Redox-responsive molecular helices with highly condensed π-clouds
Redox-responsive molecular helices with highly condensed π-clouds
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DOI：
10.1038/nchem.900
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发表时间：
2011-01-01
期刊：
影响因子：
21.8
通讯作者：
Aida, Takuzo
中科院分区：
文献类型：
--
作者：
Ohta, Eisuke;Sato, Hiroyasu;Aida, Takuzo
螺旋分子因其固有的手性结构和在分离手性化合物或构建分子机器等方面的应用潜力，长期以来一直受到化学家的关注。由于空间作用力，聚合物邻苯基采用紧密的螺旋构象，其中稠密堆积的亚苯基单元产生高度凝聚的pi-云。在这里，我们展示了一个低聚邻苯并经历了氧化还原响应的动态运动。在溶液中，螺旋发生快速反转。然而，在结晶过程中，观察到了手性对称性破坏现象，其中每个晶体只包含一种对映体形式。在非外消旋的混合物中，获得了左旋和右旋的晶体。此外，在溶液中，螺旋低聚物的动态运动被单电子氧化显著抑制。中性和氧化形式的X射线结晶学都表明，在氧化过程中产生的空穴是由重复的邻苯基共享的。这使得螺旋的构象锁定，并代表了持久的手部记忆。
Helices have long attracted the attention of chemists, both for their inherent chiral structure and their potential for applications such as the separation of chiral compounds or the construction of molecular machines. As a result of steric forces, polymeric o-phenylenes adopt a tight helical conformation in which the densely packed phenylene units create a highly condensed pi-cloud. Here, we show an oligomeric o-phenylene that undergoes a redox-responsive dynamic motion. In solution, the helices undergo a rapid inversion. During crystallization, however, a chiral symmetry-breaking phenomenon is observed in which each crystal contains only one enantiomeric form. Crystals of both handedness are obtained, but in a non-racemic mixture. Furthermore, in solution, the dynamic motion of the helical oligomer is dramatically suppressed by one-electron oxidation. X-ray crystallography of both the neutral and oxidized forms indicated that a hole, generated upon oxidation, is shared by the repeating o-phenylene units. This enables conformational locking of the helix, and represents a long-lasting chiroptical memory.