How does the cation nature affect the DES structure?

The structural properties of three deep eutectic solvents (DESs), namely a 1:2 mixture of urea and choline (Ch) chloride and two analogous DESs containing different cations in place of choline, namely benzyl(2-hydroxyethyl)dimethylammonium (BeH) and benzyltrimethylammonium (Be), were studied by means of Molecular Dynamics simulations. The presence or not of a hydroxyl group on the organic cation, as well as of a bulky substituent such as the benzyl one, was found to strongly affect the DES hydrogen bond network, giving rise to different three dimensional arrangements of all the species present in the systems. • Reline and two DESs with different ammonium-based cations were studied. • The effect of the different cations on the DES structure was highlighted. • Strong anion-urea hydrogen bonds are found in all DES systems. • The DES melting point order is not related to the urea-anion hydrogen bond strength. • The hydroxyl group on the cation strongly affects the DES hydrogen bond network.