RESUMEN
In situ high-pressure crystallization and diffraction techniques have been applied to obtain two very structurally distinct semi-clathrates of the tert-butylamine-water system with hydration numbers 5.65 and 5.8, respectively, thereby considerably reducing a notable hydration gap between the monohydrate and the 71/4 -hydrate that results when crystallization space is explored by temperature alone. Both structures can be considered as an intriguing solid-state example of hydrophobic hydration, in which the water network creates wide tert-butylamine-filled channels stabilized by cross-linking hydrogen bonds. The existence of interconnected channels might also add low hydration structures to a list of potential targets for hydrogen storage. A detailed analysis of the topology of host water and host-guest interactions is reported and extended to those of other hydrates of the compound. This analysis offers new insight into properties of the tert-butylamine-water system and provides some clues as to the occurrence of the sizable number of hydrates of this compound.
RESUMEN
The structure of a 1:1 ß-cyclodextrin-dimethylformamide hydrated complex has been determined from single-crystal X-ray diffraction data. A complete study of the structure is presented herein, including invariom refinement and interaction energy calculations. The structure has unit-cell parameters that are different from those of other ß-cyclodextrin complexes crystallizing in the same space group, but exhibits the known herringbone packing type. A structural comparison of these complexes has been carried out with XPac in order to understand the origin of the differences in packing and unit-cell parameters. The results show that the differences are most likely ascribed to variations in hydration and in the hydrogen-bonded network.