engleski

Perhalogenated amines as bifunctional donor molecules in cocrystals with nitrogen-containing acceptors

Investigating directional intermolecular interactions as predictable and efficient tools in supramolecular synthesis has been in the focal interest of crystal engineering of multi-component systems, including cocrystals [1]. While the majority of research is focused on either hydrogen (HB) or halogen bonding (XB), the examination of competition and cooperation of the two whenever they are present within the same system is gaining importance [2]. In this work, to investigate the structure- directing balance between halogen and hydrogen bonds in cocrystals, we used two perhalogenated amines, 4-bromo-2, 3, 5, 6-tetrafluoroaniline (btfa) and 4-iodo-2, 3, 5, 6-tetrafluoroaniline (itfa), as bifunctional donor molecules containing XB donor (iodine or bromine atom) and HB donor (amino group) on the same perfluorinated aromatic backbone. Using three different ditopic nitrogen- containing acceptors 4, 4'-bipyridine, 1, 2-bis(4- pyridyl)ethane and 1, 4-diazabicyclo[2.2.2]octane, we have prepared seven cocrystals by grinding and crystallization from solution. Prepared compounds were characterized by diffraction methods (single- crystal X-ray diffraction and X-ray powder diffraction), and their thermal stability was determined by differential scanning calorimetry. Structure analysis revealed that in four cocrystals both N...I or N...Br halogen and N- H...N hydrogen bonds were formed, in two cocrystals with btfa only N-H...N hydrogen bond was formed, while in one cocrystal with itfa only N...I halogen bond was formed. Based on our results, btfa is more likely to form only hydrogen bonds, while itfa has a great potential as a bifunctional donor. Utilizing itfa in crystal engineering of cocrystals could lead to the formation of supramolecular chains based on halogen and hydrogen bonds in a predictable and reliable matter.

cocrystal ; halogen bond ; bifunctional donor

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