%0 Journal Article
%A Truong, Khai-Nghi
%A Merkens, Carina
%A Meven, Martin
%A Faßbänder, Björn
%A Dronskowski, Richard
%A Englert, Ulli
%T Phase transition and proton ordering at 50 K in 3-(pyridin-4-yl)pentane-2,4-dione
%J Acta crystallographica / B
%V 73
%N 6
%@ 2052-5206
%C Oxford [u.a.]
%I Wiley-Blackwell
%M FZJ-2017-08086
%P 1172 - 1178
%D 2017
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000417608600017
%R 10.1107/S2052520617015591
%U https://juser.fz-juelich.de/record/840581