Department of Chemistry, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan.
J Am Chem Soc. 2020 Apr 29;142(17):7995-8005. doi: 10.1021/jacs.0c02455. Epub 2020 Apr 15.
The development of red or near-infrared light (NIR) switchable photochromic molecules is required for an efficient utilization of sunlight and regulation of biological activities. While the photosensitization of photochromic molecules to red or NIR light has been achieved by a two-photon absorption process, the development of a molecule itself having sensitivity to red or NIR light has been now a challenging study. Herein, we developed an efficient molecular design for realizing red or NIR-light-responsive negative photochromism based on binaphthyl-bridged imidazole dimers. The introduction of electron-donating substituents shows the red shift of the absorption band at the visible-light region because of the contribution of a charge-transfer transition. Especially, the introduction of a di(4-methoxyphenyl)amino group (TPAOMe) and a perylenyl group largely shifts the absorption edge of the stable colored form to 900 nm. In addition, because the absorption band of one of the derivatives substituted with TPAOMe covers the whole visible-light region, the colored form shows a neutral gray color. Upon red (660 nm) or NIR-light (790 nm) irradiation, we observed the negative photochromic reaction from the stable colored form to the metastable colorless form. Therefore, the substituted binaphthyl-bridged imidazole dimers constitute the attractive photoswitches within a biological window.
需要开发红光或近红外光（NIR）可切换光致变色分子，以有效利用阳光和调节生物活性。虽然光致变色分子的光致敏化作用可以通过双光子吸收过程来实现，但开发本身对红光或 NIR 光敏感的分子现在是一项具有挑战性的研究。在此，我们基于联萘基桥联咪唑二聚体开发了一种高效的分子设计，以实现红光或 NIR 光响应的负光致变色。供电子取代基的引入由于电荷转移跃迁的贡献而使可见光谱区的吸收带红移。特别是，引入二（4-甲氧基苯基）氨基（TPAOMe）和苝基基团会大大将稳定显色形式的吸收边缘移至 900nm。此外，由于一个用 TPAOMe 取代的衍生物的吸收带覆盖整个可见光区，因此显色形式呈现中性灰色。在红光（660nm）或近红外光（790nm）照射下，我们观察到从稳定显色形式到亚稳态无色形式的负光致变色反应。因此，取代的联萘基桥联咪唑二聚体在生物窗口内构成了有吸引力的光开关。
