School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
J Am Chem Soc. 2015 Aug 19;137(32):10437-42. doi: 10.1021/jacs.5b07069. Epub 2015 Aug 4.
We report on the assembly of 2,6-pyridinedicarboxamide ligands (1) with point chirality about lanthanide metal ion (Ln(3+)) templates, in which the helical chirality of the resulting entwined 3:1 ligand:metal complexes is covalently captured by ring-closing olefin metathesis to form topologically chiral molecular trefoil knots of single handedness. The ligands do not self-sort (racemic ligands form a near-statistical mixture of homoleptic and heteroleptic lanthanide complexes), but the use of only (R,R)-1 leads solely to a trefoil knot of Λ-handedness, whereas (S,S)-1 forms the Δ-trefoil knot with complete stereoselectivity. The knots and their isomeric unknot macrocycles were characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography and the expression of the chirality that results from the topology of the knots studied by circular dichroism.
我们报告了 2,6-吡啶二甲酰胺配体（1）与手性点关于镧系金属离子（Ln（3+））模板的组装，其中所得交织的 3:1 配体：金属配合物的螺旋手性通过闭环烯烃复分解反应被共价捕获，形成拓扑手性单一手性分子三叶结。配体不自旋（外消旋配体形成同系物和杂系物镧系配合物的近乎统计混合物），但仅使用（R，R）-1 仅导致 Λ-手性三叶结，而（S，S）-1 则以完全的立体选择性形成 Δ-三叶结。结及其异构的无结大环通过 NMR 光谱，质谱和 X 射线晶体学进行了表征，并通过圆二色性研究了结的拓扑结构所产生的手性的表达。
