[3-Benzoyl-2,4-bis(3-nitrophenyl)cyclobutyl](phenyl)methanone

The asymmetric unit of the title compound, C30H22N2O6, comprises a half-molecule of the cyclobutane derivative. The least-squares planes defined by the respective C atoms of the aromatic substituents intersect at angles of 76.81 (7) and 89.22 (8)° with the least-squares plane defined by the C atoms of the cyclobutane ring. In the crystal, C—H⋯O contacts connect the molecules into a three-dimensional network. The shortest centroid–centroid distance between the two different aromatic rings is 3.9601 (8) Å.

The asymmetric unit of the title compound, C 30 H 22 N 2 O 6 , comprises a half-molecule of the cyclobutane derivative. The least-squares planes defined by the respective C atoms of the aromatic substituents intersect at angles of 76.81 (7) and 89.22 (8) with the least-squares plane defined by the C atoms of the cyclobutane ring. In the crystal, C-HÁ Á ÁO contacts connect the molecules into a three-dimensional network. The shortest centroid-centroid distance between the two different aromatic rings is 3.9601 (8) Å .
The title compound, [3-benzoyl-2,4-bis(3-nitrophenyl)cyclobutyl](phenyl)methanone, features a central cyclobutane moiety that bears one aromatic substituent on each carbon atom. Due to the centrosymmetry of the molecule, the relative orientation of these substituents corresponds to cis-trans-cis-trans. The small puckering amplitude precludes a puckering analysis of this ring (Cremer & Pople, 1975). The least-squares planes defined by the respective carbon atoms of the aromatic substituents intersect with the least-squares plane defined the carbon atoms of the cyclobutane ring at angles of 76.81 (7) ° and 89.22 (8) °. The aforementioned planes of the two different aromatic moieties in the asymmetric unit enclose an angle of 24.09 (6) ° (Fig. 1).
In the crystal, intermolecular C-H···O contacts whose range falls by more than 0.1 Å below the sum of van-der-Waals radii of the respective atoms can be observed. These are supported by the hydrogen atom in para position of the nonsubstituted phenyl group as well as all methine-type hydrogen atoms while the hydrogen atoms of the nitrophenyl moiety do not take part in such contacts. All oxygen atoms present in the molecule act as acceptors. Furthermore, one intramolecular C-H···O contact between a carbonyl group and a methine-type hydrogen atom is apparent. In total, the molecules are connected to a three-dimensional network. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for these contacts is S(5)C 1 1 (8)C 1 1 (13)R 2 2 (10) on the unary level. Metrical parameters as well as information about the symmetry of these contacts are summarized in Table 1. The shortest intercentroid distance between two aromatic systems was measured at 3.9601 (8) Å and is apparent between the two different aromatic substituents (Fig.   2). The packing of the title compound in the crystal structure is shown in Figure 3.

Experimental
To a mixture of 3-nitrobenzaldehyde (1.51 g, 0.01 mol) and acetophenone (1.16 ml, 0.01 mol) in ethanol (50 ml), a sodium hydroxide solution (10%, 10 ml) was added. The mixture was stirred at 278-283 K for 3 h. The precipitate formed was collected by filtration and purified by recrystallization from ethanol. Single crystals suitable for the X-ray diffraction study were grown from methanol by slow evaporation at room temperature. The synthesized chalcone was dimerized during crystallization.

Refinement
Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic carbon atoms and C-H 1.00 Å for methine groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C).