Flexible Vertex Engineers the Controlled Assembly of Distorted Supramolecular Tetrahedral and Octahedral Cages

Shu-Jin Bao, Ze-Ming Xu, Tian-Chen Yu, Ying-Lin Song,Heng Wang,Zheng Niu,Xiaopeng Li, Brendan F. Abrahams, 

Pierre Braunstein, and Jian-Ping Lang

Designing and building unique cage assemblies attract increasing interest from supramolecular chemists but remain synthetically challenging. Herein, we propose the use of a flexible vertex with adjustable angles to selectively form highly distorted tetrahedral and octahedral cages, for the first time, in which the flexible vertex forms from the synergistic effect of coordination and covalent interactions. The inherent interligand angle of the vertex can be modulated by guest anions present, which allows for the fine-tuning of different cage geometries. Furthermore, the reversible structural transformation between tetrahedral and octahedral cages was achieved by anion exchange monitored by mass spectrometric technique, the smaller anions favoring tetrahedral cages, while the larger anions supporting octahedral cages. Additionally, the KBr-based cage thin films exhibited prominent enhancement of their third-order NLO responses in two or three orders of magnitude compared to those obtained for their corresponding solutions. This work not only provides a new methodology to build irregular polyhedral structures in a controlled and tunable way but also provides access to new kinds of promising functional optical materials.

柔性顶点工程扭曲超分子四面体和八面体笼的受控组装

设计和构建独特的笼式组件吸引了超分子化学家越来越多的兴趣，但仍然具有综合挑战性。在这里，我们首次提出使用具有可调节角度的柔性顶点来选择性地形成高度扭曲的四面体和八面体笼，其中柔性顶点是由配位和共价相互作用的协同作用形成的。顶点的固有配体间角度可以通过存在的客体阴离子进行调节，从而可以微调不同的笼子几何形状。此外，四面体和八面体笼之间的可逆结构转变是通过质谱技术监测的阴离子交换实现的，较小的阴离子有利于四面体笼，而较大的阴离子支持八面体笼。此外，与相应解决方案相比，基于 KBr 的笼状薄膜的三阶 NLO 响应显着增强了两个或三个数量级。这项工作不仅提供了一种以可控和可调的方式构建不规则多面体结构的新方法，而且还提供了获得新型有前途的功能光学材料的途径。

 DOI: 10.34133/2022/9819343