Syntheses of Uranyl Diphosphonate Compounds Using Encapsulated Cations as Structure Directing Agents

Five new uranyl phenyldiphosphonate compounds have been synthesized using cations encapsulated by a variety of crown ethers (18-crown-6, 15-crown-5, and 12-crown-4) as structure directing agents under mild hydrothermal conditions. These compounds, [(H3O)@C12H24O6]{(UO2)2[C6H4(PO3H)2]2F}·2H2O (U18C6-1), [K@C12H24O6]{(UO2)2[C6H4(PO3H)2]2F}·4H2O (U18C6-2), [(H3O)@C10H20O5]{(UO2)2[C6H4(PO3H)2]2F}·4H2O (U15C5-1), and [(H3O)C8H16O4][(UO2)(PO3HC6H4PO3H0.5)]2 (U12C4-1) are all layered, while [(H3O)C8H16O4]{(UO2)3[(PO3HC6H4PO3H0.5)2C6H4(PO3H)2]} (U12C4-2) adopts a three-dimensional channel structure. U18C6-1, U18C6-2, and U15C5-1 are constructed from UO6F pentagonal bipyramids, whereas U12C4-1 and U12C4-2 have UO7 and UO6 units, respectively. The crystal structures corroborate the proposed C3v and D3d conformational symmetries observed in H3O+ and K+ crown ether inclusion complexes, respectively. These compounds fluoresce at room temperature and display a red shift of 35 nm compared to the luminescence spectrum of uranyl nitrate hexahydrate.