1,3-bis(3-nitrophenyl)triazene

The title molecule, C12H9N5O4, has trans geometry about the azo linkage. Th e dihedral angle between the two phenyl rings is 6.2(2)degrees. The whole m olecule is almost planar and the maximum deviation from the mean plane is 0 .166(3)Angstrom. The resonance effect in the triazene group which might exp lain the antitumour activity of some triazene derivatives is discussed. In the crystal structure, while the twofold screw-related molecules are packed in a simple herringbone pattern, the inversion-centre-related molecules fo rm hydrogen-bonded dimers which are held together through pi ...pi interact ions along the [010] direction.