Physical properties of the complexes formed between heptakis(2,6-di-O-methyl)-beta-cyclodextrin, beta-cyclodextrin,...

The solid complex of chlorambucil (CHL) and heptakis-(2,6-di-O-methyl)-beta-cyclodextrin (DIMEB) has been isolated from ethanol and analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and powder X-ray diffractometry. The carbonyl stretching band of the complex, observed in the FTIR spectrum, was shifted to higher frequency, suggesting that intermolecular hydrogen bonds between CHL molecules are broken when the complex is formed. Since no melting endotherm was observed for CHL when the DSC thermogram of the complex was obtained, the crystal lattice of the compound must be disrupted upon complexation. X-ray diffraction patterns of the inclusion complex were different from those of the physical mixture and contained no peaks corresponding to free CHL, thus indicating the formation of a new crystalline material. The 1:1 CHL:beta-cyclodextrin (beta-CD) complex was isolated from aqueous solution at 3 degrees C. Results of analyses using FTIR and DSC were similar to those obtained with the CHL:DIMEB complex. The X-ray diffraction patterns of the complex suggest that its degree of crystallinity is higher than that of the CHL:DIMEB complex.