The temperature dependences of the proton spin-lattice and spin-spin relaxation times, and also the second moment of the 1H n.m.r. absorptions of (CH3NH3)2SO4 and its partially deuterated analogue, have been observed in a wide temperature range, including a new high-temperature solid phase obtainable above 428 K. X-Ray powder patterns obtained at ca. 450 K revealed that the crystal in this phase has a hexagonal structure isomorphous with the α-form of K2SO4. From 1H n.m.r. experiments it was found that the cations in the high-temperature phase undergo overall reorientation as well as translational self-diffusion. The presence of these motions suggests that this new phase is in a state resembling the plastic phase of molecular crystals. In the low-temperature phase a reorientation of the CH3 and NH3- groups of the cation about the C-N bond axis was observed. The motional parameters for these motional modes were evaluated.
|Number of pages||10|
|Journal||Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases|
|Publication status||Published - Dec 1 1989|
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