Molecular Mechanical Calculation on Cyclodextrin Inclusion Complexes. I. The Structures of α-Cyclodextrin Complexes Estimated by van der Waals Interaction Energy Calculation

The geometries of inclusion complexes of α-cyclodextrin (α-CD) with krypton, methanol, 1-propanol, and p-nitrophenol were estimated on the basis of the calculation of energies (Evdw) due to the van der Waals interactions between the CD and the guest molecules. The Evdw values were computed by the use of Hill’s potential equation. A spatial relationship at which the Evdw value became minimal was in good agreement with that observed by X-ray crystallography for such a guest molecule as 1-propanol or p-nitrophenol, which is large in size and less polar. On the other hand, a significantly large deviation was found between the observed and the calculated geometries of the inclusion complex in such polar and/or small guest molecules as methanol and krypton.