β-Cyclodextrin—α-aminopyridine interaction: A DFT study

The energy changes for two opposite complexation orientations of β-cyclodextrin (β-CD) and α-aminopyridine were calculated by the semiempirical PM3 method. The complexes with the lowest energies obtained by the PM3 method were further investigated by the density functional theory at the B3LYP/3-21G* level. The DFT results indicate that the complexation orientation, in which the amino group is located near the secondary hydroxyl rim of the β-CD cavity, is much more favorable, probably, due to effective hydrophobic interactions. The results of statistical thermodynamics calculations for p = 1 atm and T = 298.15 K suggest that the inclusion complexation processes of two different orientations are driven by enthalpy.