Polymorphism and Hirshfeld surface analysis of tetra-oxa[2]perfluoro-arene[2]triazine.

The title compound, tetra-oxa[2]perfluoro-arene[2]triazine (CHFNO), composed of two tetra-fluoro-phenyl-ene and two triazine moieties connected by four oxygen atoms, was crystallized slow evaporation of a di-chloro-methane solution, yielding two polymorphs: block- () and plate-shaped () crystals. Polymorph (triclinic, 1, = 516 Å at 173 K) was previously reported by Yang [(2015. , 4414-4417] whereas the newly identified polymorph (triclinic, 1, = 1085 Å at 100 K) shares the same space group but has a unit-cell volume twice as large, accommodating two symmetrically distinct mol-ecules, and , with a different mol-ecular arrangement. Since these crystals are expected to exhibit the characteristics of non-porous adaptive crystals, detailed analyses of inter-molecular inter-actions were conducted, revealing that C-F⋯π-hole inter-actions are more pronounced in than in . Hirshfeld surface analysis at 100 K revealed that the primary contributions to the crystal packing in polymorph were F⋯F (17.1%), F⋯H/H⋯F (21.5%), C⋯H/H⋯C (6.3%), C⋯F/F⋯C (4.5%) and C⋯O/O⋯C (9.2%) inter-actions, whereas in polymorph , these inter-actions were F⋯F (9.9% and 10.0%), F⋯H/H⋯F (20.9% and 26.5%), C⋯H/H⋯C (6.3% and 2.9%), C⋯F/F⋯C (8.5% and 10.0%) and C⋯O/O⋯C (4.9% and 4.6%) for and , respectively. Powder X-ray diffraction analysis indicates that polymorph is the more stable crystalline form, predominantly obtained through rapid precipitation or by grinding the crystals.