Role of biologically active inorganic anions Cl− and Br− in inclusion complex formation of α-cyclodextrin with some aromatic carboxylic acids

1H NMR spectroscopy was used to evaluate the effects of biologically active anions Cl− and Br− in inclusion complex formation of α-cyclodextrin with some aromatic carboxylic acids. It was demonstrated that presence of Br− anions induces the decrease in α-cyclodextrin binding affinity to carboxylic acids, while Cl− has no a noticeable effect. The observed difference was discussed in terms of selective interactions of α-cyclodextrin with Br− and Cl−. Only Br− anions are able to penetrate into α-cyclodextrin cavity and compete with carboxylic acid molecule for the macrocyclic cavity. This competition shifts the α-cyclodextrin/acid equilibrium in the direction of complex dissociation.