Conformational isomerism and self-association of calixarene building blocks in non-polar solution studied by Fourier transform infrared spectrometry

Lutz, Bert T.G. and Astarloa, Gonzalo and Maas van der, John H. and Janssen, Rob G. and Verboom, Willem and Reinhoudt, David N. (1995) Conformational isomerism and self-association of calixarene building blocks in non-polar solution studied by Fourier transform infrared spectrometry. Vibrational Spectroscopy, 10 (1). pp. 29-40. ISSN 0924-2031

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Abstract:	In order to establish the conformational equilibrium of calix[6]arene derivatives, a series of phenolic building blocks differing in chain length (oligomers) have been studied in solution by Fourier transform infrared spectrometry (FT-IR). Different intramolecular OH ¿ X interactions have been established in the calixarene building blocks, i.e. OH ¿ ¿, OH ¿ OH, OH ¿ OCH3 and a bifurcated OH ¿ OH/OCH3 or OH ¿ OH/OH one. Concentration-dependent measurements show that the ¿biphenol¿ and ¿triphenol¿ oligomers form cyclic dimers even at very low concentration (<10¿5 M). The presence of a molecular conformation where the terminal hydroxyl groups form part of a linear (cooperative) H-bond seems to promote cyclic self-association. Comparing p-tert-butylcalix[4]arene with p-tert-butylcalix[6]arene reveals that fixation of the skeleton strengthens the circular H-bond. Intramolecular OH ¿ OCH3 or OH ¿ ¿ interaction prevents the formation of associates for the building blocks with only one terminal OH group at relatively high concentration (> 10¿2 M). Preliminary MM3 calculations were performed to support conformational assignment.
Item Type:	Article
Copyright:	© 1995 Elsevier Science
Faculty:	Science and Technology (TNW)
Research Group:	Molecular Nanofabrication (MNF)
Link to this item:	http://purl.utwente.nl/publications/12399
Official URL:	http://dx.doi.org/10.1016/0924-2031(95)00024-O
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