In the title compound, C₁₄H₈Cl₃FN₂, the planes of the 4-fluorophenyl ring and the 4-chlorophenyl ring make a dihedral angle of 56.13 (13)°. In the crystal, molecules are stacked in a column along the a axis via a weak C—H...Cl hydrogen bond and face-to-face π–π stacking interactions [centroid–centroid distances = 3.8615 (18) and 3.8619 (18) Å]. The crystal packing is further stabilized by short Cl...Cl contacts. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from Cl...H/H...Cl (31.2%), H...H (14.8%), C...H/H...C (14.0%), F...H/H...F (12.8%), C...C (9.0%) and Cl...Cl (6.7%) interactions.

In the title compound, C₁₄H₈Cl₂FN₃O₂, the 4-fluorophenyl ring and the nitro-substituted benzene ring form a dihedral angle of 63.29 (8)°. In the crystal, molecules are linked by C—H...O hydrogen bonds into chains running parallel to the c axis. The crystal packing is further stabilized by C—Cl...π, C—F...π and N—O...π interactions. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H...O/O...H (15.5%), H...H (15.3%), Cl...H/H...Cl (13.8%), C...H/H...C (9.5%) and F...H/H...F (8.2%) interactions.

In the cation of the title salt, C₁₆H₁₄Cl₂N₃S⁺·Br⁻, the central thiazolidine ring adopts an envelope conformation. The phenyl ring is disordered over two sites with a refined occupancy ratio of 0.541 (9):0.459 (9). In the crystal, C—H...Br and N—H...Br hydrogen bonds link the components into a three-dimensional network with the cations and anions stacked along theb-axis direction. Weak C—H...π interactions, which only involve the minor disorder component of the ring, also contribute to the molecular packing. In addition, there are also inversion-related Cl...Cl halogen bonds and C—Cl...π (ring) contacts. A Hirshfeld surface analysis was conducted to verify the contributions of the different intermolecular interactions.

In the two isotypic title compounds, C₁₄H₈BrCl₂N₃O₂, (I), and C₁₄H₈Cl₃N₃O₂, (II), the substitution of one of the phenyl rings is different [Br for (I) and Cl for (II)]. Aromatic rings form dihedral angles of 60.9 (2) and 64.1 (2)°, respectively. Molecules are linked through weak X...Cl contacts [X = Br for (I) and Cl for (II)], C—H...Cl and C—Cl...π interactions into sheets parallel to the ab plane. Additional van der Waals interactions consolidate the three-dimensional packing. Hirshfeld surface analysis of the crystal structures indicates that the most important contributions for the crystal packing for (I) are from C...H/H...C (16.1%), O...H/H...O (13.1%), Cl...H/H...Cl (12.7%), H...H (11.4%), Br...H/H...Br (8.9%), N...H/H...N (6.9%) and Cl...C/C...Cl (6.6%) interactions, and for (II), from Cl...H / H...Cl (21.9%), C...H/H...C (15.3%), O...H/H...O (13.4%), H...H (11.5%), Cl...C/C...Cl (8.3%), N...H/H...N (7.0%) and Cl...Cl (5.9%) interactions. The crystal of (I) studied was refined as an inversion twin, the ratio of components being 0.9917 (12):0.0083 (12).

In the cation of the title salt, C₁₆H₁₅FN₃S⁺·Br⁻, 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)° with the fluorophenyl ring and the major- and minor-disorder components of the phenyl ring, respectively. The central thiazolidine ring adopts an envelope conformation. In the crystal, centrosymmetrically related cations and anions are linked into dimeric units via N—H...Br hydrogen bonds, which are further connected by weak C—H...Br hydrogen bonds into chains parallel to [110]. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H...H (44.3%), Br...H/H...Br (16.8%), C...H/H...C (13.9%), F...H/H...F (10.3%) and S...H/H...S (3.8%) interactions.