Ion-Solvent Interactions in 1:2 Lewis-Acidic Chloroaluminate Ionic Liquids

Ionic liquids (ILs) formulated by mixing an organic chloride salt with AlCl3 in a 1:2 molar ratio-classically, 1-ethyl-3-methylimidazolium chloride (EMImCl): AlCl3 = 1:2- form Lewis-acidic "1:2 ionic liquids" in which the dominant anionic species is Al2Cl7? in equilibrium with AlCl4?. These liquids show distinctive ion?solvent interactions that govern transport, reactivity, and interfacial phenomena in catalysis and electrochemistry (e.g., Al battery electrolytes and Al electrodeposition). This review synthesizes how acidity and speciation control solvation thermodynamics and dynamics, surveys experimental and computational probes (NMR, vibrational spectroscopy, solvatochromic scales, conductivity) and distills design rules for tuning solvation via composition, cation identity, and purposeful dilution.