Experimental and theoretical investigation of solvatochromic properties and ion solvation structure in DESs of reline, glyceline, ethaline and their mixtures with PEG 400

Abstract

Deep eutectic solvents (DESs) are a new class of ionic liquids which have been applied in many chemical reactions therefore, the investigation of their physicochemical properties such as hydrogen bond property and ion delocalization, are important. We measured solvatochromic parameters of three different DESs, namely urea-choline chloride (reline), ethylene glycol-choline chloride (ethaline), and glycerol-choline chloride (glyceline) and their binary mixtures with different mole fractions of poly ethylene glycol (PEG 400) as co-solvent. Solvatochromic results showed that the reline has the biggest polarity in these three DESs, but the lowest in hydrogen bond donor and acceptor abilities. In binary mixtures of DESs with PEG 400, π* and α values are decreasing with increasing the mole fraction of PEG 400 which is in good agreement with these parameters in mixed solvents. Molecular dynamic simulations confirmed that there are hydrogen bonds between urea, ethylene glycol, glycerol and choline chloride in pure DESs, and their amount calculated in all DESs and also with some mole fractions of PEG 400. Moreover, delocalization of chloride in DESs, were calculated for all compositions by MD simulations analysis. Also, MD simulations confirmed result of the experimental finding and preferential solvation model.