Over the past decade, the hexaphyrin skeleton has emerged as a multifaceted frame exhibiting strong interplay between topology, aromaticity, and metal coordination, opening new research areas beyond porphyrins. However, molecular recognition with hexaphyrins has been underexplored, mainly because of the lack of general synthetic strategies leading to sophisticated molecular hosts. Here we have developed a straightforward approach for capping the heteroannulene frame with tripodal units (e.g., tris(2-aminoethyl)amine [tren]) through postsynthetic modification of a readily accessible meso-(2-aminophenyl) tris-substituted platform. The resulting tren-capped hexaphyrins, obtained in three steps from a 5-(aryl)dipyrromethane precursor, display remarkable features: (i) Considering the 28π-conjugated system, instantaneous and site-selective Zn(II) metalation at the level of a dipyrrin versus tren unit triggers a planar-to-singly twisted conformational change and hence a Hückel antiaromatic-to-Möbius aromatic transformation. In spite of the tripodal linkage, a smooth twist and efficient π overlap are preserved. (ii) Selective and cooperative binding of both an acetato ligand and an amino ligand to zinc occurs in distinct confined environments, reminiscent of substrate discrimination at the buried metal centers of metalloenzymes. The ligand binding pockets are allosterically tuned by monoprotonation of the tren unit. (iii) Substantial chiral induction of the molecular twist is achieved using chiral amino ligands (diastereomeric excess up to 77%, the highest reported to date for a Möbius compound), to which is associated a strong chiroptical signature in circular dichroism. These results provide unprecedented insights into molecular recognition with hexaphyrins, paving the way to innovative Möbius-type molecular hosts for sensing and catalysis.

中文翻译：

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ren上限的六卟啉锌配合物：相互作用的分子识别，莫比乌斯芳香性和手性

在过去的十年中，六卟啉骨架以多面的形式出现，在拓扑结构，芳香性和金属配位之间表现出强大的相互作用，为卟啉以外的领域开辟了新的领域。然而，对六氢卟酚的分子识别尚未得到充分的研究，这主要是由于缺乏导致复杂分子宿主的通用合成策略。在这里，我们已经开发出一种简单的方法，可以通过合成后修饰易得的内消旋体，用三脚架单元（例如，三（2-氨基乙基）胺[tren]）将杂戊环骨架封端。-（2-氨基苯基）三取代的平台。分三步从5-（芳基）二吡咯甲烷前体中获得的tr封的六氢卟啉显示出显着特征：（i）考虑到28π共轭体系，瞬时和定点选择性Zn（II）金属化水平为双吡啶与tren单元触发了平面到单个扭曲的构象变化，因此引发了Hückel抗芳烃到Möbius的芳烃转化。尽管采用了三脚架联动装置，仍可保持平稳的扭转和有效的π重叠。（ii）乙酸酯配体和氨基配体与锌的选择性和协同结合发生在不同的封闭环境中，让人联想到在金属酶的埋藏金属中心的底物区分。配体结合口袋通过tren单元的单质子化进行变构调节。（iii）使用手性氨基配体（非对映体过量高达77％，是迄今为止报道的莫比乌斯化合物中最高的非对映体过量）来实现对分子扭曲的实质性手性诱导，这与圆二色性中强烈的手性签名有关。这些结果为六卟啉分子识别提供了前所未有的见识，为创新的莫比乌斯型分子宿主进行传感和催化铺平了道路。