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), C₁₂H₈N ₂·C₆H₂Cl₂O₄, in phase II, and phenazinium hydrogen chloranilate, C₁₂H ₉N₂⁺·C₆HCl₂O ₄^-, 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.