Inclusion of carvone enantiomers in cyclomaltoheptaose (β-cyclodextrin):: thermal behaviour and H → D and D → H exchange

The inclusion compounds of carvone enantiomers in cylcomaltoheptaose (beta-cyclodextrin, betaCD) are studied at defined temperatures above room temperature and in relation to H --> D and D --> H exchanges. Loss of water molecules and release of carvone molecules from the betaCD cavity are caused by increase of temperature above room temperature and are measured by the integrated intensities of the O-H and C-H Raman stretching bands, respectively. In turn, H --> D and D --> H exchanges are monitored by the integrated intensities of the O-H and O-D Raman stretching bands, respectively. All of these processes were followed in real time with a Raman spectrometer equipped with CCD detection. The results indicate that distinct carvone enantiomers lead to the formation of different betaCD inclusion hydrates that have different water content and hydration structures. In particular, the results suggest that SCarv-betaCD has a greater water content, dehydrates strongly for temperatures above room temperature, and exchanges protons faster than the RCarv-betaCD complex. (C) 2002 Elsevier Science Ltd. All rights reserved.