Tetrathiafulvalene hetero radical cation dimerization in a redox-active [2]catenane

Cheng Wang, Scott M. Dyar, Dennis Cao, Albert C. Fahrenbach, Noah Horwitz, Michael T. Colvin, Raanan Carmieli, Charlotte L. Stern, Sanjeev K. Dey, Michael R. Wasielewski, J. Fraser Stoddart

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24 Citations (Scopus)

Abstract

The electronic properties of tetrathiafulvalene (TTF) can be tuned by attaching electron-donating or electron-withdrawing substituents. An electron-rich macrocyclic polyether containing two TTF units of different constitutions, namely 4,4′-bis(hydroxymethyl)tetrathiafulvalene (OTTFO) and 4,4′-bisthiotetrathiafulvalene (STTFS), has been synthesized. On two-electron oxidation, a hetero radical dimer is formed between OTTFO and STTFS. The redox behavior of the macrocyclic polyether has been investigated by electrochemical techniques and UV-vis and electron paramagnetic resonance (EPR) spectroscopies. The [2]catenane in which the macrocyclic polyether is mechanically interlocked with the cyclobis(paraquat-p-phenylene) (CBPQT4+) ring has also been prepared using template-directed protocols. In the case of the [2]catenane, the formation of the TTF hetero radical dimer is prevented sterically by the CBPQT 4+ ring. After a one-electron oxidation, a 70:30 ratio of OTTFO to STTFS is present at equilibrium, and, as a result, two translational isomers of the [2]catenane associated with these electronically different isomeric states transpire. EPR titration spectroscopy and simulations reveal that the radical states of the two constitutionally different TTF units in the [2]catenane still experience long-range electronic intramolecular coupling interactions, despite the presence of the CBPQT 4+ ring, when one or both of them are oxidized to the radical cationic state. These findings in the case of both the free macrocyclic polyether and the [2]catenane have led to a deeper fundamental understanding of the mechanism of radical cation dimer formation between constitutionally different TTF units.

Original languageEnglish
Pages (from-to)19136-19145
Number of pages10
JournalJournal of the American Chemical Society
Volume134
Issue number46
DOIs
Publication statusPublished - Nov 21 2012

ASJC Scopus subject areas

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

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    Wang, C., Dyar, S. M., Cao, D., Fahrenbach, A. C., Horwitz, N., Colvin, M. T., Carmieli, R., Stern, C. L., Dey, S. K., Wasielewski, M. R., & Stoddart, J. F. (2012). Tetrathiafulvalene hetero radical cation dimerization in a redox-active [2]catenane. Journal of the American Chemical Society, 134(46), 19136-19145. https://doi.org/10.1021/ja307577t