New Lanthanide Mixed-Valent Vanadium(III/IV) Oxosilicates, Ln4V5‿i>xZnxSi4O22 (Ln = La, Ce, Pr, and Nd), Crystallizing in a Quasi Two-Dimensional Rutile-Based Structure

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• 作者：Dileka Abeysinghe ; Mark D. Smith ; Jeongho Yeon ; Gregory Morrison ; Hans-Conrad zur Loye
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：February 15, 2016
• 年：2016
• 卷：55
• 期：4
• 页码：1821-1830
• 全文大小：564K
• ISSN：1520-510X

文摘

A family of lanthanide mixed-valent vanadium(III/IV) oxosilicates Ln₄V_5–xZn_xSi₄O₂₂ (Ln = La, Ce, Pr, and Nd) was synthesized as high-quality single crystals via a high-temperature molten salt method. An in situ reduction of V(V) to V(III/IV) as well as of Ce(IV) to Ce(III) was achieved utilizing Zn metal as the reducing agent, some of which is incorporated into the crystal structure. Ce₄V_4.77Zn_0.23Si₄O₂₂, to the best of our knowledge, is the first example of a cerium-containing mixed-valent vanadium silicate. The crystal structures were determined by single-crystal X-ray diffraction, and the four isostructural oxosilicates were determined to crystallize in the chevkinite-structure type in the monoclinic space group I2/a. The unit cells of the Ln₄V_5–xZn_xSi₄O₂₂ (Ln = La, Ce, Pr, and Nd) series are related to the reported C2/m phases Ln₄V₅Si₄O₂₂ (Ln = La, Pr, and Nd) by a doubling of the c-axis and a loss of a mirror plane. The three-dimensional crystal structure consist of two-dimensional rutile-based vanadium oxide and lanthanide oxide layers linked via Si₂O₇ groups. The temperature dependence of the magnetic susceptibility of these compounds was measured, and only the Nd analogue exhibited a magnetic transition at 5 K; all samples displayed a discontinuity or deviation from linearity at ca. 130–150 K.