Crystal structure and Hirshfeld surface analysis of 3-amino-5-phenylthiazolidin-2-iminium bromide

In the crystal of the title salt, the cations and anions are linked via N—H⋯Br hydrogen bonds to form a three-dimensional network.

In the cation of the title salt, C 9 H 12 N 3 S + ÁBr À , the thiazolidine ring adopts an envelope conformation with the C atom adjacent to the phenyl ring as the flap. In the crystal, N-HÁ Á ÁBr hydrogen bonds link the components into a threedimensional network. Weakstacking interactions between the phenyl rings of adjacent cations also contribute to the molecular packing. A Hirshfeld surface analysis was conducted to quantify the contributions of the different intermolecular interactions and contacts.

Chemical context
As well as their synthetic utility, thiazolidine derivatives possess a broad spectrum of biological activities such as antimalarial, antibacterial, antimicrobial, anti-inflammatory, anticancer, etc. The biological activities of compounds containing a thiazolidine core, such as 1,3-thiazolidines, 2,4dione-, 4-oxo-thiazolidine, etc. were summarized in a recent review (Makwana & Malani, 2017). On the other hand, as hydrazones these N-containing ligands have been widely used in the synthesis of coordination compounds (Gurbanov et al., 2018a,b). The non-covalent donor or acceptor properties of Ncontaining ligands can also contribute to their catalytic activity, among other properties (Mahmudov et al., 2019;Zubkov et al., 2018). As part of our ongoing work in this area, we now describe the synthesis and structure of the title molecular salt, C 9 H 12 N 3 S + ÁBr À , (I).

Supramolecular features and Hirshfeld surface analysis
In the crystal, each cation forms N-HÁ Á ÁBr hydrogen bonds (Table 1) as well as aromaticstacking interactions between the phenyl rings of adjacent cations [Cg2Á Á ÁCg2 iv = 3.7758 (16) Å ; symmetry code: (iv) 1 À x, 1 À y, 2 À z; where Cg2 is the centroid of the phenyl ring of the cation]: chains of cations form along the [101] direction (Fig. 2). Taking into account the hydrogen bonding andstacking, the overall connectivity is three-dimensional.

Figure 2
Part of the crystal structure of the title compound, showing the formation of N-HÁ Á ÁBr hydrogen bonds in the ac plane. addition, there are also inversion-related ClÁ Á ÁCl halogen bonds and C-ClÁ Á Á(ring) contacts. In the other structures, the 3-N atom carries a C substituent: the first three crystal structures were determined for racemic (WILBIC; Marthi et al., 1994) and two optically active samples (WILBOI and WILBOI01; Marthi et al., 1994) of 3-(2 0 -chloro-2 0 -phenylethyl)-2-thiazolidiniminium p-toluenesulfonate. In all three structures, the most disordered fragment of these molecules is the asymmetric C atom and the Cl atom attached to it. The disorder of the cation in the racemate corresponds to the presence of both enantiomers at each site in the ratio 0.821 (3): 0.179 (3). The system of hydrogen bonds connecting two cations and two anions into 12-membered rings is identical in the racemic and in the optically active crystals. YITCEJ (Martem'yanova et al., 1993a) is a product of the interaction of 2-amino-5-methylthiazoline with methyl iodide, with alkylation at the endocylic nitrogen atom, while YITCAF (Martem'yanova et al., 1993b) is a product of the reaction of 3-nitro-5-methoxy-, 3-nitro-5-chloro-, and 3-bromo-5-nitrosalicylaldehyde with the heterocyclic base to form the salt-like complexes.

Synthesis and crystallization
To a solution of 2.2 mmol (0.6 g) (1,2-dibromoethyl)benzene in 20 ml of ethanol were added 2.3 mmol (0.3 g) of thiosemicarbazide hydrochloride; 3-4 drops of piperidine were added and the mixture was refluxed for 7 h. The reaction mixture was cooled to room temperature and the solid product was precipitated from solution, collected by filtration and recrystallized from ethanol solution to give colourless crystals of (I) with a yield of 88%, m.

Figure 3
The refined using a riding model. The N-bound hydrogen atoms were located from difference-Fourier maps and relocated to idealized locations (N-H = 0.90 Å ) and refined as riding atoms. The constraint U iso (H) = 1.2U eq (carrier) was applied in all cases. One outlier (101) was omitted in the final cycles of refinement.

3-Amino-5-phenylthiazolidin-2-iminium bromide
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.