Wang Ya, Ma Yue, Ogumi Keisuke, Wang Bing, Nakagawa Takafumi, Fu Yao, Matsuo Yutaka
Hefei National Laboratory for Physical Sciences at the Microscale, School of Chemistry and Materials of Science, University of Science and Technology of China, 96 Jinzhai Road, 230026, Hefei, Anhui, China.
Department of Chemical System Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan.
Commun Chem. 2020 Jul 24;3(1):93. doi: 10.1038/s42004-020-00345-6.
Chromic materials, an important class of stimuli-responsive materials, have aroused extensive attention in recent years. Normally, their color is based on changes in morphology. Few examples of chromic material based on conformational isomerization, such as in overcrowded alkenes, have been reported previously. Furthemore, experimental thermodynamic studies of overcrowded bistricyclic aromatic enes have not been carried out to our knowledge. Here, we show that N-phenyl-substituted fluorenylidene-acridanes, with a properly modified fluorene moiety, performs chromisms originating from conformational changes. Thermodynamic studies determine equilibrium constants, changes in enthalpy, entropy, and free energy in solution, enabling in-depth understanding of the equilibrium behavior of overcrowded alkenes and providing useful information for designing functional chromic compounds. Single-crystal X-ray diffraction analysis of fluorenylidene-acridanes in this work clearly shows well-tuned charge transfer from the acridane to the fluorene moiety. Various chromic behaviors such as mechanochromism, thermochromism, solvatochromism, vapochromism, and proton-induced chromism also support understanding of conformational isomerism.
变色材料作为一类重要的刺激响应材料，近年来引起了广泛关注。通常情况下，它们的颜色基于形态变化。此前鲜有基于构象异构化的变色材料实例报道，如过度拥挤烯烃类。此外，据我们所知，尚未对过度拥挤的双环芳香烯进行过实验热力学研究。在此，我们表明，具有适当修饰芴基部分的N-苯基取代芴叉吖啶会发生源于构象变化的变色现象。热力学研究确定了溶液中的平衡常数、焓变、熵变和自由能变化，有助于深入理解过度拥挤烯烃的平衡行为，并为设计功能性变色化合物提供有用信息。这项工作中芴叉吖啶的单晶X射线衍射分析清楚地表明了从吖啶到芴基部分的电荷转移得到了良好调控。各种变色行为，如机械变色、热变色、溶剂变色、气致变色和质子诱导变色，也有助于理解构象异构现象。
