4,4′-Dinitro-2,2′-[propane-1,3-diylbis(iminiumylmethanylyl­idene)]diphenolate

The title compound, C(17)H(16)N(4)O(6), is a Schiff base, which is found as a bis-zwitterion in the solid state. The geometry around the iminium N atom indicates sp (2)-hybridization. The diiminiumpropyl­ene chain is in an approximate double-gauche conformation, with average N—C—C—C torsion angles of 69.3°. The zwitterion shows strong intra­molecular N—H⋯O hydrogen bonds between the iminium N and phenolate O atom. In the crystal, bifurcated N—H⋯(O,O) hydrogen bonds assemble pairs of molecules into inversion dimers.