2-[(E)-2,5-Dimethoxybenzylidene]indan-1-one

In the title compound, C18H16O3, the mean plane of the nine-membered indane system makes a dihedral angle of 3.71 (17)° with the benzene ring of the dimethoxyphenyl group. The molecular conformation is stabilized by intramolecular C—H⋯O hydrogen contacts. The crystal structure is stabilized by intermolecular C—H⋯O interactions, which link neighbouring molecules into one-dimensional extended chains along the [100] direction. In the structure, C—H⋯π interactions are also observed.

In the title compound, C 18 H 16 O 3 , the mean plane of the ninemembered indane system makes a dihedral angle of 3.71 (17) with the benzene ring of the dimethoxyphenyl group. The molecular conformation is stabilized by intramolecular C-HÁ Á ÁO hydrogen contacts. The crystal structure is stabilized by intermolecular C-HÁ Á ÁO interactions, which link neighbouring molecules into one-dimensional extended chains along the [100] direction. In the structure, C-HÁ Á Á interactions are also observed.

Related literature
For styryl dyes and their applications, see: Ying et al. (1990); He et al. (1995). For bond-length data, see: Allen et al. (1987). For details of the Flack parameter, see : Flack & Schwarzenbach (1988 Table 1 Hydrogen-bond geometry (Å , ). In the title compound (I) (Fig. 1), all bond lengths (Allen et al., 1987) and angles are within normal ranges. The ninemembered indane ring is almost planar, with the maximum deviations of -0.017 (4) and 0.021 (4) Å for atoms C6 and C8, respectively. The mean plane of the indane ring makes a dihedral angle of 3.71 (17) °, with the benzene ring of the dimethoxy phenyl group.
The molecular conformation is stabilized by intramolecular C-H···O hydrogen contacts (Table 1). The crystal structure is stabilized by intermolecular C-H···O interactions, which link neighbouring molecules into 1-D extended chains along the [100] direction (Fig. 2). In the structure, C-H···π interactions are also observed (Table 1).

Experimental
An equivalent molar quantities of 2,5-dimethoxybenzaldehyde (4.40 g, 26.5 mmol) and 1-indanone (3.5 g, 26.5 mmol) were dissolved in 25 ml e thanol, and then heated at reflux. Pipyridine (1 ml) was added to the solution, and reflux was continued for 5 h. The solution was cooled to room temperature, and the solid products were filtered, and washed with ethanol (25 ml) to give yellow crystals.

Refinement
All H atoms bonded to the C atoms were positioned geometrically, with C-H distances in the range 0.93-0.97 Å, and refined using a riding approximation model, with U iso (H) = 1.5U eq of the carrier atom for methyl H and 1.2U eq for the remaining H atoms. The calculation of the Flack (Flack & Schwarzenbach, 1988) parameter was suppressed by the use of the MERG 4 instruction in SHELXL97 (Sheldrick, 2008), as the lack of anomalous scatterers did not allow the determination of the absolute configuration from the X-ray measurements.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )