Observation of the Same New Sheet Topology in Both the Layered Uranyl Oxide-Phosphate Cs(11)[(UO(2))(12)(PO(4))(3)O(13)] and the Layered Uranyl Oxyfluoride-Phosphate Rb(11)[(UO(2))(12)(PO(4))(3)O(12)F(2)] Prepared by Flux Crystal Growth

Single crystals of four new layered uranyl phosphates, including three oxyfluoride-phosphates, were synthesized by molten flux methods using alkali chloride melts, and their structures were determined by single-crystal X-ray diffraction. Cs(11)[(UO(2))(12)(PO(4))(3)O(13)] (1) and Rb(11)[UO(2))(12)(PO(4))(3)O(12)F(2)] (2) contain uranyl phosphate layers exhibiting a new sheet topology that can be related to that of β-U(3)O(8), while Cs(4.4)K(0.6)[(UO(2))(6)O(4)F(PO(4))(4)(UO(2))] (3) and Rb(4.4)K(0.6)[(UO(2))(6)O(4)F(PO(4))(4)(UO(2))] (4) contain layers of a known isomer of the prominent phosphuranylite topology. The location of the fluorine in structures 2-4 is discussed using bond valence sums. First principles calculations were used to explore why a pure oxide structure is obtained for the Cs containing phase (1) and in contrast an oxyfluoride phase for the Rb containing phase (2). Ion exchange experiments were performed on 1 and 2 and demonstrate the ability of these structures to exchange approximately half of the parent alkali cation with a target alkali cation in an aqueous concentrated salt solution. Optical measurements were performed on 1 and 2 and the UV-vis and fluorescence spectra show features characteristic of the [Formula: see text] uranyl group.