Adaptive Planar Chirality of Pillar[5]arenes Invertible by n-Alkane Lengths
Adaptive Planar Chirality of Pillar[5]arenes Invertible by n-Alkane Lengths
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DOI：
10.1021/jacs.3c01019
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发表时间：
2023-04-12
影响因子：
15
通讯作者：
Ogoshi, Tomoki
中科院分区：
文献类型：
--
作者：
Adachi, Keisuke;Fa, Shixin;Ogoshi, Tomoki
客体分子可以诱导和/或反转主体分子的手性。然而，使主体的手性适应正构烷烃的长度仍然是一个巨大的挑战，因为正构烷烃是中性、非手性和线性分子，导致与大多数化合物的相互作用较弱。在此，我们报告了一种具有适合正烷烃长度的手性系统，使用基于柱[5]芳烃的大环主体S-Br，其在每个边缘上包含五个立体碳和五个末端溴原子。 S-Br 的富电子空腔可以包含正构烷烃和平面手性异构体，其响应于络合正构烷烃的长度而敏感地反转。包含诸如正戊烷的短正烷烃使得S-Br更倾向于pS-形式，而包含诸如正庚烷的长正烷烃则更倾向于pR-形式。异构体稳定性的差异得到了晶体结构和理论计算的支持。此外，温度驱动 S-Br 与正烷烃的适应性手性。中等长度的正烷烃正己烷在较高温度下显示出 S-Br 的 pR 形式的优势，而在较低温度下则显示出 pS 形式。
Chirality of host molecules can be induced and/or inverted by the guest molecules. However, the adapting chirality of hosts to the length of n-alkanes remains a great challenge because n-alkanes are neutral, achiral, and linear molecules, resulting in a weak interaction with most compounds. Herein, we report a system with chirality adapted to n-alkane lengths, using a pillar[5]arene-based macrocyclic host, S-Br, which contains five stereogenic carbons and five terminal bromine atoms on each rim. The electron-rich cavity of S-Br could include n-alkanes and the planar-chiral isomers sensitively inverted in response to the lengths of the complexed n-alkanes. The inclusion of a short n-alkane such as n-pentane made S-Br more inclined to be in the pS-form, whereas the inclusion of long n-alkanes such as n-heptane made the pR-form more favorable. The difference in the stability of the isomers was supported by the crystal structures and the theoretical calculations. Furthermore, temperature drives the adaptive chirality of S-Br with n-alkanes. An n-alkane with middle length, n-hexane, showed the dominance of the pR-form of S-Br at a higher temperature, whereas the pS-form was shown at a lower temperature.