Radical-cation dimerization overwhelms inclusion in [N]pseudorotaxanes

Katia Nchimi-Nono, Parastoo Dalvand, Kuldeep Wadhwa, Selbi Nuryyeva, Shaikha Alneyadi, Thirumurugan Prakasam, Albert C. Fahrenbach, John Carl Olsen, Zouhair Asfari, Carlos Platas-Iglesias, Mourad Elhabiri, Ali Trabolsi

Research output: Contribution to journalArticle

Abstract

Suppression of the dimerization of the viologen radical cation by cucurbit[7]uril (CB7) in water is a well-known phenomenon. Herein, two counter-examples are presented. Two viologen-containing thread molecules were designed, synthesized, and thoroughly characterized by 1H DOSY NMR spectrometry, UV/Vis absorption spectrophotometry, square-wave voltammetry, and chronocoulometry: BV4+, which contains two viologen subunits, and HV12+, which contains six. In both threads, the viologen subunits are covalently bonded to a hexavalent phosphazene core. The corresponding [3]- and [7]pseudorotaxanes that form on complexation with CB7, that is, BV 4+⊂(CB7)2 and HV12+⊂(CB7)6, were also analyzed. The properties of two monomeric control threads, namely, methyl viologen (MV2+) and benzyl methyl viologen (BMV2+), as well as their [2]pseudorotaxane complexes with CB7 (MV2+⊂CB7 and BMV2+⊂CB7) were also investigated. As expected, the control pseudorotaxanes remained intact after one-electron reduction of their viologen-recognition stations. In contrast, analogous reduction of BV 4+⊂(CB7)2 and HV12+⊂(CB7)6 led to host-guest decomplexation and release of the free threads BV 2(.+) and HV6(. +), respectively. 1H DOSY NMR spectrometric and chronocoulometric measurements showed that BV2(. +) and HV6(.+) have larger diffusion coefficients than the corresponding [3]- and [7]pseudorotaxanes, and UV/Vis absorption studies provided evidence for intramolecular radical-cation dimerization. These results demonstrate that radical-cation dimerization, a relatively weak interaction, can be used as a driving force in novel molecular switches.

Original languageEnglish (US)
Pages (from-to)7334-7344
Number of pages11
JournalChemistry - A European Journal
Volume20
Issue number24
DOIs
StatePublished - Jun 10 2014

Keywords

  • electrochemistry
  • host-guest systems
  • molecular recognition
  • pseudorotaxanes
  • radical ions

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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    Nchimi-Nono, K., Dalvand, P., Wadhwa, K., Nuryyeva, S., Alneyadi, S., Prakasam, T., Fahrenbach, A. C., Olsen, J. C., Asfari, Z., Platas-Iglesias, C., Elhabiri, M., & Trabolsi, A. (2014). Radical-cation dimerization overwhelms inclusion in [N]pseudorotaxanes. Chemistry - A European Journal, 20(24), 7334-7344. https://doi.org/10.1002/chem.201400069