Crystal structure of cyclomaltoheptaose (beta-cyclodextrin) complexes with p-aminobenzoic acid and o-aminobenzoic acid.

Crystal structures of cyclomaltoheptaose (beta-cyclodextrin) complexes with p-aminobenzoic acid and o-aminobenzoic acid have been determined by single-crystal X-ray diffraction. The space group of the beta-cyclodextrin-p-aminobenzoic acid complex is P2(1) with a host:guest stoichiometry of 1:1, and that of the beta-cyclodextrin-o-aminobenzoic acid complex is P1 with a stoichiometry of 2:3. The different structures of the guest molecules lead to the different molecular packing structures of the two complexes. Intermolecular hydrogen-bond interactions are the main force that stabilize the supramolecular systems. In both crystals, there are water molecules located near the cavity rims and in interstices between molecules of beta-cyclodextrin participating in formation of intermolecular hydrogen bonds.