Department of Chemistry and Biochemistry, University of South Carolina , Columbia, South Carolina 29208, United States.
J Am Chem Soc. 2014 Mar 12;136(10):3955-63. doi: 10.1021/ja412725r. Epub 2014 Mar 4.
A family of rare U(IV)-containing quaternary fluorides, Na4MU6F30 (M = Mn(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)), was synthesized in single crystal form via a mild hydrothermal technique utilizing an in situ U(VI) to U(IV) reduction step. The modified hydrothermal route is described, and the conditions to obtain single crystals in high yield are detailed. The crystal structures were determined by single crystal X-ray diffraction. The isostructural fluorides crystallize in a new structure type in the trigonal space group P3̅c1. They exhibit a complex three-dimensional crystal structure consisting of corner- and edge-shared UF9 and MF6 polyhedra. The main building block, a U6F30(6-) group, is arranged to create two distinct hexagonal channels, inside which MF6 octahedra and Na(+) cations are located. The copper-containing member of the series, Na4CuU6F30, is unusual in that the Cu(2+) cation exhibits a rare symmetrical coordination environment consisting of six identical Cu-F bond distances, indicating the lack of the expected Jahn-Teller distortion. Magnetic susceptibility measurements of Na4ZnU6F30 yielded an effective magnetic moment of 3.42 μB for the U(4+) (f(2)) cation in the structure. Measurements of the other members containing magnetic transition-metal cations in addition to U(4+), Na4MU6F30 (M = Mn(2+), Co(2+), Ni(2+), and Cu(2+)) yielded total effective magnetic moments of 10.2, 9.84, 8.87, and 8.52 μB for the Mn-, Co-, Ni-, and Cu-containing materials, respectively. No evidence for long-range magnetic ordering was found down to 2 K. Measurements of the magnetization as a function of applied magnetic field at 2 K for Na4MnU6F30 confirmed that the U(4+) magnetic cation exhibits a nonmagnetic singlet ground state at low temperature. Thermal stability measurements and UV-vis diffuse reflectance spectroscopy are also reported.
一种新型的含铀（IV）的四元氟化物家族，Na4MU6F30（M=Mn(2+)，Co(2+)，Ni(2+)，Cu(2+)，和 Zn(2+)），通过一种温和的水热技术，利用原位 U(VI)到 U(IV)的还原步骤，在单晶形式下被合成。描述了改进的水热路线，并详细说明了获得高产单晶的条件。晶体结构通过单晶 X 射线衍射确定。等结构的氟化物在新的三方晶系 P3̅c1 中结晶。它们表现出复杂的三维晶体结构，由角和边缘共享的 UF9 和 MF6 多面体组成。主要的建筑块，U6F30(6-)基团，被安排来创建两个不同的六方通道，在这些通道中，MF6 八面体和 Na(+)阳离子被定位。该系列的铜成员，Na4CuU6F30，是不寻常的，因为 Cu(2+)阳离子表现出罕见的对称配位环境，由六个相同的 Cu-F 键距离组成，表明缺乏预期的 Jahn-Teller 畸变。Na4ZnU6F30 的磁化率测量结果表明，结构中 U(4+)（f(2)）阳离子的有效磁矩为 3.42 μB。对其他除 U(4+)之外还含有磁性过渡金属阳离子的成员的测量，Na4MU6F30（M=Mn(2+)，Co(2+)，Ni(2+)，和 Cu(2+）），分别得到 Mn-、Co-、Ni-和 Cu- 含量材料的总有效磁矩为 10.2、9.84、8.87 和 8.52 μB。在 2 K 以下没有发现长程磁有序的证据。对 2 K 下 Na4MnU6F30 的磁化强度与外加磁场关系的测量证实，U(4+)磁性阳离子在低温下表现出非磁性单重态基态。还报告了热稳定性测量和紫外-可见漫反射光谱。
