Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins

Modulation of spin-spin interaction and redox sensitivity

Xiaoli Tan, Yuguang Song, Huiqiang Liu, Qinwen Zhong, A. Rockenbauer, Frederick A. Villamena, Jay L. Zweier, Yangping Liu

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Supramolecular host-guest interactions of trityl-nitroxide (TN) biradicals CT02-VT, CT02-AT and CT02-GT with methyl-β-cyclodextrin (M-β-CD), hydroxypropyl-β-cyclodextrin (H-β-CD) and γ-cyclodextrin (γ-CD) were investigated by EPR spectroscopy. In the presence of cyclodextrins (i.e., γ-CD, M-β-CD and H-β-CD), host-guest complexes of CT02-VT are formed where the nitroxide and linker parts possibly interact with the cyclodextrins' cavities. Complexation with cyclodextrins leads to suppression of the intramolecular through-space spin-spin exchange coupling in CT02-VT, thus allowing the determination of the through-bond spin-spin exchange coupling which was calculated to be 1.6 G using EPR simulations. Different types of cyclodextrins have different binding affinities with CT02-VT in the order of γ-CD (95 M-1) > M-β-CD (70 M-1) > H-β-CD (32 M-1). In addition, the effect of the linkers in TN biradicals on the host-guest interactions was also investigated. Among the three TN biradicals studied, CT02-VT has the highest association constant with one designated cyclodextrin derivative. On the other hand, the complexes of CT02-GT (∼22 G) and CT02-AT (7.7-9.0 G) with cyclodextrins have much higher through-bond spin-spin exchange couplings than those of CT02-VT (1.6 G) due to the shorter linkers than those of CT02-VT. Furthermore, the stability of TN biradicals towards ascorbate was significantly enhanced after the complexation with CDs, with an almost 2-fold attenuation of the second-order rate constants for all the biradicals. Therefore, the supramolecular host-guest interactions with cyclodextrins will be an alternative method to modulate the magnitude of the spin-spin interactions and redox sensitivity of TN biradicals, and the resulting complexes are promising as highly efficient DNP polarizing agents as well as EPR redox probes.

Original languageEnglish
Pages (from-to)1694-1701
Number of pages8
JournalOrganic and Biomolecular Chemistry
Volume14
Issue number5
DOIs
Publication statusPublished - Feb 7 2016

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Cyclodextrins
Oxidation-Reduction
Modulation
spin exchange
modulation
sensitivity
interactions
Exchange coupling
Paramagnetic resonance
affinity
attenuation
retarding
Complexation
cavities
probes
spectroscopy
simulation
Rate constants
Spectrum Analysis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Biochemistry

Cite this

Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins : Modulation of spin-spin interaction and redox sensitivity. / Tan, Xiaoli; Song, Yuguang; Liu, Huiqiang; Zhong, Qinwen; Rockenbauer, A.; Villamena, Frederick A.; Zweier, Jay L.; Liu, Yangping.

In: Organic and Biomolecular Chemistry, Vol. 14, No. 5, 07.02.2016, p. 1694-1701.

Research output: Contribution to journalArticle

Tan, Xiaoli ; Song, Yuguang ; Liu, Huiqiang ; Zhong, Qinwen ; Rockenbauer, A. ; Villamena, Frederick A. ; Zweier, Jay L. ; Liu, Yangping. / Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins : Modulation of spin-spin interaction and redox sensitivity. In: Organic and Biomolecular Chemistry. 2016 ; Vol. 14, No. 5. pp. 1694-1701.
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