Molecular motion of methyl rotor in a zeolite:
proton
NMR lineshapes of CH3CN-2HZSM-5
adsorption complex
Jelena Sepa, R. J. Gorte, B. H. Suits, and David White
Abstract
Proton lineshapes of methyl group in spatially isolated stoichiometric
1:1 CH3CN-2HZSM-5 adsorption complexes are
shown as a function of temperature. At 78 K, the methyl group
dipolar lineshape is characteristic of a fixed-axis tunneling
planar rotator. With increasing temperature, one observes
motional averaging associated with the reorientation of the
symmetry axis of the hydrogen-bonded acetonitrile at the
acid site. Since changes in dipolar anisotropy with temperature
are determined by confinement interactions, lineshape measurements
can be used to explore dispersion interactions in zeolitic
frameworks. These interactions are highly dependent on differences
in size, geometry and rigidity of zeolite cavities.
Chemical Physics Letters 289, 281-286 (1998).
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