Thermodynamics of binding between α- and β-cyclodextrins and some p-nitro-aniline derivatives: reconsidering the enthalpy–entropy compensation effect

The thermodynamics of binding between native α- and β-cyclodextrin towards several p-nitro-aniline derivatives was examined, in order to gain further insights about the occurrence of different interaction modes for the two hosts. Valuable information was achieved regarding the ‘expanded hydrophobic sphere’ of α-cyclodextrin. Furthermore, very interesting and unexpected aspects of the behavior of β-cyclodextrin were enlightened, such as the crucial role played by hydrogen bond interactions. Experimental data were examined under the perspective of the ‘enthalpy–entropy compensation effect’, and some ideas about this topic are discussed.