(E)-2-[(2-Hydroxy-5-nitrophenyl)iminiomethyl]-4-nitrophenolate

The title molecule, C13H9N3O6, consists of a 2-hydroxy-5-nitrophenyliminio group and a 4-nitrophenolate group bonded to a methylene C atom with both of the planar six-membered rings nearly in the plane of the molecule [dihedral angle = 1.3 (4)degrees]. Each of the nitro O atoms is twisted slightly out of the plane of the molecule. The amine group forms an intramolecular hydrogen bond with both nearby O atoms, each of which has partial occupancy of attached H atoms [0.36 (3) and 0.64 (3)]. An extended pi-delocalization throughout the entire molecule exists producing a zwitterionic effect in this region of the molecule. The shortened phenolate C-O bond [1.2749 (19)degrees], in concert with the slightly longer phenol C-O bond [1.3316 (19) angstrom], provides evidence for this effect. The crystal packing is influenced by extensive strong intermolecular O-H center dot center dot center dot O hydrogen bonding between the depicted phenolate and hydroxy O atoms and their respective H atoms within the pi-delocalized region of the molecule. As a result, molecules are linked into an infinite polymeric chain diagonally along the [110] plane of the unit cell in an alternate inverted pattern. A MOPAC AM1 calculation provides support for these observations.