Charge Spreading in Deep Eutectic Solvents

Ab initio molecular dynamic simulations reveal significantly reduced ion charges in several choline-based deep eutectic solvents, which are cheap and eco-friendly alternatives to ionic liquids. Increasing hydrogen bond strength between the anion and the organic compound enhances charge spreading from the anion to the organic compound while the positive charge is stronger located at the cation. Nonetheless, the negative charge transferred from chloride to urea in choline chloride urea mixtures is negligible. Thus, it seems questionable if charge delocalization occurring through hydrogen bonding between the halide anion and the organic compound is responsible for the deep eutectic melting point.