Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.
School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China.
J Am Chem Soc. 2022 Sep 21;144(37):17232-17240. doi: 10.1021/jacs.2c07682. Epub 2022 Sep 6.
We report the synthesis of molecular prime and composite knots by social self-sorting of 2,6-pyridinedicarboxamide (pdc) ligands of differing topicity and stereochemistry. Upon mixing achiral monotopic and ditopic pdc-ligand strands in a 1:1:1 ratio with Lu(III), a well-defined heteromeric complex featuring one of each ligand strand and the metal ion is selectively formed. Introducing point-chiral centers into the ligands leads to single-sense helical stereochemistry of the resulting coordination complex. Covalent capture of the entangled structure by ring-closing olefin metathesis then gives a socially self-sorted trefoil knot of single topological handedness. In a related manner, a heteromeric molecular granny knot (a six-crossing composite knot featuring two trefoil tangles of the same handedness) was assembled from social self-sorting of ditopic and tetratopic multi-pdc strands. A molecular square knot (a six-crossing composite knot of two trefoil tangles of opposite handedness) was assembled by social self-sorting of a ditopic pdc strand with four ()-centers and a tetratopic strand with two ()- and six ()-centers. Each of the entangled structures was characterized by H and C NMR spectroscopy, mass spectrometry, and circular dichroism spectroscopy. The precise control of composition and topological chirality through social self-sorting enables the rapid assembly of well-defined sequences of entanglements for molecular knots.
我们报告了通过具有不同主题和立体化学的 2,6- 吡啶二甲酰胺 (pdc) 配体的社会自组装合成分子原丝和复合纽结。在将手性单核和双核 pdc-配体链以 1:1:1 的比例与 Lu(III)混合时,选择性地形成了具有每种配体链和金属离子之一的均相杂化复合物。在手性配体中引入点手性中心会导致所得配位化合物具有单一感螺旋立体化学。然后,通过闭环烯烃复分解反应共价捕获缠结结构,得到具有单一拓扑手性的社会自组装三叶纽结。以类似的方式,通过双核和四核多 pdc 链的社会自组装,组装了杂合分子老奶奶纽结(一种具有相同手性的两个三叶结的六交叉复合纽结)。通过双核 pdc 链与四个 ()-中心和四核链与两个 ()-和六个 ()-中心的社会自组装,组装了分子方结(一种具有相反手性的两个三叶结的六交叉复合纽结)。每个缠结结构均通过 1 H 和 13 C NMR 光谱、质谱和圆二色光谱进行了表征。通过社会自组装精确控制组成和拓扑手性,能够快速组装具有明确缠结序列的分子纽结。