Crystal structure and Hirshfeld surface analysis of (E)-3-[(2,3-dichlorobenzylidene)amino]-5-phenylthiazolidin-2-iminium bromide

In the crystal, the cations and anions stacked along the b-axis direction are linked by C—H⋯Br and N—H⋯Br hydrogen bonds, forming a three-dimensional network. In addition, weak C—H⋯π (ring) interactions, which only involve the minor disorder component. Inversion-related Cl⋯Cl halogen bonds and C—Cl⋯π (ring) contacts also help to stabilize the packing.


Supramolecular features and Hirshfeld surface analysis
In the crystal, each cation forms C-HÁ Á ÁBr and N-HÁ Á ÁBr hydrogen bonds along with inversion-related Cl1Á Á ÁCl1 halogen bonds and C7-Cl2Á Á ÁCg3 iv and C7-Cl2Á Á ÁCg4 iv contacts (Table 1; Fig. 2). Chains of cations form along the aaxis direction (Fig. 3). The crystal structure is further stabilized by C13 0 -H13BÁ Á ÁCg3 ii and C13 0 -H13BÁ Á ÁCg4 ii interactions involving the minor disorder component (Table 1). Overall, cations and anions are stacked along the b-axis direction ( Fig. 4) The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) of the title salt was generated by CrystalExplorer3.1 (Wolff et al., 2012), and comprised d norm surface plots and two dimensional fingerprint plots (Spackman & McKinnon, 2002). A d norm surface plot of the title salt is shown in Fig. 5. This plot The molecular structure of the title salt. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms are shown as spheres of arbitrary radius. The minor disorder component is omitted for clarity. Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
View of the full complement of contacts to an individual cation in the title salt. Only the major disorder component is shown. The symmetryequivalent position for the cation with the label Cg3 is Àx + 1, y À 1 2 , Àz + 3/2. was generated to quantify and visualize the intermolecular interactions and to explain the observed crystal packing. The dark-red spots on the d norm surface arise as a result of short interatomic contacts, while the other weaker intermolecular interactions appear as light-red spots.
The d norm surface of the title salt shows a dark-red spot at the N-H hydrogen atom and on the bromide atom, which is the result of the strong N3-H3AÁ Á ÁBr1 i and N3-H3BÁ Á ÁBr1 hydrogen bonds present in the structure (Fig. 5). Beside these two short intermolecular contacts, the C-HÁ Á ÁBr interaction is shown as light-red spots on the d norm surface. The short interatomic contacts in the title salt are given in Table 2.
A quantitative analysis of the intermolecular interactions can be made by studying the fingerprint plots that are shown with characteristic pseudo-symmetry wings in the d e and d i diagonal axes [d e and d i represent the distances from a point on the Hirshfeld surface to the nearest atoms outside (external) and inside (internal) the surface, respectively].

Figure 4
Overall packing of the title salt viewed along the b axis. Only the major disorder component is shown.

Figure 5
Hirshfeld surface of the title salt mapped with d norm , showing the C-HÁ Á ÁBr and N-HÁ Á ÁBr hydrogen bonds.
tage contributions of other intermolecular contacts are less than 6% in the Hirshfeld surface mapping (Table 3).

Database survey
A search of the Cambridge Structural Database (CSD Version 5.39, Nov 2017 plus three updates; Groom et al., 2016) yielded six hits for 2-thiazolidiniminium compounds with four of them reporting essentially the same cation: [WILBIC (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)]. In all cases, the 3-N atom carries a C substituent, not N 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-(2 0 -chloro-2 0 -phenylethyl) À2-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.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. The H atoms were positioned geometrically [N-H = 0.90 Å and C-H = 0.93-0.97 Å ] and were refined using a riding model, with U iso (H) = 1.2U eq (C,N). The phenyl ring in the cation is disordered over two positions with a site occupancy ratio of 0.541 (9):0.459 (9). Using DFIX, the bond distances in the two disorder components of the phenyl ring were set to 1.40 Å . Corresponding displacement parameters were also held to be the same using EADP.  Computer programs: APEX2 and SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), ORTEP-3 for Windows (Farrugia, 2012), Mercury (Macrae et al., 2008) and PLATON (Spek, 2003).

Table 2
Summary of short interatomic contacts (Å ) in the title salt.
Atoms marked with an asterisk (*) are from the minor component (C11/C12 0 -C16 0 ) of the disordered phenyl ring of the cation.

Computing details
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); 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.