Host‐Guest Interaction in α‐Cyclodextrin Inclusion Complexes

We measured XAFS spectra of aqueous Br− and I− ion‐α‐cyclodextrin solutions in which α‐cyclodextrin forms inclusion complexes, and compared the experimental data with results of molecular dynamics calculations. In the Br− system, little difference in XANES spectra was observed upon formation of inclusion complex. In the I− system, slight difference in line shape was observed. This suggests that there are changes in the electronic and local geometric structure around an I− ion when it is included in the cavity of an α‐cyclodextrin molecule. Molecular dynamics calculation showed that Br− ion is included in α‐cyclodextrin together with its first hydration shell. In contrast, I− ion is dehydrated upon inclusion.