Bis(2-hydroxyphenyl)methanone

In the title compound, C13H10O3, a benzophenone derivative, the least-squares planes defined by the C atoms of the 2-hydroxyphenyl rings intersect at an angle of 45.49 (3)°. The substituents on the aromatic systems are both orientated towards the central O atom. Intra- as well as intermolecular O—H⋯O hydrogen bonds are observed, the latter giving rise to the formation of centrosymmetric dimers. The closest centroid–centroid distance between two π-systems is 3.7934 (7) Å.

In the title compound, C 13 H 10 O 3 , a benzophenone derivative, the least-squares planes defined by the C atoms of the 2hydroxyphenyl rings intersect at an angle of 45.49 (3) . The substituents on the aromatic systems are both orientated towards the central O atom. Intra-as well as intermolecular O-HÁ Á ÁO hydrogen bonds are observed, the latter giving rise to the formation of centrosymmetric dimers. The closest centroid-centroid distance between two -systems is 3.7934 (7) Å .

Comment
Chelate ligands have found widespread use in coordination chemistry due to the enhanced thermodynamic stability of resultant coordination compounds in relation to coordination compounds exclusively applying comparable monodentate ligands (Gade, 1998). Combining two identical donor atoms in different states of hybridization seemed to be useful to us to accomodate a large variety of metal centers of variable Lewis acidity. To enable comparative studies in terms of bond lengths and angles in envisioned coordination compounds, we determined the molecular and crystal structure of the title compound.
The title compound is a symmetrical substitution product of benzophenone bearing one hydroxyl group in ortho-position of each phenyl ring. Both aromatic moieties adopt a conformation in which the substituents are orientated towards the central oxygen atom. The least-squares planes defined by the respective carbon atoms of both ortho-hydroxyphenyl rings intersect at an angle of 45.49 (3) °. Intracyclic C-C-C angles hardly deviate from the ideal value of 120 °.
In the crystal structure, intra-as well as intermolecular hydrogen bonds are observed. In both cases, the sp 2 -hybridized oxygen atom acts as acceptor, but while one of the hydroxyl groups exclusively forms an intramolecular hydrogen bond, the other hydroxyl group forms a bifurcated hydrogen bond to the keto group's oxygen atom of a neighbouring molecule as well. In total, two molecules are connected to centrosymmetric dimers. The descriptor for the hydrogen bonding system in terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995) is DDR 2 2 (12) on the unitary level. The shortest intercentroid distance between two π-systems is 3.7934 (7) Å and is apparent between two different aromatic moieties.
The packing of the title compound in the crystal structure is shown in Figure 3.

Experimental
The compound was obtained commercially (Aldrich). Crystals suitable for the X-ray diffraction study were taken directly from the provided product.

Refinement
Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C). The hydrogen atoms of the hydroxyl groups were allowed to rotate with a fixed angle around the O-C bonds to best fit the experimental electron density (HFIX 147 in the SHELX program suite (Sheldrick, 2008 Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level).