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Stereoselective synthesis of a composite knot with nine crossings

DOI: 10.1038/s41557-018-0124-6 DOI Help

Authors: Liang Zhang (University of Manchester) , Alexander J. Stephens (University of Manchester) , Alina L. Nussbaumer (University of Manchester) , Jean-francois Lemonnier (University of Manchester) , Pia Jurček (University of Manchester) , Iñigo J. Vitorica-yrezabal (University of Manchester) , David Leigh (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Chemistry , VOL 111

State: Published (Approved)
Published: September 2018
Diamond Proposal Number(s): 17379

Abstract: The simultaneous synthesis of a molecular nine-crossing composite knot that contains three trefoil tangles of the same handedness and a 9 3 7 973 link (a type of cyclic [3]catenane topologically constrained to always have at least three twists within the links) is reported. Both compounds contain high degrees of topological writhe (w = 9), a structural feature of supercoiled DNA. The entwined products are generated from the cyclization of a hexameric Fe(ii) circular helicate by ring-closing olefin metathesis, with the mixture of topological isomers formed as a result of different ligand connectivity patterns. The metal-coordinated composite knot was isolated by crystallization, the topology unambiguously proven by tandem mass spectrometry, with X-ray crystallography confirming that the 324-atom loop crosses itself nine times with matching handedness (all Δ or all Λ) at every metal centre within each molecule. Controlling the connectivity of the ligand end groups on circular metal helicate scaffolds provides an effective synthetic strategy for the stereoselective synthesis of composite knots and other complex molecular topologies.

Journal Keywords: Interlocked molecules; Self-assembly

Subject Areas: Chemistry, Materials, Biology and Bio-materials


Instruments: I19-Small Molecule Single Crystal Diffraction