Observation of the Same New Sheet Topology in Both the Layered Uranyl Oxide-Phosphate Cs[(UO)(PO)O] and the Layered Uranyl Oxyfluoride-Phosphate Rb[(UO)(PO)OF] 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[(UO)(PO)O] () and Rb[UO)(PO)OF] () contain uranyl phosphate layers exhibiting a new sheet topology that can be related to that of β-UO, while CsK[(UO)OF(PO)(UO)] () and RbK[(UO)OF(PO)(UO)] () contain layers of a known isomer of the prominent phosphuranylite topology. The location of the fluorine in structures - 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 () and in contrast an oxyfluoride phase for the Rb containing phase (). Ion exchange experiments were performed on and 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 and and the UV-vis and fluorescence spectra show features characteristic of the uranyl group.