### 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.

Original language | English |
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Pages (from-to) | 323-326 |

Number of pages | 3 |

Journal | Journal of Chemical and Engineering Data |

Volume | 54 |

Issue number | 2 |

DOIs | |

Publication status | Published - 2009 |

### Keywords

- cucurbit[n]urils
- diffusion coefficient

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## Cite this

Grant, M., Wheate, N. J., & Aldrich-Wright, J. R. (2009). Diffusion coefficient of cucurbit[n]urils (n = 6 or 7) at different concentrations, temperatures and pH.

*Journal of Chemical and Engineering Data*,*54*(2), 323-326. https://doi.org/10.1021/je800347u