Kang Hao-Wen, Liu Yu-Chiao, Shao Wei-Kai, Wei Yu-Chen, Hsieh Chi-Tien, Chen Bo-Han, Lu Chih-Hsuan, Yang Shang-Da, Cheng Mu-Jeng, Chou Pi-Tai, Chiang Ming-Hsi, Wu Yao-Ting
Department of Chemistry, National Cheng Kung University, 70101, Tainan, Taiwan.
Institute of Chemistry, Academia Sinica, 11529, Taipei, Taiwan.
Nat Commun. 2023 Aug 28;14(1):5248. doi: 10.1038/s41467-023-40990-8.
The rotation of a C = C bond in an alkene can be efficiently accelerated by creating the high-strain ground state and stabilizing the transition state of the process. Herein, the synthesis, structures, and properties of several highly twisted alkenes are comprehensively explored. A facile and practical synthetic approach to target molecules is developed. The twist angles and lengths of the central C = C bonds in these molecules are 36-58° and 1.40-1.43 Å, respectively, and confirmed by X-ray crystallography and DFT calculations. A quasi-planar molecular half with the π-extended substituents delivers a shallow rotational barrier (down to 2.35 kcal/mol), indicating that the rotation of the C = C bond is as facile as that of the aryl-aryl bond in 2-flourobiphenyl. Other versatile and unique properties of the studied compounds include a broad photoabsorption range (from 250 up to 1100 nm), a reduced HOMO-LUMO gap (1.26-1.68 eV), and a small singlet-triplet energy gap (3.65-5.68 kcal/mol).
通过创造高应变基态并稳定该过程的过渡态，可以有效地加速烯烃中C = C键的旋转。在此，对几种高度扭曲的烯烃的合成、结构和性质进行了全面探索。开发了一种简便实用的合成目标分子的方法。这些分子中中心C = C键的扭转角和长度分别为36 - 58°和1.40 - 1.43 Å，并通过X射线晶体学和密度泛函理论（DFT）计算得到证实。具有π-扩展取代基的准平面分子半部具有较低的旋转势垒（低至2.35 kcal/mol），这表明C = C键的旋转与2-氟联苯中芳基-芳基键的旋转一样容易。所研究化合物的其他通用且独特的性质包括宽光吸收范围（从250到1100 nm）、减小的最高占据分子轨道（HOMO）-最低未占据分子轨道（LUMO）能隙（1.26 - 1.68 eV）和小的单重态-三重态能隙（3.65 - 5.68 kcal/mol）。
