Activation and de-activation of fluorine synthons by nitrogen substitution in fluorinated aza-distyrylbenzenes

Abstract

Three derivatives of E,E-1,4-bis[2-(2,3,4,5,6-pentafluorophenyl)ethenyl]benzene, two of which bear nitrogen atoms in the ethenyl spacers, while in a third the central benzene ring is replaced by a pyrazine moiety, have been synthesized. The supramolecular structures of the resulting set of four compounds have been studied using single-crystal X-ray diffraction to gauge the influence of the position of the nitrogen atoms on the organisation of the molecules in the solid state. The crystal packing patterns were analyzed in terms of intermolecular interactions involving the fluorine and nitrogen atoms, i.e., CH⋯F, F⋯F, F⋯π and CH⋯N interactions. The analysis shows that in two of the three solid-state structures the main effect of the nitrogen atoms is an indirect one: they do not participate in intermolecular contacts themselves, but activate nearby hydrogen atoms and phenyl rings in fluorine synthons to form new interactions.