Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa, Japan.
J Phys Chem A. 2011 May 12;115(18):4650-6. doi: 10.1021/jp201969q. Epub 2011 Apr 15.
The photochromic [2.2]paracyclophane-bridged imidazole dimers show instantaneous coloration upon exposure to UV light and rapid fading in the dark. Experimental details for the enhancement of the photosensitivity and the unique photoisomerization of newly designed [2.2]paracyclophane-bridged imidazole dimers are demonstrated. We explored the structure-property relationships and demonstrated an efficient strategy for designing high-performance fast-photochromic molecules with increased photosensitivity to solar UVA radiation. The [2.2]paracyclophane-bridged imidazole dimer consists of two types of imidazole rings, Im1 and Im2. Im1 is characterized by a 6π electron system with an electron-donating characteristic, whereas Im2 is distinguished by a 4π electron system with an electron-withdrawing characteristic. The introduction of electron-donating substituents into the phenyl rings attached to the electron-withdrawing Im2 was proved to enhance the photosensitivity with the aid of the intramolecular charge transfer transitions. The unique photoisomerization resulting from the changes in the bonding manner between two imidazole rings was also investigated in detail.
光致变色[2.2]并环桥联咪唑二聚体在暴露于紫外光时会立即显色，并在黑暗中迅速褪色。本文展示了增强光敏感性和新设计的[2.2]并环桥联咪唑二聚体独特光异构化的实验细节。我们探索了结构-性质关系，并展示了一种设计具有高灵敏度的高性能快速光致变色分子的有效策略，以增加对太阳 UVA 辐射的敏感性。[2.2]并环桥联咪唑二聚体由两种类型的咪唑环组成，Im1 和 Im2。Im1 具有 6π 电子系统，具有供电子特性，而 Im2 则具有 4π 电子系统，具有吸电子特性。事实证明，在与吸电子 Im2 相连的苯环上引入供电子取代基，借助分子内电荷转移跃迁，可提高光敏感性。还详细研究了两个咪唑环之间键合方式变化引起的独特光异构化。
