The role of charge transfer interactions in the inclusion complexation of anionic guests with α-cyclodextrin

Two-parameter correlation models for the inclusion complexation of 30 carboxylic acids and their conjugated basis with α-cyclodextrin were obtained in terms of guest desolvation free energy (G_desolv), guest global softness (S) and a host-guest charge transfer parameter (ΔN) defined in the frame of Density Functional Theory (DFT). From the obtained models, it was concluded that charge transfer interactions are relevant in the stabilization of anionic inclusion complexes with α-cyclodextrin. Finally, an orbital picture is proposed in order to account for the charge transfer process between α-cyclodextrin and anionic species.