| Abstract
| - Dynamic properties of perdeuterated pyrazine (pyrazine-d4) guest molecules in the layeredα-zirconium phosphate host structure have been established from solid-state 2H NMR line-shape analysis and 2H NMR spin−lattice relaxation time measurements. Both techniquesindicate that the intercalation compound contains two different types of pyrazine-d4 guestmolecules, which undergo different dynamic processes. The relative proportions of the twotypes of pyrazine-d4 guest molecules are approximately 30% (component A) and 70%(component B). The pyrazine-d4 molecules representing component B undergo two-site 180°jumps about the N···N axis of the molecule, whereas the pyrazine-d4 molecules representingcomponent A undergo an effectively isotropic motion. The activation energy for the two-site180° motion of component B is estimated to be 39 kJ mol-1 from the 2H NMR spin−latticerelaxation time measurements and 49 kJ mol-1 from the 2H NMR line-shape analysis.Structurally, it may be inferred that component B comprises guest molecules for which theN···N axis has a restricted orientation in space, presumably because of direct interactionswith the α-zirconium phosphate host structure, whereas component A comprises guestmolecules that are held rather weakly in the host structure (or on its external surfaces)such that their reorientation is relatively unrestricted. Thermogravimetric analysis providesdirect evidence for the existence of two different types of pyrazine guest molecules in theα-zirconium phosphate host structure, with different strengths of binding and withpopulations in the approximate ratio 30:70. High-resolution solid-state 15N NMR and 13CNMR spectra provide further support for the existence of two different types of pyrazineguest species within the α-zirconium phosphate host structure and provide direct evidencethat the pyrazine guest molecules of component B are N-protonated (from the host structure).
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