Rotational dynamics of the imidazolium ion in cyanide-bridged dielectric framework materials.
Chem Commun (Camb)
; 56(79): 11791-11794, 2020 Oct 11.
Article
em En
| MEDLINE
| ID: mdl-33021277
ABSTRACT
Reorientation of organic cations in the cubic interstices of cyanoelpasolite molecular perovskites results in a variety of structural phase transitions, but far less is known about these cations' dynamics. We report quasielastic neutron scattering from the materials (C3H5N2)2K[MIII(CN)6], M = Fe,Co, which is directly sensitive to the rotation of the imidazolium ion. The motion is well described by a circular three-site hopping model, with the ion rotating within its plane in the intermediate-temperature phase, but tilting permanently in the high-temperature phase. Thus the two rhombohedral phases, which are crystallographically rather similar, have markedly different dynamics. The activation energy of rotation is about 10 kJ mol-1 and the barrier between orientations is 6 kJ mol-1. Our results explain two anomalous features in these materials' dielectric constants.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Chem Commun (Camb)
Assunto da revista:
QUIMICA
Ano de publicação:
2020
Tipo de documento:
Article
País de afiliação:
Reino Unido