Two polymorphs of 1,8-dichloroanthracene

A second, monoclinic, polymorph of the title compound, C14H8Cl2, has been found. In addition to the structure of this monoclinic form, the structure of the previously described orthorhombic form [Desvergne, Chekpo & Bouas-Laurent (1978). J. Chem. Soc. Perkin Trans. 2, pp. 84-87; Benites, Maverick & Fronczek (1996). Acta Cryst. C52, 647-648] has been redetermined at low temperature and using modern methods. The low-temperature structure of the orthorhombic form is of significantly higher quality than the previously published structure and additional details can be derived. A comparison of the crystal packing of the two forms with a focus on weak intermolecular C - H ⋯Cl interactions shows the monoclinic structure to have one such interaction linking the molecules into infinite ribbons, while two crystallographically independent C - H ⋯Cl interactions give rise to an interesting infinite three-dimensional network in the orthorhombic crystal form.