Polyol-based Deep Eutectic Solvents as ubiquitous and sustainable mixtures: from organic chemistry to electrochemical energy storage

Deep Eutectic Solvents (DES) are an emerging class of solvents, generally claimed as biocompatible, low cost and sustainable. 1 They are usually based on a halide salt (organic or inorganic), which acts as a hydrogen bond acceptor (HBA), and an alcohol/organic acid, which acts as a hydrogen bond donor (HBD). Albeit a consensus on the physical-chemical interaction behind the DES formation is far to be reached, they have found applications in different field, from organic and inorganic synthesis to electrochemical devices. 2 In this contribution, we would like to show the multiple field in which we are exploiting polyol (e.g. glycerol or ethylene glycol)-based Deep Eutectic Solvents. More in details, after an elucidation on what DESs are and about their truly sustainability, we would disuss two paragadigmatic example, such (i) the exploitation of glycerol/fluoride-based DES in the reactivity of diazonium salts 3 and (ii) the application of ethylene glycol/chloride-based DES as electrolytes for electrochemical energy storage. In doing so, a specific lens is focused on the chemical-physical properties of the proposed DES in order to establish pivotal structure-properties relationships.