MOLECULAR MODELING AND SOLID-STATE NMR OF SHORT-CHAIN MOLECULES IN DIANINS COMPOUND AND ZEOLITE 5A

We have investigated the reorientational mobility of n-hexane and n-pe ntanol guest molecules in Dianin's compound and in zeolite 5A by molec ular mechanics/dynamics calculations (MM/MD) and temperature-dependent solid-state H-2 NMR. To choose the proper motional models for the dif ferent host-guest systems, MM calculations were first performed and mi nimum-energy structures for the compounds were established. The calcul ations were performed on a crystallographic unit cell, with periodic b oundary conditions to minimize edge effects. MD methods were then appl ied to the minimized structures and provided an insight into the diffe rent dynamic modes experienced by the guest molecules in their host ca ges. Several structural parameters of the host-guest systems were moni tored for a total simulation period of up to 100 ps both at low temper ature (77 K) and high temperature (300 K). H-2 NMR spectra of perdeute rated and specifically deuterated guest molecules in their inclusion c ompounds were acquired as a function of temperature. After detection t he observed Line shapes were analyzed in terms of motional models, tak ing into account experimental parameters and the results of the MD cal culations. The solid-state H-2 NMR showed a very high degree of agreem ent with the results of the molecular modeling calculations.