13 C and 27 Al NMR Relaxation Studies of an Acidic Chloroaluminate Melt

Abstract

The microdynamics of a 2:1 A1C1₃-1-ethyl-3-methylimidazoliumc chloride (MEICI) room-temperature melt are studied using ¹³C and ²⁷Al NMR relaxation methods. The ¹³C and ²⁷Al NMR correlation times for MEI⁺ and A1₂CI₇⁻ are compared with viscosity measurements corrected for temperature. The Dual Spin Probe (DSP) method is used to calculate an ²⁷Al nuclear quadrupole coupling constant (χ) of 4.86 MHZ for A1₂C1₇⁻ in the 2:1 melt. Theoretical (ab initio-gas phase) calculations at the HF/3–21 G(d) and HF/6–31 (d) levels yield ²⁷Al nuclear quadrupole coupling constants of 8.015 and 11.211 MHZ for A1₂Cl₇⁻. Finally, a linear relationship between ²⁷Al correlation times of A1₂C1₇⁻ and reciprocal conductivity is reported.