Hydrogen-bond-directed supramolecular arrays in 4,4'-bipyridinium tetrachloroterephthalate dihydrate and bis(1,10-phenanthrolinium) tetrachloroterephthalate tetrachloroterephthalic acid trihydrate.

The title compounds, C10H10N(2)(2+).C8Cl4O(4)(2-).2H2O, (I), and 2C12H9N2+.C8Cl4O(4)(2-).C8H2Cl4O4.3H2O, (II), both crystallize as charge-transfer organic salts with the dianionic or neutral acid components lying on inversion centres. The acid and base subunits in (I) arrange alternately to generate a linear tape motif via N-H...O hydrogen bonds; these tapes are further combined into a three-dimensional architecture through multiple O-H...O and C-H...O interactions involving solvent water molecules. In contrast, the neutral and anionic acid components in (II) are linked to form a zigzag chain by means of O-H...O hydrogen bonds between acid groups, with dangling 1,10-phenanthrolinium units connected to these chains by carboxylate-pyridinium interactions with R(2)(2)(7) hydrogen-bond notation. Adjacent chains are further extended to result in a two-dimensional corrugated layer network via pi-pi interactions. Inter-ion Cl...O interactions are also found in both (I) and (II).