Diffusion coefficient of cucurbit[n]urils (n = 6 or 7) at different concentrations, temperatures and pH

M. Grant, Nial J. Wheate, Janice R. Aldrich-Wright

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The diffusion coefficient of cucurbit[6]uril (CB[6]) and cucurbit[7]uril (CB[7]) was determined using pulsed gradient spin−echo nuclear magnetic resonance spectroscopy. Both CB[6] and CB[7] diffuse faster through H2O than D2O with increasing temperature, consistent with the Stokes−Einstein equation where diffusion is proportional to temperature divided by viscosity. The activation energy (EA) was also determined and is larger for CB[n] in 90 % H2O/10 % D2O v/v than in D2O. Both compounds aggregate with increasing concentration between (0.25 and 2)·10−3 mol·L−1. The pH of the solution does not significantly affect the diffusion coefficient of CB[6] and CB[7], except at very low pH where protonation of the carbonyl groups induces aggregation, which slows their rate of diffusion.
LanguageEnglish
Pages323-326
Number of pages3
JournalJournal of Chemical and Engineering Data
Volume54
Issue number2
DOIs
Publication statusPublished - 2009

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Temperature
Protonation
Nuclear magnetic resonance spectroscopy
Agglomeration
Activation energy
Viscosity
cucurbit(7)uril
cucurbit(6)uril

Keywords

  • cucurbit[n]urils
  • diffusion coefficient

Cite this

Grant, M. ; Wheate, Nial J. ; Aldrich-Wright, Janice R. / Diffusion coefficient of cucurbit[n]urils (n = 6 or 7) at different concentrations, temperatures and pH. In: Journal of Chemical and Engineering Data. 2009 ; Vol. 54, No. 2. pp. 323-326.
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Diffusion coefficient of cucurbit[n]urils (n = 6 or 7) at different concentrations, temperatures and pH. / Grant, M.; Wheate, Nial J.; Aldrich-Wright, Janice R.

In: Journal of Chemical and Engineering Data, Vol. 54, No. 2, 2009, p. 323-326.

Research output: Contribution to journalArticle

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AU - Grant, M.

AU - Wheate, Nial J.

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AB - The diffusion coefficient of cucurbit[6]uril (CB[6]) and cucurbit[7]uril (CB[7]) was determined using pulsed gradient spin−echo nuclear magnetic resonance spectroscopy. Both CB[6] and CB[7] diffuse faster through H2O than D2O with increasing temperature, consistent with the Stokes−Einstein equation where diffusion is proportional to temperature divided by viscosity. The activation energy (EA) was also determined and is larger for CB[n] in 90 % H2O/10 % D2O v/v than in D2O. Both compounds aggregate with increasing concentration between (0.25 and 2)·10−3 mol·L−1. The pH of the solution does not significantly affect the diffusion coefficient of CB[6] and CB[7], except at very low pH where protonation of the carbonyl groups induces aggregation, which slows their rate of diffusion.

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