Isolation and Crystallographic Characterization of Sm@C2v(3)-C80 Through Cocrystal Formation with NiII(octaethylporphyrin) or Bis(ethylenedithio)tetrathiafulval

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• 作者：Hua Yang ; Zhimin Wang ; Hongxiao Jin ; Bo Hong ; Ziyang Liu ; Christine M. Beavers ; Marilyn M. Olmstead ; Alan L. Balch
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：February 4, 2013
• 年：2013
• 卷：52
• 期：3
• 页码：1275-1284
• 全文大小：699K
• 年卷期：v.52,no.3(February 4, 2013)
• ISSN：1520-510X

文摘

Sm@C_2v(3)-C₈₀ has been separated from the carbon soot produced by electrical arc vaporization of graphite rods doped with Sm₂O₃ and purified. Its structure has been determined by single crystal X-ray diffraction using cocrystals obtained from either Ni^II(octaethylporphyrin) (Ni^II(OEP)) to form Sm@C_2v(3)-C₈₀路Ni^II(OEP)路1.68(toluene)路0.32(benzene) or bis(ethylenedithio)-tetrathiafulvalene (ET) to produce Sm@C_2v(3)-C₈₀路ET路0.5(toluene). Thus, this study offers the first opportunity to compare a common endohedral fullerene in two different cocrystals. Both cocrystals provide consistent information on the basic structure of Sm@C_2v(3)-C₈₀ but show that the distribution of samarium ion sites inside the carbon cage depends upon whether Ni^II(OEP) or ET is present. The samarium ion is disordered in both structures, but the prominent sites lie slightly off the 2-fold symmetry axis of the cage. Computational studies at the B3LYP level indicate that Sm@C_2v(3)-C₈₀ is more stable than any of the other six isomers of Sm@C₈₀ that obey the isolated pentagon rule (IPR). The surface electrostatic potential of the interacting components in the cocrystals has been examined to identify factors responsible for the ordering of the fullerene cages. The regions of the Ni^II(OEP) or ET molecules that are closest to the fullerene display negative potential, while the corresponding regions of the endohedral fullerene show positive potential in a consistent fashion in both cocrystals.