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

Oliver S. Hammond; Ria Atri; Daniel T. Bowron; Karen J. Edler

doi:10.1002/chem.202200566

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

Oliver S. Hammond, Ria Atri, Daniel T. Bowron, Karen J. Edler

Research output: Contribution to journal › Article › peer-review

7 Citations (SciVal)

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 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.

Original language	English
Article number	e202200566
Journal	Chemistry - A European Journal
Volume	28
Issue number	41
Early online date	13 Jun 2022
DOIs	https://doi.org/10.1002/chem.202200566
Publication status	Published - 20 Jul 2022

Bibliographical note

Funding Information:
The authors thank the EPSRC for a PhD studentship in the CSCT CDT at the University of Bath for O.S.H and R.A. (EP/L016354/1). ISIS Neutron & Muon Source are thanked for co-funding O.S.H. (STFC Studentship Agreement 3578) and neutron diffraction access and support on NIMROD under beamtime allocation RB1720287. Raw experimental neutron diffraction data are available through ISIS-ICAT, DOI: 10.5286/ISIS.E.RB1720287. Processed diffraction datasets are available through the University of Bath research data archive system, DOI: https://doi.org/10.15125/BATH-01138.

Publisher Copyright:
© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

Keywords

deep eutectic solvents
green chemistry
heterocycles
neutron diffraction
pi interactions

ASJC Scopus subject areas

Catalysis
Organic Chemistry

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10.1002/chem.202200566Licence: CC BY

Cite this

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

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 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 = "Hammond, {Oliver S.} and Ria Atri and Bowron, {Daniel T.} and Edler, {Karen J.}",

note = "Funding Information: The authors thank the EPSRC for a PhD studentship in the CSCT CDT at the University of Bath for O.S.H and R.A. (EP/L016354/1). ISIS Neutron & Muon Source are thanked for co-funding O.S.H. (STFC Studentship Agreement 3578) and neutron diffraction access and support on NIMROD under beamtime allocation RB1720287. Raw experimental neutron diffraction data are available through ISIS-ICAT, DOI: 10.5286/ISIS.E.RB1720287. Processed diffraction datasets are available through the University of Bath research data archive system, DOI: https://doi.org/10.15125/BATH-01138. Publisher Copyright: {\textcopyright} 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.",

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AU - Edler, Karen J.

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N2 - 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.

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

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Datasets

Dataset supporting "Neutron diffraction study of indole solvation in deep eutectic systems of choline chloride, malic acid, and water"

Cite this