Mass spectrometric measurements have provided unequivocal evidence that calix[n]arenes (2n), which are so far believed to exist as discrete monomers in solution because of strong intramolecular hydrogen bonding, aggregate partially to form dimers and trimers through intermolecular hydrogen bonds. This trend is particularly conspicuous in 28 and next in 27 and only a very weak dimer peak is observable for 26. In contrast, such an aggregate peak is not detected for 24 and 2 5. The results are consistent with the prediction offered on the basis of theoretical calculations that 24 and 25 can adopt a stable C4- and C5-symmetrical ring structure, respectively, as well as a stable intramolecular hydrogen-bonding array, whereas 26, 27 and 28 feature a pinched ring conformation as their most stable structure which destabilizes the intramolecular hydrogen-bonding array. The new finding reasonably explains several curious aspects of the behaviour of 2n such as very poor solubility of 28 and gelation in organic fluids.
|Number of pages
|Journal of the Chemical Society. Perkin Transactions 2
|Published - Apr 1996
All Science Journal Classification (ASJC) codes
- General Chemistry