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A synthetic molecular pentafoil knot

Nature Chemistry volume 4, pages 1520 (2012) | Download Citation

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Abstract

Knots are being discovered with increasing frequency in both biological and synthetic macromolecules and have been fundamental topological targets for chemical synthesis for the past two decades. Here, we report on the synthesis of the most complex non-DNA molecular knot prepared to date: the self-assembly of five bis-aldehyde and five bis-amine building blocks about five metal cations and one chloride anion to form a 160-atom-loop molecular pentafoil knot (five crossing points). The structure and topology of the knot is established by NMR spectroscopy, mass spectrometry and X-ray crystallography, revealing a symmetrical closed-loop double helicate with the chloride anion held at the centre of the pentafoil knot by ten CH···Cl hydrogen bonds. The one-pot self-assembly reaction features an exceptional number of different design elements—some well precedented and others less well known within the context of directing the formation of (supra)molecular species. We anticipate that the strategies and tactics used here can be applied to the rational synthesis of other higher-order interlocked molecular architectures.

  • Compound C26H22N4O2

    5,5'-([2,2'-Bipyridine]-5,5'-diylbis(ethane-2,1-diyl))dipicolinaldehyde

  • Compound C6H15N

    Hexylamine

  • Compound C8H11N

    4-Methylbenzylamine

  • Compound C7H9N

    Benzylamine

  • Compound C8H11N

    2-Phenylethylamine

  • Compound C9H13N

    3-Phenylpropylamine

  • Compound C10H15N

    4-Phenylbutylamine

  • Compound C3H9NO

    (R)-2-Aminopropan-1-ol

  • Compound C3H9NO

    (S)-2-Aminopropan-1-ol

  • Compound C190H240Fe5N3010+

    Hexylamine-derived pentameric cyclic helicate

  • Compound C210H200Fe5N3010+

    Methylbenzylamine-derived pentameric cyclic helicate

  • Compound C200H180Fe5N3010+

    Benzylamine-derived pentameric cyclic helicate

  • Compound C210H200Fe5N3010+

    2-Phenylethylamine-derived pentameric cyclic helicate

  • Compound C220H220Fe5N3010+

    3-Phenylpropylamine-derived pentameric cyclic helicate

  • Compound C230H240Fe5N3010+

    4-Phenylbutylamine-derived pentameric cyclic helicate

  • Compound C170H200Fe5N3010+

    (R)-2-Aminopropan-1-ol-derived (M)-pentameric cyclic helicate

  • Compound C170H200Fe5N3010+

    (S)-2-Aminopropan-1-ol-derived (P)-pentameric cyclic helicate

  • Compound C6H16N2O2

    2,2'-(Ethylenedioxy)bis(ethylamine)

  • Compound C160H170Fe5N30O1010+

    Pentafoil knot

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Acknowledgements

The authors thank the Diamond Light Source (UK) for synchrotron beamtime on I19 (XR029), the Engineering and Physical Sciences Research Council (EPSRC) National Crystallography Service for data collection, and the EPSRC National Mass Spectrometry Service Centre (Swansea, UK) and C.L. Mackay (SIRCAMS, University of Edinburgh) for high-resolution mass spectrometry. J.E.B. and D.S. are Swiss National Science Foundation postdoctoral fellows. This research was funded by the EPSRC and the Academy of Finland (K.R., projects 212588 and 218325).

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Affiliations

  1. School of Chemistry, University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JJ, UK

    • Jean-François Ayme
    • , Jonathon E. Beves
    • , David A. Leigh
    • , Roy T. McBurney
    •  & David Schultz
  2. Department of Chemistry, Nanoscience Center, University of Jyväskylä, P.O. Box 35, 40014 JYU, Finland

    • Kari Rissanen

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Contributions

J-F.A., J.E.B., R.T.M. and D.S. carried out the synthesis and characterization studies, helped plan the experiments, and participated in the preparation of the manuscript. K.R. solved the crystal structure. D.A.L. helped plan the experiments and prepare the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to David A. Leigh.

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    Crystallographic data for compound 6

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DOI

https://doi.org/10.1038/nchem.1193

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