Crystal structure and Hirshfeld surface analysis of (E)-3-[(4-chlorobenzylidene)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. In the 1H NMR spectra of this compound, the NH iminium protons are observed at δ = 10.46 p.p.m., which confirms the strong charge-assisted hydrogen bonding (CAHB) in the =HN+—H⋯Br− synthon.


Supramolecular features and Hirshfeld surface analysis
In the crystal, centrosymmetrically related cations and anions are linked into dimeric units via N-HÁ Á ÁBr hydrogen bonds, which are further connected by weak C-HÁ Á ÁBr contacts, into chains parallel to the a-axis direction (Table 1; Figs. 2 and 3). Furthermore, C-HÁ Á Á interactions (Table 1) andstacking interactions [Cg4 Á Á ÁCg4(2 À x, À y, 1 À z) = 3.897 (2) Å where Cg4 is the centroid of the major component of the disordered phenyl ring] contribute to the stabilization of the molecular packing.
Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) was used to quantify and visualize the intermolecular interactions and to explain the observed crystal packing. Crystal-Explorer3.1 (Wolff et al., 2012) was used to generate d norm surface plots and two-dimensional fingerprint plots (Spackman & McKinnon, 2002). The Hirshfeld surface mapped over d norm using a standard surface resolution with a 1176 Duruskari et al. The molecular structure of the title salt. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as spheres of arbitrary radius. Only the major component of the disorder is shown for clarity.

Figure 2
Packing viewed along the a-axis direction showing the N-HÁ Á ÁBr and C-HÁ Á ÁBr interactions (dashed lines).

Figure 3
A perspective view of the crystal structure of the title compound. fixed colour scale of À0.4687 (red) to 1.2270 a.u. (blue) is shown in Fig. 4. The shape-index of the Hirshfeld surface is a tool to visualizestacking interactions by the presence of adjacent red and blue triangles; if there are no adjacent red and/or blue triangles, then there are nointeractions. Fig. 5 clearly suggest that there areinteractions present in the title salt. Fig. 6a shows the two-dimensional fingerprint for the sum of the contacts contributing to the Hirshfeld surface represented in normal mode (Tables 1 and 2). The fingerprint plots delineated into HÁ Á ÁH (30.5%), BrÁ Á ÁH/HÁ Á ÁBr (21.2%), CÁ Á ÁH/HÁ Á ÁC (19.2%), ClÁ Á ÁH/HÁ Á ÁCl (13.0%) and SÁ Á ÁH/ HÁ Á ÁS (5.0%) interactions are shown in Fig. 6b-f, respectively. The most significant intermolecular interactions are the HÁ Á ÁH interactions (30.5%; ig. 6b). The various contributions to the Hirshfeld surface are listed in Table 3. Hirshfeld surface of the title salt mapped with d norm .

Figure 5
Hirshfeld surface of the title salt mapped with shape-index.   Table 2 Summary of short interatomic contacts (Å ) in the title salt.
Cg3 is the centroid of the C5-C10 benzene ring of the chlorophenyl moiety.
Cg4 and Cg5 are the centroids of the major and minor components of the disordered phenyl ring, respectively.

D-HÁ
Àx þ 2; Ày; Àz þ 1; (iii) Àx þ 1; Ày þ 1; Àz þ 2; (iv) x; y; z À 1.  (Marthi et al., 1994), WILBOI (Marthi et al., 1994), WILBOI01 (Marthi et al., 1994), YITCEJ (Martem'yanova et al., 1993a), YITCAF (Martem'yanova et al., 1993b) and YOPLUK (Marthi et al., 1995). The structure of BOBWIB (Khalilov et al., 2019) is isotypic with that of the title salt. In BOBWIB, the phenyl ring is disordered over two sets of sites with a refined occupancy ratio of 0.503 (4):0.497 (4). The mean plane of the thiazolidine ring makes dihedral angles of 13.51 (14), 48.6 (3) and 76.5 (3) , respectively, with the fluorophenyl ring and the major-and minor-disorder components of the phenyl ring. The central thiazolidine ring adopts an envelope conformation. In the crystal, centrosymmetrically related cations and anions are linked into dimeric units via N-HÁ Á ÁBr hydrogen bonds, which are further connected by weak C-HÁ Á ÁBr hydrogen bonds into chains parallel to [110]. In the crystal of UDELUN (Akkurt et al., 2018), C-HÁ Á ÁBr and N-HÁ Á ÁBr hydrogen bonds link the components into a three-dimensional network with the cations and anions stacked along the b-axis direction. Weak C-HÁ Á Á interactions, which only involve the minordisorder component of the ring, also contribute to the molecular packing. In addition, there are inversion-related ClÁ Á ÁCl halogen bonds and C-ClÁ Á Á(ring) contacts. In the remaining structures, the 3-N atom carries a C-atom substituent instead of an N-atom substituent, as found in the title compound. 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-(20-chloro-20-phenylethyl)-2-thiazolidiniminium ptoluenesulfonate. In all three structures, the most disordered fragment of the 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 the product of the interaction of 2-amino-5-methylthiazoline with methyl iodide, with alkylation at the endocyclic N atom, while YITCAF (Martem'yanova et al., 1993b) is the product of the reaction of 3-nitro-5-methoxy-, 3-nitro-5-chloro-and 3bromo-5-nitrosalicylaldehyde with the heterocyclic base to form the salt-like complexes.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. All C-bound H atoms were placed at calculated positions using a riding model, with aromatic C-H = 0.95-1.00 Å , and with U iso (H) = 1.2U eq (C). Hydrogen atoms of the amino groups were located directly from difference-Fourier maps and were constrained with AFIX 3 instructions (N-H = 0.90 Å ) in order to ensure a chemically reasonable environment for these groups. These hydrogen atoms were modelled with isotropic thermal displacement parameters fixed at 1.2U eq (N). One outlier (001) was omitted in the final cycles of refinement. The phenyl group and the carbon atom of the 1,3-thiazolidine group attached to it were refined as positionally disordered over two sets of sites with refined occupancies of 0.570 (3)

Computing details
Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2003).  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.