Tong Xun, Qiu Yuan, Zhao Xiaoyu, Xiong Bijin, Liao Rongzhen, Peng Haiyan, Liao Yonggui, Xie Xiaolin
Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Soft Matter. 2019 Aug 21;15(31):6411-6417. doi: 10.1039/c9sm01310e. Epub 2019 Jul 23.
Photoresponsive supramolecular gels have aroused continuous attention because of their extensive applications; however, most studies utilize UV light, which inevitably brings about some health and environmental issues. The halogen bond is an important driving force for constructing supramolecules due to its high directionality, tunable strength, good hydrophobicity, and large size of the halogen atoms. Yet, it still remains a formidable challenge to utilize halogen bonds as a driving force to fabricate a visible light responsive gel. In this work, to fabricate such a gel, azopyridine-containing Azopy-C (n = 8, 10, 12) was selected as a halogen bond acceptor, while 1,2-bis(2,3,5,6-tetrafluoro-4-iodophenyl)diazene (BTFIPD) was chosen as both the halogen bond donor and visible light responsive moiety. The visible light response of BTFIPD resulted from the significant separation of n-π* energy levels between trans and cis isomers due to the introduction of an electron-withdrawing group (fluorine) to azobenzene at the ortho-position. Interestingly, the gel exhibited a good gel-to-sol transition behavior upon green light irradiation. At the same time, the morphologies varied from uniform narrow flakes to broad sheets with increasing illumination time. We provide an environmentally-friendly visible light-triggered method to regulate the phase transition of supramolecular materials in applications ranging from energy conversion to information storage.
光响应超分子凝胶因其广泛的应用而引起了持续关注；然而，大多数研究使用紫外光，这不可避免地带来了一些健康和环境问题。卤键由于其高方向性、可调强度、良好的疏水性以及卤原子的大尺寸，是构建超分子的重要驱动力。然而，利用卤键作为驱动力来制备可见光响应凝胶仍然是一个巨大的挑战。在这项工作中，为了制备这样一种凝胶，选择含偶氮吡啶的Azopy-C（n = 8、10、12）作为卤键受体，而1,2-双（2,3,5,6-四氟-4-碘苯基）二氮烯（BTFIPD）既被选作卤键供体又作为可见光响应部分。BTFIPD的可见光响应是由于在邻位向偶氮苯引入吸电子基团（氟）导致反式和顺式异构体之间n-π*能级的显著分离。有趣的是，该凝胶在绿光照射下表现出良好的凝胶-溶胶转变行为。同时，随着光照时间的增加，形态从均匀的窄薄片变为宽片。我们提供了一种环境友好的可见光触发方法，用于在从能量转换到信息存储等应用中调节超分子材料的相变。
