2,3-Dichloro-5,8-dimethoxy-1,4-naphthoquinone

In the crystal structure of the title compound, C12H8Cl2O4, molecules crystallize in planes parallel to (-204) with an interplanar distance of 3.288 (2) Å [centroid–centroid distance = 3.819 (2) and slippage = 1.932 (2) Å]. The structure features C—H⋯O interactions involving methoxy and aromatic H atoms and the carbonyl O atoms as well as a C—H⋯Cl interaction involving an aromatic H atom. In addition there are short interhalogen contacts between adjoining molecules [Cl⋯Cl = 3.3709 (5) Å].

Data collection: CrysAlis PRO (Oxford Diffraction, 2007); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL. Compounds with the methoxy and chloro groups on the 1, 4-naphthoquinone skeleton were reported to show inhibitory effects on cancerous cells (Huang et al., 1998;Lien et al., 1997). 2,3-Dichloro-5,8-dimethoxy-1,4-naphthoquinone, C 12 H 8 Cl 2 O 4 , was synthesized as a potential anticancer agent and has been reported to exhibit anti-inflammatory, antiplatelet, anti-allergic and anticancer activities (Huang et al., 1998;Copeland et al., 2007). This biological function is based on chemical properties inherent in molecule. To understand its biological behavior, therefore, it is of great importance to determine the structural property and its molecular dimensions. The methoxy and chloro group in the quinoid ring give it interesting redox and biological properties as well as an excellent coordination site (Driebergen et al., 1986;Scheuermann et al., 2009). The coordinating potential of the molecule could be used as a tool for the formation of new organometallic compounds (Scheuermann et al., 2009).
The molecules in the title compound crystallize in planes parallel to (-2 0 4) with an interplanar distance of 3.288Å forming a charge transfer complex. The distance between the overlapping planes of neighboring molecules is 3.385 (3) Å and 3.653 (3) Å. There are intermolecular interactions between both a methoxy hydrogen and an aromatic hydrogen and the carbonyl O atoms. Intermolecular interactions are also observed between chlorine atom and the aromatic and methoxy H atoms. In addition there are short interhalogen contacts between adjoining molecules (Cl1···Cl2 3.3709 (5) Å) These C -H···Cl, C-H···O and Cl···Cl interactions in the crystal structure link the molecules to produce a three dimensional network.

Figure 1
Diagram of C 12 H 8 Cl 2 O 4 with atomic displacement parameters drawn at 30% probability.

Figure 2
The molecular packing for C 12 H 8 Cl 2 O 4 viewed along the c axis. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq