(Z)-3-(Anthracen-9-yl)-1-(2-ethoxyphenyl)prop-2-en-1-one1

The molecule of the title chalcone, C25H20O2, consisting of 2-ethoxyphenyl and anthracene rings bridged by a prop-2-en-1-one unit, is twisted and exists in the Z configuration with respect to the central C=C bond. The dihedral angle between the benzene and anthracene rings is 78.17 (9)°. The propene unit makes dihedral angles of 44.5 (2) and 81.1 (2)° with the benzene and anthracene rings, respectively. The ethoxy substituent is almost coplanar with the attached benzene ring [C—O—C—C torsion angle = 178.57 (19)°]. In the crystal, molecules are linked into chains along the a axis by weak C—H⋯O interactions. The crystal structure is further stabilized by C—H⋯π interactions.

The molecule of the title chalcone, C 25 H 20 O 2 , consisting of 2ethoxyphenyl and anthracene rings bridged by a prop-2-en-1one unit, is twisted and exists in the Z configuration with respect to the central C C bond. The dihedral angle between the benzene and anthracene rings is 78.17 (9) . The propene unit makes dihedral angles of 44.5 (2) and 81.1 (2) with the benzene and anthracene rings, respectively. The ethoxy substituent is almost coplanar with the attached benzene ring [C-O-C-C torsion angle = 178. 57 (19) ]. In the crystal, molecules are linked into chains along the a axis by weak C-HÁ Á ÁO interactions. The crystal structure is further stabilized by C-HÁ Á Á interactions.
We have previously reported the crystal structures of several chalcone derivatives containing the anthracene moiety which show interesting fluorescence properties Chantrapromma et al., 2009Chantrapromma et al., , 2010. Due to its various interesting properties the title chalcone derivative (I) was synthesized in order to study its NLO and fluorescence properties.
The title compound crystallizes in the orthorhombic noncentrosymmetric space group P2 1 2 1 2 1 and therefore it should exhibit second-order non-linear optic properties. In addition our experiment shows that (I) has fluorescence property. Herein the crystal structure of (I) is reported.
The molecule of (I) (  (Allen et al., 1987) and are comparable with those found in related structures Suwunwong et al., 2009).
In the crystal packing, the molecules are linked into chains along the a axis through the prop-2-en-1-one unit by weak C-H···O interactions (Fig. 2). The crystal structure is further stabilized by C-H···π interactions (Table 1); Cg 1 and Cg 2 are the centroids of the C1-C6 and C10-C11/C16-C18/C23 rings, respectively.

Experimental
The title compound was synthesized by the condensation of anthracene-9-carbaldehyde (2 mmol, 0.41 g) with 2-ethoxyacetophenone (2 mmol, 0.33 g) in ethanol (40 ml) in the presence of NaOH(aq) (5 ml, 20%). After stirring for 4 hr at room temperature, a yellow solid appeared and was then collected by filtration, washed with distilled water and dried in air. Yellow plate-shaped single crystals of the title compound suitable for X-ray structure determination were recrystalized from methanol by slow evaporation of the solvent at room temperature after several days, Mp. 419-421 K.

Refinement
All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic and CH, 0.97 Å for CH 2 and 0.96 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom supplementary materials sup-2 for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 0.80Å from atom C8 and the deepest hole is located at 0.76 Å from atom C10. A total of 2321 Friedel pairs were merged before final refinement as there is no large anomalous dispersion for the determination of the absolute configuration. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme.