Simple and efficient synthetic routes to topologically complex mechanically interlocked molecules remain scarce owing to the sophisticated three-dimensional entanglement of their structures. We report herein the coordination-driven self-assembly from a trefoil knot to a structure comprising two interlocked homochiral trefoil knots by increasing the length of the ligands. The quadruple interlocking of two trefoil knots of the same handedness gives the resulting molecular prime double trefoil link with a total of 14 crossings. Molecular trefoil knots of single topological chirality are formed via enantiopure ligands. Likewise, a pair of topological enantiomers of the double trefoil link are separately and stereoselectively constructed through chirality transfer from the constituent ligands. The synthesis and topological chirality of the trefoil knot and the double trefoil link have been confirmed using single-crystal X-ray diffraction, mass spectrometry, NMR spectroscopy and circular dichroism spectroscopy. Construction of molecular links from non-trivial knots rather than just trivial macrocycles provides a synthetic strategy for topologically complex mechanically interlocked molecules.
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Crystallographic data for the structures reported in this Article are available from the Cambridge Crystallographic Data Centre with the following codes: Δ-1 (CCDC 2143574), Λ2-2 (CCDC 2143575) and Δ2-2 (CCDC 2143576). Other data that support the findings of this study are available in the paper and Supplementary Information.
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This work was supported by the National Science Foundation of China (22031003 and 21720102004 (G.-X.J.)) and the Shanghai Science Technology Committee (19DZ2270100 (G.-X.J.)).
The authors declare no competing interests.
Peer review information
Nature Synthesis thanks Kari Rissanen and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling editor: Alison Stoddart, in collaboration with the Nature Synthesis team.
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Supplementary Tables 1 and 2, Figs. 1–55, experimental details, X-ray crystallographic details and refs. 1–41.
Crystallographic data for Δ-1 (CCDC 2143574).
Crystallographic data for Λ2-2 (CCDC 2143575).
Crystallographic data for Δ2-2 (CCDC 2143576).
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Cui, Z., Jin, GX. Construction of a molecular prime link by interlocking two trefoil knots. Nat. Synth 1, 635–640 (2022). https://doi.org/10.1038/s44160-022-00094-5
Nature Synthesis (2022)