Size selective supramolecular cages from aryl-bisimidazolium derivatives and cucurbit[8]uril.

A series of bisimidazolium salts were synthesized as novel guests for the macrocyclic host molecule cucurbit[8]uril (CB[8]). These bisimidazolium-CB[8] binary complexes exhibited a unique cage structure with the imidazolium rings acting as lids, leading to a size-dependent binding selectivity by altering the hydrophobic linker between the two imidazolium moieties. This new class of CB[8] complexes was also capable of binding small solvent molecules, including acetone, acetonitrile, diethyl ether, and tetrahydrofuran (THF) in an aqueous environment.