Krivovichev S V, Cahill C L, Burns P C
Department of Civil Engineering and Geological Sciences, University of Notre Dame, 156 Fitzpatrick Hall, Notre Dame, Indiana 46556, USA.
Inorg Chem. 2003 Apr 7;42(7):2459-64. doi: 10.1021/ic020516e.
Single crystals of (NH(4))(4)(UO(2))(5)(MoO(4))(7)(5) have been synthesized hydrothermally using (NH(4))(6)Mo(7)O(24), (UO(2))(CH(3)COO)(2).2H(2)O, and H(2)O at 180 degrees C. The phase has been characterized by single-crystal X-ray diffraction using a merohedrally twinned single crystal: it is hexagonal, P6(1), a = 11.4067(5) A, c = 70.659(5) A, V = 7961.9(7) A(3), and Z = 6. The structure is based upon an open framework with composition (UO(2))(5)(MoO(4))(7) that is composed of UO(7) pentagonal bipyramids that share vertexes with MoO(4) tetrahedra. The framework has large channels (effective pore size: 4.8 x 4.8 A(2)) parallel to the c axis and a system of smaller channels (effective pore size: 2.5 x 3.6 A(2)) parallel to [100], [110], [010], [110], [110], and [110]. The channels are occupied by NH(4)(+) cations and H(2)O molecules. The topological structure of the uranyl molybdate framework can be described either in terms of fundamental chains of UO(7) pentagonal bipyramids and MoO(4) tetrahedra or in terms of tubular building units parallel to the c axis.
使用(NH₄)₆Mo₇O₂₄、(UO₂)(CH₃COO)₂·2H₂O和H₂O在180℃水热合成了(NH₄)₄(UO₂)₅(MoO₄)₇₅的单晶。该相已通过使用一个缺面体孪晶单晶进行的单晶X射线衍射表征：它是六方晶系，P6₁，a = 11.4067(5) Å，c = 70.659(5) Å，V = 7961.9(7) ų，Z = 6。结构基于一个开放骨架，其组成为[(UO₂)₅(MoO₄)₇]⁴⁻，由UO₇五角双锥与MoO₄四面体共享顶点构成。该骨架具有平行于c轴的大通道（有效孔径：4.8×4.8 Ų）以及平行于[100]、[110]、[010]、[110]、[110]和[110]的较小通道体系（有效孔径：2.5×3.6 Ų）。通道中填充有NH₄⁺阳离子和H₂O分子。铀酰钼酸盐骨架的拓扑结构既可以用UO₇五角双锥和MoO₄四面体的基本链来描述，也可以用平行于c轴的管状结构单元来描述。
