Supramolecular receptor design: anion-triggered binding of C60.
Supramolecular receptor design: anion-triggered binding of C60.
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DOI：
10.1002/anie.200602724
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发表时间：
2006-10
影响因子：
--
通讯作者：
K. Nielsen;Won-seob Cho;G. Sarova;B. Petersen;A. Bond;J. Becher;F. Jensen;D. Guldi;J. Sessler;J. Jeppesen
中科院分区：
文献类型：
--
作者：
K. Nielsen;Won-seob Cho;G. Sarova;B. Petersen;A. Bond;J. Becher;F. Jensen;D. Guldi;J. Sessler;J. Jeppesen
在没有阴离子的情况下，吡咯，1主要存在于1，3-交替构象中。然而，在卤化溶剂中，1与氯离子结合非常紧密--在298K时，1与氯离子在1，2-二氯乙烷(DCE)中的络合反应的结合常数(KA)为2.5 106m±1，从而使其采用碗状构象(图1C)。在1的情况下，得到的碗形受体系统具有TTF衍生的富电子“壁”，因此有望作为缺乏电子的球形客体的受体，例如富勒烯。支持1的富电子TTF衍生的壁将稳定与电子缺乏客体C60的相互作用的观点来自于对从四丁基氯化铵、受体1和C60在甲苯中的混合物得到的晶体[41]进行的X射线晶体结构研究。这一结构揭示了[42]一个特殊的立方系综[(1·Cl)6(C60)8(甲苯)5]6±(图2)，其中8个C60分子定义了立方体的角部，1·Cl±单元位于每个立方体面上锁定在碗状构象中。氯离子位于立方体的内部，立方体还包裹着五个甲苯溶剂分子。每个1·Cl±单元上的四个TTF亚基都与C60分子相互作用，每个C60部分位于由富含电子的TTF亚基定义的三重对称空腔内。在固体状态下，碗形的内腔
pyrroles, 1 exists (Figure1B) predominantly in the 1, 3-alternate conformation in the absence of anions. However, in halogenated solvents 1 binds chloride anions very tightly—a binding constant (Ka) of 2.5 106 mÀ1 has been reported [39, 40] for the complexation of 1 with chloride ions in 1, 2-dichloroethane (DCE) at 298 K, thus leading it to adopt (Figure 1 C) a bowl-like conformation. In the case of 1, the resulting bowlshaped receptor system possesses TTF-derived electron-rich “walls” and was thus expected to act as a receptor for electron-deficient spherical guests such as fullerene, for example.Support for the notion that the electron-rich TTF-derived walls of 1 would stabilize interactions with the electrondeficient guest C60 came from an X-ray crystal structural study carried out on crystals [41] obtained from a mixture of tetrabutylammonium chloride, receptor 1, and C60 in toluene. This structure revealed [42] an extraordinary cubic ensemble [(1· Cl) 6 (C60) 8 (toluene) 5] 6À (Figure 2), in which eight C60 molecules define the corners of a cube and 1· ClÀ units lie within each cube face locked in the bowl-shaped conformation. The chloride anions lie to the inside of the cube, which also encapsulates five toluene solvent molecules. All four TTF-derived subunits on each 1· ClÀ unit interact with C60 molecules, and each C60 moiety lies within a threefold symmetric cavity defined by the electron-rich TTF subunits. In the solid state, the internal cavities of the bowl-shaped