Novel Class of Asymmetric Zwitterionic Rotaxanes Based on α-Cyclodextrin

Journal of the American Chemical Society

Volumn 113, Issue 21, 1991, Pages 8188-8190

  Isnin, Rahimah ^a   Kaifer, Angel E ^a  

^a UNIVERSITY OF MIAMI   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000440835     PISSN: 00027863     EISSN: 15205126     Source Type: Journal    
DOI: 10.1021/ja00021a067     Document Type: Article

References (9)

1. Schill, G. Catenaries, Rotaxanes, and Knots; Academic Press: New York, 1971.
2. Ogino, H. J. Am. Chem. Soc. 1981, 103, 1303.
3. Yamanari, K.; Shimura, Y. Bull. Chem. Soc. Jpn. 1983, 56, 2283. Several rotaxanes reported on this work are not completely symmetric because the end (capping) groups show optical isomerism.
4. Ventaka, T.; Rao, S.; Lawrence, D. S. J. Am. Chem. Soc. 1990, 112, 3614.
5. Isnin, R.; Salam, C.; Kaifer, A. E. J. Org. Chem. 1991, 56, 35.
6. We have measured the binding constant between 2 and α-CD in acidic and neutral media. At a pH of 2.6, at which the carboxylic acid is fully protonated, the binding constant was found to be 425 M−1. Conversely, at a pH of 8.0, at which the carboxylic acid is ionized, the binding constant was determined to be 71 M−1.
7. The possibility that the observed NMR splittings resulted from the CD shuttling back and forth along the alkyl chain was ruled out by the lack of spectral sensitivity to temperature changes. The relative peak areas of both amidic protons indicate that the ratio of isomers in the mixture is approximately 6:4 (5a/5b and 4a/4b). Elemental analyses (C & H) were within 0.30% of theory for the 5a/5b and 4a/4b mixtures (see supplementary material).
8. For other recent examples of electroactive rotaxanes, see: Anelli, P. L.; Ashton, P. R.; Ballardini, R.; Balzani, V.; Delgado, M.; Gandolfi, M. T.; Goodnow, T. T.; Kaifer, A. E.; Philip, D.; Pietraszkiewicz, M.; Prodi, L.; Reddington, M. V.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Vicent, C.; Williams, D. J. J. Am. Chem. Soc., in press.
9. Stoddart, and co-workers have also recently synthesized a fascinating rotaxane in which a tetracationic “bead” moves back and forth between two identical “stations”, thus behaving as a molecular shuttle: Anelli, P. L.; Spencer, N.; Stoddart, J. F. J. Am. Chem. Soc. 1991, 113, 5131.