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Halogen bonded cocrystals of 4-benzoylpyridine with perhalogenated compounds

Over last two decades, halogen bond has become a versatile design tool in crystal engineering and materials chemistry [1]. Following our previous research with 4-benzoylpyridine (4bzpy) as halogen bond acceptor [2, 3], in this work four new cocrystals of 4bzpy with 1, 4- dibromotetrafluorobenzene (14tfbb), 1, 4- diiodotetrafluorobenzene (14tfib), iodopentafluorobenzene (ipfb) and 1, 4- diiodooctafluorobutane (ofib) were prepared by crystallization from solution and liquid- assisted grinding. Single crystal X-ray diffraction experiments revealed that in all four cocrystals, a pyridine nitrogen is employed in halogen bonding via the X···N (X = Br or I) halogen bond. Cocrystallization of 4bzpy with 14tfbb, 14tfib and ofib, resulted in cocrystals exhibiting 2 : 1 stoichiometry with a very similar supramolecular trimer. Cocrystallization with ipfb, resulted in cocrystals exhibiting 1 : 1 stoichiometry. The X···N distances in cocrystals range from 2.793 Å to 2.972 Å with angle C-X···N from 169 to 178°. As all iodine or bromine atoms of donors are involved in halogen bonds with the pyridine, no halogen donors are available for binding to the carbonyl oxygen. The carbonyl group in all cases participates in contacts with aromatic rings of neighboring molecules. [1] G. Cavallo, et al, Chem. Rev. 116 (2016) 2478. [2] V. Stilinović, et al, Chem.-Eur. J. 23 (2017) 5244. [3] M. Eraković, et al, Cryst.Growth Des. 18 (2018) 1182.

halogen-bonded cocrystals, 4-benzoylpyridine, liquid-assisted grinding

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