But the space inside a carcerand is like no other chemical environment, and the guest molecule finds itself locked up for life.
Strong acids, for example, tend to break down the bonds of a carcerand cage, releasing any trapped molecules.
Carcerands themselves turn out to be highly insoluble.
Last year, Cram reported linking two bowl assemblies to make the first "molecular cells," which he also calls carcerands because small molecules get trapped inside when the bowl rims meet.
Cram expects next to build new carcerands by linking a pair of box cavities to make an elongated box with a bulge in the middle.