C-13 NMR relaxation and H-1 diffusion (DOSY) studies of an acidic chloroaluminate melt

C-13 NMR relaxation studies of a 2:1 AlCl3:1-ethyl-3-methylimidazolium chloride (MEICl) melt between 26 and 57 degrees C provide rotational correlation times for MEI(+) which are compared with viscosities and diffusion coefficients. Diffusion coefficients for MEICl in a 2:1 AlCl3-MEICl melt are determined using H-1 diffusion ordered spectroscopy (DOSY) between 26 and 57 degrees C. All MEI(+) diffusion coefficients (ring, methyl, and ethyl protons) are virtually identical at a given temperature. The MEI(+) diffusion coefficients are viscosity dependent and correlate with conductivity and C-13 NMR rotational correlation times, indicating that the transport properties of the 2:1 AlCl3-MEICl melt are determined by the molar quantities of salt and not by the properties of the individual ions. Microviscosity factors provide reasonable values for the radius of MEI(+) from both viscosity and C-13 NMR rotational correlation times. The ''slip'' model is used to describe the movement of MEI(+) in the 2:1 AlCl3-MEICl melt where Al2Cl7- is the predominant anion. The ab initio structures of AlCl4- and Al2Cl7- have been calculated at the HF/6-31G(d) level.