NMR relaxation in the double clathrate hydrate tetrahydrofuran/hydrogen sulfide

Nuclear magnetic proton relaxation times T1 are reported for the double clathrate hydrate tetrahydrofuran/hydrogen sulfide in the temperature range 4-285 K at frequencies 60 and 300 MHz. The guest molecules contained alternatively light and heavy hydrogen isotopes. This permitted the molecular motion of both guests to be studied separately. Data analysis of tetrahydrofuran shows that between 15 and 120 K isotropic rotation with activation energy of 5 kJ/mol occurs. Data analysis of hydrogen sulfide points to strong interactions with the cage wall, less at lower than at higher temperature resulting in two different activation energies of 0.3 kJ/mol below and 3 kJ/mol above 26 K.