Crystal structure and Hirshfeld surface analysis of (E)-3-[(4-fluorobenzylidene)amino]-5-phenylthiazolidin-2-iminium bromide

In the crystal of the title salt, cations and anions are linked by N–H⋯Br hydrogen bonds forming inversion-related dimers. The dimers are connected by weak C–H⋯Br hydrogen bonds into chains.


Chemical context
Noncovalent interactions, both intermolecular and intramolecular, occur in virtually every substance and play an important role in the synthesis, catalysis, design of materials and biological processes (Akbari et al., 2017;Gurbanov et al., 2018;Kopylovich et al., 2011;Maharramov et al., 2010;Mahmoudi et al., 2018a,b,c;Mahmudov et al., 2011Mahmudov et al., , 2013Mahmudov et al., , 2014aMahmudov et al., ,b, 2015Mahmudov et al., , 2017aMahmudov et al., ,b, 2019Shixaliyev et al., 2013Shixaliyev et al., , 2018. On the other hand, Schiff bases and related hydrazone ligands and their complexes have attracted attention over the past decades due to their potential biological, pharmacological and analytical applications Mahmoudi et al., 2018a,b,c;Mahmudov et al., 2013). Hetercyclic amines are also widely used in the synthesis of Schiff bases, which provide different kinds of noncovalent interactions. As a further study in this field, we report herein the crystal structure and Hirshfeld surface analysis of the title compound. ISSN 2056-9890

Supramolecular features and Hirshfeld surface analysis
In the crystal, centrosymmetrically related cations and anions are linked via pairs of N-HÁ Á ÁBr hydrogen bonds (Table 1) into dimeric units forming rings of R 2 4 (8) graph-set motif (Fig. 2). The dimers are further connected by weak C-HÁ Á ÁBr interactions to form chains running parallel to [110].
Hirshfeld surface analysis was used to investigate the presence of hydrogen bonds and intermolecular interactions in the crystal structure. 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 2D fingerprint plots (Spackman & McKinnon, 2002). The plots of the Hirshfeld surface mapped over d norm using a standard surface resolution with a fixed colour scale of À1.4747 (red) to 1.2166 a.u. (blue) is shown in Fig. 3. This plot was generated to quantify and visualize the intermolecular interactions and to explain the observed crystal packing.
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 The molecular structure of the title salt. Displacement ellipsoids are drawn at the 30% probability level. H atoms are shown as spheres of arbitrary radius. The minor-disorder component has been omitted for clarity Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) Àx þ 1; Ày; Àz þ 1; (ii) x þ 1; y þ 1; z.

Figure 2
A view of the intermolecular N-HÁ Á ÁBr hydrogen bonds of the title salt in the unit cell. The minor-disorder component has been omitted for clarity Figure 3 Hirshfeld surface of the title salt mapped with d norm .
triangles, then there are nointeractions. Fig. 4 clearly suggest that there are nointeractions present in the title salt.

Figure 4
Hirshfeld surface of the title salt mapped with shape index.

Figure 5
The 2D (Fig. 6b). All the contributions to the Hirshfeld surface are given in Table 2.
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 minor-disorder component of the ring, also contribute to the molecular packing. In addition, there are also inversion-related ClÁ Á ÁCl halogen bonds and C-ClÁ Á Á(ring) contacts.
In the remaining structures, the 3-N atom carries a Csubstituent instead of an N-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-(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 N atom, while YITCAF (Martem'yanova et al., 1993b) is a product of the reaction of 3-nitro-5-methoxy-, 3-nitro-5chloro-and 3-bromo-5-nitrosalicylaldehyde with the heterocyclic base to form the salt-like complexes.

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); 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (