Two‐ and three‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the isomeric monoaminobenzoic acids

The crystal structures of the 1:1 proton‐transfer compounds of 4,5‐dichlorophthalic acid with the three isomeric monoaminobenzoic acids, namely the hydrate 2‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate dihydrate, C 7 H 8 NO 2 + ·C 8 H 3 Cl 2 O 4 − ·2H 2 O, (I), and the anhydrous salts 3‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate, C 7 H 8 NO 2 + ·C 8 H 3 Cl 2 O 4 − , (II), and 4‐carboxyanilinium 2‐carboxy‐4,5‐dichlorobenzoate, C 7 H 8 NO 2 + ·C 8 H 3 Cl 2 O 4 − , (III), have been determined at 130 K. Compound (I) has a two‐dimensional hydrogen‐bonded sheet structure, while (II) and (III) are three‐dimensional. All three compounds feature sheet substructures formed through anilinium N + —H...O carboxyl and anion carboxylic acid O—H...O carboxyl interactions and, in the case of (I), additionally linked through the donor and acceptor associations of the solvent water molecules. However, (II) and (III) have additional lateral extensions of these substructures though cyclic R 2 2 (8) associations involving the carboxylic acid groups of the cations. Also, (II) and (III) have cation–anion π–π aromatic ring interactions. This work provides further examples illustrating the regular formation of network substructures in the 1:1 proton‐transfer salts of 4,5‐dichlorophthalic acid with the bifunctional aromatic amines.