Complexation in a β-cyclodextrin-salicylic acid system

Inclusion host-guest complexes are synthesized from β-cyclodextrin and salicylic acid, which is a nonsteroid anti-inflammatory drug with a wide range of action. By IR and UV spectroscopy, and X-ray diffraction, and thermogravimetry, it is established that axial 1:1 complexes of the “tail forward” type are formed due to the dispersion interactions between internal hydrophobic cavities of β-cyclodextrin molecules and salicylic acid aromatic rings. Salicylic acid is stabilized due to the fact that its carboxyl group is located in the plane of the upper edge of β-cyclodextrin molecule and weak hydrogen bond is formed between phenyl hydroxyl and glycoside oxygen. The encapsulation of salicylic acid changes its crystal structure and thermal stability.