Measurement of the ground-state distributions in bistable mechanically interlocked molecules using slow scan rate cyclic voltammetry

Albert C. Fahrenbach, Jonathan C. Barnes, Hao Li, Diego Benítez, Ashish N. Basuray, Lei Fang, Chi Hau Sue, Gokhan Barin, Sanjeev K. Dey, William A. Goddard, J. Fraser Stoddart*

*Corresponding author for this work

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

In donor-acceptor mechanically interlocked molecules that exhibit bistability, the relative populations of the translational isomers - present, for example, in a bistable [2]rotaxane, as well as in a couple of bistable [2]catenanes of the donor-acceptor vintage - can be elucidated by slow scan rate cyclic voltammetry. The practice of transitioning from a fast scan rate regime to a slow one permits the measurement of an intermediate redox couple that is a function of the equilibrium that exists between the two translational isomers in the case of all three mechanically interlocked molecules investigated. These intermediate redox potentials can be used to calculate the ground-state distribution constants, K. Whereas, (i) in the case of the bistable [2]rotaxane, composed of a dumbbell component containing π-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two π-electron-deficient bipyridinium units), a value for K of 10 ± 2 is calculated, (ii) in the case of the two bistable [2]catenanes - one containing a crown ether with tetrathiafulvalene and dioxynaphthalene recognition sites for the tetracationic cyclophane, and the other, tetrathiafulvalene and butadiyne recognition sites - the values for K are orders (one and three, respectively) of magnitude greater. This observation, which has also been probed by theoretical calculations, supports the hypothesis that the extra stability of one translational isomer over the other is because of the influence of the enforced side-on donor - acceptor interactions brought about by both ±-electron-rich recognition sites being part of a macrocyclic polyether.

Original languageEnglish (US)
Pages (from-to)20416-20421
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number51
DOIs
StatePublished - Dec 20 2011

Keywords

  • Density functional theory
  • Donor-acceptor molecules
  • Electrochemistry
  • Isomerism
  • Switches

ASJC Scopus subject areas

  • General

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