Oligorotaxane radicals under orders

Yuping Wang, Marco Frasconi, Wei Guang Liu, Junling Sun, Yilei Wu, Majed S. Nassar, Youssry Y. Botros, William A. Goddard, Michael R Wasielewski, J Fraser Stoddart*

*Corresponding author for this work

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components-namely oligoviologens-in which different numbers of 4,4'-bipyridinium (BIPY2+) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT4+) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY•+ radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne-azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers.

Original languageEnglish (US)
Pages (from-to)89-98
Number of pages10
JournalACS Central Science
Volume2
Issue number2
DOIs
StatePublished - Feb 24 2016

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

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    Wang, Y., Frasconi, M., Liu, W. G., Sun, J., Wu, Y., Nassar, M. S., Botros, Y. Y., Goddard, W. A., Wasielewski, M. R., & Stoddart, J. F. (2016). Oligorotaxane radicals under orders. ACS Central Science, 2(2), 89-98. https://doi.org/10.1021/acscentsci.5b00377