Synthesis and Characterization of Novel Ternary Deep Eutectic Solvents

A series of novel, moisture-stable, ternary deep eutectic solvents (TDESs) has been prepared and characterized by mixing appropriate molar ratios of 1-butyl-3-methylimidazolium halide ([BMIM]X, X=Cl, Br), zinc halide (ZnX₂, X=Cl, Br) and various amides (acetamide, urea and N,N’-dimethyl urea). The synthesized ternary deep eutectic solvents are liquid at ambient temperatures and have interesting solvent properties. It shows that the most synthesized TDESs have much lower melting points than the conventional binary system according to the data of differential scanning calorimetry (DSC). Data on the melting point, viscosity and conductivity are presented and these are shown to be significantly different to other reported binary system. The [BMIM]Cl-ZnCl₂-(Acetamide)₂ system showed the lowest melting points (<-60°C), lowest viscosity and highest conductivity in all synthesized TDESs. The results showed that both viscosity and conductivity of all synthesized TDESs decrease with increasing temperatures and can be fitted by Arrhenius equation versus temperature. The data of conductivity and viscosity also fits well to the Walden’s Rule. The influence of amides, halides and molar ratio of amides in ternary mixtures on the physical properties of the synthesized TDESs has been investigated.