(E)-Methyl 3-(10-bromoanthracen-9-yl)acrylate

In the title molecule, C18H13BrO2, the anthracene unit forms an angle of 46.91 (2)° with the mean plane of the methyl acrylate moiety. In the crystal, the molecules arrange themselves into strands parallel to [010] and, due to the crystal symmetry, there are eight strands crossing the unit cell. In each strand, molecules form short C—H⋯O and C—H⋯π contacts and have their anthracene groups parallel to each other. Neighboring strands, related by a c-glide operation, are connected via C—H⋯O interactions and form a layer parallel to (100). The arrangement of the acrylate and anthracene groups in the crystal do not allow for [2 + 2] or [4 + 4] cycloaddition.

In the title molecule, C 18 H 13 BrO 2 , the anthracene unit forms an angle of 46.91 (2) with the mean plane of the methyl acrylate moiety. In the crystal, the molecules arrange themselves into strands parallel to [010] and, due to the crystal symmetry, there are eight strands crossing the unit cell. In each strand, molecules form short C-HÁ Á ÁO and C-HÁ Á Á contacts and have their anthracene groups parallel to each other. Neighboring strands, related by a c-glide operation, are connected via C-HÁ Á ÁO interactions and form a layer parallel to (100). The arrangement of the acrylate and anthracene groups in the crystal do not allow for [2 + 2] or [4 + 4] cycloaddition.

Experimental
Cg1 is the centroid of the C2-C7 ring. Data collection: CrysAlis PRO (Agilent, 2013); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) within OLEX2 (Dolomanov et al., 2009); molecular graphics: PLATON (Spek, 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 and PLATON. In our interest in [2 + 2]-photocycloaddition of anthracene derivatives in the crystal (Sonoda, 2011;Schmidt, 1964) (Table 1) and form a layer parallel to (100). The close contacts C16-H16···O2 and C15-H15···Cg1 (π) (Table 1) link the neighboring molecules within each strand ( Figure 2). The average plane of an anthracenyl unit of a molecule in one strand forms an angle of 78.37 (2)° with an anthracenyl unit of a molecule in the neighboring strand.While the anthracenyl units of the molecules in one strand are parallel to each other and exhibit an off-set that would be beneficial for π-π interaction, they are too far apart (distance between the averaged planes of the respective anthracenyl units: 3.362 (2) Å) to exhibit a strong π-π interaction, in contrast with the non-brominated parent compound (Bugenhagen et al., 2013).
The closest distance between double bonds of two molecules, which are molecules in one strand, is 5.321 (3) Å.

Refinement
All carbon-bound hydrogen atoms were placed in calculated positions with C-H distances of 0.93 -0.96 Å and refined as riding with U iso (H) =xU eq (C), where x = 1.5 for methyl and x = 1.2 for all other H-atoms.

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.