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Chemistry inside molecular containers in the gas phase

Nature Chemistry volume 5, pages 376382 (2013) | Download Citation

Abstract

Inner-phase chemical reactions of guest molecules encapsulated in a macromolecular cavity give fundamental insight into the relative stabilization of transition states by the surrounding walls of the host, thereby modelling the situation of substrates in enzymatic binding pockets. Although in solution several examples of inner-phase reactions are known, the use of cucurbiturils as macrocyclic hosts and bicyclic azoalkanes as guests has now enabled a systematic mass spectrometric investigation of inner-phase reactions in the gas phase, where typically the supply of thermal energy results in dissociation of the supramolecular host–guest assembly. The results reveal a sensitive interplay in which attractive and repulsive van der Waals interactions between the differently sized hosts and guests need to be balanced with a constrictive binding to allow thermally activated chemical reactions to compete with dissociation. The results are important for the understanding of supramolecular reactivity and have implications for catalysis.

  • Compound C5H8N2

    2,3-Diazabicyclo[2.2.1]hept-2-ene

  • Compound C6H10N2

    2,3-Diazabicyclo[2.2.2]oct-2-ene

  • Compound C7H12N2

    6,7-Diazabicyclo[3.2.2]non-6-ene

  • Compound C36H36N24O12

    Cucurbit[6]uril

  • Compound C42H42N28O14

    Cucurbit[7]uril

  • Compound C48H48N32O16

    Cucurbit[8]uril

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Acknowledgements

A.I.L., W.M.N. and K.I.A. thank the Deutsche Forschungsgemeinschaft (DFG, grant number NA-686/5), the Deutsche Akademische Austauschdienst (DAAD) and the Center for Functional Materials and Nanomolecular Science (NanoFun) for financial support, including graduate fellowships for A.I.L. and K.I.A. The Academy of Finland is acknowledged by E.K. for financial support (project number 127941). The FT-ICR facility is supported by Biocenter Finland. The authors thank L. Isaacs for making a reference sample of inverted CB7 available, M. Olivucci for donating computing time and D. V. Dearden for helpful comments on the results.

Author information

Affiliations

  1. Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK

    • Tung-Chun Lee
    •  & Oren A. Scherman
  2. Department of Chemistry, University of Jyväskylä, Survontie 9, 40500 Jyväskylä, Finland

    • Elina Kalenius
  3. School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany

    • Alexandra I. Lazar
    • , Khaleel I. Assaf
    • , Nikolai Kuhnert
    •  & Werner M. Nau
  4. Unilever R&D Vlaardingen, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands

    • Christian H. Grün
  5. Department of Chemistry, University of Eastern Finland, Joensuu Campus, Yliopistokatu 7, 80100 Joensuu, Finland

    • Janne Jänis

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Contributions

T-C.L. initiated this project with E.K., O.A.S. and W.M.N. The manuscript was co-written by T-C.L., A.I.L. and W.M.N. and commented on by all the authors. All mass spectrometry experiments were conducted by E.K. and A.I.L. in the laboratories of J.J. and N.K., and C.H.G. conducted the ion-mobility experiments. K.I.A. performed the quantum-chemical and cross-section calculations. W.M.N. and A.I.L. analysed the data in terms of the model potentials. The student authors T-C.L. and A.I.L. contributed equally.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Elina Kalenius or Werner M. Nau.

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https://doi.org/10.1038/nchem.1618

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