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@ARTICLE{Truong:840581,
author = {Truong, Khai-Nghi and Merkens, Carina and Meven, Martin and
Faßbänder, Björn and Dronskowski, Richard and Englert,
Ulli},
title = {{P}hase transition and proton ordering at 50 {K} in
3-(pyridin-4-yl)pentane-2,4-dione},
journal = {Acta crystallographica / B},
volume = {73},
number = {6},
issn = {2052-5206},
address = {Oxford [u.a.]},
publisher = {Wiley-Blackwell},
reportid = {FZJ-2017-08086},
pages = {1172 - 1178},
year = {2017},
abstract = {Single-crystal neutron diffraction experiments at 100 and
2.5 K have been performed to determine the structure of
3-(pyridin-4-yl)pentane-2,4-dione (HacacPy) with respect to
its protonation pattern and to monitor a low-temperature
phase transition. Solid HacacPy exists as the enol tautomer
with a short intramolecular hydrogen bond. At 100 K, its
donor···acceptor distance is 2.450 (8) Å and the
compound adopts space group C2/c, with the N and para-C
atoms of the pyridyl ring and the central C of the
acetylacetone substituent on the twofold crystallographic
axis. As a consequence of the axial symmetry, the bridging
hydrogen is disordered over two symmetrically equivalent
positions, and the carbon–oxygen bond distances adopt
intermediate values between single and double bonds. Upon
cooling, a structural phase transition to the t2 subgroup
$P\bar$ 1 occurs; the resulting twins show an ordered
acetylacetone moiety. The phase transition is fully
reversible but associated with an appreciable hysteresis in
the large single crystal under study: transition to the
low-temperature phase requires several hours at 2.5 K and
heating to 80 K is required to revert the transformation.
No significant hysteresis is observed in a powder sample, in
agreement with the second-order nature of the phase
transition.},
cin = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
(München) ; JCNS-FRM-II / JCNS-2},
ddc = {530},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-2-20110106},
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)HEIDI-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000417608600017},
doi = {10.1107/S2052520617015591},
url = {https://juser.fz-juelich.de/record/840581},
}