organic compounds
The monohydrate chloride and bromide salts of theophylline are mutually isostructural, with the cations and anions lying on crystallographic mirror planes (Z' = ). The BF4 salt structure is based on planar hydrogen-bonded theopylline cation dimers, with the anions interacting with the dimers in a pendant fashion. The anhydrous chloride salt structure has Z' = 2 and forms one-dimensional chains of cations and anions propagating parallel to the crystallographic c direction.