Journal of Physical Chemistry B, Vol.122, No.18, 4821-4827, 2018
Charge Determines Guest Orientation: A Combined NMR and Molecular Dynamics Study of beta-Cyclodextrins and Adamantane Derivatives
The strong binding of the adamantyl moiety to the cavity of beta-cyclodextrin makes it a common binding motif in supramolecular chemistry and a common model system. Despite the attention, there are still unresolved questions regarding the orientation of the adamantane derivatives in the inclusion complexes do they protrude from the wide or narrow opening of the cyclodextrin hosts? A combined analysis of ROESY NMR and molecular dynamics simulations allows the conclusion that positively charged adamantane derivatives are oriented with the hydrophilic group protruding from the wider opening of the cyclodextrin, while negatively charged adamantane derivatives form two coexisting types of complexes where the hydrophilic group respectively protrudes from the wide and narrow opening. Interestingly, structural modifications of the cyclodextrin host only have a slight impact on guest orientation.