In the arena of molecular recognition and sensing, the development of polypyrrolic macrocycles capable of anion chelation has gained significant attention over the last two decades. The host-guest chemistry of calixpyrroles, in particular, has led to a better understanding of the guest recognition by tailoring the size, geometry, and binding modes of the receptors. Calix[4]pyrrole (C4P), a very well-known member of the calix[n]pyrrole family, has smaller binding cavity to bind the larger anions. In order to modulate the molecular recognition and sensing properties of the C4P-based receptor, various structural modifications have successfully been realized. However, the core expansion of C4P has attracted vast attention due to the fact that it offers larger cavity size compared to the parent C4P-system. This opens the door towards the development of synthetically challenging higher ordered or expanded calixpyrroles for the effective and selective binding of large-sized guest entities. These rigid/preorganized macrocyclic architectures holds the multiple binding sites for enhanced binding affinities. Supramolecular synthetic chemists have expanded research on expanded calixpyrroles, and have achieved several milestones in this regard. This comprehensive review article covers both the synthetic approaches and recognition characteristics of the expanded calixpyrrole architectures. Apart from the expanded calixpyrroles, information on the synthetic approaches and recognition properties of contracted macrocyclic systems have also been revealed. To our knowledge, no comprehensive account of the synthetic challenges and peculiar recognition properties on the expanded and contracted calixpyrroles appeared in the literature until we almost finished this particular write-up. The authors believe that the current account will serve as a guide for the synthetic supramolecular chemists seeking novel design concepts for the construction of selective and efficient higher ordered macrocyclic systems with real-world applications.

中文翻译：

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膨胀和收缩的杯吡咯：对合成和分子识别特征的见解

在分子识别和传感领域，能够阴离子螯合的聚吡咯大环化合物的开发在过去二十年中引起了广泛关注。特别是杯吡咯的主客体化学，通过调整受体的大小、几何形状和结合模式，可以更好地理解客体识别。杯[4]吡咯 (C4P) 是杯[n]吡咯家族中众所周知的成员，具有较小的结合腔以结合较大的阴离子。为了调节基于C4P的受体的分子识别和传感特性，已经成功实现了各种结构修饰。然而，C4P 的核心扩展引起了广泛关注，因为与母体 C4P 系统相比，它提供了更大的空腔尺寸。这为开发具有合成挑战性的高阶或扩展杯吡咯打开了大门，以有效和选择性地结合大尺寸客体实体。这些刚性/预组织的大环结构具有多个结合位点，以增强结合亲和力。超分子合成化学家扩大了对膨胀杯吡咯的研究，并在这方面取得了几个里程碑。这篇综合综述文章涵盖了扩展杯吡咯结构的合成方法和识别特征。除了扩展的杯吡咯之外，还揭示了有关收缩大环系统的合成方法和识别性质的信息。据我们所知，直到我们几乎完成这篇特别的文章之前，文献中还没有对膨胀和收缩的杯吡咯的合成挑战和特殊识别特性进行全面的描述。作者相信，当前的叙述将为合成超分子化学家寻求新颖的设计概念以构建具有实际应用的选择性和高效的高阶大环系统提供指导。