3-(4-Nitrobenzyl)-4H-chromen-4-one

In the title compound, C16H11NO4, the dihedral angle between the ten-membered chromen-4-one ring system (r.m.s. deviation = 0.0095 Å) and the benzene ring is 86.16 (5)°. In the crystal, molecules are linked into a three-dimensional network by weak C—H⋯O hydrogen bonds. The crystal studied was a non-merohedral twin, with the minor twin component refining to 0.093 (1).


Hong Su Comment
Homoisoflavonoids are a group of naturally occurring oxygen heterocyclic compounds, related to the flavonoids, which consists of a chromone skeleton with a benzyl or benzylidene group at C-3. In the 3-benzyl-4-chromonanone class of homoisoflavonoid, an extra methylene group exists between the phenyl group and the chromone skeleton. They are commonly synthesized by either the acid or base catalysed condensation of an aromatic aldehyde with chromanone (Desideri et al., 2011, Valkonen et al., 2012. Naturally occurring homoisoflavonoids are normally oxygenated and have shown a wide range of biological activities (Abegaz et al., 2007).
The molecular structure of the title compound is shown in Fig. 1. The dihedral angle between the 10-membered coplanar chromone ring and the nitrated phenyl ring is 86.16 (5)°. In the crystal, the inter-moclecular weak hydrogen bonds C-H···O link the molecules into a three dimentional network, as shown in Fig.2. The details of the hydrogen bonds are shown in Table 1.

Experimental
A mixture of chroman-4-one (1.02 g, 6.749 mmol), 4-nitrobenzaldehyde (1.22 g, 8.099 mmol) and 10-15 drops of piperidine was heated at 80°C for 12 hrs. The reaction mixture was monitored for completion by thin layer chromatography. Upon completion, the reaction mixture was cooled, diluted with water and neutralized using 10% HCl.
To the viscous reaction mixture, 20 ml of ethyl acetate was added. Upon the addition of hexane to the reaction mixture, the homoisoflavonoid precipitated out. The powdered product was filtered, washed with hexane and dried under vacuum.

Refinement
The crystal was a non-merohedral twin. Two domains were indexed using CELL_NOW1 and the intensity data for each domain was then integrated, reduced using the program SAINT. The combined data were scaled and absorption correction performed using TWINABS. The structure was solved by direct methods using SHELXS97 and refined by full-matrix least-squares methods based on F2 using SHELXL97. All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were placed in idealized positions and refined with geometrical constraints. The structure was refined to R factor = 0.0504, BASF = 0.093 (1) for HKLF5.

Special details
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.  (7) 0.0303 (7) 0.0077 (7) 0.0045 (6)  Symmetry codes: (i) −x+3/2, y−1/2, −z+1/2; (ii) x−1/2, −y+3/2, z−1/2; (iii) −x+5/2, y−1/2, −z+1/2; (iv) −x+1, −y+1, −z+1; (v) x+1, y, z.