Date Published: May 01, 2009
Publisher: International Union of Crystallography
Author(s): Gianluca Bartolucci, Bruno Bruni, Silvia A. Coran, Massimo Di Vaira.
The structure [Danilovski et al. (2001 ▶). Croat. Chim. Acta74, 103–120] of the T–N (non-solvated) polymorph of torasemide, C16H20N4O3S, a diuretic drug used in the treatment of hypertension, has been redetermined at low temperature. The zwitterionic form of the molecule is confirmed, although GAUSSIAN03 calculations suggest that this form is less stable in the gas phase. The unit-cell contraction between 298 and 100 K is approximately isotropic and the largest structual change is in a C—N—C—C torsion angle, which differs by 11.4 (3)° between the room-temperature and low-temperature structures. There are two molecules in the asymmetric unit, both of which contain an intramolecular N—H⋯N hydrogen bond. In the crystal structure, both molecules form inversion dimers linked by pairs of N—H⋯N hydrogen bonds. Further N—H⋯N and N—H⋯O hydrogen bonds lead to a three-dimensional network. The different hydrogen-bond arrangements and packing motifs in the polymorphs of torasemide are discussed in detail.
For the crystal structures of polymorphs of torasemide, see: Dupont et al. (1978 ▶); Danilovski et al. (2001 ▶). For the structure of the water–methanol solvated T–II form of torasemide, see: Bartolucci et al. (2009 ▶).