Formation of highly stable heterodimers in aqueous solution between beta-cyclodextrin derivatives bearing multiple opposite charges

Two water-soluble perfunctionalized beta-cyclodextrins bearing amino or carboxyl groups were used to examine the possibility of obtaining stable heterodimers in water. The acidobasic properties of both compounds may be accounted for on the basis of a theoretical interpretation of the potentiometric titration of polyelectrolytes. The association constants between positively and negatively charged beta-cyclodextrins were determined by potentiometric titrations. The Gibbs energies of association between cyclodextrins are shown to depend on the product of elementary charges borne by each interacting species. The results obtained are significant for evaluation of electrostatic contributions to molecular recognition.