Aromatic amide and hydrazide foldamer-based responsive host-guest systems.
Aromatic amide and hydrazide foldamer-based responsive host-guest systems.
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DOI：
10.1021/ar5000242
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发表时间：
2014-03
影响因子：
18.3
通讯作者：
Dan‐Wei Zhang;Xin Zhao;Zhanting Li
中科院分区：
文献类型：
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作者：
Dan‐Wei Zhang;Xin Zhao;Zhanting Li
摘要：在主客体化学中，较大的主体分子选择性地、非共价地与较小的客体分子或离子结合。早期的主客体化学研究主要集中在环状冠醚等大环主体对球形金属或氨离子的识别。在这些系统中，预组织使它们的结合部位能够合作地联系和吸引客人。虽然一些开链冠醚类似物具有相似的结合亲和力，但通常较低，但非环分子识别主体的设计仍然具有挑战性。最成功的例子之一是刚性分子镊子，它是一种非环共价键合的预先组织的宿主分子，具有开放的空腔，当它们变硬时，它们会紧密结合。根据原子骨架的长度，氢键驱动的芳香酰胺折叠体可以形成开放或闭合的空腔。通过合理设计主干和引入附加的官能团，研究人员可以调节空洞的形状和大小。氢键的方向性和芳香酰胺单元的固有刚性使研究人员能够预测芳香酰胺折叠剂空腔的形状和大小。因此，研究人员随后可以设计出结构与空腔形状、大小和结合部位相匹配的客体分子。此外，由于氢键是动态的，研究人员可以设计出能够适应外界刺激的结构，以产生响应性的超分子结构。在这篇文章中，我们讨论了氢键诱导的芳香酰胺和肼类化合物如何产生响应性的主客体系统，这是基于我们团队和其他人的研究成果。首先，我们强调了在溶液中发生结合时诱导的螺旋手性，包括手性客体在寡聚和聚合物折叠体中的诱导螺旋性，手性客体主体和客体之间非对映异构体的形成，以及手性客体诱导螺旋手性形成固有的柔性骨架。此外，分子或离子对客体可以在有机凝胶状态下产生超分子螺旋手性。这种结构表现出显著的时间依赖性和“中士和士兵”效应，这是已报道的其他双组分有机凝胶没有观察到的。我们进一步说明，芳香酰胺折叠链段的可逆折叠行为可以调节基于给体-受体相互作用的[2]轮烷的开关行为。最后，我们展示了折叠的低聚物可以在一个或两个连接的固有柔性低聚物中诱导折叠，这是一个溶剂响应型分子内主客体系统的例子。
CONSPECTUS: In host-guest chemistry, a larger host molecule selectively and noncovalently binds to a smaller guest molecule or ion. Early studies of host-guest chemistry focused on the recognition of spherical metal or ammonium ions by macrocyclic hosts, such as cyclic crown ethers. In these systems, preorganization enables their binding sites to cooperatively contact and attract a guest. Although some open-chain crown ether analogues possess similar, but generally lower, binding affinities, the design of acyclic molecular recognition hosts has remained challenging. One of the most successful examples was rigid molecular tweezers, acyclic covalently bonded preorganized host molecules with open cavities that bind tightly as they stiffen. Depending on the length of the atomic backbones, hydrogen bonding-driven aromatic amide foldamers can form open or closed cavities. Through rational design of the backbones and the introduction of added functional groups, researchers can regulate the shape and size of the cavity. The directionality of hydrogen bonding and the inherent rigidity of aromatic amide units allow researchers to predict both the shape and size of the cavity of an aromatic amide foldamer. Therefore, researchers can then design guest molecules with structure that matches the cavity shape, size, and binding sites of the foldamer host. In addition, because hydrogen bonds are dynamic, researchers can design structures that can adapt to outside stimuli to produce responsive supramolecular architectures. In this Account, we discuss how aromatic amide and hydrazide foldamers induced by hydrogen bonding can produce responsive host-guest systems, based on research by our group and others. First we highlight the helical chirality induced as binding occurs in solution, which includes the induction of helicity by chiral guests in oligomeric and polymeric foldamers, the formation of diastereomeric complexes between chiral foldamer hosts and guests, and the induction of helical chirality by chiral guests into inherently flexible backbones. In addition, molecular or ion-pair guests can produce supramolecular helical chirality in the organogel state. Such structures exhibit remarkable time-dependence and a "Sergeants and Soldiers" effect that are not observed for other two-component organogels that have been reported. We further illustrate that the reversible folding behavior of an aromatic amide foldamer segment can modulate the switching behavior of donor-acceptor interaction-based [2]rotaxanes. Finally we show that a folded oligomer can induce folding in one or two attached intrinsically flexible oligomers, an example of a solvent-responsive intramolecular host-guest system.