Hydrogen bonding in two solid phases of phenazine–chloranilic acid (1/1) determined at 170 and 93 K

The crystal structures in two solid phases, i.e. phase II stable between 146 and 253 K and phase IV below 136 K, of the title compound [phenazine–chloranilic acid (1/1), C₁₂H₈N₂·C₆H₂Cl₂O₄, in phase II, and phenazinium hydrogen chloranilate, C₁₂H₉N₂⁺·C₆HCl₂O₄⁻, in phase IV], have been determined. Both phases crystallize in P2₁, and each structure was refined as an inversion twin. In phase II, the phenazine and chloranilic acid mol­ecules are arranged alternately through two kinds of O—H...N hydrogen bonds. In phase IV, salt formation occurs by donation of one H atom from the chloranilic acid molecule to the phenazine mol­ecule; the resulting monocation and monoanion are linked by N—H...O and O—H...N hydrogen bonds.