Conformational dimorphism of 2,2′-methylenebis(isoindoline-1,3-dione)

A new monoclinic polymorph of 2,2′-methylenebis(isoindoline-1,3-dione) with Z′ = 1 is reported.

In this study, a new monoclinic polymorph (space group C2/c) of 2,2 0 -methylenebis(isoindoline-1,3-dione), C 17 H 10 N 2 O 4 , is reported and compared to the previously reported triclinic polymorph (space group P1). Similarly, both polymorphs consist of a unique molecule in the asymmetric unit (Z 0 = 1). The molecular conformations of the two polymorphs are very similar, as shown by the r.m.s. deviation of 0.368 Å (excluding all H atoms). The intermolecular interactions of both polymorphs are described along with the Hirshfeld surface analysis, and the lattice energies are calculated.

Hirshfeld surface analysis
The Hirshfeld surface analysis and two-dimensional fingerprint plots were performed using CrystalExplorer version 17.5 (Spackman & Jayatilaka, 2009;Spackman & McKinnon, 2002;Turner et al., 2017). The HÁ Á ÁO/OÁ Á ÁH contact is the most populated contact and contributes 38.2 and 34.4% of the total intermolecular contacts of 1 and 1 (Fig. 4), respectively. The large red spots on the Hirshfeld surface mapped over d norm for 1 (Fig. 5) correspond to the intermolecular C3-H3AÁ Á ÁO3 and C15-H15AÁ Á ÁO2 hydrogen-bonds. The tips of the pseudo-mirrored sharp spikes at d e + d i ' 2.32 Å represent the shortest HÁ Á ÁO/OÁ Á ÁH contacts, corresponding to the intermolecular C3-H3AÁ Á ÁO3 hydrogen-bond. The HÁ Á ÁH contact is the second most populated contact and contributes An overlay diagram for the molecules of 1 (red) and 1 (blue).

Figure 3
A partial crystal packing diagram of 1 viewed along the b axis. Dashed lines represent weak intermolecular C-HÁ Á ÁO hydrogen bonds. Hydrogen atoms which are not involved in hydrogen bonding are omitted for clarity.

Figure 5
The Hirshfeld surface mapped over d norm for the molecule in the asymmetric unit of 1 hydrogen-bonded to two neighbouring molecules.

Figure 6
The Hirshfeld surface mapped over shape-index for 1.

Figure 7
The Hirshfeld surface mapped over curvedness for 1.

Lattice energy calculation
The C-H bond lengths in 1 and 1 were normalized to 1.08 Å and the lattice energies were calculated by using the CLP-PIXEL software package (Gavezzotti, 2003(Gavezzotti, , 2008. The calculated lattice energy of 1 (130.3 kJ mol À1 ) is slightly larger than for 1 (128.5 kJ mol À1 ), indicating that 1 is slightly more stable than 1 under ambient conditions.

Synthesis and crystallization
Single crystals of 1 were obtained from an unsuccessful synthesis of 2-{[(3-iodopyridin-4-yl)amino]methyl}isoindoline-1,3-dione by reacting N-(bromomethyl)phthalimide (1 mmol) and 4-amino-3-iodopyridine (1 mmol) in N,N-dimethylformamide (8 ml) with the presence of a catalytic amount of anhydrous potassium carbonate. The reaction solution was stirred for about 2 h at room temperature. Once the reaction was complete, the resultant mixture was poured into a beaker of ice-cooled water to obtain a precipitate , which was then filtered, washed with distilled water and dried. Crystals suitable for X-ray analysis were obtained by slow evaporation of a methanol solution.

2,2′-Methylenebis(isoindoline-1,3-dione)
Crystal data 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.