Sc2@C66 Revisited: An Endohedral Fullerene with Scandium Ions Nestled within Two Unsaturated Linear Triquinanes

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• 作者：Michio Yamada ; Hiroki Kurihara ; Mitsuaki Suzuki ; Jing Dong Guo ; Markus Waelchli ; Marilyn M. Olmstead ; Alan L. Balch ; Shigeru Nagase ; Yutaka Maeda ; Tadashi Hasegawa ; Xing Lu ; Takeshi Akasaka
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：May 28, 2014
• 年：2014
• 卷：136
• 期：21
• 页码：7611-7614
• 全文大小：277K
• 年卷期：v.136,no.21(May 28, 2014)
• ISSN：1520-5126

文摘

The geometries of fullerenes are governed by the isolated pentagon rule (IPR), which states that stable fullerenes have each of their 12 pentagons surrounded by five hexagons. At the dawn of fullerene science, it was widely believed that the IPR would also be applicable for endohedral fullerenes. In 2000, that idea was altered by the discovery of the first non-IPR fullerenes, Sc₂@C₆₆ and Sc₃N@C₆₈. The structural data for Sc₂@C₆₆ were interpreted to indicate the presence of a pair of doubly fused pentagons. However, that structure has remained a long-standing mystery, since it is thermodynamically unfavorable. Here, we demonstrate definitively that Sc₂@C₆₆ does not have the structure that was long believed to be but a brand new type. 2D NMR spectroscopic and single-crystal X-ray analyses disclose that Sc₂@C₆₆ has a C_2v(4059)-C₆₆ cage containing two sets of unsaturated linear triquinanes (ULTs), in which three pentagons abut one another and two scandium ions are located within the folds of each of the ULT units.