Cyclodextrin complexation of the tetracyanoquinodimethane anion radical: The chemical consequences of cavity size and alkyl derivatization

Jackie L. Beckett, Cynthia J Hartzell, Nathan L. Eastman, Theodore Blake, Michael P. Eastman

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9 Citations (Scopus)

Abstract

Optical spectroscopy shows that in aqueous solution the tetracyanoquinodimethane anion radical (TCNQ-) exists in equilibrium with its π-π dimer (Boyd and Phillips). A study of the effect of various cyclodextrins on this equilibrium shows strikingly different results depending on cavity size and on alkyl derivatization. The equilibrium is unaffected by the presence of α-cyclodextrin. In contrast, γ-cyclodextrin complexes and stabilizes the π-π dimer. EPR and optical spectroscopy show that the anion radical is included and stabilized by heptakis(2,6-di-o-methyl)-β-cyclodextrin and a 2-hydroxypropyl derivative of β-cyclodextrin. Of great interest is the observation that the complex formed by TCNQ- and β-cyclodextrin rapidly reacts to form a diamagnetic product. Aqueous solutions of this diamagnetic product give evidence of appreciable concentrations of TCNQ- when heated or when low dielectric solvents like methanol are added. NMR indicates that the diamagnetic product is a dianion formed by the σ bonding of two β-cyclodextrin complexed anion radicals. σ-Bonded dimers of TCNQ- have been previously observed only in the solid phase (Vu Dong et al., Harms et al.). The tetrafluorotetracyanoquinodimethane anion radical exhibits the same general cyclodextrin chemistry as TCNQ-.

Original languageEnglish (US)
Pages (from-to)4173-4179
Number of pages7
JournalJournal of Organic Chemistry
Volume57
Issue number15
StatePublished - 1992

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Cyclodextrins
Complexation
Anions
Dimers
tetracyanoquinodimethane
Paramagnetic resonance
Methanol
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Cyclodextrin complexation of the tetracyanoquinodimethane anion radical : The chemical consequences of cavity size and alkyl derivatization. / Beckett, Jackie L.; Hartzell, Cynthia J; Eastman, Nathan L.; Blake, Theodore; Eastman, Michael P.

In: Journal of Organic Chemistry, Vol. 57, No. 15, 1992, p. 4173-4179.

Research output: Contribution to journalArticle

Beckett, Jackie L. ; Hartzell, Cynthia J ; Eastman, Nathan L. ; Blake, Theodore ; Eastman, Michael P. / Cyclodextrin complexation of the tetracyanoquinodimethane anion radical : The chemical consequences of cavity size and alkyl derivatization. In: Journal of Organic Chemistry. 1992 ; Vol. 57, No. 15. pp. 4173-4179.
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