(E)-3-(4-Methylphenyl)-1-(4-nitrophenyl)prop-2-en-1-one

The asymmetric unit of the title compound, C16H13NO3, contains two independent molecules related approximately by a pseudo-twofold rotation axis. The dihedral angle between the nitrobenzene and methylphenyl rings is 42.18 (6)° in one molecule and 12.97 (6)° in the other. In both molecules, the nitro group is slightly twisted away from the attached benzene ring. In the crystal structure, the molecules are stacked along the b axis and are linked via C—H⋯O and C—H⋯π interactions.


S1. Comment
Substituted chalcones exhibit second-harmonic generation in crystalline form and possess optical limiting behavior with femtosecond laser pulse at 780 nm wavelength (Gu et al., 2008;Patil et al., 2006Patil et al., , 2007cAgrinskaya et al., 1999). The main idea behind the above studies was to introduce various donor/acceptor substituents [OCH 3 , N(CH 3 ) 2 , NH 2 , F, Cl, Br, CH 3 , NO 2 ] on either side of benzene rings and to observe the structure-activity relationship. In view of the importance of substituted chalcones, the title compound was synthesized and its crystal structure is reported here.
In the crystal structure ( Fig. 2), the molecules are stacked in as anti-parallel pairs approximately along the b axis. The crystal structure is stabilized by weak C-H···O hydrogen bonds and C-H···π interactions (Table 1) involving the C10A-C15A (centroid Cg1) and C1B-C6B (centroid Cg2) benzene rings.

S2. Experimental
The title compound was synthesized by the condensation of p-tolualdehyde (0.01 mol) with 4-nitroacetophenone (0.01 mol) in methanol (60 ml) in the presence of a catalytic amount of sodium hydroxide solution (5 ml, 30%). After stirring for 2 hr, the contents of the flask were poured into ice-cold water (500 ml) and left to stand for 5 hr. The resulting crude solid was filtered and dried. Yellow single crystals of the title compound suitable for X-ray structure determination were recrystallized from N,N-dimethylformamide (DMF).

S3. Refinement
All H atoms were placed in calculated positions, with d(C-H) = 0.93 Å, U iso (H) = 1.2U eq (C) for and aromatic H and d(C -H) = 0.96 Å, U iso (H) = 1.5U eq (C) for methyl H atoms. A rotating group model was used for the methyl groups.  The asymmetric unit of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering.
Weak C-H···O intramolecular interactions are drawn as dashed lines.

Figure 2
The crystal packing of the title compound, viewed along the a axis showing stacking of anti-parallel pairs of molecules approximately along the b axis. Hydrogen bonds are drawn as dashed lines.

3-(4-methylphenyl)-1-(4-nitrophenyl)prop-2-en-1-one
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.38 e Å −3 Δρ min = −0.26 e Å −3 Special details Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.