Comparison of the structure of (E)-2-(2-benzylidenehydrazinylidene)quinoxaline with those of its chloro- and bromobenzylidene analogues.

(E)-2-(2-Benzylidenehydrazinylidene)quinoxaline, C₁₅H₁₂N₄, crystallized with two molecules in the asymmetric unit. The structures of six halogen derivatives of this compound were also investigated: (E)-2-[2-(2-chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)-2-[2-(3-chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)-2-[2-(4-chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)-2-[2-(2-bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)-2-[2-(3-bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)-2-[2-(4-bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄. The 3-Cl and 3-Br compounds are isomorphous, as are the 4-Cl and 4-Br compounds. In all of these compounds, it was found that the supramolecular structures are governed by similar predominant patterns, viz. strong intermolecular N-H...N(pyrazine) hydrogen bonds supplemented by weak C-H∙∙∙N(pyrazine) hydrogen-bond interactions in the 2- and 3-halo compounds and by C-H∙∙∙Cl/Br interactions in the 4-halo compounds. In all compounds, there are π-π stacking interactions.