1,10-Phenanthroline-5,6-dione ethanol monosolvate

In the title compound, C12H6N2O2·C2H5OH, the molecule of the 1,10-phenanthroline-5,6-dione is approximately planar, with a maximum deviation of 0.051 (1) Å. In the crystal, molecules are linked by O—H⋯N and weak C—H⋯O hydrogen bonds, forming supramolecular chains propagating along [110]. π–π stacking interactions are observed between the pyridine rings of neighbouring chains, the centroid–centroid separations being 3.6226 (11) and 3.7543 (11) Å.


Synthesis and crystallization
The title compound was prepared according to literature method (Paw & Eisenberg, 1997). An ice-cold mixture of concentrated H 2 SO 4 (40 mL) and HNO 3 (20 mL) was added to 4 g of 1,10-phenanthroline (0.02 mol) and 4 g of KBr (0.03 mol). The mixture was heated at 90 o C for 3 h. The hot yellow solution was poured over 200 mL of ice and neutralized carefully with sodium hydroxide until neutral to slightly acidic pH. Extraction with CH 2 Cl 2 (4*100 mL) followed by drying with Na 2 SO 4 and removal of solvent gave 2.8 g (yield = 67%) of 1,10-phenanthroline-5,6-dione. This product was purified further by crystallization from ethanol.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. Carbon-bound H-atoms were placed in calculated positions and were included in the refinement in the riding model approximation with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for the others. The hydroxy H atom was located in a difference Fourier map, and was refined with distance restraints of O-H = 0.84±0.01, U iso (H) = 1.2U eq (O).
According to the structural analysis, the bond lengths and angles of the title compound are generally within normal ranges. The asymmetric unit of the title compound consists of one 1,10-phenanthroline-5,6-dione molecule and one  Crystal structure of the title compound with labeling and displacement ellipsoids drawn at the 30% probability level.

Figure 2
Crystal packing of the title compound. Intermolecular O-H···N and C-H···O hydrogen bonds are shown as green dashed lines, and π-π stacking interactions between molecules are shown as blue dashed lines.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.