An Investigation of the Inclusion Complex of -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)Å, ß = 107.816(5)°, 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.