Crystal structure of 1,4-dieth­oxy-9,10-anthra­quinone

The asymmetric unit of the title compound, C18H16O4, contains two crystallographically independent mol-ecules. The anthra-quinone ring systems are slightly bent with dihedral angles of 2.33 (8) and 13.31 (9)° between the two terminal benzene rings. In the crystal, the two independent mol-ecules adopt slipped-parallel π-overlap with an average inter-planar distance of 3.45 A, forming a dimer; the centroid-centroid distances of the π-π inter-actions are 3.6659 (15)-3.8987 (15) A. The mol-ecules are also linked by C-H⋯O inter-actions, forming a tape structure along the a-axis direction. The crystal packing is characterized by a dimer-herringbone pattern.