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Investigation of Bistetramethylammonium Hydrogencyclotriphosphate—A Molecular Rotor?
Author(s) -
Mangstl Martin,
Weber Johannes,
JardónÁlvarez Daniel,
Burghaus Olaf,
Roling Bernhard,
Schmedt auf der Günne Jörn
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201800980
Subject(s) - activation energy , magic angle spinning , chemistry , rotational dynamics , phase transition , dielectric spectroscopy , spectral line , molecular dynamics , crystallography , proton , analytical chemistry (journal) , materials science , nuclear magnetic resonance spectroscopy , physics , stereochemistry , molecule , condensed matter physics , computational chemistry , organic chemistry , electrode , quantum mechanics , astronomy , chromatography , electrochemistry
The crystalline phase β‐[N(CH 3 ) 4 ] 2 HP 3 O 9 undergoes a reversible phase transition to γ‐[N(CH 3 ) 4 ] 2 HP 3 O 9 , which was studied by dynamic scanning calorimetry and X‐ray diffraction. The rotational dynamics of the anion [P 3 O 9 ] 3− were evident from variable temperature 31 P magic angle spinning (MAS) NMR spectroscopy. The rotational dynamics could be simulated with a 3‐site jump model, which yields spectra in good agreement with experiment. An activation energy of 0.6 eV could be estimated from line shape analysis. Impedance spectra reflect a bulk proton conductivity of γ‐[N(CH 3 ) 4 ] 2 HP 3 O 9 of 6.9×10 −5 S cm −1 at 240 °C and an activation energy of approximately 1.0 eV. Thus this salt features bulk protonic motion, while local rotational anionic motion happens with activation energies of the same order, as suggested by the paddle‐wheel mechanism.