CATION DYNAMICS IN [N(CH3)4]3SB2CL9 (TEMACA)-NMR STUDY

Molecular motions in TEMACA, which shows structural phase transitions at 223 and 156 K, are studied through proton spin-lattice relaxation and linewidth measurements at two Larmor frequencies. The results show that tetramethylammonium groups undergo isotropic tumbling with more hindrance in the phase below 223 K compared to the high temperature phase. The results also show that the methyl groups exist in dynamically inequivalent sites. There is no signature of a 156 K transition in the data. Various activation energies associated with the dynamics of the cation groups and the threefold reorientations of the methyl groups below the phase transition are calculated.