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Molecular Meccano, 48Probing Co-Conformational Changes in Chiral [2]Rotaxanes by 1H-NMR Spectroscopy

✍ Scribed by Peter R. Ashton; José A. Bravo; Françisco M. Raymo; J. Fraser Stoddart; Andrew J. P. White; David J. Williams


Book ID
101279120
Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
420 KB
Volume
1999
Category
Article
ISSN
1434-193X

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✦ Synopsis


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


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