Selective pairwise encapsulation using directional interactions.

Trimethylamine N-oxide and trimethylphosphine oxide guests are pairwise encapsulated in a dimeric capsule self-assembled from a tetraurea aryl extended calix[4]pyrrole. The capsule possesses polar functional groups in its interior capable of controlling the orientation of the included guests. A modest selectivity is observed during the encapsulation process that is beyond the controls of size or shape exclusion.