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Halogen bonded cocrystals of acridine and phenazine with octafluoro-1, 4-diiodobutane

These days, the halogen bond has become a very common tool in crystal engineering. It is also relevant in liquid crystals, systems for the separation of hydrocarbon derivatives and in biomolecular systems (Cavallo et al., 2016). Studies of halogen bonding have largely focused on cocrystals of perfluorohalocarbons. It has recently been reported that this type of cocrystals can be used as a model system for studying storage of volatile halogen bond donors, such as iodo-substituted perfluoroalkanes, in crystalline solids (Aakeröy et al., 2015). Herein, we present two cocrystals of octafluoro-1, 4-diiodobutane (ofib) with acridine (acr) and phenazine (phen), prepared by both mechanochemical synthesis (liquid-assisted grinding) and the conventional solution-based method. Considering the difference in topicity and nitrogen atom basicity of acr and phen, differences in the supramolecular outcome were expected. Crystal structure determination by single crystal X-ray diffraction reveals that in both cocrystals molecules are connected into 2:1 halogen bonded complexes via I∙∙∙N halogen bonds. The I∙∙∙N distances in (acr)2(ofib) and (phen)2(ofib) are 3.045 Å and 2.914 Å, respectively, or 13.7 and 17.5 % less than the sum of the van der Waals radii of nitrogen (1.55 Å) and iodine (1.98 Å). In the crystal structure of (phen)2(ofib) halogen bonded complexes are connected into 1D chains via C–H∙∙∙N hydrogen bonds formed between adjacent phen molecules. In the crystal structure of (acr)2(ofib) halogen bonded complexes are connected into a 3D network via C–H∙∙∙C and C–H∙∙∙F contacts.

acridine ; phenazine ; cocrystals ; halogen bond ; octafluoro-1, 4-diiodobutane

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