Unexpected Structural Complexity in Cesium Thorium Molybdates

Three
cesium thorium molybdates [Cs2Th­(MoO4)3, Cs2Th3(MoO4)7, and
Cs4Th­(MoO4)4] were
synthesized via the high-temperature solid-state method. Cs2Th­(MoO4)3 crystallizes in orthorhombic space
group Pnnm, containing [Th­(MoO4)3]2– chains extending along the [100] direction.
Cs2Th3(MoO4)7 is based
on an open framework with channels occupied by Cs+ ions
and running parallel through the [100] direction. It is the first
case in which thorium atoms coordinate simultaneously in three distinct
environments, namely, 7-coordinated pentagonal bipyramid, 8-coordinated
square antiprism, and 9-coordinated tricapped trigonal prism. Cs4Th­(MoO4)4 is monoclinic, built from
[Th­(MoO4)4]4– sheets formed
by vertex sharing of MoO4 tetrahedra and ThO8 antiprisms. The Raman and infrared spectra were recorded, and the
vibrations related to internal and external Mo–O bonds in the
MoO42– coordination geometry were discussed.

本研究通过高温固相法合成了三种铯钍钼酸盐，分别为Cs₂Th(MoO₄)₃、Cs₂Th₃(MoO₄)₇与Cs₄Th(MoO₄)₄。Cs₂Th(MoO₄)₃属正交晶系，空间群为Pnnm，其结构中含有沿[100]方向延伸的[Th(MoO₄)₃]²⁻链。Cs₂Th₃(MoO₄)₇具有开放骨架结构，内部存在由Cs⁺离子占据且沿[100]方向平行延伸的孔道，该化合物是首例钍原子同时处于三种不同配位环境的体系，分别为7配位五角双锥、8配位四方反棱柱以及9配位三帽三角棱柱。Cs₄Th(MoO₄)₄为单斜晶系，其结构由[Th(MoO₄)₄]⁴⁻片层构成，该片层通过MoO₄四面体与ThO₈反棱柱的顶点共享连接形成。本研究测试了三种化合物的拉曼光谱与红外光谱，并对MoO₄²⁻配位几何中与Mo-O键内、外振动相关的谱峰进行了讨论。