Vahideh ALIZADEH1, Jan BLASIUS1, Tom FRÖMBGEN1, Barbara KIRCHNER1
1Mulliken Center for Theoretical Chemistry, University of Bonn, Bonn, Germany
Ion pairing is the association of oppositely charged ions in electrolyte solutions to form distinct chemical species called ion pairs. It is well known that ion pair formation in ionic solvents like ionic liquids influences their properties and applications. However, deep eutectic solvents (DESs) as a kindship of ionic liquids are a new class of green solvents. DESs are eutectic mixtures of Lewis and/or Bronsted acids and bases, termed hydrogen bond donors/acceptors, with a significantly depressed melting point as compared to those of the parent compounds. DESs have great potential in different applications, for instance as electrolytes for electrochemical processes, energy storage, as well as gas absorption.
To provide a predictive understanding for the design of DESs for specific applications, it is necessary to understand how ion pairing in DESs influences the structural rearrangment and charge dynamics. Thus, in this study, ab initio molecular dynamics and polarizable force field simulations are employed to investigate ion pairing in Choline chloride: Ethylene glycol ([Ch][Cl]:EG) [1:1, 1:2, 1:3, 1:4.85(eutectic point), 2:1 and 3:1] mixtures. We observe ion paring formation in the [Ch][Cl]:EG mixtures which is, however, influenced by the concentration of the hydrogen bond donor.