Selective Inclusion of a Hetero-Guest Pair in a Molecular Host: Formation of Stable Charge-Transfer Complexes in Cucurbit[8]uril

Two different molecules are selectively included in cucurbit[8]uril to form a stable 1:1:1 ternary complex, which has been characterized by X-ray crystallography (see picture). The inclusion of a hetero-guest pair (a pyridinium derivative (blue) and 2,6-dihydroxynaphthalene (magenta)) in the molecular host is driven and stabilized by a charge-transfer interaction between the electron-rich and electron-deficient guests.