High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid
Full article
| Journal |
Chemistry - A European Journal
ISSN: 0947-6539
, E-ISSN: 1521-3765
|
| Output data |
Year: 2022,
Volume: 28,
Number: 23,
Article number
: e202200257,
Pages count
: 13
DOI:
10.1002/chem.202200257
|
| Tags |
QUADRUPOLE COUPLING-CONSTANTS; NUCLEAR-MAGNETIC-RESONANCE; CRYSTALS; WATER;
H-2; MOLECULES; DYNAMICS; ROTATION; CLUSTERS; D2O |
| Authors |
Khudozhitkov Alexander E.
1,2
,
Donoshita Masaki
3
,
Stepanov Alexander G.
1,2
,
Philippi Frederik
4
,
Rauber Daniel
4
,
Hempelmann Rolf
4
,
Kitagawa Hiroshi
3
,
Kolokolov Daniil I.
1,2
,
Ludwig Ralf
5,6,7
|
| Affiliations |
| 1 |
Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090 (Russia)
|
| 2 |
Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090 (Russia)
|
| 3 |
Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto, 606-8502 (Japan)
|
| 4 |
Physikalische Chemie, Universität des Saarlandes, Campus B2.2, 66123 Saarbrücken (Germany)
|
| 5 |
Department LL&M, University of Rostock, Albert-Einstein-Str. 25, 18059 Rostock (Germany)
|
| 6 |
Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock (Germany)
|
| 7 |
Leibniz-Institut für Katalyse, Universität Rostock, e.V.Albert-Einstein-Str. 29a, 18059 Rostock (Germany)
|
|
Funding (7)
|
1
|
Russian Science Foundation
|
21-13-00047
|
|
2
|
German Research Foundation
|
LU 506/14-1
|
|
3
|
German Research Foundation
|
LU 506/14-2 (286149019)
|
|
4
|
Ministry of Science and Higher Education of the Russian Federation
|
0239-2021-0003
|
|
5
|
Japan Science and Technology Agency
|
JPMJAC1501
|
|
6
|
Alexander von Humboldt Foundation
|
|
|
7
|
Rostock University
|
|
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.