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| Home > Publications database > Phase transition and proton ordering at 50 K in 3-(pyridin-4-yl)pentane-2,4-dione |
| Journal Article | FZJ-2017-08086 |
; ; ; ; ;
2017
Wiley-Blackwell
Oxford [u.a.]
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Please use a persistent id in citations: doi:10.1107/S2052520617015591
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.
Keyword(s): Chemical Reactions and Advanced Materials (1st) ; Crystallography (2nd) ; Chemistry (2nd)
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