An investigation of the inclusion complex of β-cyclodextrin with 8-nitro-quinoline in the solid state

A supramolecular inclusion complex (1) was prepared between ss-cyclodextrin and 8-nitro-quinoline, and its bound structure was investigated by X-ray crystallography in the solid state. The crystallographic study has shown that the inclusion complex 1 belongs to the Monoclinic system (space group: C2) with unit cell dimensions a = 19.269(5), b = 24.395(7), c = 16.095(4)angstrom, ss = 107.816(5)degrees, and forms a channel-type polymeric supramolecule. In the crystal structure, the ss-cyclodextrins exist as a head-to-head dimer by means of extensive hydrogen bonding across the secondary hydrogen groups of two symmetry-dependent ss-cyclodextrins. Two guest molecules are included in the cavity of the different ss-cyclodextrins, respectively, and the third is sandwiched in the interface of the dimer. The results indicate that the different inclusion behavior of 8-nitro-quinoline in ss-cyclodextrin cavity results from differing host-guest hydrogen bonding as well as spatial constraints.