What is "carcerand"

n. (context chemistry English) any of a class of complex polycyclic compounds, based on calixarenes, that form a sphere within which a guest molecule may be held

A carcerand is a host molecule that completely entraps its guest so that it will not escape even at high temperatures. This type of molecule was first described by Donald J. Cram in 1985 and is derived from the Latin carcer, or prison. The complexes formed by a carcerand with permanently imprisoned guests are called carceplexes.

In contrast hemicarcerands allow guests to enter and exit the cavity at high temperatures but will form stable complexes at ambient temperatures. The complexes formed by a hemicarcerand and a guest are called hemicarceplexes.