TY - JOUR

T1 - Dynamics, Phase Transitions, and Hydrogen Bonding Motifs in Protic Ionic Liquids: Cations Make the Difference

AU - Khudozhitkov, Alexander E.

AU - Stange, Peter

AU - Stepanov, Alexander G.

AU - Schröder, Daniel

AU - Rauber, Daniel

AU - Philippi, Frederik

AU - Kolokolov, Daniil I.

AU - Ludwig, Ralf

N1 - This work has been supported by the Russian Science Foundation (grant no. 24-73-00032, https://rscf.ru/en/project/24-73-00032/). R.L. is grateful to the Deutsche Forschungsgemeinschaft (DFG) for financing the projects LU 506/17-1, No. 470038970.

PY - 2025/7/31

Y1 - 2025/7/31

N2 - Compared with their ammonium analogues, phosphonium ionic liquids (PILs) have better thermal stabilities, higher conductivities, and lower viscosities. PILs are therefore more suitable electrolytes for gaining high discharge capacities and rechargeabilities as well as lower Coulombic efficiencies. For understanding the favorable properties at the molecular level in terms of interaction strength and dynamics, we compare the IL tributylammonium methanesulfonate [N 444-H][OMs] and tributylphosphonium methanesulfonate [P 444-H][OMs] by means of 2H NMR spectroscopy in both solid and liquid states. The shape of the 2H NMR spectral lines and the spin relaxation times provide information about the interaction strength and hydrogen bonding arrangements, as well as the phase transition phenomena for these ILs. The 2H NMR spin relaxation in the liquid state characterizes the cation dynamics and allows for the investigation of the microscopic viscosity. We support our experimental observations by quantum chemical calculations of IL clusters consisting of different numbers of ion pairs.

AB - Compared with their ammonium analogues, phosphonium ionic liquids (PILs) have better thermal stabilities, higher conductivities, and lower viscosities. PILs are therefore more suitable electrolytes for gaining high discharge capacities and rechargeabilities as well as lower Coulombic efficiencies. For understanding the favorable properties at the molecular level in terms of interaction strength and dynamics, we compare the IL tributylammonium methanesulfonate [N 444-H][OMs] and tributylphosphonium methanesulfonate [P 444-H][OMs] by means of 2H NMR spectroscopy in both solid and liquid states. The shape of the 2H NMR spectral lines and the spin relaxation times provide information about the interaction strength and hydrogen bonding arrangements, as well as the phase transition phenomena for these ILs. The 2H NMR spin relaxation in the liquid state characterizes the cation dynamics and allows for the investigation of the microscopic viscosity. We support our experimental observations by quantum chemical calculations of IL clusters consisting of different numbers of ion pairs.

UR - https://www.scopus.com/pages/publications/105012786373

UR - https://www.mendeley.com/catalogue/cca9d649-b870-33ca-92e0-dce72112e6c9/

U2 - 10.1021/acs.jpcb.5c02460

DO - 10.1021/acs.jpcb.5c02460

M3 - Article

C2 - 40692308

VL - 129

SP - 7796

EP - 7805

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 30

ER -