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Title: Molecular and ionic diffusion in aqueous - deep eutectic solvent mixtures: probing inter-molecular interactions using PFG NMR
Authors: D'Agostino, C.
Gladden, L. F.
Mantle, M. D.
Abbott, Andrew P.
Ahmed, Essa I.
Al-Murshedi, Azhar Y. M.
Harris, Robert C.
First Published: 15-May-2015
Publisher: Royal Society of Chemistry
Citation: Physical Chemistry Chemical Physics, 2015, 17 (23), pp. 15297-15304 (8)
Abstract: Pulsed field gradient (PFG) NMR has been used to probe self-diffusion of molecular and ionic species in aqueous mixtures of choline chloride (ChCl) based deep eutectic solvents (DESs), in order to elucidate the effect of water on motion and inter-molecular interactions between the different species in the mixtures, namely the Ch+ cation and hydrogen bond donor (HBD). The results reveal an interesting and complex behaviour of such mixtures at a molecular level. In general, it is observed that the hydroxyl protons (1H) of Ch+ and the hydrogen bond donor have diffusion coefficients significantly different from those measured for their parent molecules when water is added. This indicates a clear and significant change in inter-molecular interactions. In aqueous Ethaline, the hydroxyl species of Ch+ and HBD show a stronger interaction with water as water is added to the system. In the case of Glyceline, water has little effect on both hydroxyl proton diffusion of Ch+ and HBD. In Reline, it is likely that water allows the formation of small amounts of ammonium hydroxide. The most surprising observation is from the self-diffusion of water, which is considerably higher that expected from a homogeneous liquid. This leads to the conclusion that Reline and Glyceline form mixtures that are inhomogeneous at a microscopic level despite the hydrophilicity of the salt and HBD. This work shows that PFG NMR is a powerful tool to elucidate both molecular dynamics and inter-molecular interactions in complex liquid mixtures, such as the aqueous DES mixtures.
DOI Link: 10.1039/c5cp01493j
ISSN: 1463-9076
eISSN: 1463-9084
Version: Post-print
Type: Journal Article
Rights: Archived with reference to SHERPA/RoMEO and publisher website. Version of record:
Description: Corrected by DOI: 10.1039/C6CP90299E
Appears in Collections:Published Articles, Dept. of Chemistry

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