Inclusion of nonopiate analgesic drugs in cyclodextrins.: I.: X-ray structure of a 1 : 1 β-cyclodextrin-p-bromoacetanilide complex

The preparation and X-ray crystal structure of a 1 : 1 complex between beta-cyclodextrin (beta-CD) and the analgesic p-bromoacetanilide are reported. Thermogravimetric and UV spectrophotometric analyses of single crystals grown from an aqueous solution containing host and guest in 1 : 1 molar ratio yielded the composition beta-CD . p-bromoacetanilide . 13.5H(2)O. Crystals of the complex are triclinic, space group P1, with a = 15.197(3), b = 15.613(2), c = 15.743(4) Angstrom, alpha = 87.16(2), beta = 98.29(2), gamma = 103.39(1)degrees and Z = 2 crystallographically independent complex units per unit cell. The beta-CD molecules form head-to-head dimers which pack in the channel-mode. Each dimer contains two guest molecules whose acetylamino substituents are located at the dimer interface while the bromine atoms protrude from the beta-CD primary faces. The acetyl residues of both guest molecules were found to be disordered but the X-ray data permitted successful resolution and modelling of this feature.