Experimental

R factor = 0.057; wR factor = 0.171; data-to-parameter ratio = 12.9. In the asymmetric unit of the title compound, C19H16O2, there are two symmetry-independent molecules (A and B) that differ in the conformation of the ester ethoxy group. In the crystal, the molecules form inversion dimers via pairs of C— H O interactions. Within the dimers, the anthracenyl units have interplanar distances of 0.528 (2) and 0.479 (2) A ̊ for dimers of molecules A and B, respectively. Another short C— H O contact between symmetry-independent dimers links them into columns parallel to [101]. These columns are arranged into (111) layers and there are – stacking interactions [centroid–centroid distances = 3.6446 (15) and 3.6531 (15) Å] between the anthracenyl units from the neighbouring columns. In addition, there are C—H interactions between the anthracenyl unit of dimers A and dimers B within the same column. Related literature For an analogous preparation of the title compound, see: Nguyen & Weizman (2007). For modeling of the title compound at the B3LYP/6–31G * level, see: Coleman (2007). For crystal structures of photodimerizable arylenes, see: Vishnumurthy et al. (2002); Mascitti & Corey (2006); Sonoda (2011); Schmidt (1964). For the photodimerization of anthra-cenes in the crystal, see: Schmidt (1971); Ihmels et al. (2000)