TY  - JOUR
AU  - Truong, Khai-Nghi
AU  - Merkens, Carina
AU  - Meven, Martin
AU  - Faßbänder, Björn
AU  - Dronskowski, Richard
AU  - Englert, Ulli
TI  - Phase transition and proton ordering at 50 K in 3-(pyridin-4-yl)pentane-2,4-dione
JO  - Acta crystallographica / B
VL  - 73
IS  - 6
SN  - 2052-5206
CY  - Oxford [u.a.]
PB  - Wiley-Blackwell
M1  - FZJ-2017-08086
SP  - 1172 - 1178
PY  - 2017
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000417608600017
DO  - DOI:10.1107/S2052520617015591
UR  - https://juser.fz-juelich.de/record/840581
ER  -