Experimental-computational study on the competition between 1,2-dimethoxyethane and tetrahydrofuran in a MACC-based electrolyte

The 1:1 MgCl2:AlCl3 (MACC)-based electrolyte was spectroscopically investigated for the first time in the presence of an equimolal 1,2-dimethoxyethane (DME):tetrahydrofuran (THF) mixture. Composition-dependent Raman spectra suggested that the new bands at 896 and 883 cm−1 correspond to the mixed νCO and νCC vibrations of both ethers coordinated to Mg(II) ions. A signal at 219 cm−1, which is assigned to the νMgCl vibration, was only observed for the highest acid-base pair content, in contrast to the behavior exhibited in the acyclic ether alone. Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations revealed that the [MgCl(DME)(THF)3]+ and [MgCl(DME)2THF]+ monomers may be associated to the experimental bands observed at the solvent region, thus being predicted at 867 and 858 cm−1, respectively. The [Mg2(μ-Cl)2(DME)4]2+ dimer has a theoretical band at 216 cm−1, which is related to the experimentally observed signal at the low wavenumber region. The preferential solvation effect is discussed in detail for the studied solvates.