Three Crystal Structures of Terephthalic Acid Salts of Simple Amines

Diphenethylamine forms two adducts (1 : 1, 1a and 2 : 1, 1b) with terephthalic acid (H2TPA). The former is bis(diphenethylammonium)H2TPA・TPA2− and the latter is bis(diphenethylammonium) ・TPA2−. The amine cis-2,6-dimethylpiperidine forms a hydrated 2 : 1 adduct, bis(2,6-dimethylpiperidinium) ・TPA2−・H2O (2). The crystal structures of all three compounds were determined. All H2TPA and TPA2− residues display inversion symmetry, while the water oxygen atom of 2 lies on a twofold axis. Packing analyses have identified some supramolecular synthons known from related structures.