TY - JOUR

T1 - The Influence of Deuterium Isotope Effects on Structural Rearrangements, Ensemble Equilibria, and Hydrogen Bonding in Protic Ionic Liquids

AU - Khudozhitkov, Alexander E.

AU - Stange, Peter

AU - Paschek, Dietmar

AU - Stepanov, Alexander G.

AU - Kolokolov, Daniil I.

AU - Ludwig, Ralf

N1 - Funding Information: This work has been supported by the Russian Science Foundation (grant N 21‐13‐00047). R.L. is grateful to the Deutsche Forschungsgemeinschaft (DFG) for financing the projects LU 506/15‐1 (grant N 401427621). D.I.K thanks the Humboldt Foundation (AvH) for awarding a Humboldt Research Fellowship for Experienced Researchers. Open Access funding enabled and organized by Projekt DEAL. o o Publisher Copyright: © 2022 The Authors. ChemPhysChem published by Wiley-VCH GmbH.

PY - 2022/12/5

Y1 - 2022/12/5

N2 - We report strong isotope effects for the protic ionic liquid triethylammonium methanesulfonate [TEA][OMs] by means of deuterium solid-state NMR spectroscopy covering broad temperature ranges from 65 K to 313 K. Both isotopically labelled PILs differ in non-deuterated and fully deuterated ethyl groups of the triethyl ammonium cations. The N−D bond of both cations is used as sensitive probe for hydrogen bonding and structural ordering. The 2H NMR line shape analysis provides the deuteron quadrupole coupling constants and the characteristics of a broad heterogeneous phase with simultaneously present static and mobile states indicating plastic crystal behavior. The temperatures where both states are equally populated differ by about 80 K for the two PILs, showing that deuteration of the ethyl groups in the trialkylammonium cations tremendously shifts the equilibrium towards the static state. In addition, it leads to a significant less cooperative transition, associated with a significantly reduced standard molar transition entropy.

AB - We report strong isotope effects for the protic ionic liquid triethylammonium methanesulfonate [TEA][OMs] by means of deuterium solid-state NMR spectroscopy covering broad temperature ranges from 65 K to 313 K. Both isotopically labelled PILs differ in non-deuterated and fully deuterated ethyl groups of the triethyl ammonium cations. The N−D bond of both cations is used as sensitive probe for hydrogen bonding and structural ordering. The 2H NMR line shape analysis provides the deuteron quadrupole coupling constants and the characteristics of a broad heterogeneous phase with simultaneously present static and mobile states indicating plastic crystal behavior. The temperatures where both states are equally populated differ by about 80 K for the two PILs, showing that deuteration of the ethyl groups in the trialkylammonium cations tremendously shifts the equilibrium towards the static state. In addition, it leads to a significant less cooperative transition, associated with a significantly reduced standard molar transition entropy.

KW - heterogeneities

KW - hydrogen bonding

KW - ionic liquids

KW - Isotope effects

KW - solid-stateNMR

KW - Hydrogen Bonding

KW - Magnetic Resonance Spectroscopy

KW - Deuterium/chemistry

KW - Cations

KW - Ionic Liquids/chemistry

UR - http://www.scopus.com/inward/record.url?scp=85137356034&partnerID=8YFLogxK

U2 - 10.1002/cphc.202200557

DO - 10.1002/cphc.202200557

M3 - Article

C2 - 35944124

AN - SCOPUS:85137356034

VL - 23

JO - ChemPhysChem

JF - ChemPhysChem

SN - 1439-4235

IS - 23

M1 - e202200557

ER -