A comparative study of intermolecular interactions in the crystal structures of phenyl/phenyl end-capped oligoanilines

Three crystal structures have been analysed from the point of view of intermolecular interactions: N,N′‐di­phenyl‐1,4‐benzo­quinone di­imine, C18H14N2, (I), its reduced form N,N′‐di­phenyl‐1,4‐phenyl­enedi­amine, C18H16N2, (II), and N,N′‐di­phenyl‐1,4‐phenyl­enedi­ammonium bis(p‐toluene­sulfonate), C18H18N22+·2C7H7O3S−, (III), which contains fully protonated (II) with p‐toluene­sulfonic acid. The local molecular Ci symmetry is preserved in all three structures and the packing seems to be dominated by the mutual arrangement of the simple polyaniline oligomers in the different protonation states. In (I), the most significant molecular interactions are stacking forces, forming columns of mol­ecules along [001]. Close packing of the columns results in C‐centring of the structure. In (II), only van der Waals interactions can be observed. In the structure of (III), the p‐toluene­sulfonate ions serve as acceptors in relatively strong N—H⋯O hydrogen bonds. The N,N′‐di­phenyl‐1,4‐phenyl­enedi­ammonium cation intercalates between two anions related by a centre of symmetry.