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• 作者：Hongyun Fang ; Hailin Cong ; Mitsuaki Suzuki ; Lipiao Bao ; Bing Yu ; Yunpeng Xie ; Naomi Mizorogi ; Marilyn M. Olmstead ; Alan L. Balch ; Shigeru Nagase ; Takeshi Akasaka ; Xing Lu
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：July 23, 2014
• 年：2014
• 卷：136
• 期：29
• 页码：10534-10540
• 全文大小：432K
• ISSN：1520-5126

文摘

The endohedral fullerene once erroneously identified as Sc₃@C₈₂ was recently shown to be Sc₃C₂@I_h-C₈₀, the first example of an open-shell cluster metallofullerene. We herein report that benzyl bromide (1) reacts with Sc₃C₂@ I_h-C₈₀ via a regioselective radical addition that affords only one isomer of the adduct Sc₃C₂@I_h-C₈₀(CH₂C₆H₅) (2) in high yield. An X-ray crystallographic study of 2 demonstrated that the benzyl moiety is singly bonded to the fullerene cage, which eliminates the paramagnetism of the endohedral in agreement with the ESR results. Interestingly, X-ray results further reveal that the 3-fold disordered Sc₃C₂ cluster adopts two different configurations inside the cage. These configurations represent the so-called 鈥減lanar鈥?form and the computationally predicted, but not crystallographically characterized, 鈥渢rifoliate鈥?form. It is noteworthy that this is the first crystallographic observation of the 鈥渢rifoliate鈥?form for the Sc₃C₂ cluster. In contrast, crystallographic investigation of a Sc₃C₂@I_h-C₈₀/Ni(OEP) cocrystal, in which the endohedral persists in an open-shell structure with paramagnetism, indicates that only the former form occurs in pristine Sc₃C₂@ I_h-C₈₀. These results demonstrate that the cluster configuration in EMFs is highly sensitive to the electronic structure, which is tunable by exohedral modification. In addition, the electrochemical behavior of Sc₃C₂@I_h-C₈₀ has been markedly changed by the radical addition, but the absorption spectra of the pristine and the derivative are both featureless. These results suggest that the unpaired electron of Sc₃C₂@I_h-C₈₀ is buried in the Sc₃C₂ cluster and does not affect the electronic configuration of the cage.