Channels occupancy and distortion in new lithium uranyl phosphates with three-dimensional open-frameworks
Channels occupancy and distortion in new lithium uranyl phosphates with three-dimensional open-frameworks
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DOI：
10.1016/j.jssc.2009.02.024
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发表时间：
2009-06
影响因子：
3.3
通讯作者：
C. Renard;S. Obbade;F. Abraham
中科院分区：
文献类型：
--
作者：
C. Renard;S. Obbade;F. Abraham
合成并研究了三种新的磷酸铀酰锂：Li_2（UO_2）_3（PO_4）_2 O（1）、Li（UO_2）_4（PO_4）_3（2）和Li_3（UO_2）_7（PO_4）_5 O（3）。通过固相反应合成了化合物1和化合物2的粉末，并将粉末1和化合物2熔融得到了三种化合物的单晶。三个化合物的结构已解决和从单晶X-射线衍射数据的改进。在这三种化合物中，铀原子占据正方形和五角双锥。铀正方双锥和磷酸盐四面体通过顶点连接形成两种类型的层，分别表示为S和D，具有钙铀云母片阴离子拓扑结构∞2[（UO 2）（PO 4）2]4-和∞2[（UO 2）2（PO 4）3]5-。铀酰五角双锥共享相对的赤道边缘，形成∞1[UO 5]4-无限链。相互垂直的链条悬挂在板的每一侧，以构建具有容纳锂离子的非交叉垂直通道的框架。S层和D层的各种堆叠顺序S-S、D-D和S-D分别在1、2和3中产生三种不同的框架。这些化合物与最近报道的钒酸盐类似物相似。然而，磷酸盐四面体，小于钒酸盐四面体，使层的变形和对称性的降低和/或周期性的变化。使用阻抗谱法测量1和2的电导率。锂阳离子的电导率相当低，这可以通过晶体结构和隧道内的Li+位置来解释。这些结果证实了类似的三维碱性钒酸铀酰。晶体学数据：293 K，BRUKER X8-APEX 2 X射线衍射仪，4K CCD检测器，MoKα，λ= 0.71073 Å，基于F. 1，四面体对称，空间群I41/amd，Z=4，a=7.1109（2）<$，c=25.0407（8）<$，R=0.034，wR=0.047，38个参数，479个独立反射，I <$3 σ（I）。2，单斜对称，空间群P21/c，Z=4，a=9.8829（2）<$，B=9.8909（2）<$，c=17.4871（4）<$，β=106.198（1）°，R=0.021，wR=0.031。3，四轴对称，空间群P4 <$21 m，a=9.9305（2）<$，c=14.5741（3）<$，R=0.035，wR=0.038，137个参数，4527个独立反射，i <$3 σ（I）。
Three new lithium uranyl phosphates, Li2(UO2)3(PO4)2O (1), Li(UO2)4(PO4)3(2) and Li3(UO2)7(PO4)5O (3) were synthesized and studied. Powders of 1 and 2 were synthesized via solid state reaction, and single crystals of the three compounds were obtained by melting of 1 and 2 powders. The structures of the three compounds have been solved and refined from single crystal X-ray diffraction data. In the three compounds, the uranium atoms occupy square and pentagonal bipyramids. The uranium square bipyramids and phosphate tetrahedra are connected by vertices to form two types of layers with autunite sheet anion-topology∞2[(UO2)(PO4)2]4-and∞2[(UO2)2(PO4)3]5-denoted S and D, respectively. The uranyl pentagonal bipyramids share opposite equatorial edges to form∞1[UO5]4-infinite chains. Mutually perpendicular chains are hung on each side of the sheets to build frameworks with non-crossing perpendicular channels that accommodate the lithium ions. Various stacking sequences of the S and D layers, S–S, D–D and S–D, generate three different frameworks in 1, 2 and 3, respectively. These compounds are similar to the recently reported vanadate analogous. However, the phosphate tetrahedra, smaller than the vanadate ones, gives distortion of the layers and a lowering of the symmetry and/or a change of periodicity. The electrical conductivity of 1 and 2 was measured using impedance spectroscopy method. The rather low conductivity of the lithium cations is explained by the crystal structure and the Li+position within the tunnels. These results corroborate those on the analogous three-dimensional alkaline uranyl vanadates. Crystallographic data: 293K, BRUKER X8-APEX2 X-ray diffractometer, 4K CCD detector, MoKα, λ=0.71073Å, full-matrix least-squares refinement on the basis of F. 1, Tetragonal symmetry, space group I41/amd, Z=4 with a=7.1109(2)Å and c=25.0407(8)Å, R=0.034 and wR=0.047 for 38 parameters with 479 independent reflections with I⩾3σ(I). 2, monoclinic symmetry, space group P21/c, Z=4 and a=9.8829(2)Å, b=9.8909(2)Å, c=17.4871(4)Å and β=106.198(1)°, R=0.021 and wR=0.031 for 249 parameters with 4201 independent reflections with I⩾3σ(I). 3, Tetragonal symmetry, space group P4¯21m with a=9.9305(2)Å and c=14.5741(3)Å, R=0.035 and wR=0.038 for 137 parameters with 4527 independent reflections with i⩾3σ(I).