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Dynamics of Molecular Crystals by Means of 1 H NMR Relaxometry: Dynamical Heterogeneity versus Homogenous Motion
Author(s) -
Kruk Danuta,
FlorekWojciechowska Małgorzata,
Jakubas Ryszard,
Chaurasia Sujeet K.,
Brym Szczepan
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600151
Subject(s) - relaxometry , chemistry , molecular dynamics , motional narrowing , pyridinium , dynamics (music) , nuclear magnetic resonance , dynamical heterogeneity , chemical physics , molecular physics , computational chemistry , spectral line , physics , spin echo , magnetic resonance imaging , medicine , polymer , organic chemistry , glass transition , radiology , astronomy , medicinal chemistry , acoustics
1 H NMR relaxometry was used to reveal information on the dynamical properties of the molecular crystal (PyH) 5 Bi 2 Br 11 (PyH=C 5 H 6 N, pyridinium cation), chosen as an example of a solid that exhibits a complex structure and rotational‐like dynamics. Experimental studies were performed over a very broad frequency range, from 4 kHz to 40 MHz (referring to the 1 H resonance frequency) versus temperature. The extensive set of data was thoroughly analyzed in terms of two motional models differing with respect to the assumed mechanism (heterogeneous versus homogenous) of the motion of the PyH cations. A Cole–Davidson distribution of the correlation times describing the assumed motional heterogeneity was tested against a concept of two correlation times characterizing the rotation‐like dynamics of the PyH cation around the perpendicular axes differing by about one order of magnitude. The parameters describing the dynamics of the cation, obtained by means of both models, were compared and discussed.