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A molecular endless (74) knot

DOI: 10.1038/s41557-020-00594-x DOI Help

Authors: David Leigh (East China Normal University; University of Manchester) , Jonathan J. Danon (University of Manchester) , Stephen D. P. Fielden (University of Manchester) , Jean-francois Lemonnier (University of Manchester) , George F. S. Whitehead (University of Manchester) , Steffen L. Woltering (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Chemistry , VOL 56

State: Published (Approved)
Published: December 2020
Diamond Proposal Number(s): 17379

Abstract: Current strategies for the synthesis of molecular knots focus on twisting, folding and/or threading molecular building blocks. Here we report that Zn(II) or Fe(II) ions can be used to weave ligand strands to form a woven 3 × 3 molecular grid. We found that the process requires tetrafluoroborate anions to template the assembly of the interwoven grid by binding within the square cavities formed between the metal-coordinated criss-crossed ligands. The strand ends of the grid can subsequently be joined through within-grid alkene metathesis reactions to form a topologically trivial macrocycle (unknot), a doubly interlocked [2]catenane (Solomon link) and a knot with seven crossings in a 258-atom-long closed loop. This 74 knot topology corresponds to that of an endless knot, which is a basic motif of Celtic interlace, the smallest Chinese knot and one of the eight auspicious symbols of Buddhism and Hinduism. The weaving of molecular strands within a discrete layer by anion-template metal–ion coordination opens the way for the synthesis of other molecular knot topologies and to woven polymer materials.

Journal Keywords: Chemistry; Interlocked molecules; Self-assembly; Supramolecular chemistry

Subject Areas: Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction