Anthracene-1,4,9,10-tetraone

The asymmetric unit of the title compound, C14H6O4, contains three independent molecules (A, B and C). In molecule C, there are two disordered sets of two carbonyl O atoms [occupancies = 0.643 (11) and 0.357 (11)]. All three molecules are non-planar due to repulsion between two O atoms in peri positions on the anthracene ring, showing a slight difference in deviation of the carbonyl O atoms. The intramolecular distances between the two nearest O atoms are in the range of 2.685 (10)–2.766 (10) Å. In the crystal, molecules are linked by C—H⋯O and π–π [centroid–centroid distances = 3.615 (2), 3.844 (2) and 3.921 (2) Å] interactions, which lead to the formation of a herringbone-like arrangement.

The asymmetric unit of the title compound, C 14 H 6 O 4 , contains three independent molecules (A, B and C). In molecule C, there are two disordered sets of two carbonyl O atoms [occupancies = 0.643 (11) and 0.357 (11)]. All three molecules are non-planar due to repulsion between two O atoms in peri positions on the anthracene ring, showing a slight difference in deviation of the carbonyl O atoms. The intramolecular distances between the two nearest O atoms are in the range of 2.685 (10)-2.766 (10) Å . In the crystal, molecules are linked by C-HÁ Á ÁO and -[centroid-centroid distances = 3.615 (2), 3.844 (2) and 3.921 (2) Å ] interactions, which lead to the formation of a herringbone-like arrangement.

Comment
1,4,9,10-Anthracenetetraone (quinizarindiquinone) derivatives are important electrode matetrials (Isikli & Díaz, 2012) as well as effective dienophiles for Diels-Alder reaction (Adeva et al., 1997). Furthermore, the antitumor activity was also investigated (Jin et al., 1998). We have recently investigated the solid-state electrochemical properties of quinone compounds. To elucidate the molecular and packing structures, the crystallographic study of the title compound was carried out. The title compound (I) was synthesized as previously reported (Yoshino et al. (1981)). The title compound, C 14 H 6 O 4 , crystallizes with three molecules in the asymmetric unit, as shown in components A, B, and C ( Fig. 1). All the molecules are not planar because of the mutual repulsion of two oxygen atoms on the same side on the anthracene ring.

Experimental
The title compound was prepared according to the literature procedure (Yoshino et al., 1981). Single crystals suitable for X-ray analysis were obtained by recrystallization from ethyl acetate.

Refinement
All the H atoms were positioned geometrically and refined using a riding model with C-H = 0.94 Å and U iso (H) = 1.2U eq (C) for aromatic C-H. In molecule C, two O atoms on the peri positions of the anthracene ring are disordered over two positions with site occupancies of 0.643 (11) and 0.357 (11). During the refinement, the two O atoms were refined with a restrained C-O distance of 1.21 Å.

PROCESS-AUTO
Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 2012).  The molecular structure of the title compound, showing the atomic numbering and 40% probability displacement ellipsoids.

Figure 2
The packing diagram of the title compound. C-H···O interactions are shown as blue lines.

Data collection
Rigaku R-AXIS RAPID diffractometer Radiation source: fine-focus sealed x-ray tube Graphite monochromator Detector resolution: 10 pixels mm -1 φ and ω scans 27613 measured reflections 7016 independent reflections 3239 reflections with I > 2σ(I)