Scissor‐Shaped Photochromic Dyads: Hierarchical Self‐Assembly and Photoresponsive Property

Unique relationships between hierarchically organized biological nanostructures and functions have motivated chemists to construct sophisticated artificial nanostructured systems from small and simple synthetic molecules through self‐assembly. As one of such sophisticated systems, we have investigated scissor‐shaped photochromic dyads that can hierarchically self‐assemble into discrete nanostructures showing photoresponsive properties. We synthesized various azobenzene dyads and found that these dyads adopt intramolecularly folded conformation like a closed scissor, and then self‐assemble into toroidal nanostructures by generating curvature. The toroids further organize into nanotubes and further into helical supramolecular fibers depending on the nature of alkyl substituents. All of these nanostructures can be dissociated and reorganized through the photoisomerization of azobenzene units. On the other hand, the introduction of stilbene chromophores instead of azobenzenes leads to one‐dimensional supramolecular polymerization, which upon the intramolecular photocyclization of stilbene chromophores shifts to curved self‐assembly leading to helicoidal fibers with distinct supramolecular chirality.

层次化组织的生物纳米结构与功能之间的独特关系激励着化学家通过自组装由小而简单的合成分子构建复杂的人工纳米结构体系。作为此类复杂体系之一，我们研究了剪刀状光致变色二聚体，它们能够分级自组装成具有光响应特性的离散纳米结构。我们合成了各种偶氮苯二聚体，发现这些二聚体呈现出像闭合剪刀一样的分子内折叠构象，然后通过产生曲率自组装成环形纳米结构。根据烷基取代基的性质，这些环面进一步组装成纳米管，并进一步组装成螺旋状超分子纤维。所有这些纳米结构都可以通过偶氮苯单元的光异构化进行解离和重组。另一方面，引入芪发色团代替偶氮苯会导致一维超分子聚合，芪发色团发生分子内光环化时，会转变为弯曲自组装，形成具有独特超分子手性的螺旋状纤维。