H-1-NMR RELAXATION STUDIES OF MOLTEN-SALTS CONTAINING ETHYLALUMINUM DICHLORIDE

The microdynamics of the 1-ethyl-3-methylimidazolium cation (Im(+)) in EtAlCl(2) containing binary (ImCl/EtAlCl(2)) and ternary (AlCl3/ImCl/EtAlCl(2)) room temperature molten salts are examined by H-1 NMR relaxation methods at sub-ambient temperatures. The intramolecular dipole-dipole relaxation model is used to determine the correlation time of the Im(+) ring using adjacent hydrogens. The methyl and ethyl hydrogen relaxation times of Im(+) are fitted to a model of two (methylene) and three (methyl) spin systems that includes the effect of cross correlation. Im(+) molecular tumbling correlation times, methyl and methylene spinning axis reorientational correlation times, and methyl and methylene group rotational correlation times are all determined for Im(+) in the binary and ternary melts. Correlation times obtained from semiempirical model calculations (MOPAC) describe the mobility of Im(+) as a function of temperature.