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Nuclear magnetic resonance (NMR) provides means to investigate molecular dynamics at every state of
matter. Features characteristic for the gas phase, liquid-like layers and immobilized methanol-d
4
molecules in NaX and NaY zeolites were observed in the temperature range from 300 K down to 20 K.
The NMR spectra at low temperature are consistent with the model in which molecules are bonded at
two positions: horizontal (methanol oxygen bonded to sodium cation) and vertical (hydrogen bonding
of hydroxyl deuteron to zeolite framework oxygen). Narrow lines were observed at high temperature
indicating an isotropic reorientation of a fraction of molecules. Deuteron spin–lattice relaxation gives
evidence for the formation of trimers, based on observation of different relaxation rates for methyl and
hydroxyl deuterons undergoing isotropic reorientation. Internal rotation of methyl groups and fixed
positions of hydrogen bonded hydroxyl deuterons in methyl trimers provide relaxation rates observed
experimentally. A change in the slope of the temperature dependence of both relaxation rates indicates
a transition from the relaxation dominated by translational motion to prevailing contribution of
reorientation. Trimers undergoing isotropic reorientation disintegrate and separate molecules become
localized on adsorption centers at 166.7 K and 153.8 K for NaX and NaY, respectively, as indicated by
extreme broadening of deuteron NMR spectra. Molecules at vertical position remain localized up to
high temperatures. That indicates the dominating role of the hydrogen bonding. Mobility of single
molecules was observed for lower loading (86 molecules/uc) in NaX. A direct transition from
translation to localization was observed at 190 K.