Tunable, shape-shifting capsule for dicarboxylates

A cylindrical amide-based tricycle provides a ditopic framework for encapsulating both aliphatic and aromatic dicarboxylate anions. Due to the flexible spacer between the two macrocyclic receptor sites, it can modulate its shape to conform to dicarboxylates of varying lengths. In the uncomplexed form, the host is elongated along its cylindrical axis, but when encapsulating the guest, it compresses to ensure the best structural fit.