| Résumé | This crystal structure study examines systematically the effect of guest size and guest substituents on the guest-host interactions in a number of simple p-tert-butylcalix[4]arene host-guest compounds. With increasing chain length, the guest conformation becomes increasingly complex, going from a simple all-trans (C6) to s-shaped (C8) and helical (C12) conformations. For Cl-substituted alkanes, the Cl atom is excluded from the deep cavity, again by the chain taking on complex conformations. However, the Cl atom can be forced into the deep cavity with rigid guests such as 1,4-dichlorobenzene. The results suggest that it is space filling rather than specific interactions that give these compounds stability, and that they should be properly described as clathrates rather than as stoichiometric host-guest materials. |
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