2-{2-[2-(1,3-Dioxoisoindol-2-yl)ethoxy]ethyl}isoindole-1,3-dione

In the molecule of the title compound, C20H16N2O5, the phthalimide fragments are almost planar, with r.m.s. deviations of 0.018 and 0.020 Å, and make a dihedral angle of 53.64 (3)°. The molecular and crystal structures are stabilized by a weak intermolecular C—H⋯O, C—H⋯π and C=O⋯π [2.883 (1) Å] interactions and aromatic π–π stacking interactions with a centroid–centroid distance of 3.6189 (7) Å.

In the molecule of the title compound, C 20 H 16 N 2 O 5 , the phthalimide fragments are almost planar, with r.m.s. deviations of 0.018 and 0.020 Å , and make a dihedral angle of 53.64 (3) . The molecular and crystal structures are stabilized by a weak intermolecular C-HÁ Á ÁO, C-HÁ Á Á and C OÁ Á Á [2.883 (1) Å ] interactions and aromaticstacking interactions with a centroid-centroid distance of 3.6189 (7) Å .

Experimental
The title compound is received by the slightly modified technique (Yatsimirskii et al.,1987). 24 g (0.12 mole) potassium phthalimide and 8 ml (0.05 mole) β,β'-dichloroethyl ether were taken in a three-necked round-battomed flask supplied with a reflux condenser and a mechanical stirrer. Reaction is carried out at 463-473 K within 2.5 hours by stirring. After corresponding chemical treatments (Yatsimirskii et al.,1987) reaction product was recrystallized from 1:1 mixture of ethanol and chloroform. 13.99 g (56 %) title compound , with m.p. of 421-423 K was received.

Refinement
Carbon-bound H atoms were positioned geometrically and treated as riding on their C atoms, with C-H distances of 0.93 Å (aromatic) and 0.97 Å (CH 2 ) and were refined with Uiso(H)=1.2Ueq(C). Fig. 1. Molecular structure of the title compound with 50% probability displacement ellipsoids for non-H atoms.  supplementary materials sup-3

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.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.