Tetramethylammonium hemi(terephthalate) dihydrate

In the title compound, (CH3)4N+·0.5C8H4O42 ·2H2O, the complete terephthalate dianion is completed by twofold symmetry and has a dihedral angle of 23.5 (2)° between the carboxylate group and its parent ring. Two independent water molecules serve as both donors and acceptor in the construction of undulating hydrogen-bonded host layers with various O—H...O contacts ocurring between the anion and two water molecules. At the same time, the tetramethylammonium cations, as the sphere-like guest species, are arranged in two rows between neighboring host layers, with an approximate interlayer distance of 7.36 , forming a sandwich-like crystal structure.