Quantum chemical investigation on the structural and electronic properties of α-, β-, and γ-cyclodextrin complexes: DFT and QTAIM analysis

To characterize the structural, thermochemical and electronic aspects in complexes of leucine, vanillin and mechlorethamine with α-, β-, and γ-cyclodextrins (CDs), a density functional theory (DFT) study has been conducted in combination with quantum theory of atoms in molecules (QTAIM) analysis. The QTAIM method has been utilized to explore the nature of various possible interactions between leucine, vanillin and mechlorethamine with CDs in terms of bond critical points (BCPs). HOMO and LUMO and atomic charges studies show charge transfer occurs between drugs and cyclodextrins. This behavior has been also investigated via QTAIM charge analysis. On the other hand, based on QTAIM electronic energy indicators we have discussed electrostatic character of interactions between vanillin, leucine and mechlorethamine with inner surface CDs in the coordination sphere.