Xie Fan, Ouyang Guanghui, Qin Long, Liu Minghua
CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Collaborative Innovation Centre of Chemical Science and Engineering, Tianjin, 300072, P. R. China.
Chemistry. 2016 Dec 12;22(50):18208-18214. doi: 10.1002/chem.201603998. Epub 2016 Nov 10.
A novel amphiphilic dendron (AZOC GAc) with three l-glutamic acid units and an azobenzene moiety covalently linked by an alkyl spacer has been designed. The compound formed hydrogels with water at very low concentration and self-assembled into chiral-twist structures. The gel showed a reversible macroscopic volume phase transition in response to pH variations and photo-irradiation. During the photo-triggered changes, although the gel showed complete reversibility in its optical absorptions, only an incomplete chiroptical property change was achieved. On the other hand, the dendron could form a 1:1 inclusion complex through a host-guest interaction with α-cyclodextrin (α-CD), designated as supra-dendron gelator AZOC GAc/α-CD. The supra-dendron showed similar gelation behavior to that of AZOC GAc, but with enhanced photoisomerization-transition efficiency and chiroptical switching capacity, which was completely reversible in terms of both optical and chiroptical performances. The self-assembly of the supra-dendron is a hierarchical or multi-supramolecular self-assembling process. This work has clearly illustrated that the hierarchical and multi-supramolecular self-assembling system endows the supramolecular nanostructures or materials with superior reversible optical and chiroptical switching.
设计了一种新型两亲性树枝状分子（AZOC GAc），其具有三个L-谷氨酸单元和一个通过烷基间隔基共价连接的偶氮苯部分。该化合物在极低浓度下与水形成水凝胶，并自组装成手性扭曲结构。该凝胶在响应pH变化和光照射时表现出可逆的宏观体积相变。在光触发变化过程中，尽管凝胶在光吸收方面表现出完全可逆性，但在手性光学性质变化方面仅实现了不完全可逆。另一方面，该树枝状分子可以通过与α-环糊精（α-CD）的主客体相互作用形成1:1包合物，称为超树枝状分子凝胶剂AZOC GAc/α-CD。该超树枝状分子表现出与AZOC GAc相似的凝胶化行为，但具有更高的光异构化转变效率和手性光学开关能力，在光学和手性光学性能方面都是完全可逆的。超树枝状分子的自组装是一个分级或多超分子自组装过程。这项工作清楚地表明，分级和多超分子自组装系统赋予超分子纳米结构或材料优异的可逆光学和手性光学开关性能。
