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Halogen bonded cocrystals of trifluoro-1,3,5- triiodobenzene and benzoylpyridines

In the past few decades, halogen bonding (XB) has become a prominent design tool in crystal engineering and materials chemistry [1]. Research of halogen-bonded cocrystals has largely been focused on acceptors containing a pyridine or an amine nitrogen atom [2]. Less explored are halogen bonds containing an oxygen atom, such as carbonyl, methoxy or hydroxy groups. Following our previous research [3, 4] and in order to explore competition between pyridyl nitrogen and carbonyl oxygen atoms as halogen bond acceptors, in this work we have prepared three cocrystals of benzoylpyridine isomers (2bzpy, 3bzpy, 4bzpy) as potential ditopic acceptors with trifluoro-1, 3, 5- triiodobenzene (135titfb) as a potentially tritopic halogen bond donor. Single crystal X- ray diffraction experiments revealed that in two cocrystals, (2bzpy)(135titfb) and (4bzpy) (135titfb), each carbonyl oxygen is connected with 135titfb by an I···O halogen bond. The carbonyl oxygen atom turned out to be competitive with the pyridyl nitrogen atom. However, the dominant intermolecular interaction in all three cocrystals is the I···N halogen bond. In (2bzpy)(135titfb) and (4bzpy)(135titfb), 135titfb is a tritopic halogen bond donor. Besides interacting with pyridyl nitrogen and/or carbonyl oxygen, 135titfb connects with iodine or fluorine atoms of neigbouring molecules to stabilize the structure. References: [1] G. Cavallo, P. Metrangolo, R. Milani, T. Pilati, A. Priimagi, G. Resnati, G. Terraneo, Chem. Rev. 2016, 116, 2478–2601. [2] C. R. Groom, I. J. Bruno, M. P. Lightfoot, S. C. Ward, Acta Cryst. B 2016, 72, 171. [3] V. Nemec, L. Fotović, T. Friščić, D. Cinčić, Cryst.Growth Des. 2017, 17, 6169–6173. [4] V. Nemec, L. Fotović, T. Vitasović, D.Cinčić, CrystEngComm, 2019, 21, 3251–3255.

halogen bond ; cocrystal

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