2,7-Dimethoxy-1-(4-nitrobenzoyl)-naphthalene

In the title compound, C19H15NO5, the dihedral angle between the naphthalene ring system and the benzene ring is 61.97 (5)°. The dihedral between the naphthalene ring system and the bridging carbonyl C—C(=O)—C plane is 54.68 (6)°, far larger than that [12.54 (7)°] between the phenyl group and the bridging carbonyl group. The nitro group and the phenyl ring are almost coplanar [O—N—C—C torsion angle = 2.94 (19)°]. In the crystal, molecules are linked by C—H⋯π interactions and the phenyl rings are involved in a centrosymmetric π–π interaction with a perpendicular distance of 3.523 Å and a lateral offset of 1.497 Å. In addition, weak intermolecular C—H⋯O hydrogen bonds are formed between an H atom of one methoxy group and a nearby carbonyl O atom.

In the title compound, C 19 H 15 NO 5 , the dihedral angle between the naphthalene ring system and the benzene ring is 61.97 (5) . The dihedral between the naphthalene ring system and the bridging carbonyl C-C( O)-C plane is 54.68 (6) , far larger than that [12.54 (7) ] between the phenyl group and the bridging carbonyl group. The nitro group and the phenyl ring are almost coplanar [O-N-C-C torsion angle = 2. 94 (19) ]. In the crystal, molecules are linked by C-HÁ Á Á interactions and the phenyl rings are involved in a centrosymmetricinteraction with a perpendicular distance of 3.523 Å and a lateral offset of 1.497 Å . In addition, weak intermolecular C-HÁ Á ÁO hydrogen bonds are formed between an H atom of one methoxy group and a nearby carbonyl O atom.

Comment
In the course of our study on electrophilic aromatic aroylation of 2,7-dimethoxynaphthalene, peri-aroylnaphthalene compounds have proven to be formed regioselectively with the aid of suitable acidic mediators (Okamoto & Yonezawa, 2009).
The molecular structure of (I) is displayed in Fig. 1 The molecular packing of (I) is mainly stabilized by van der Waals interactions. The molecules are aligned consecutively in stacks along the c axis ( Fig. 2). Adjacent 4-nitrophenyl groups related by crystallographic inversion centers are exactly antiparallel and the perpendicular distance between the mean planes is 3.523 Å (Fig. 3). The centroid-centroid distance between the two antiparallel phenyl rings is 3.8283 (8) Å and the lateral offset is 1.497 Å, indicating the presence of a π-π interaction.
Moreover, molecules are linked by two types of C-H···π interactions. The naphthalene ring acts as a hydrogen-bond donor and the π system of the naphthalene ring [C1-C10 ring (with centroid Cg1)] of an adjacent molecule acts as an accepter (C3-H3···π i ) (Fig. 4). The methyl group acts as a hydrogen-bond donor and the π system of the naphthalene ring [C1-C10 ring (with centroid Cg1)] of an adjacent molecule acts as an accepter (C19-H19C···π ii ) .
The crystal packing is additionally stabilized by intermolecular weak C-H···O hydrogen bonding between the carbonyl oxygen and a hydrogen atom of a nearby methyl group (C18-H18B···O1 iii ; Fig. 4 and Table 1).

Refinement
All the H atoms were found in difference maps and were subsequently refined as riding atoms, with C-H = 0.93 (aromatic) and 0.96 (methyl) Å, and U iso (H) = 1.2U eq (C). Fig. 1. Molecular structure of (I), with the atom-labeling scheme and displacement ellipsoids drawn at the 50% probability level.

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 > 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.