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Schiff bases as halogen bond donors in crystal engineering of cocrystals

In the past two decades, halogen bonding has been shown as an effective and predictable tool in crystal engineering [1]. It has been predominantly investigated in multicomponent crystals consisting of organic perhalogenated compounds as halogen bond donors and various organic and metal-organic compounds as halogen bond acceptors [2]. While many multicomponent systems contain Schiff bases as halogen bond acceptors [3], there are scarce examples of those that contain them as halogen bond donors [4]. In this work, we have prepared two peripherally perhalogenated Schiff bases by reaction of 2, 3, 5, 6-tetrafluoro-4-iodoaniline with salicylaldehyde (itfasal) or ortho- vanillin (itfaovan). Both Schiff bases were cocrystallized in 2:1 molar ratio with selected acceptors: 4, 4’- bipyridine (bpy), 1, 4- diazabicyclo[2.2.2]octane (dabco) and 1, 2- bis(4-pyridyl)ethane (bpean). Cocrystals were prepared by liquid-assisted grinding and crystallization from ethanol and characterized by X-ray diffraction methods. Structural characterization revealed that in all six cocrystals itfasal and itfaovan are bonded with acceptors via I∙∙∙N halogen bonds. [1] G. Cavallo, P. Metrangolo, R. Milani, T. Pilati, A. Priimagi, G. Resnati, G. Terraneo, Chem. Rev. 116 (2016) 2478. [2] C. R. Groom, I. J. Bruno, M. P. Lightfoot, S. C. Ward, Acta Cryst. B 72 (2016), 171. [3] A. Carletta, M. Zbačnik, M. Vitković, N. Tumanov, V. Stilinović, J. Wouters, D. Cinčić, CrystEngComm 36 (2018), 5332. [4] Y. Wang, H. Shang, B. Li, H. Zhang, S. Jiang, CrystEngComm 19 (2017) 3801.

Schiff base ; halogen bond ; cocrystal

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