A Simple and Versatile Strategy for Rapid Color Fading and Intense Coloration of Photochromic Naphthopyran Families
A Simple and Versatile Strategy for Rapid Color Fading and Intense Coloration of Photochromic Naphthopyran Families
复制标题
DOI：
10.1021/jacs.7b06293
复制
发表时间：
2017-09-27
影响因子：
15
通讯作者：
Abe, Jiro
中科院分区：
文献类型：
--
作者：
Inagaki, Yuki;Kobayashi, Yoichi;Abe, Jiro
苯环铬，即萘吡喃，是众所周知的光致变色分子，在光照射下发生光化学开环反应，形成两种颜色的开环异构体，即反体顺式和反体反式。虽然在热作用下，trans -cis - form返回到未着色的封闭形式，但由于其较高的热稳定性，trans - transform - form的衰落速率非常慢。这种变换变换的缓慢褪色行为导致残留颜色持续几分钟到几小时，并阻碍了此类分子在快速光电开关材料中的应用。我们发现了一种新的简单而通用的策略，通过在氮化铬的1位上引入烷氧基，即8h -吡喃喹啉，从而大大减少了不希望的长寿命的有色trans -trans - form的数量。烷氧基有效地减少了trans -trans型的形成，因为在trans -cis型中，C-H中心点中心点中心点O分子内氢键。此外，在3位上引入缩合芳环可以有效地提高开环反应的光敏性。这种策略也可以应用于萘吡喃衍生物，并有助于开发快速光响应光致变色透镜和快速光开关应用，如动态全息材料和分子致动器。
Benzo-annulated chromenes, i.e., naphthopyrans, are well-known photochromic molecules that undergo photochemical ring-opening reactions to form two colored open-ring isomers, the transoid-cis and transoid-trans forms, upon light irradiation. Though the transoid-cis form returns thermally to the uncolored closed form, the fading rate of the transoid-trans form is extremely slow because of its higher thermal stability. This slow fading behavior of the transoidtrans form is responsible for the persistence of residual color for several minutes to hours, and prevents the application of such molecules to fast photoswitching materials. We have found a new simple and versatile strategy to substantially reduce the amount of the undesirable long-lived colored transoid-trans form by introducing an alkoxy group at the 1-position of azino-fused chromenes, i.e., 8H-pyranoquinazolines. The alkoxy group effectively reduces the formation of the transoid-trans form due to C-H center dot center dot center dot O intramolecular hydrogen bonding in the transoid-cis form. Moreover, the introduction of a condensed aromatic ring at the 3-position was found to be effective to increase the photosensitivity of the ring-opening reaction. This strategy can also be applied for naphthopyran derivatives and is useful for the development of fast photoresponsive photochromic lenses and fast photoswitching applications such as dynamic holographic materials and molecular actuators.