31P Magic Angle Spinning NMR Spectroscopy of Paramagnetic Rare-Earth-Substituted Keggin and Wells-Dawson Solids

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• 作者：Wenlin Huang ; Mark Schopfer ; Cheng Zhang ; Robertha C. Howell ; Louis Todaro ; Becky A. Gee ; Lynn C. Francesconi ; Tatyana Polenova
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：January 16, 2008
• 年：2008
• 卷：130
• 期：2
• 页码：481 - 490
• 全文大小：433K
• 年卷期：v.130,no.2(January 16, 2008)
• ISSN：1520-5126

文摘

Paramagnetic rare-earth elements have been examined as NMR structural probes in polyoxoanionic solids, which have a variety of applications as luminescent materials that are usually disordered andtherefore intractable by traditional structural methods. Thirteen Keggin and Wells-Dawson polyoxotungstatescontaining substitutions with lanthanides of different effective magnetic moments have been examined by³¹P magic angle spinning NMR spectroscopy. The electron-nuclear dipolar interaction dominating thespinning sideband envelopes is determined by the lanthanide's magnetic moment and was found to be asensitive probe of the nature of the polyoxoanion, of the positional isomerism, and of the ion stoichiometry.Electron-nuclear dipolar anisotropies computed based on the point-dipole approximation are generallyin good agreement with the experimental results. The choice of a specific lanthanide as a structural probecan be tailored to the desired distance range between the phosphorus atoms and the paramagnetic centersto be probed. This approach is expected to be particularly useful in the paramagnetic polyoxoanionicmaterials lacking long-range order.