Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
Acc Chem Res. 2014 Jul 15;47(7):2026-40. doi: 10.1021/ar5000677. Epub 2014 May 30.
Synthetic macrocyclic hosts have played key roles in the development of host-guest chemistry. Crown ethers are a class of macrocyclic molecules with unique flexible structures. They have served as the first generation of synthetic hosts, and researchers have extensively studied them in molecular recognition. However, the flexible structures of simple crown ethers and their relatively limited modes of complexation with guests have limited the further applications of these molecules. In recent years, researchers have moved toward fabricating interlocking molecules, supramolecular polymers, and other assemblies with specific structures and properties. Therefore, researchers have developed more complex crown ether-based macrocyclic hosts with multicavity structures and multicomplexation modes that provide more diverse and sophisticated host-guest systems. In this Account, we summarize our research on the synthesis and characterization of iptycene-derived crown ether hosts, their use as host molecules, and their applications in self-assembled complexes. Iptycenes including triptycenes and pentiptycenes are a class of aromatic compounds with unique rigid three-dimensional structures. As a result, they are promising building blocks for the synthesis of novel macrocyclic hosts and the construction of novel self-assembled complexes with specific structures and properties. During the last several years, we have designed and synthesized a new class of iptycene-derived crown ether hosts including macrotricyclic polyethers, molecular tweezer-like hosts, and tritopic tris(crown ether) hosts, which are all composed of rigid iptycene building blocks linked by flexible crown ether chains. We have examined the complexation behavior of these hosts with different types of organic guest molecules. Unlike with conventional crown ethers, the combination of iptycene moieties and crown ether chains provides the iptycene-derived crown ether hosts with complexation properties that differ based on the structure of the guests. The rigid iptycene moieties within these synthetic host molecules both maintain their inherent three-dimensional cavities and generate multicavity structures. The flexible crown ether chains allow the iptycene-derived hosts to adjust their conformations as they encapsulate guest molecules. Moreover, the expanded complexation properties also allow the host-guest systems based on the iptycene-derived crown ethers to respond to multiple external stimuli, resulting in a variety of supramolecular assemblies. Finally, we also describe the construction of mechanically interlocked self-assemblies, molecular switches/molecular machines, and supramolecular polymers using these new host molecules. We expect that the unique structural features and diverse complexation properties of these iptycene-derived crown ether hosts will lead to increasing interest in this field and in supramolecular chemistry overall.
合成大环主体在主客体化学的发展中发挥了关键作用。冠醚是一类具有独特柔性结构的大环分子。它们是第一代合成主体，研究人员在分子识别方面对其进行了广泛研究。然而，简单冠醚的柔性结构及其与客体结合的相对有限模式限制了这些分子的进一步应用。近年来，研究人员致力于制造具有特定结构和性质的互锁分子、超分子聚合物和其他组装体。因此，研究人员开发了具有多腔结构和多配位模式的更复杂的冠醚大环主体，为更广泛、更复杂的主客体体系提供了更多样化和复杂的主体。在本报告中，我们总结了我们在基于异丙叉冠醚主体的合成和表征及其作为主体分子的应用，以及在自组装配合物中的应用。异丙叉衍生物包括三亚苯和五亚苯，是一类具有独特刚性三维结构的芳香族化合物。因此，它们是合成新型大环主体和构建具有特定结构和性质的新型自组装配合物的有前途的构建块。在过去的几年中，我们设计并合成了一类新型的异丙叉衍生冠醚主体，包括大环聚醚、分子钳状主体和三齿三（冠醚）主体，它们均由刚性异丙叉砌块通过柔性冠醚链连接而成。我们研究了这些主体与不同类型有机客体分子的配合物行为。与传统冠醚不同，异丙叉部分和冠醚链的结合为异丙叉衍生冠醚主体提供了基于客体结构的不同的配合物性质。这些合成主体分子内的刚性异丙叉砌块既保持了其固有三维空腔，又产生了多腔结构。柔性冠醚链允许异丙叉衍生主体在包裹客体分子时调整其构象。此外，扩展的配合物性质还允许基于异丙叉衍生冠醚的主体-客体系统对外界刺激做出响应，从而产生各种超分子组装体。最后，我们还描述了使用这些新主体分子构建机械互锁自组装体、分子开关/分子机器和超分子聚合物。我们期望这些具有独特结构特征和多样化配合物性质的异丙叉衍生冠醚主体将引起人们对该领域和整个超分子化学的兴趣不断增加。
