Closer look into the structures of tetrabutylammonium bromide–glycerol-based deep eutectic solvents and their mixtures with water

Abstract In recent years, deep eutectic solvents (DES) and it’s mixture with water have become more and more attention as green solvents used in chemistry. However, there are only a few theoretical studies on the mechanisms of pure DES and DES-water complex formation. Therefore, the structural properties of tetrabutylammonium bromide–glycerol-based deep eutectic solvents and their mixtures with water have been investigated by means of Molecular Dynamics simulations. The obtained results indicate that three types of H-bonds exist in the pure DES structures, and all of these interactions play an important role in DES formation. In addition, between hydrogen bond donors (HBDs) and hydrogen bond acceptor (HBA) weaker non-bonded interactions, i.e. van der Waals exist, which also contribute to the formation of stable DES structures and to lower the melting point of DES compared to pure substances. The small addition of water to DES provides the formation of a stable complex, however, a further increase in water content (higher than 50% v/v) provide to the destruction of the most important hydrogen bonds (O–H···Br) in DES structure.