Comparative thermodynamic study on complex formation of native and hydroxypropylated cyclodextrins with benzoic acid

Complex formation of native and hydroxypropylated α-, β- and γ-cyclodextrins with benzoic acid in water was studied by means of calorimetry of solution at 298.15 K. The 1:1 complexes are formed with α- and β-cyclodextrins, while 1:2 binding stoichiometry was observed for γ-cyclodextrins. Thermodynamic parameters of complex formation of hydroxypropylated cyclodextrins were determined for the first time and analyzed. Comparison of binding affinity of native and modified cyclodextrins was carried out.

► Comparative calorimetric study on complexation of benzoic acid by native and modified cyclodextrins was performed. ► Van der Waals interactions are responsible for complex formation with α-cyclodextrins. ► Complex formation of β-cyclodextrins is governed by dehydration and hydrophobic interactions. ► Binding of two benzoic acid molecules by γ-cyclodextrins is driven by van der Waals interactions and solvent reorganization. ► Hydroxypropyl groups favor binding of benzoic acid only with hydroxypropyl-β-cyclodextrin.