Publication at Faculty of Mathematics and Physics |
2006
Abstract
Thiacalix[4]arene contains a circular array of four equivalent hydrogen bonds on its lower rim. The array undergoes a flip-flop motion between two possible directions.
The rate of this motion in the temperature range 223 313 K is assessed by means of measurements of the nuclear spin relaxation. The values of the activation enthalpy (38.7 kJ.mol-1) and of the activation entropy (15 J.mol-1.K-1) were determined.
In addition, correlation times of molecular tumbling have been determined in the same temperature range. The measured properties of thiacalix[4]arene are compared to those of the 'classical' calix[4]arene in order to utilize them for fine tuning of the building blocks in supramolecular chemistry.