2-(1,2-Dihydro-2-oxopyridin-3-yl)-1,3-benzothiazol-3-ium bromide monohydrate

The title hydrated molecular salt, C12H9N2OS+·Br−·H2O, the aza-substituted six-membered ring is present as its keto tautomer instead of its aromatic tautomer. The dihedral angle between the fused ring system and the pyridinone ring in the cation is 6.91 (6)°. In the crystal, bifurcated N—H⋯(O,Br) and O—H⋯Br hydrogen bonds and S⋯O contacts [S⋯O = 3.0526 (10) Å] connect the components into a three-dimensional network. The closest centroid–centroid distance between two π-systems is 3.7420 (7) Å between two benzene rings.

The title hydrated molecular salt, C 12 H 9 N 2 OS + ÁBr À ÁH 2 O, the aza-substituted six-membered ring is present as its keto tautomer instead of its aromatic tautomer. The dihedral angle between the fused ring system and the pyridinone ring in the cation is 6.91 (6) . In the crystal, bifurcated N-HÁ Á Á (O,Br) and O-HÁ Á ÁBr hydrogen bonds and SÁ Á ÁO contacts [SÁ Á ÁO = 3.0526 (10) Å ] connect the components into a three-dimensional network. The closest centroid-centroid distance between two -systems is 3.7420 (7) Å between two benzene rings.

Comment
In our continuous efforts to create new radio-pharmaceuticals (Gerber et al., 2011), we attempted the coordination reaction of a bidentate ligand towards a rhenium(V) precursor upon which a crystalline reaction product was obtained. The crystal structure analysis showed the unintentional synthesis of a protonated derivative of the ligand. The structure of 2-(ohydroxyphenyl)benzothiazole is apparent in the literature (Stenson, 1970;Aydin et al., 1999;Jia & Jin, 2009).
In the molecule, the -possible -hydroxy-pyridine moiety is present as its keto-tautomer. Protonation took place on the nitrogen atom of the five-membered heterocyclic subunit. The molecule is essentially flat, the least-squares planes defined by the ring atoms of the benzothiazol moiety and the ring atoms of the hydroxy-pyridine tautomer enclose an angle of only 6.91 (6) °. One molecule of solvent water is present in the crystal structure ( Fig. 1).
In the crystal structure, hydrogen bonds as well as S···O contacts (whose range falls by more than 0.2 Å below the sum of van-der-Waals radii of the respective atoms) are present. While the hydrogen bonds originating from the solvent water as well as the protonated nitrogen atom of the five-membered heterocyclic subunit exclusively have the bromide anion as acceptor, the water molecule's oxygen atom serves as acceptor for the hydrogen atom of the intracyclic NH group in the six-membered heterocycle. The pattern formed by the water molecules connecting the bromide anions is reminiscent of a parallelogram (Fig. 2). The S···O contacts give rise to the formation of centrosymmetric dimers. In total, the components of the crystal structure are connected to a three-dimensional network. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the hydrogen bonding system is DDDD on the unitary level. The parallelogram shaped pattern necessitates a R 4 2 (8) descriptor on the binary level. The description of the S···O contacts is possible by a R 2 2 (10) descriptor on the unitary level. The closest intercentroid distance between two π-systems was found at 3.7420 (7) Å and was observed between two phenyl-moieties.
The packing of the title compound is shown in Figure 3.

Experimental
The compound was unintentionally obtained upon reacting ReOBr 3 (PPh 3 ) 2 and the unprotonated title compound in methanol. Crystals suitable for the X-ray diffraction study were obtained upon free evaporation of the solvent at room temperature in the course of three days.