Li Xiaowei, Yuan Xiangyang, Deng Pengchi, Chen Lixi, Ren Yi, Wang Chengyuan, Wu Lixin, Feng Wen, Gong Bing, Yuan Lihua
College of Chemistry , Key Laboratory for Radiation Physics and Technology of Ministry of Education , Analytical & Testing Center , Sichuan University , Chengdu 610064 , Sichuan , China . Email:
State Key Laboratory of Supramolecular Structure and Materials , Jilin University , Changchun 130012 , China.
Chem Sci. 2017 Mar 1;8(3):2091-2100. doi: 10.1039/c6sc04714a. Epub 2016 Nov 22.
Examples of using two-dimensional shape-persistent macrocycles, those having noncollapsible and geometrically well-defined skeletons, for constructing mechanically interlocked molecules are scarce, which contrasts the many applications of these macrocycles in molecular recognition and functional self-assembly. Herein, we report the crucial role played by macrocyclic shape-persistency in enhancing multipoint recognition for the highly efficient template-directed synthesis of rotaxanes. Cyclo[6]aramides, with a near-planar conformation, are found to act as powerful hosts that bind bipyridinium salts with high affinities. This unique recognition module, composed of two macrocyclic molecules with one bipyridinium ion thread through the cavity, is observed both in the solid state and in solution, with unusually high binding constants ranging from ∼10 M to ∼10 M in acetone. The high efficacy of this recognition motif is embodied by the formation of compact [3]rotaxanes in excellent yields based on either a "click-capping" (91%) or "facile one-pot" (85%) approach, underscoring the great advantage of using H-bonded aromatic amide macrocycles for the highly efficient template-directed synthesis of mechanically interlocked structures. Furthermore, three cyclo[6]aramides bearing different peripheral chains demonstrate high specificity in the synthesis of a [3]rotaxane from and , and a [2]rotaxane from a "facile one-pot" approach, in each case as the only isolated product. Analysis of the crystal structure of the [3]rotaxane reveals a highly compact binding mode that would be difficult to access using other macrocycles with a flexible backbone. Leveraging this unique recognition motif, resulting from the shape-persistency of these oligoamide macrocycles, in the template-directed synthesis of compact rotaxanes may open up new opportunities for the development of higher order interlocked molecules and artificial molecular machines.
使用二维形状持久大环（即具有不可折叠且几何形状明确的骨架的大环）构建机械互锁分子的例子很少，这与这些大环在分子识别和功能自组装中的众多应用形成对比。在此，我们报道了大环形状持久性在增强对轮烷高效模板导向合成的多点识别中所起的关键作用。发现具有近平面构象的环[6]芳酰胺可作为强大的主体，以高亲和力结合联吡啶盐。在固态和溶液中均观察到这种独特的识别模块，它由两个大环分子和一个穿过空腔的联吡啶离子组成，在丙酮中的结合常数异常高，范围从～10⁶ M到～10⁷ M。这种识别基序的高效性体现在基于“点击封端”（91%）或“简便一锅法”（85%）方法以优异产率形成紧密的[3]轮烷，突出了使用氢键连接的芳族酰胺大环进行机械互锁结构高效模板导向合成的巨大优势。此外，三种带有不同外围链的环[6]芳酰胺在通过“简便一锅法”由[具体反应物1]和[具体反应物2]合成[3]轮烷以及由[具体反应物3]合成[2]轮烷时表现出高特异性，在每种情况下都是唯一分离出的产物。对[3]轮烷晶体结构的分析揭示了一种高度紧密的结合模式，使用具有柔性主链的其他大环很难实现。利用这些寡酰胺大环的形状持久性所产生的这种独特识别基序，在紧密轮烷的模板导向合成中可能为高阶互锁分子和人工分子机器的开发开辟新机会。
