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• 作者：Jeongho Yeon ; Mark D. Smith ; Joshua Tapp ; Angela M枚ller ; Hans-Conrad zur Loye
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：March 12, 2014
• 年：2014
• 卷：136
• 期：10
• 页码：3955-3963
• 全文大小：523K
• 年卷期：v.136,no.10(March 12, 2014)
• ISSN：1520-5126

文摘

A family of rare U(IV)-containing quaternary fluorides, Na₄MU₆F₃₀ (M = Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺), 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鈥?/sup> 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, Na₄CuU₆F_30, is unusual in that the Cu2+ cation exhibits a rare symmetrical coordination environment consisting of six identical Cu鈥揊 bond distances, indicating the lack of the expected Jahn鈥揟eller distortion. Magnetic susceptibility measurements of Na₄ZnU₆F₃₀ yielded an effective magnetic moment of 3.42 渭_B for the U4+ (f2) cation in the structure. Measurements of the other members containing magnetic transition-metal cations in addition to U4+, Na₄MU₆F₃₀ (M = Mn2+, Co2+, Ni2+, and Cu2+) yielded total effective magnetic moments of 10.2, 9.84, 8.87, and 8.52 渭_B 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 U4+ magnetic cation exhibits a nonmagnetic singlet ground state at low temperature. Thermal stability measurements and UV鈥搗is diffuse reflectance spectroscopy are also reported.}