Molecular meccano, 51. - Diastereoselective self-assembly of [2]catenanes

Peter R. Ashton, Aaron M. Heiss, Dario Pasini, Francisco M. Raymo, Andrew N. Shipway, J. Fraser Stoddart, Neil Spencer

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Two chiral π-electron-rich crown ethers incorporating either a binaphthol or two D-mannitol units have been synthesized and their abilities to bind bipyridinium guests demonstrated. Both crown ethers could be interlocked mechanically with cyclobis(paraquat-p-phenylene) to afford two chiral [2]catenanes. Furthermore, these crown ethers were also mechanically interlocked with a tetracationic cyclophane incorporating a 2,2'-dihydroxy- 1,1'-binaphthyl spacer to afford mixtures of diastereoisomeric [2]catenanes. The composition of these mixtures was determined by 1H-NMR-spectroscopic and HPLC analyses which revealed that modest diastereoselection (56:44-67:33) occurs during the kinetically controlled self-assembly of the catenanes. The free energy barriers (12.8-16.8 kcal mol-1) associated with the circumrotation of one macrocyclic component through the cavity of the other and vice versa were determined by variable-temperature 1H-NMR spectroscopy. In addition, another dynamic process involving the 'rocking' of the mean planes of the mechanically interlocked macrocycles with respect to each other was also identified and the associated free energy barriers (10.3-10.4 kcal mol-1) determined.

Original languageEnglish (US)
Pages (from-to)995-1004
Number of pages10
JournalEuropean Journal of Organic Chemistry
Issue number5
DOIs
StatePublished - May 1999

Keywords

  • Catenanes
  • Diastereoselectivity
  • Molecular Recognition
  • Self- Assembly
  • Template-Directed Synthesis

ASJC Scopus subject areas

  • Organic Chemistry

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