Nanostructured Magnetic Cuprate Cluster: Synthesis, Structure, UV-Vis Spectroscopy, and Magnetic Properties of a New Copper(II) Arsenate NaCuAsO4 Containing Discrete [Cu4O16

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• 作者：Mutlu Ulutagay-Kartin ; Shiou-Jyh Hwu ; and Jeffrey A. Clayhold
• 刊名：Inorganic Chemistry
• 出版年：2003
• 出版时间：April 7, 2003
• 年：2003
• 卷：42
• 期：7
• 页码：2405 - 2409
• 全文大小：134K
• 年卷期：v.42,no.7(April 7, 2003)
• ISSN：1520-510X

文摘

Crystals of copper(II) arsenate NaCuAsO₄ were grown by conventional high-temperature, solid-state methods inmolten-salt media. The compounds were characterized by single crystal X-ray diffraction, UV-vis spectroscopy,and magnetic susceptibility measurements. NaCuAsO₄ crystallizes in a monoclinic lattice with a = 6.002 (1) Å,b = 10.853 (2) Å, c = 10.373 (2) Å, = 91.50 (3), and V = 675.4(2) ų; P2₁/c (No. 14); Z = 8. The newlyisolated sodium copper(II) arsenate reveals a pseudo-one-dimensional channel structure where the sodium cationsreside. The extended framework contains nanostructured [Cu₄O₁₆]^24- magnetic clusters that are interlinked byclosed-shell, nonmagnetic AsO₄^3- oxy anions via sharing vertex oxygen atoms of the CuO₅ and AsO₄ polyhedralunits. Each [Cu₄O₁₆]^24- cluster consists of four CuO₅ square pyramidal units in a chair configuration centered bya center of inversion. The two crystallographically independent Cu²⁺ cations adopt the [4 + 1] CuO₅ Jahn-Tellerdistortion giving rise to an intense d-d transition in UV-vis absorption spectra. The magnetic susceptibilitymeasurements reveal that the title compound is antiferromagnetic. At high temperatures, the data follows a pureCurie law, suggesting noninteracting spins, but with a rapid suppression of the effective spin below T = 70 K. Atlow temperature, the susceptibility collapses, indicating spin gap formation as the magnetic-cluster material settlesinto the lowest energy magnetic singlet state. The current work in the exploratory synthesis of oxy compoundscontaining nanostructured transition-metal-oxide magnetic clusters leads to new materials for experimental andtheoretical developments of magnetic models.