Synthesis, crystal structure and crystal packing of diaza[5]helicenes

Analysis of the crystalline packing of known aza[5]helicenes is presented together with some newly synthesized diaza[5]helicenes species, characterized by NMR spectroscopy and X-ray diffraction. The comparison with carbo[5]helicenes and monoaza[5]helicenes emphasizes the importance of the ‘‘shape factor’’ (responsible of the isomorphism between some species in the series) as well as the lack of a unique supramolecular effect organizing the molecules in the crystals (responsible for the polymorphism observed for some compounds).