Solution 31P NMR Study of the Acid-Catalyzed Formation of a Highly Charged {U24Pp12} Nanocluster, [(UO2)24(O2)24(P2O7)12]48–, and Its Structural Characterization in the Solid State Using Single-Crystal Neutron Diffraction

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• 作者：Mateusz Dembowski ; Travis A. Olds ; Kristi L. Pellegrini ; Christina Hoffmann ; Xiaoping Wang ; Sarah Hickam ; Junhong He ; Allen G. Oliver ; Peter C. Burns
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：July 13, 2016
• 年：2016
• 卷：138
• 期：27
• 页码：8547-8553
• 全文大小：508K
• 年卷期：0
• ISSN：1520-5126

文摘

The first neutron diffraction study of a single crystal containing uranyl peroxide nanoclusters is reported for pyrophosphate-functionalized Na₄₄K₆[(UO₂)₂₄(O₂)₂₄(P₂O₇)₁₂][IO₃]₂·140H₂O (1). Relative to earlier X-ray studies, neutron diffraction provides superior information concerning the positions of H atoms and lighter counterions. Hydrogen positions have been assigned and reveal an extensive network of H-bonds; notably, most O atoms present in the anionic cluster accept H-bonds from surrounding H₂O molecules, and none of the surface-bound O atoms are protonated. The D_4h symmetry of the cage is consistent with the presence of six encapsulated K cations, which appear to stabilize the lower symmetry variant of this cluster. ³¹P NMR measurements demonstrate retention of this symmetry in solution, while in situ ³¹P NMR studies suggest an acid-catalyzed mechanism for the assembly of 1 across a wide range of pH values.