Hydrogen-1 nuclear magnetic resonance, differential thermal analysis, X-ray powder diffraction and electrical conductivity studies on the motion of cations, including self-diffusion in crystals of propylammonium chloride and bromide as well as their n-deuterated analogues

Abstract

¹ H N.m.r. measurements and differential thermal analyses have been performed on solid propylammonium chloride and bromide, including their N-deuterated analogues. X-Ray powder diffraction and electrical conductivity were measured for the highest-temperature solid phase of NH₃(n-C₃H₇)Cl. The corresponding highest-temperature solid phase of the bromide was determined. These salts have three solid phases below the respective melting temperature. In the highest-temperature phase, having a structure consisting of cation and anion layers, it was found for the chloride that the cations perform self-diffusion in two-dimensional layers. A non-linear log T₁vs. T^–1 curve observed in the room-temperature phase of propylammonium chloride and bromide could be well explained by assuming a non-Arrhenius type thermal process for the random reorientation of the cation along the cationic chain axis. The broad T₁ minimum of NH₃(n-C₃H₇)Br observed in its low-temperature phase has been assigned to two closely spaced T₁ minima due to the C₃ reorientation of the CH₃ and NH⁺₃ groups. Motional parameters for the above cationic motions in the three phases of the present salts have been evaluated, and the features of these motions are discussed.