Post-assembly processing of [2]rotaxanes

Sheng Hsien Chiu, Stuart J. Rowan, Stuart J. Cantrill, J. Fraser Stoddart, Andrew J P White, David J. Williams

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

The concept of using [2]rotaxanes that carry one or more surrogate stoppers which can subsequently be converted chemically into other structural units, resulting in the formation of new interlocked molecular compounds, is introduced and exemplified. Starting from simple NH2 +-centered/crownether-based [2]rotaxanes, containing either one or two benzylic triphenylphosphonium stoppers, the well-known Wittig reaction has been employed to make, 1) other [2]rotaxanes, 2) higher order rotaxanes, 3) branched rotaxanes, and 4) molecular shuttles - all isolated as pure compounds, following catalytic hydrogenations of their carbon-carbon double bonds, obtained when aromatic aldehydes react with the ylides produced when the benzylic triphenylphosphonium derivatives are treated with strong base. The two starting [2]rotaxanes were characterized fully in solution and also in the solid state by X-ray crystallography. The new interlocked molecular compounds that result from carrying out post-assembly Wittig reactions on two [2]rotaxanes were characterized by (dynamic) 1H NMR spectroscopy. In the case of a molecular shuttle in which the crown ether component is dibenzo[24]-crown-8 (DB24C8), shuttling is slow on the 1H NMR timescale, even at high temperatures. However, when DB24C8 is replaced by benzometaphenylene[25]-crown-8 as the ring component in the molecular shuttle, the frequency of the shuttling is observed to be around 100 Hz in [D4] methanol at 63 °C.

Original languageEnglish
Pages (from-to)5170-5183
Number of pages14
JournalChemistry - A European Journal
Volume8
Issue number22
DOIs
Publication statusPublished - 2002 Nov 15
Externally publishedYes

Keywords

  • Mechanical bond
  • Molecular recognition
  • Molecular shuttle
  • Template synthesis
  • Wittig reactions

ASJC Scopus subject areas

  • Chemistry(all)

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  • Cite this

    Chiu, S. H., Rowan, S. J., Cantrill, S. J., Stoddart, J. F., White, A. J. P., & Williams, D. J. (2002). Post-assembly processing of [2]rotaxanes. Chemistry - A European Journal, 8(22), 5170-5183. https://doi.org/10.1002/1521-3765(20021115)8:22<5170::AID-CHEM5170>3.0.CO;2-S