Ligand-directed symmetry reduction and stereoselective assembly of C₃-symmetric topologically chiral trefoil knots.
- 1Key Laboratory of Green Chemical Media and Reactions (Ministry of Education), Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, School of Chemistry and Chemical Engineering, Henan Normal University Xinxiang Henan 453007 P. R. China [email protected] [email protected] [email protected].
Abstract
The stereoselective synthesis of low-symmetry topologically chiral molecular knots remains challenging because lowering symmetry creates competing assembly pathways. Here we report a ligand-directed strategy that couples symmetry reduction with handedness control in molecular trefoil knots. Coordination-driven self-assembly of an l-β-homoalanine-derived oriented ligand, (S)-L1, with three related binuclear half-sandwich Rh/Ir organometallic building blocks affords C3-symmetric Λ-handed trefoil knots Λ-Rh-1, Λ-Rh-1Br and Λ-Ir-1. The head-to-tail ligand arrangement removes the C2 symmetry elements of a D3-like framework while retaining the C3 rotational relationship among the three repeat units. The amino-acid stereocenter relays local point chirality into global topological handedness. The enantiomeric ligand (R)-L1 gives the mirror-related Δ-handed knots Δ-Rh-1, Δ-Rh-1Br and Δ-Ir-1. Crystallographic analysis, NMR spectroscopy, high-resolution mass spectrometry and mirror-image circular dichroism spectra collectively corroborate the trefoil-knot assignments, molecular compositions and enantiomeric relationships. Assembly from an equimolar mixture of (S)-L1 and (R)-L1 supports homochiral self-sorting into a racemic mixture of trefoil knots. An analogue of (S)-L1 with less differentiated coordination termini gives D-shaped metallacycles, whereas analogues with shorter amino-acid segments give access to figure-eight knots and tetranuclear metallomacrocycles. These results show that ligand directionality and point chirality can be integrated to control both the symmetry and handedness of molecular trefoil knots.
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BibTeX
@article{cui2026liganddirected,
title = {{Ligand-directed symmetry reduction and stereoselective assembly of C₃-symmetric topologically chiral trefoil knots.}},
author = {Zheng Cui and Junli Guo and Liyan Hao and Huiyong Wang and Jianji Wang},
journal = {Chemical science},
year = {2026},
month = oct,
doi = {10.1039/d6sc05627j},
url = {https://europepmc.org/article/MED/42953453},
note = {CC BY},
}
RIS
TY - JOUR
TI - Ligand-directed symmetry reduction and stereoselective assembly of C₃-symmetric topologically chiral trefoil knots.
AU - Zheng Cui
AU - Junli Guo
AU - Liyan Hao
AU - Huiyong Wang
AU - Jianji Wang
PY - 2026
DA - 2026/10/23
JO - Chemical science
DO - 10.1039/d6sc05627j
UR - https://europepmc.org/article/MED/42953453
AB - The stereoselective synthesis of low-symmetry topologically chiral molecular knots remains challenging because lowering symmetry creates competing assembly pathways. Here we report a ligand-directed strategy that couples symmetry reduction with handedness control in molecular trefoil knots. Coordination-driven self-assembly of an l-β-homoalanine-derived oriented ligand, (S)-L1, with three related binuclear half-sandwich Rh/Ir organometallic building blocks affords C3-symmetric Λ-handed trefoil knots Λ-Rh-1, Λ-Rh-1Br and Λ-Ir-1. The head-to-tail ligand arrangement removes the C2 symmetry elements of a D3-like framework while retaining the C3 rotational relationship among the three repeat units. The amino-acid stereocenter relays local point chirality into global topological handedness. The enantiomeric ligand (R)-L1 gives the mirror-related Δ-handed knots Δ-Rh-1, Δ-Rh-1Br and Δ-Ir-1. Crystallographic analysis, NMR spectroscopy, high-resolution mass spectrometry and mirror-image circular dichroism spectra collectively corroborate the trefoil-knot assignments, molecular compositions and enantiomeric relationships. Assembly from an equimolar mixture of (S)-L1 and (R)-L1 supports homochiral self-sorting into a racemic mixture of trefoil knots. An analogue of (S)-L1 with less differentiated coordination termini gives D-shaped metallacycles, whereas analogues with shorter amino-acid segments give access to figure-eight knots and tetranuclear metallomacrocycles. These results show that ligand directionality and point chirality can be integrated to control both the symmetry and handedness of molecular trefoil knots.
SN - 2041-6520
SN - 2041-6539
ER -