Molecular meccano, 48 [(+)] - Probing co-conformational changes in chiral [2]rotaxanes by 1H-NMR spectroscopy

Peter R. Ashton, José A. Bravo, Francisco Raymo, J. Fraser Stoddart, Andrew J P White, David J. Williams

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The template-directed syntheses of three [2]rotaxanes possessing either chiral centers or elements of planar chirality, in one of their two mechanically interlocked components, have been realized and their solid-state structures have been analyzed by X-ray crystallography. In one instance, an enantiomerically pure dumbbell-shaped component incorporating a 1,5- dioxynaphthalene recognition site and two (1R,2S,5R)-menthyl stoppers was employed to template the formation of the achiral tetracationic cyclophane, cyclobis(paraquat-p-phenylene). The resulting enantiomerically pure [2]rotaxane was isolated in a yield of 55%. In the other two instances, an achiral 1,5-dioxynaphthalene-based dumbbell-shaped component was employed to template the formation of bipyridinium-based cyclophanes possessing either one or two elements of planar chirality. The resulting [2]rotaxane, possessing one element of planar chirality, was isolated as a racemate in a yield of 24%. The related [2]rotaxane, possessing two elements of planar chirality, was isolated as a mixture of a meso form and an enantiomeric pair in an overall yield of 28%. The 1H-NMR-spectroscopic analysis of this mixture revealed a diastereoisomeric ratio of 4:1. A degenerate coconformational change was identified by variable-temperature 1H-NMR spectroscopy in all [2]rotaxanes. The symmetry loss arising from the introduction of one or two elements of planar chirality enabled the elucidation of the mechanism of this dynamic process in two instances.

Original languageEnglish
Pages (from-to)899-908
Number of pages10
JournalEuropean Journal of Organic Chemistry
Issue number4
StatePublished - Apr 1 1999
Externally publishedYes

Fingerprint

Rotaxanes
Chirality
chirality
Nuclear magnetic resonance spectroscopy
nuclear magnetic resonance
templates
spectroscopy
Paraquat
Spectroscopic analysis
X ray crystallography
spectroscopic analysis
crystallography
Nuclear magnetic resonance
solid state
symmetry
synthesis
x rays

Keywords

  • Co-conformation
  • Molecular recognition
  • Planar chirality
  • Rotaxanes
  • Template-directed synthesis

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Ashton, P. R., Bravo, J. A., Raymo, F., Stoddart, J. F., White, A. J. P., & Williams, D. J. (1999). Molecular meccano, 48 [(+)] - Probing co-conformational changes in chiral [2]rotaxanes by 1H-NMR spectroscopy. European Journal of Organic Chemistry, (4), 899-908.

Molecular meccano, 48 [(+)] - Probing co-conformational changes in chiral [2]rotaxanes by 1H-NMR spectroscopy. / Ashton, Peter R.; Bravo, José A.; Raymo, Francisco; Stoddart, J. Fraser; White, Andrew J P; Williams, David J.

In: European Journal of Organic Chemistry, No. 4, 01.04.1999, p. 899-908.

Research output: Contribution to journalArticle

Ashton, Peter R. ; Bravo, José A. ; Raymo, Francisco ; Stoddart, J. Fraser ; White, Andrew J P ; Williams, David J. / Molecular meccano, 48 [(+)] - Probing co-conformational changes in chiral [2]rotaxanes by 1H-NMR spectroscopy. In: European Journal of Organic Chemistry. 1999 ; No. 4. pp. 899-908.
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