3,7-Dihydroxy-3,7-diphenyl-2H,6H-pyrrolo[3,4-f]isoindole-1,5(3H,7H)-dione methanol disolvate

The asymmetric unit of the title compound, C22H16N2O4·2CH4O, contains one half-molecule and a methanol solvent molecule. The aromatic ring is oriented at a dihedral angle of 82.91 (3)° with respect to the planar indole ring systems. In the crystal structure, intermolecular O—H⋯O and N—H⋯O hydrogen bonds link the molecules into chains along the b axis.

The asymmetric unit of the title compound, C 22 H 16 N 2 O 4 Á-2CH 4 O, contains one half-molecule and a methanol solvent molecule. The aromatic ring is oriented at a dihedral angle of 82.91 (3) with respect to the planar indole ring systems. In the crystal structure, intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds link the molecules into chains along the b axis.

Comment
The title compound is an important intermediate used to synthesize the monomer 2,5-dibenzoyl-1,4-phenylenediamine, which can be utilized to synthesize organic semiconductors and conjugated polymers (Tonzola et al., 2003), which are of wide current interest for applications in electronic and optoelectronic devices including light-emitting diodes (Kolosov et al., 2002), thin film transistors and photovoltaic cells (Antoniadis et al., 1994). We report herein the crystal structure of the title compound, which is of interest to us in the field.
In the crystal structure, intermolecular O-H···O and N-H···O hydrogen bonds (Table 1) link the molecules into chains along b axis (Fig. 2), in which they may be effective in the stabilization of the structure.

Experimental
The title compound was prepared according to the literature method (Liu et al., 2008). Crystals suitable for X-ray analysis were obtained by dissolving the title compound (0.5 g) in methanol (50 ml), and evaporating the solvent slowly at room temperature for about 30 d.

Data collection
Enraf-Nonius CAD-4 diffractometer R int = 0.075 Radiation source: fine-focus sealed tube θ max = 26.0º Monochromator: graphite θ min = 2.1º T = 298(2) K h = −21→21 ω/2θ scans k = 0→8 Absorption correction: ψ scan (North et al., 1968) l = −24→24 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 > σ(F 2 ) is used only for calculating Rfactors(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.