Ito Shunichiro, Yaegashi Misao, Tanaka Kazuo, Chujo Yoshiki
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 6158510, Japan.
Chemistry. 2021 Jun 25;27(36):9302-9312. doi: 10.1002/chem.202101107. Epub 2021 May 27.
Leakage of volatile organic compounds (VOCs) is one of the most severe industrial problems, because it can cause environmental pollution, global warming, fire, and explosion. Hence, the visualization of leakage is an essential technology to detect it at an early stage. Molecular crystals, fluorescence color of which can be changed by the exposure to VOCs could potentially serve as the sensing materials for realizing rapid and facile VOC detection. However, these materials usually require harsh conditions, such as heating or a vacuum, to recover their initial phases for reuse. Therefore, it remains a challenge to obtain completely reversible sensing systems without such energy-consuming recycling processes. Herein, the reversible color change of fluorescence from the crystals of a propeller-shaped boron β-diketiminate complex is reported. The complex was crystallized in distinct crystalline phases having different luminescent colors. Importantly, these phases were interconverted very rapidly (time constant <60 s) and repeatedly upon exposure to the vapors of the appropriate VOCs. The small energy differences between conformers of the complex could lead to this pseudopolymorphic behavior. This finding could be applied for the development of further eco-friendly reversible sensing materials based on four-coordinated boron complexes.
挥发性有机化合物（VOCs）泄漏是最严重的工业问题之一，因为它会导致环境污染、全球变暖、火灾和爆炸。因此，泄漏可视化是早期检测泄漏的一项关键技术。分子晶体在暴露于VOCs时荧光颜色会发生变化，有可能用作实现快速简便的VOC检测的传感材料。然而，这些材料通常需要加热或真空等苛刻条件来恢复其初始状态以便重复使用。因此，在没有这种耗能回收过程的情况下获得完全可逆的传感系统仍然是一个挑战。在此，报道了一种螺旋桨状硼β-二酮配合物晶体荧光的可逆颜色变化。该配合物以具有不同发光颜色的不同晶相结晶。重要的是，这些相在暴露于适当VOCs的蒸汽时会非常迅速地相互转化（时间常数<60秒）并反复进行。配合物构象异构体之间的小能量差异可能导致这种假多晶型行为。这一发现可应用于基于四配位硼配合物的进一步环保可逆传感材料的开发。
