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pyrrolo[3,4-c]pyrrole-1,4-dione can be applicable as useful pigments. One of them, 3,6-bis(4-chlorophenyl)pyrrolo[3,4c]pyrrole-1,4-dione, is now on the market. Several structural studies have been undertaken on compounds consisting of this choromophore system.1 Most of them have aromatic substituents at the 3 positions of the chromophore and no large substituents at the nitrogen atom. In order to understand the effect of large substituents at the nitrogen atom on the molecular structure, we undertook an X-ray analysis of the title compound (Fig.1(I)). A peony needle crystal with dimensions of 0.5 × 0.1 × 0.1 mm was obtained by sublimation, and was used for diffraction experiments. The crystal and experimental data are given in Table 1. The structure was solved by direct methods and refined by full-matrix least-squares methods with anisotropic temperature factors for the non-H atoms. All of the H atoms were located by geometrical calculations, and were refined with isotropic temperature factors. The atomic parameters for the non-hydrogen atoms are listed in Table 2. Selected bond distances and angles are listed in Table 3. An ORTEP III4 drawing of the title compound together with the atomic numbering is shown in Fig. 2. The molecule, which belongs to the point group Ci, is not planar. Although the pyrrolo[3,4-c]pyrrole ring system is essentially planar, the dihedral angles between the least-squares planes of the pyrrole ring and naphthalene and benzene rings are 12.74(6) and 92.73(7) ̊, respectively. In 2,5-dimethyl-3,6diphenylpyrrolo[3,4-c]pyrrole-1,4-dione (Fig. 1(II)),1 the dihedral angle between the least-squares planes of the pyrrole and phenyl rings is 30.5(2) ̊. The C3–C20 distance of 1.463(2)Å is significantly shorter than the value of 1.496(3)Å found for biphenyl.5 A similarly shortened bond of 1.460(6)Å is observed for (II). The values of the bond distances and the angles in the chromophore moiety are in good agreement with those for (II). This indicates that the benzyl group attached at the nitrogen atom does not significantly influence the geometry of the chromophore. There is an intramolecular CH···O hydrogen bond between the C21 and O1 atoms [C21···O1 3.099(2), C21–H 0.99(2), H···O1 2.15(2)Å and C21–H···O1 159(2) ̊]. 221 ANALYTICAL SCIENCES FEBRUARY 2002, VOL. 18 2002 © The Japan Society for Analytical Chemistry

Crystal Structure of 2,5-Bis-(3,5-dimethylbenzyl)-3,6-dinaphthalen-2-yl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione