Conformational properties of propargyloxy-calix[4]arene tricarboxamides: NMR and DFT studies on the O-through-the-annulus rotation

The size limit of substituents allowing O-through-the-annulus rotation of substituted calix[4]arenes was further extended to the propargyloxy group in 24-propargyloxy-25,26,27-tris(N,N-dimethylcarbamoylmethoxy)-p-tert-butylcalix[4]arene by demonstrating its free but slow motion affording equilibrium...

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Bibliographic Details
Published in:Supramolecular chemistry 2014-12, Vol.26 (10-12), p.722-728
Main Authors: Czirok, János B., Tarcsay, Ákos, Mezei, Pál D., Simon, András, Balázs, László, Bitter, István
Format: Article
Language:English
Subjects:
1,2-alternate
calixarene
conformational equilibrium
partial cone
propargyloxy group rotation
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Summary:The size limit of substituents allowing O-through-the-annulus rotation of substituted calix[4]arenes was further extended to the propargyloxy group in 24-propargyloxy-25,26,27-tris(N,N-dimethylcarbamoylmethoxy)-p-tert-butylcalix[4]arene by demonstrating its free but slow motion affording equilibrium between the partial cone and 1,2-alternate conformers. The effect of solvent and upper rim substituents R 1 on the conformational inversion was investigated by means of 1 H NMR. The rotational isomerisation of the parent (R 1 = H) analogue could not unambiguously be detected. The experimental results were supported by comprehensive density functional theory studies.
ISSN:1061-0278
1029-0478
DOI:10.1080/10610278.2013.860229