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.