Reproducible Preparation of Polymorphs of the Thiacalix[4]Arene Derivative by Saturating a Solid Host with Solvent Vapors.

An efficient method to prepare polymorphs (including the unknown previously) is proposed for tert-butylthiacalix[4]arene tetrasubstituted with ethylcarboxymethyloxy groups at the lower rim by saturating this host and its inclusion compounds by solvent vapors. By means of this method and by heating this calixarene capable of the enantiotropic transition, it is shown that mutual transformations of polymorphs into each other can be controlled. Polymorphs and intermediate saturation products are characterized by a combination of thermogravimetry, differential scanning calorimetry, and powder X-ray diffraction. To reveal factors promoting polymorphism, the structures of two inclusion compounds and one of the polymorphs of calixarene studied are determined by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]