Centre for Systems Chemistry, Stratingh Institute for Chemistry, and Zernike Institute for Advanced Materials, Faculty of Mathematics and Natural Sciences, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
J Org Chem. 2014 May 16;79(10):4446-55. doi: 10.1021/jo500411z. Epub 2014 Apr 25.
Overcrowded alkenes are among the most promising artificial molecular motors because of their ability to undergo repetitive light-driven unidirectional rotary motion around the central C═C bond. The exceptional features of these molecules render them highly useful for a number of applications in nanotechnology. Many of these applications, however, would benefit from higher rotation rates. To this end, a new molecular motor was designed, and the isomerization processes were studied in detail. The new motor comprises a fluorene lower half and a five-membered-ring upper half; the upper-half ring is fused to a p-xylyl moiety and bears a tert-butyl group at the stereogenic center. The kinetics of the thermal isomerization was studied by low-temperature UV-vis spectroscopy as well as by transient absorption spectroscopy at room temperature. These studies revealed that the tert-butyl and p-xylyl groups in the five-membered-ring upper half may be introduced simultaneously in the molecular design to achieve an acceleration of the rotation rate of the molecular motor that is larger than the acceleration obtained by using either one of the two groups individually. Furthermore, the new molecular motor retains unidirectional rotation while showing remarkably high photostationary states.
由于其能够在中央 C═C 键周围进行重复的光驱动单向旋转运动，因此过度拥挤的烯烃是最有前途的人工分子马达之一。这些分子的特殊性质使它们在纳米技术的许多应用中非常有用。然而，许多这些应用都将受益于更高的旋转速度。为此，设计了一种新型分子马达，并详细研究了其异构化过程。新型马达由芴的下半部分和五元环的上半部分组成；上半部分环与对二甲苯基部分融合，并在立体中心带有叔丁基。通过低温紫外可见光谱以及室温下的瞬态吸收光谱研究了热异构化的动力学。这些研究表明，五元环上半部分的叔丁基和对二甲苯基基团可以同时引入分子设计中，以实现分子马达的旋转速度的加速，其加速作用大于使用两个基团中的任一个单独获得的加速作用。此外，新型分子马达在保持单向旋转的同时表现出非常高的光稳定状态。
