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Neutron Diffraction Study of Indole Solvation in Deep Eutectic Systems of Choline Chloride, Malic Acid, and Water

Hammond, Oliver S. ; Atri, Ria ; Bowron, Daniel T. and Edler, Karen J. LU orcid (2022) In Chemistry - A European Journal 28(41).
Abstract

Deep eutectic systems are currently under intense investigation to replace traditional organic solvents in a range of syntheses. Here, indole in choline chloride-malic acid deep eutectic solvent (DES) was studied as a function of water content, to identify solute interactions with the DES which affect heterocycle reactivity and selectivity, and as a proxy for biomolecule solvation. Empirical Potential Structure Refinement models of neutron diffraction data showed [Cholinium]+ cations associate strongly with the indole π-system due to electrostatics, whereas malic acid is only weakly associated. Trace water is sequestered into the DES and does not interact strongly with indole. When water is added to the DES, it does not... (More)

Deep eutectic systems are currently under intense investigation to replace traditional organic solvents in a range of syntheses. Here, indole in choline chloride-malic acid deep eutectic solvent (DES) was studied as a function of water content, to identify solute interactions with the DES which affect heterocycle reactivity and selectivity, and as a proxy for biomolecule solvation. Empirical Potential Structure Refinement models of neutron diffraction data showed [Cholinium]+ cations associate strongly with the indole π-system due to electrostatics, whereas malic acid is only weakly associated. Trace water is sequestered into the DES and does not interact strongly with indole. When water is added to the DES, it does not interact with the indole π-system but is exclusively in-plane with the heterocyclic rings, forming strong H-bonds with the -NH group, and also weak H-bonds and thus prominent hydrophobic hydration of the indole aromatic region, which could direct selectivity in reactions.

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author
; ; and
publishing date
type
Contribution to journal
publication status
published
subject
keywords
deep eutectic solvents, green chemistry, heterocycles, neutron diffraction, pi interactions
in
Chemistry - A European Journal
volume
28
issue
41
article number
e202200566
pages
8 pages
publisher
Wiley-Blackwell
external identifiers
  • pmid:35510678
  • scopus:85131751286
ISSN
0947-6539
DOI
10.1002/chem.202200566
language
English
LU publication?
no
additional info
Publisher Copyright: © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
id
ee70b73f-fd8a-48ed-98f5-6a0b6936dc0c
date added to LUP
2022-07-12 13:57:53
date last changed
2024-06-25 15:32:01
@article{ee70b73f-fd8a-48ed-98f5-6a0b6936dc0c,
  abstract     = {{<p>Deep eutectic systems are currently under intense investigation to replace traditional organic solvents in a range of syntheses. Here, indole in choline chloride-malic acid deep eutectic solvent (DES) was studied as a function of water content, to identify solute interactions with the DES which affect heterocycle reactivity and selectivity, and as a proxy for biomolecule solvation. Empirical Potential Structure Refinement models of neutron diffraction data showed [Cholinium]<sup>+</sup> cations associate strongly with the indole π-system due to electrostatics, whereas malic acid is only weakly associated. Trace water is sequestered into the DES and does not interact strongly with indole. When water is added to the DES, it does not interact with the indole π-system but is exclusively in-plane with the heterocyclic rings, forming strong H-bonds with the -NH group, and also weak H-bonds and thus prominent hydrophobic hydration of the indole aromatic region, which could direct selectivity in reactions.</p>}},
  author       = {{Hammond, Oliver S. and Atri, Ria and Bowron, Daniel T. and Edler, Karen J.}},
  issn         = {{0947-6539}},
  keywords     = {{deep eutectic solvents; green chemistry; heterocycles; neutron diffraction; pi interactions}},
  language     = {{eng}},
  number       = {{41}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Chemistry - A European Journal}},
  title        = {{Neutron Diffraction Study of Indole Solvation in Deep Eutectic Systems of Choline Chloride, Malic Acid, and Water}},
  url          = {{http://dx.doi.org/10.1002/chem.202200566}},
  doi          = {{10.1002/chem.202200566}},
  volume       = {{28}},
  year         = {{2022}},
}