Combining experimental and theoretical vibrational spectroscopy to study magnesium aluminum chloride complex electrolytes

Abstract

Measurements of the Far-IR and Raman spectra of 1:1 MACC-ether electrolytes were carried out. [(μ-Cl)2Mg2]2+ is the major dimer in DME solution and the bands at 250 and 222 cm−1 may be used as markers in the respective IR and Raman spectra. On the other hand, [MgCl]+ stands out in the THF-based electrolyte, where an IR band at 286 cm−1 is here reported for the first time in the literature and may be employed as sensor. The [(μ-Cl)3Mg2]+ dimer, which is usually formed at the 2:1 MACC-THF electrolyte and deemed the electrochemically active species on the electrode, is also identified at the 1:1 ratio. AIMD-simulated IR spectra of the dimer and monomer are in good agreement with the experimental data and were pivotal to characterize the [MgCl(THF)5]+ complex. QC calculations helped assign a few bands in the Raman spectra and Gibbs free energies explained the preferential formation of Mg species in each medium.