A Family of Layered Phosphates Crystallizing in a Rare Geometrical Isomer of the Phosphuranylite Topology: Synthesis, Characterization, and Computational Modeling of A4[(UO2)3O2(PO4)2] (A = Alkali Metal) Exhibiting Intralayer Ion Exchange
Single crystals of eight new layered uranyl phosphates were grown from alkali chloride fluxes: Cs1.4K2.6[(UO2)3O2(PO4)2], Cs0.7K3.3[(UO2)3O2(PO4)2], Rb1.4K2.6[(UO2)3O2(PO4)2], K4[(UO2)3O2(PO4)2], K2.9Na0.9Rb0.2[(UO2)3O2(PO4)2], K2.1Na0.7Rb1.2[(UO2)3O2(PO4)2], Cs1.7K4.3[(UO2)5O5(PO4)2], and Rb...
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Published in: | Inorganic chemistry 2018-04, Vol.57 (8), p.4726-4738 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | Single crystals of eight new layered uranyl phosphates were grown from alkali chloride fluxes: Cs1.4K2.6[(UO2)3O2(PO4)2], Cs0.7K3.3[(UO2)3O2(PO4)2], Rb1.4K2.6[(UO2)3O2(PO4)2], K4[(UO2)3O2(PO4)2], K2.9Na0.9Rb0.2[(UO2)3O2(PO4)2], K2.1Na0.7Rb1.2[(UO2)3O2(PO4)2], Cs1.7K4.3[(UO2)5O5(PO4)2], and Rb1.6K4.4[(UO2)5O5(PO4)2]. All structures crystallize in the monoclinic space group, P21/c and contain uranyl phosphate layers with alkali metals located between the layers for charge balance. Ion exchange experiments on Cs0.7K3.3[(UO2)3O2(PO4)2], Rb1.4K2.6[(UO2)3O2(PO4)2], and K4[(UO2)3O2(PO4)2] demonstrated that Cs and Rb cations cannot be exchanged for K cations; however, K cations can be readily exchanged for Na, Rb, and Cs. Enthalpies of formation were calculated from density functional theory (DFT) and volume-based thermodynamics (VBT) for all six structures. A value for the enthalpy of formation of the phosphuranylite sheet, [(UO2)3O2(PO4)2]4–, was derived using single-ion additive methods coupled with VBT. DFT and VBT calculations were used to justify results of the ion exchange experiments. Cs0.7K3.3[(UO2)3O2(PO4)2], Rb1.4K2.6[(UO2)3O2(PO4)2], and K4[(UO2)3O2(PO4)2] exhibit typical luminescence of the uranyl group. |
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ISSN: | 0020-1669 1520-510X |
DOI: | 10.1021/acs.inorgchem.8b00434 |