Inelastic neutron scattering study of reline: shedding light on the hydrogen bonding network of deep eutectic solvents

• DOI: 10.1039/c7cp01286a
• Publication Date: 2017-06-23T14:34:12Z
• Authors: C. F. Araujo; J. A. P. Coutinho; M. M. Nolasco; S. F. Parker; P. J. A. Ribeiro-...; S. Rudić; B. I. G. Soares; P. D. Vaz
• Keywords: Choline chloride; Deep eutectic solvent

The solids choline chloride and urea, mixed in a 1 : 2 molar proportion, form the iconic deep eutectic solvent "Reline". A combination of computational vibrational spectroscopy tools, including inelastic neutron scattering (INS), have been used to probe intermolecular interactions mixture. Reline's experimental spectra were estimated using discrete periodic ab initio calculations molecular aggregate with two four urea units. This is minimum size required achieve satisfactory agreement experiment, as smaller clusters cannot represent all reline's significant interactions. INS spectrum reline, compared that pure chloride, reveals displacement anions away from their preferred positions on top choline's methyl groups, whose torsional movement becomes less hindered Urea, which adopts planar (sp2) shape crystal, non-planar (sp3) feature herein discussed for first time. In molecules wide range hydrogen bonds, soft contacts stronger associations, latter being responsible deviation ideality. chloride's are largely conserved at hydroxyl end while becoming weaker cationic headgroup. interplay strong confers flexibility newly formed hydrogen-bond network allows ensemble remain liquid room temperature.