Hamatani Shota, Kitagawa Daichi, Kobatake Seiya
Department of Chemistry and Bioengineering, Graduate School of Engineering, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka, 558-8585, Japan.
Angew Chem Int Ed Engl. 2024 Dec 16;63(51):e202414121. doi: 10.1002/anie.202414121. Epub 2024 Oct 24.
Exploring novel molecular photoswitches plays a crucial role in the field of photo-functional materials chemistry. In this study, we synthesized aza-diarylethenes with benzothiophene-S,S-dioxide as a part of the hexatriene structure and investigated their photochromic properties. Unlike previously reported aza-diarylethenes, which exhibit fast thermally reversible photochromism, the compounds synthesized here exhibited pseudo-photochemically reversible photochromism. Due to their thermal stability, we successfully isolated the colored isomer. X-ray crystallographic analysis revealed for the first time that the colored isomer adopts a closed-ring structure with a bond between carbon and nitrogen atoms. Remarkably, these aza-diarylethenes exhibited not only photochemical ring-closing and ring-opening reactions but also thermal ring-closing and ring-opening reactions, driven by a thermal equilibrium between the open- and closed-ring isomers. This behavior, unprecedented for common diarylethenes, was elucidated through kinetic analysis, revealing an energy-level diagram for the thermal equilibrium between these isomers. Furthermore, H NMR spectroscopy revealed that both photochemically and thermally generated closed-ring isomers adopt the same molecular structure, which was well explained based on the reaction mechanism of photochemical and thermal ring-closing reactions. These findings not only advance the field of aza-diarylethenes but also inspire future research in the development of new photoswitches.
探索新型分子光开关在光功能材料化学领域起着至关重要的作用。在本研究中，我们合成了以苯并噻吩 - S,S - 二氧化物作为己三烯结构一部分的氮杂二芳基乙烯，并研究了它们的光致变色性能。与先前报道的表现出快速热可逆光致变色的氮杂二芳基乙烯不同，这里合成的化合物表现出假光化学可逆光致变色。由于它们的热稳定性，我们成功分离出了有色异构体。X射线晶体学分析首次揭示，有色异构体采用了在碳原子和氮原子之间形成键的闭环结构。值得注意的是，这些氮杂二芳基乙烯不仅表现出光化学闭环和开环反应，还表现出由开环和闭环异构体之间的热平衡驱动的热闭环和开环反应。这种行为对于常见的二芳基乙烯来说是前所未有的，通过动力学分析得以阐明，揭示了这些异构体之间热平衡的能级图。此外，核磁共振光谱表明，光化学和热产生的闭环异构体都采用相同的分子结构，这基于光化学和热闭环反应的反应机理得到了很好地解释。这些发现不仅推动了氮杂二芳基乙烯领域的发展，也为新型光开关的开发激发了未来的研究。
