Crystal structure and Hirshfeld surface analysis of (E)-3-[(4-methylbenzylidene)amino]-5-phenylthiazolidin-2-iminium bromide N,N-dimethylformamide monosolvate

In the crystal, each cation is connected to two anions by N—H⋯ Br hydrogen bonds, forming an (8) motif parallel to the (10) plane, while the N,N-dimethylformamide molecules are linked to the cations by C—H⋯O contacts.


Figure 1
The molecular structure of the title salt, showing displacement ellipsoids drawn at the 30% probability level.

Figure 3
Crystal packing for the title salt viewed along the a-axis direction. Dashed lines indicate N-HÁ Á ÁBr hydrogen bonds and C-HÁ Á ÁO contacts.

Supramolecular features
In the crystal, each cation is connected to two anions by N-HÁ Á ÁBr hydrogen bonds forming an R 2 4 (8) motif parallel to the (101) plane, while N,N-dimethylformamide molecules are linked to the cations by C-HÁ Á ÁO contacts (Table 1; Figs. 2, 3 and 4). Furthermore, van der Waals interactions between the cations, anions and N,N-dimethylformamide molecules stabilize the crystal structure in three dimensions.

Hirshfeld surface analysis
Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) was used to investigate the hydrogen bonds and intermolecular interactions in the crystal structure. This was performed using CrystalExplorer3.1 (Wolff et al., 2012), and comprised d norm surface plots and two-dimensional fingerprint plots (Spackman & McKinnon, 2002). The shorter and longer contacts are indicated as red and blue spots, respectively, on the Hirshfeld surfaces, and contacts with distances approximately equal to the sum of the van der Waals radii are represented as white spots. The contribution of interatomic contacts (Table 2) to the d norm surface of the title compound is shown in Fig. 5. Fig. 6 indicates by the absence of red and blue triangles on the shape-index surface thatstacking interactions are not present in the crystal structure. Fig. 7(a) shows the 2D fingerprint plot of the sum of the contacts contributing to the Hirshfeld surface represented in normal mode while those delineated into HÁ Á ÁH, CÁ Á ÁH/ HÁ Á ÁC and BrÁ Á ÁH/HÁ Á ÁBr contacts are given in Fig. 7b Table 2 Summary of short interatomic contacts (Å ) in the title salt.

Figure 5
A view of the three-dimensional Hirshfeld surface for the title salt, plotted over d norm in the range À0.4961 to 1.2178 a.u. N-HÁ Á ÁBr hydrogen bonds and C-HÁ Á ÁO contacts are shown.

Table 3
Percentage contributions of interatomic contacts to the Hirshfeld surface for the title salt.

Database survey
The other closely related compounds are UDELUN (Akkurt et al., 2018a) and ZIJQAN (Akkurt et al., 2018b). In the crystal structure of UDELUN, the 3-N atom of the cation carries an N substituent, as found in the title compound. In the crystal, 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 and inversion-related ClÁ Á ÁCl halogen bonds and C-ClÁ Á Á(ring) contacts also contribute to the molecular packing. In the crystal of ZIJQAN, the cations, anions and water molecules are linked into a three-dimensional network, which forms cross layers parallel to the (120) and (120) planes via O-HÁ Á ÁBr, N-HÁ Á ÁBr and N-HÁ Á ÁN hydrogen bonds. Furthermore, C-HÁ Á Á interactions also help in the stabilization of the molecular packing.
Furthermore, in WILBIC, the thiazolidine ring adopts a twist conformation. In one of two molecules in the asymmetric unit of WILBOI, the thiazolidine ring is essentially planar, in the other it adopts a twist conformation. In the two molecules in the asymmetric unit of WILBOI01 and in YOPLUK, the thiazolidine rings exhibit a twist conformation. In YITCAF, the disordered thiazolidine ring has two components, which are planar. In YOPLUK, the thiazolidine ring is slightly puckered, with the nitrogen atom in an almost planar configuration. In the cations of UDELUN and ZIJQAN, the thiazolidine rings have an envelope conformation.

Synthesis and crystallization
To a solution of 3-amino-5-phenylthiazolidin-2-iminium bromide (1 mmol) in ethanol (20 ml) was added 4-methylbenzaldehyde (1 mmol). The mixture was refluxed for 2 h and then cooled. The reaction product precipitated from the reaction mixture as colorless crystals, was collected by filtration, washed with cold acetone (yield 54%; m.p. 501-502 K), and recrystallized from dimethylformamide to obtain single crystals.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. All H atoms were placed geometrically (N-H = 0.90 Å and C-H = 0.93-0.98 Å ) and refined as riding atoms with U iso (H) = 1.2 or 1.5U eq (C, N).