H NMR Reveals Liquid State-Like Dynamics of Arene Guests Inside Hexameric Pyrogallol[4]arene Capsules in the Solid State.

The dynamics of guests in molecular encapsulation complexes have been studied extensively in solution, but the corresponding behavior of those guests when the capsules are present in the solid state is not as well understood. Here we report on comparative solution H and solid-state H NMR measurements of encapsulation complexes of fluorene(- ), fluoranthene(- ), and pyrene-(- ) in pyrogallol[4]arene hexamers assembled in the solid state by ball milling. In solution, the H spectra show that these rigid guests tumble and exchange positions quickly within the capsules' interiors, with the exception of pyrene, which has slower tumbling and positional exchange.