Acid-base controllable molecular shuttles

Peter R. Ashton, Roberto Ballardini, Vincenzo Balzani*, Ian Baxter, Alberto Credi, Matthew C T Fyfe, Maria Teresa Gandolfi, Marcos Gómez-López, M. Victoria Martínez-Díaz, Arianna Piersanti, Neil Spencer, J. Fraser Stoddart, Margherita Venturi, Andrew J P White, David J. Williams

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

343 Scopus citations


Two novel [2]rotaxanes, comprised of a dibenzo[24]crown-8 (DB24C8) macroring bound mechanically to a chemical 'dumbbell' possessing two different recognition sites - viz., secondary dialkylammonium (NH2+) and 4,4'-bipyridinium (Bpym2+) units - have been synthesized by using the supramolecular assistance to synthesis provided by, inter alia, hydrogen bonding interactions. One of these rotaxanes bears a fluorescent and redox- active anthracene (Anth) stopper unit. NMR spectroscopy and X-ray crystallography have demonstrated that the DB24C8 macroring exhibits complete selectivity for the NH2+ recognition sites, i.e., that the [2]rotaxanes exist as only one of two possible translational isomers. Deprotonation of the rotaxanes' NH2+ centers effects a quantitative displacement of the DB24C8 macroring to the Bpym2+ recognition site, an outcome that can be reversed by acid treatment. The switching processes have been investigated by 1H NMR spectroscopy and, for the Anth-bearing rotaxane, by electrochemical and photophysical measurements. Furthermore, it is possible to drive the DB24C8 macroring from the dumbbell's Bpym2+ unit, in the deprotonated form of the Anth-bearing rotaxane, by destroying the stabilizing DB24C8-Bpym2+ charge- transfer interactions via electrochemical reduction. The photochemical and photophysical properties of this rotaxane (in both its protonated and deprotonated states) have also been investigated.

Original languageEnglish (US)
Pages (from-to)11932-11942
Number of pages11
JournalJournal of the American Chemical Society
Issue number46
StatePublished - Nov 25 1998

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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