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@ARTICLE{Rok:858951,
author = {Rok, M. and Bator, G. and Medycki, W. and Zamponi, M. and
Balčiūnas, S. and Šimėnas, M. and Banys, J.},
title = {{R}eorientational dynamics of organic cations in
perovskite-like coordination polymers},
journal = {Dalton transactions},
volume = {47},
number = {48},
issn = {0300-9246},
address = {London},
publisher = {Soc.},
reportid = {FZJ-2018-07777},
pages = {17329 - 17341},
year = {2018},
abstract = {Here we report the dynamics of organic cations as guest
molecules in a perovskite host-framework. The molecular
motion of CH3NH3+ (MAFe), (CH3)2NH2+ (DMAFe) and (CH3)3NH+
(TrMAFe) in the cage formed by KFe(CN)63− units was
studied using a combination of experimental methods: (i)
thermal analysis, (ii) dielectric and electric studies,
(iii) optical observations, (iv) EPR and 1H NMR spectroscopy
and (v) quasielastic neutron scattering (QENS). In the case
of MAFe and TrMAFe, the thermal analysis reveals one
solid-to-solid phase transition (PT) and two PTs for the
DMAFe crystal. A markedly temperature-dependent dielectric
constant indicates the tunable and switchable properties of
the complexes. Also, their semiconducting properties are
confirmed by a dc conductivity measurement. The broadband
dielectric relaxation is analyzed for the TrMAFe sample in
the frequency range of 100 Hz–1 GHz. QENS shows that we
deal rather with the localized motion of the cation than a
diffusive one. Three models, which concern the simultaneous
rotation of the CH3 and/or NH3 group, π-flips and free
rotations of the organic cation, are used to fit the elastic
incoherent structure factor. The 1H NMR spin–lattice
relaxation time for all compounds under study, as well as
the second moments, has been measured in a wide temperature
range. In all studied samples, the temperature dependence of
the second moment of the proton NMR line indicated the
gradual evolution of the molecular movements from the rigid
state up to a highly disordered one},
cin = {JCNS-FRM-II / JCNS-1},
ddc = {540},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-1-20110106},
pnm = {6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
Neutron Research (JCNS) (POF3-623)},
pid = {G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4},
experiment = {EXP:(DE-MLZ)SPHERES-20140101},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:30475377},
UT = {WOS:000453550900014},
doi = {10.1039/C8DT03372B},
url = {https://juser.fz-juelich.de/record/858951},
}