title: Lanthanide Template Synthesis of Trefoil Knots of Single Handedness.
abstract: 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.
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Gen
authors.initials: G
authors.lastname: Zhang
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Guzmán
authors.initials: G
authors.lastname: Gil-Ramírez
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Augustinas
authors.initials: A
authors.lastname: Markevicius
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Colm
authors.initials: C
authors.lastname: Browne
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Iñigo J
authors.initials: IJ
authors.lastname: Vitorica-Yrezabal
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: David A
authors.initials: DA
authors.lastname: Leigh
mesh_terms: D000475:Alkenes / Q000737:chemistry; D060326:Chemistry Techniques, Synthetic; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000475:Alkenes; D028581:Lanthanoid Series Elements; D008024:Ligands