Bis(2-aminothiazolium) succinate succinic acid

In the title compound, 2C3H5N2S+·C4H4O4 2−·C4H6O4, the thiazolium ring is almost planar, with the maximum deviation from planarity being 0.0056 (8) Å for the C atom carrying the amine substituent. The N atom of the 2-aminothiazole molecule is protonated. Both the anion and the acid lie across inversion centres. The crystal packing is consolidated by intermolecular O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds. Molecules are stacked down the b axis.

In the title compound, 2C 3 H 5 N 2 S + ÁC 4 H 4 O 4 2À ÁC 4 H 6 O 4 , the thiazolium ring is almost planar, with the maximum deviation from planarity being 0.0056 (8) Å for the C atom carrying the amine substituent. The N atom of the 2-aminothiazole molecule is protonated. Both the anion and the acid lie across inversion centres. The crystal packing is consolidated by intermolecular O-HÁ Á ÁO, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds. Molecules are stacked down the b axis.
The bond lengths and bond angles of the succinate and succinic acid are found to have normal values (Gopalan et al., 2000;Leviel & Auvert, 1981). The crystal packing is consolidated by O-H···O, N-H···O and C-H···O intermolecular hydrogen bonds (Table 1)  Experimental 2-Aminothiazole (0.100 g, 1 mmol) and succinic acid (0.118 g, 1 mmol) were dissolved in ethanol (25 ml) in a 1:1 molar ratio. The clear brown solution obtained was refluxed for 6 h at a temperature of 323 K. Brown coloured crystals were harvested after two weeks on slow evaporation of the solvent.

Refinement
All the hydrogen atoms were located from the Fourier map and were allowed to refine freely with isotropic displacement parameters.
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom numbering scheme. [symmetry operators used to generate equivalent atoms are (i) -x + 1, -y + 2, -z and (ii) -x + 2, -y + 2, -z for the anion and acid respectively].

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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 Rfactors(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.