4-(3-Methyl-anilino)-N-[N-(1-methyl-ethyl)carbamo-yl]pyridinium-3-sulfon-amidate (torasemide T-N): a low temperature redetermination.

The structure [Danilovski et al. (2001 ▶). Croat. Chim. Acta74, 103-120] of the T-N (non-solvated) polymorph of torasemide, C(16)H(20)N(4)O(3)S, a diuretic drug used in the treatment of hypertension, has been redetermined at low temperature. The zwitterionic form of the mol-ecule 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 mol-ecules in the asymmetric unit, both of which contain an intra-molecular N-H⋯N hydrogen bond. In the crystal structure, both mol-ecules 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.