High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid

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High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid. / Khudozhitkov, Alexander E.; Donoshita, Masaki; Stepanov, Alexander G. et al.

In: Chemistry - A European Journal, Vol. 28, No. 23, e202200257, 22.04.2022.

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

BibTeX

@article{7447591c3003459ba7c639e4a4d63cf7,

title = "High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid",

abstract = "We report the complex phase behavior of the glass forming protic ionic liquid (PIL) d3-octylphosphonium bis(trifluoromethylsulfonyl)imide [C8H17PD3][NTf2] by means of solid-state NMR spectroscopy. Combined line shape and spin relaxation studies of the deuterons in the PD3 group of the octylphosphonium cation allow to map and correlate the phase behavior for a broad temperature range from 71 K to 343 K. In the solid PIL at 71 K, we observed a static state, characterized by the first deuteron quadrupole coupling constant reported for PD3 deuterons. A transition enthalpy of about 12 kJ mol−1 from the static to the mobile state with increasing temperature suggests the breaking of a weak, charge-enhanced hydrogen bond between cation and anion. The highly mobile phase above 100 K exhibits an almost disappearing activation barrier, strongly indicating quantum tunneling. Thus, we provide first evidence of tunneling driven mobility of the hydrogen bonded P−D moieties in the glassy state of PILs, already at surprisingly high temperatures up to 200 K. Above 250 K, the mobile phase turns from anisotropic to isotropic motion, and indicates strong internal rotation of the PD3 group. The analyzed line shapes and spin relaxation times allow us to link the structural and dynamical behavior at molecular level with the phase behavior beyond the DSC traces.",

keywords = "ion pairing, ionic liquids, molecular mobility, quantum tunnelling, solid state NMR",

author = "Khudozhitkov, {Alexander E.} and Masaki Donoshita and Stepanov, {Alexander G.} and Frederik Philippi and Daniel Rauber and Rolf Hempelmann and Hiroshi Kitagawa and Kolokolov, {Daniil I.} and Ralf Ludwig",

note = "Funding Information: This work has been supported by the Deutsche Forschungsgemeinschaft (DFG) within the projects LU 506/14‐1 and LU 506/14‐2 and in part by the Russian Science Foundation (grant N 21‐13‐00047). R.L. also thanks the University of Rostock for a Baltic Mare Fellowship provided for D.I.K. A.G.S. acknowledge financial support by the Ministry of Science and Higher Education of the Russian Federation (budget Project no. AAAA‐A21‐121011390053‐4 for Boreskov Institute of Catalysis). D.I.K thanks the Humboldt Foundation (AvH) for awarding a Humboldt Research Fellowship for Experienced Researchers. We also acknowledge the support from the JST ACCEL program Grant Number JPMJAC1501. Open Access funding enabled and organized by Projekt DEAL. o Publisher Copyright: {\textcopyright} 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.",

year = "2022",

month = apr,

day = "22",

doi = "10.1002/chem.202200257",

language = "English",

volume = "28",

journal = "Chemistry - A European Journal",

issn = "0947-6539",

publisher = "Wiley-VCH Verlag",

number = "23",

}

RIS

TY - JOUR

T1 - High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid

AU - Khudozhitkov, Alexander E.

AU - Donoshita, Masaki

AU - Stepanov, Alexander G.

AU - Philippi, Frederik

AU - Rauber, Daniel

AU - Hempelmann, Rolf

AU - Kitagawa, Hiroshi

AU - Kolokolov, Daniil I.

AU - Ludwig, Ralf

N1 - Funding Information: This work has been supported by the Deutsche Forschungsgemeinschaft (DFG) within the projects LU 506/14‐1 and LU 506/14‐2 and in part by the Russian Science Foundation (grant N 21‐13‐00047). R.L. also thanks the University of Rostock for a Baltic Mare Fellowship provided for D.I.K. A.G.S. acknowledge financial support by the Ministry of Science and Higher Education of the Russian Federation (budget Project no. AAAA‐A21‐121011390053‐4 for Boreskov Institute of Catalysis). D.I.K thanks the Humboldt Foundation (AvH) for awarding a Humboldt Research Fellowship for Experienced Researchers. We also acknowledge the support from the JST ACCEL program Grant Number JPMJAC1501. Open Access funding enabled and organized by Projekt DEAL. o Publisher Copyright: © 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

PY - 2022/4/22

Y1 - 2022/4/22

N2 - We report the complex phase behavior of the glass forming protic ionic liquid (PIL) d3-octylphosphonium bis(trifluoromethylsulfonyl)imide [C8H17PD3][NTf2] by means of solid-state NMR spectroscopy. Combined line shape and spin relaxation studies of the deuterons in the PD3 group of the octylphosphonium cation allow to map and correlate the phase behavior for a broad temperature range from 71 K to 343 K. In the solid PIL at 71 K, we observed a static state, characterized by the first deuteron quadrupole coupling constant reported for PD3 deuterons. A transition enthalpy of about 12 kJ mol−1 from the static to the mobile state with increasing temperature suggests the breaking of a weak, charge-enhanced hydrogen bond between cation and anion. The highly mobile phase above 100 K exhibits an almost disappearing activation barrier, strongly indicating quantum tunneling. Thus, we provide first evidence of tunneling driven mobility of the hydrogen bonded P−D moieties in the glassy state of PILs, already at surprisingly high temperatures up to 200 K. Above 250 K, the mobile phase turns from anisotropic to isotropic motion, and indicates strong internal rotation of the PD3 group. The analyzed line shapes and spin relaxation times allow us to link the structural and dynamical behavior at molecular level with the phase behavior beyond the DSC traces.

AB - We report the complex phase behavior of the glass forming protic ionic liquid (PIL) d3-octylphosphonium bis(trifluoromethylsulfonyl)imide [C8H17PD3][NTf2] by means of solid-state NMR spectroscopy. Combined line shape and spin relaxation studies of the deuterons in the PD3 group of the octylphosphonium cation allow to map and correlate the phase behavior for a broad temperature range from 71 K to 343 K. In the solid PIL at 71 K, we observed a static state, characterized by the first deuteron quadrupole coupling constant reported for PD3 deuterons. A transition enthalpy of about 12 kJ mol−1 from the static to the mobile state with increasing temperature suggests the breaking of a weak, charge-enhanced hydrogen bond between cation and anion. The highly mobile phase above 100 K exhibits an almost disappearing activation barrier, strongly indicating quantum tunneling. Thus, we provide first evidence of tunneling driven mobility of the hydrogen bonded P−D moieties in the glassy state of PILs, already at surprisingly high temperatures up to 200 K. Above 250 K, the mobile phase turns from anisotropic to isotropic motion, and indicates strong internal rotation of the PD3 group. The analyzed line shapes and spin relaxation times allow us to link the structural and dynamical behavior at molecular level with the phase behavior beyond the DSC traces.

KW - ion pairing

KW - ionic liquids

KW - molecular mobility

KW - quantum tunnelling

KW - solid state NMR

UR - http://www.scopus.com/inward/record.url?scp=85127369493&partnerID=8YFLogxK

U2 - 10.1002/chem.202200257

DO - 10.1002/chem.202200257

M3 - Article

C2 - 35187737

AN - SCOPUS:85127369493

VL - 28

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 23

M1 - e202200257

ER -

ID: 35825792