Anatomy of a deep eutectic solvent: structural properties of choline chloride : sesamol 1 : 3 compared to reline

Abstract

The structural properties of the deep eutectic solvent (DES) formed by choline chloride (ChCl) and sesamol in 1:3 ratio have been investigated and compared to those of reline (ChCl:urea 1:2)....

On the Role of Water in the Formation of a Deep Eutectic Solvent Based on NiCl2·6H2O and Urea

“… 36 , 37 All the stretching vibrations involving the hydrogen atoms were constrained with the LINCS algorithm. 38 The employed simulation protocol is reported elsewhere, 4 , 39 − 43 though details are provided in the SI .…”

Fate of a Deep Eutectic Solvent upon Cosolvent Addition: Choline Chloride–Sesamol 1:3 Mixtures with Methanol

“…These bands were previously observed to be red-shifted with respect to the O−H absorption of the pure components, evidencing the formation of the eutectic through the establishment of strong HBs between the chloride anion with the choline cation and the sesamol molecule. 15,37 The additional spectral features at lower wavenumbers are assigned exclusively to the sesamol moiety, in particular the C=C stretching at 1610 cm −1 , the C−H bending region (1500−1300 cm −1 ), the strong C−O stretching absorption between 1300 and 1000 cm −1 , and the out-of-plane ring deformation (δ ring (sesamol)) at 765 cm −1 . 63 Unfortunately, bands related to ChCl only are too weak and unresolved to be employed in the analysis.…”

“…This picture is in agreement with previous findings describing the structure of this eutectic as formed by discrete chloride clusters that see almost the entire amount of sesamol and choline molecules involved, packed to maximize the HB interactions. 36,37 When MeOH is added to the DES, the N value for the Cl−MeOH interaction (Figure 3a) between the chloride anion and the hydroxyl group of MeOH increases sharply with increasing MeOH concentration (Figure 3d). In detail, an average number of 1.3 MeOH molecules is found in the coordination sphere of the chloride anion for M = 2, while the chloride anion is coordinated by 3.7 MeOH molecules for M = 24.…”

“…However, in the ChCl/sesamol 1:3 DES, the chloride anion was also found to interact with the two hydrogen atoms of the sesamol dioxolane functionality and with the choline molecule cationic core. 37 Despite these interactions being weaker with respect to those involving the hydroxyl groups of the components, they also take part in the eutectic structural arrangement, since such interacting sesamol and choline molecules are in turn able to coordinate different chloride anions with the hydroxyl groups and to bridge between the discrete chloride anion clusters. 37 When MeOH is added to the eutectic, these additional interactions are drastically reduced, as the Cl − anion prefers to form HBs with the MeOH molecules.…”

Deep Eutectic Solvents (DESs) and Their Application in Biosensor Development

“…The structures of their components strongly influence all DESs’ physicochemical properties, such as melting point, density, conductivity, and viscosity [ 12 ]. Moreover, studies on the three-dimensional structure of DESs revealed that the interaction between HBDs and HBAs depends mainly on hydrogen bonds, but they also interact with the anion by arranging themselves around it [ 13 ]. In general, the presence of a broad hydrogen-bonding network among the components is responsible for the high viscosity of DESs and the restrained mobility of free species inside the solvent.…”