Molecular dynamics in [(CH3)4N]2 CdI4

Proton spin-lattice relaxation experiments (at Larmor frequencies 10, 20, and 30 MHz), and second moment measurements are carried out on [(CH3)4N]2 CdI4 in the temperature range 77 to 400 K. The results are interpreted based on a molecular dynamical model of randomly reorienting methyl groups and isotropically tumbling tetramethyl ammonium group. The relaxation data show contributions from spin-rotation interaction at high temperatures and presence of inequivalent methyl groups. The correlation times and associated activation energies, connected with this model, are calculated from the data. The structure in the absorption line and in the free-induction decay signal at 77 K indicates the possibility of tunnelling motion of the methyl groups. (author)