A VARIABLE-TEMPERATURE C-13 CROSS-POLARIZATION MAGIC ANGLE SPINNING NMR-STUDY OF SOME UNUSUAL DYNAMIC AND PHASE PROPERTIES OF (+/-)-3,4-DI-O-ACETYL-1,2,5,6-TETRA-O-BENZYL-MYO-INOSITOL, JUMPING CRYSTALS

Variable-temperature C-13 CP/MAS NMR experiments were carried out on crystalline (+/-)-3,4-di-O-acetyl-1,2,5,6-tetra-O-benzyl-myo-inositol. Three distinct phases can be distinguished from their NMR characteristics, each stable over a well defined temperature range, in accord with previous calorimetric studies. The differences between the spectra of the distinct phases suggest that structural variations between them are small. At least two of the aromatic ring moieties of the molecule were shown to be experiencing motional averaging in each of the three phases. Transitions between the phases, monitored by following changes in the NMR spectra, exhibited significant hysteresis but showed no evidence for pre-organizational behaviour in the form of intermediate species. These results are discussed in the context of the unusual 'jumping' motion of the crystals associated with passage through the phase II-III and III-II transitions.