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 P2(1), 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.