, and Properties of Compounds in the NaHSO_4−CsHSO_4 System. 1. Crystal Structures of Cs_2Na(HSO_4)_3 and CsNa_2(HSO_4_)3

Abstract

Exploratory synthesis in the NaHSO₄-CsHSO₄ system, aimed at discovering novel proton conducting solids, resulted in the new compounds CsNa₂(HSO₄)₃ and Cs₂Na(HSO₄)₃. Single-crystal X-ray diffraction (performed at room temperature) revealed CsNa₂(HSO₄)₃ to crystallize in the cubic space group P2₁3 with lattice parameters a=10.568(2)Å and Z=4, whereas CS2Na(HSO₄)₃, studied by both single-crystal neutron and X-ray methods, crystallizes in the hexagonal space group P6₃/m. The latter compound has lattice parameters a=8.5712(17) and c=9.980(2)Å, and Z=2. The unit cell volumes are 1180.4(4) and 634.9(2)ų, respectively, giving calculated densities of 2.645 and 3.304 mg m⁻³. Refinement using all observed reflections yielded a weighted residual, R-w(F²), of 0.0515 based on F² X-ray values for CsNa₂(HSO₄)₃. For Cs₂Na(HSO₄)₃ the analogous X-ray and neutron values were 0.0483 and 0.1715, respectively. Both structures contain a single, crystallographically distinct, asymmetric hydrogen bond (as confirmed by NMR investigations) and unique, three-membered (HSO₄)₃ rings. The geometric match between the NaO₆ octahedra and the rings suggests the sodium polyhedra may serve to template the (HSO₄)₃ unit. In CsNa₂(HSO₄)₃ the rings form a distorted cubic close-packed array. The Cs atoms are located within the "octahedral" sites of this array, and the Na atoms, within the "tetrahedral" sites. The rings in CS₂Na(HSO₄)₃ are linked together by NaO6 octahedra to form infinite Na(HSO₄)₃ chains that extend along 001. The hexagonal compound exhibits disorder about the sulfate tetrahedron that suggests a P6₃/m → P6 phase transition may occur upon cooling.

Additional Information

© 2001 American Chemical Society. Received December 14, 2000. Revised Manuscript Received April 3, 2001. Publication Date (Web): July 17, 2001. CM000976A. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract DE-AC05-00OR22725. Work at BNL was carried out under Contract DE-AC02-98CH10886 with the U.S. Department of Energy, Office of Basic Energy Sciences. The authors are pleased to acknowledge the assistance of Dr. Sonjong Hwang with the NMR data collection and analysis. Prof. George Rossman kindly provided guidance with the optical microscopy investigations. This work was funded by the National Science Foundation and by the Irvine Foundation.

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