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Figure 4
Comparison of the refined triclinic crystal structures of p-C6H4Me2:C6F5H at 160 K (phase I, left) and 120 K (phase II, right) with the molecular column axis set along c. Thermal ellipsoids are shown at 50% probability (except for hydrogen atoms which have a fixed radius) using the program Mercury from the CCDC (Macrae et al., 2008BB18). Both structures are triclinic and centrosymmetric, but on cooling, the C6F5H molecules order leading to a doubling of the structure along the column axis (i.e. the c direction) and loss of the crystallographic centre of symmetry (shown as blue open circles) at the middle of the C6F5H ring. To enable an easier comparison between the two structures as shown here, phase II was refined in space group I1 with a unit cell 4× the volume of phase I. Crystallographic labelling of the atoms is given in Figs. S17 and S18.

IUCrJ
Volume 10| Part 6| November 2023| Pages 720-728
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523008163