Lanthanide Template Synthesis of Trefoil Knots of Single Handedness

We report on the assembly of 2,6-pyridinedicarboxamide ligands (<b>1</b>) with point chirality about lanthanide metal ion (Ln³⁺) 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 (<i>R</i>,<i>R</i>)-<b>1</b> leads solely to a trefoil knot of Λ-handedness, whereas (<i>S</i>,<i>S</i>)-<b>1</b> 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