Type III eutectics, formed from choline chloride and hydrogen bond donors, have been of interest due to their ability to solvate a wide range of transition metal species, including chlorides and oxides.A range of hydrogen bond donors have been studied to date, with deep eutectic solvents formed using amides, carboxylic acids, and alcohols (see Figure 1). These liquids are simple to prepare, and relatively unreactive with water; many are biodegradable and are relatively low cost. The wide range of hydrogen bond donors available means that this class of deep eutectic solvents is particularly adaptable. The physical properties of the liquid are dependent upon the hydrogen bond donor and can be easily tailored for specific applications. Although the electrochemical windows are significantly smaller than those for some of the imidazolium salt−discrete anion ionic liquids, they are sufficiently wide to allow the deposition of metals such as Zn
with high current efficiencies. This class of deep eutectic solvents have been shown to be particularly versatile, with a wide range of possible applications investigated including the removal of glycerol from biodiesel, processing of metal oxides, and the synthesis of cellulose derivatives