(3aS,4R,5R,6S,7aR)-4,5-Dibromo-2-[4-(trifluoromethyl)phenyl]-2,3,3a,4,5,6,7,7a-octahydro-3a,6-epoxy-1H-isoindol-1-one: crystal structure and Hirshfeld surface analysis

In the crystal structure, molecule pairs generate rings with (8) motifs by dimeric C—H⋯O hydrogen bonds. These pairs of molecules form molecular layers parallel to the (100) plane by C—H⋯π and C—Br⋯π interactions. Interlayer van der Waals interactions stabilize the molecular packing.

Isoindoles are important structural units in many natural products and are widely used as drugs and as building-blocks for the construction of new N-containing heterocyclic compounds and functional materials (Nadirova et al., 2019;Zubkov et al., 2011Zubkov et al., , 2014. The biological and physical properties of N-heterocycles are dependent on the attached functional groups (Grudova et al., 2020;Zaytsev et al., 2017Zaytsev et al., , 2019Zaytsev et al., , 2020Asgarova et al., 2019;Khalilov et al., 2011;Yin et al., 2020). Thus, the functionalization of isoindole moieties with non-covalent bond donor/acceptor sites can improve their biological and photophysical properties as well as coordination ability (Wicholas et al., 2006).

Structural commentary
The asymmetric unit of the title compound ( Fig. 2) contains two crystallographically molecules of similar shape, hereafter referred to as molecules A (including atom C1) and B (including atom C21). The conformational differences between molecules A and B are highlighted in an overlay diagram shown in Fig. 3. The r.m.s. deviation of the overlay between the molecules A and B is 0.278 Å .

Figure 2
The two molecules (A and B) in the asymmetric unit of the title compound with displacement ellipsoids for the non-hydrogen atoms drawn at the 30% probability level. Hydrogen atoms are shown as spheres of arbitrary radius. The minor components of the disordered CF 3 groups were omitted for clarity. hydrogen bonds (Table 1). These pairs of molecules form a tetrameric supramolecular motif, by self-complementary C-HÁ Á Á connections (Fig. 4). Additionally, these building units are self-assembled via C-BrÁ Á Á interactions, generating a two-dimensional supramolecular network parallel to the (100) plane (Fig. 5). Interlayer van der Waals and interhalogen interactions stabilize molecular packing.

Hirshfeld surface analysis
For both molecules A and B, the intermolecular interactions (Table 2) were quantified using Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated twodimensional fingerprint plots (McKinnon et al., 2007) generated. The calculations and visualization were performed using CrystalExplorer17 (Turner et al., 2017). Fig. 6 shows the Hirshfeld surface of the title compound mapped over d norm in a fixed color scale of À0.2089 (red) to +1.1825 (blue) arbitrary units for molecule A and À0.2105 (red) to +1.2372 (blue) arbitrary units for molecule B, where the red spots indicate the intermolecular contacts shorter than the van der Waals separations. Fig. 7 shows the full two-dimensional fingerprint plot ( Fig. 7a) Table 1 Hydrogen-bond geometry (Å , ).

Figure 4
A view of the intermolecular C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á and C-BrÁ Á Á interactions in the unit cell of the title compound. Only the major components of the disordered CF 3 groups are shown.

Figure 5
A view of the molecular packing of the title compound along the a axis.
Only the major components of the disordered CF 3 groups are shown.

Table 2
Summary of short interatomic contacts (Å ) in the title compound.
Asterisks indicate symmetry-generated atoms Contact Distance Symmetry operation Fig.7c

Figure 6
Hirshfeld surfaces of molecules A and B of the title compound mapped with d norm .
In the crystal of IMUBIE, the molecules are linked into dimers by pairs of C-HÁ Á ÁO hydrogen bonds, thus generating R 2 2 (18) rings. The crystal packing is dominated by HÁ Á ÁH, BrÁ Á ÁH, HÁ Á Á and BrÁ Á Á interactions. In the crystal structures of OMEMAX, AGONUH, TIJMIK, YAXCIL, UPAQEI and ERIVIL, the molecules are linked by predominantly C-HÁ Á ÁO hydrogen bonds describing different hydrogen-bonding pattern connectivities. In OMEMAX, molecules form sheets lying parallel to the (002) plane. These sheets are connected only by weak van der Waals interactions. In the crystal of AGONUH, the molecules are connected in zigzag chains running along the b-axis direction. In TIJMIK, two types of C-HÁ Á ÁO hydrogen bonds are found, viz. R 2 2 (20) and R 4 4 (26) rings, with adjacent rings running parallel to the ac plane. Additionally, C-HÁ Á ÁO hydrogen bonds form a C(6) chain, linking the molecules in the b-axis direction. In the crystal of ERIVIL, the molecules are connected into R 2 2 (8) and R 2 2 (14) rings along the b-axis direction. In MIGTIG, the molecules are linked only by weak van der Waals interactions.

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 = 0.93-0.98 Å , and with U iso (H) = 1.2U eq (C). The F atoms of the trifluoromethyl groups (CF 3 ) of both molecules are disordered over two sets of sites with refined site occupancies      program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2020). 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. (