A supramolecular inclusion complex was prepared between β-cyclodextrin (β-CD) and 8-hydroxyquinoline, and its crystal structure was investigated by single-crystal X-ray crystallography. The asymmetric unit consists of two β-CDs, one 8-hydroxyquinoline, two ethanol and thirty water molecules. Two β-CDs form a head-to-head dimer by means of extensive hydrogen bonding across the secondary hydroxyl groups. One 8-hydroxyquinoline molecule is sandwiched in the interface of the dimer and is parallel to the plane of β-CD macrocycle. Each β-CD of the dimer includes one ethanol molecule in its cavity. Thirty water molecules are distributed in the interstices between β-CD dimers. The results indicate that the interface of the β-CD dimer has stronger inclusion ability than the cavity of β-CD for some suitable planar molecules. The novel inclusion structure results from the competitive inclusion of 8-hydroxyquinoline and ethanol molecules.

Key words: β-cyclodextrin, 8-hydroxyquinoline, crystal structure, inclusion complex