7-[(3-Chloro-6-methyl-6,11-dihydrodibenzo[c,f][1,2]thiazepin-11-yl)amino]heptanoic acid S,S-dioxide hydrochloride

In the title compound, C21H26ClN2O4S.Cl, also known as tianeptine hydrochloride, the seven-membered ring adopts a boat conformation. The dihedral angle between the mean planes of the benzene rings is 44.44 (7)°. There is an intramolecular hydrogen bond formed via S= O⋯H—N. In the crystal, molecules are connected via pairs of N—H.·O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, forming inversion dimers, which are consolidated by C—H⋯O interactions. The dimers are linked by C—H⋯O and C—H⋯Cl interactions, forming a two-dimensional network lying parallel to (011).

The crystal structures of tianeptine polymorphs have been reported recently (Orola et al., 2012). The title structure is more similar with polymorph A structure in which tianeptine molecules are linked via hydrogen bonds between amine and carboxyl groups. The tianeptine molecules in the structure of tianeptine polymorph B are in a zwiterrion form.

Experimental
Tianeptine sodium salt (0.5 g;1.09 mmol) was dissolved in 20 ml deionized water in a Erlenmeyer flask and added ~3 mmol of hydrochloric acid. Mixture were stirred for 6 h. After 6 h suspension was filtered and washed with cold water.
The product was dried and recrystallized from water by slow evaporation at room temperature.

Refinement
All hydrogen atoms were positioned geometrically with C-H distances ranging from 0.93 to 0.97 Å and refined as riding on their parent atoms with U iso (H) = 1.5 U eq (C) for methyl groups and U iso (H) = 1.2 U eq (C) for others.  The molecular structure of the title compound showing 50% probability ellipsoids and hydrogen atoms are shown as small spheres of arbitrary radii.

Figure 2
Packing diagram of the title compound viewed along the c axis. Blue lines indicate hydrogen bonds. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.