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 UO 2 2 + uranyl group.