Tetrabenzo[8]circulene: Aromatic Saddles from Negatively Curved Graphene
Tetrabenzo[8]circulene: Aromatic Saddles from Negatively Curved Graphene
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DOI：
10.1021/ja407842z
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发表时间：
2013-09-25
影响因子：
15
通讯作者：
Suzuki, Toshiyasu
中科院分区：
文献类型：
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作者：
Sakamoto, Youichi;Suzuki, Toshiyasu
芳香鞍是由具有负高斯曲率的假设三维石墨烯（Schwarzite P192）设计而成。通过环状八苯撑前体的 Scholl 反应合成了两种芳香鞍，四苯并[8]环烯 (TB8C) 及其八甲基衍生物 OM-TB8C。 TB8C的结构大大偏离平面性，并且通过单晶X射线晶体学证实了深鞍形。有两个具有 S-4 对称性的构象异构体，与 DFT 结构 (D-2d) 相比，它们是扭曲的。理论研究表明TB8C通过平面过渡态(125 kcal mol(-1))的相互转化是不可能的。然而，赝旋转通过非平面过渡态（7.3 kcal mol(-1)）导致低能管到管反转。由于晶体堆积力和低能赝旋转，TB8C在溶液中的基态结构与X射线结构有很大不同。 OM-TB8C 是良好的电子给体，可作为 p 型半导体。
An aromatic saddle was designed from the hypothetical three-dimensional graphene with the negative Gaussian curvature (Schwarzite P192). Two aromatic saddles, tetrabenzo[8]circulene (TB8C) and its octamethyl derivative OM-TB8C, were synthesized by the Scholl reaction of cyclic octaphenylene precursors. The structure of TB8C greatly deviates from planarity, and the deep saddle shape was confirmed by single-crystal X-ray crystallography. There are two conformers with the S-4 symmetry, which are twisted compared to the DFT structure (D-2d). The theoretical studies propose that the interconversion of TB8C via the planar transition state (125 kcal mol(-1)) is not possible. However, the pseudorotation leads to a low-energy tub-to-tub inversion via the nonplanar transition state (7.3 kcal mol(-1)). The ground-state structure of TB8C in solution is quite different from the X-ray structure because of the crystal-packing force and low-energy pseudorotation. OM-TB8C is a good electron donor and works as the p-type semiconductor.