Research Article: 5-Chloro-N-(4,5-dihydro-1H-imidazol-2-yl)-2,1,3-benzothia­diazol-4-amine (tizanidine)

Date Published: April 01, 2011

Publisher: International Union of Crystallography

Author(s): Peter John, Islam Ullah Khan, Mehmet Akkurt, Muhammad Shahid Ramzan, Shahzad Sharif.


There are two independent mol­ecules (A and B) with similar conformations in the asymmetric unit of the title compound, C9H8ClN5S. The benzothia­diazole ring systems of both mol­ecules are essentially planar [maximum deviation = 0.021 (2) Å in mol­ecule A and 0.022 (1) Å in mol­ecule B] and make dihedral angles of 68.78 (9) and 54.39 (8)°, respectively, with the mean planes of their 4,5-dihydro-1H-imidazole rings. An intra­molecular N—H⋯Cl hydrogen bond occurs in mol­ecule B. In the crystal, both mol­ecules form centrosymmetric dimers through π-stacking of their benzothia­diazole rings, with inter­planar distances of 3.3174 (7) and 3.2943 (6) Å. These dimers are further linked via pairs of N—H⋯N hydrogen bonds with the dihydro­imidazole rings as the hydrogen-bonding donors and one of the benzothia­diazole N atoms as the acceptors, generating R22(16) ring motifs. The A2 and B2 dimers in turn form additional N—H⋯N hydrogen bonds with the secondary amine as the H-atom donor and the dihydro­imidazole N atom as the acceptor. These R22(8)-type inter­actions connect the A2 and B2 dimers with each other, forming infinite chains along [11].

Partial Text

For the medicinal importance of tizanidine, see: Koch et al. (1989 ▶); Shellenberger et al. (1999 ▶); Tse et al. (1987 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶).




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