(2-Hydroxy-4-methoxyphenyl)(2-hydroxyphenyl)methanone

The title compound, C14H12O4, is an asymmetric substitution product of benzophenone. Both hydroxy groups are orientated towards the O atom of the keto group. Intramolecular as well as intermolecular O—H⋯O hydrogen bonds can be observed in the crystal structure, with the latter connecting the molecules into chains along the crystallographic b axis. C—H⋯O contacts [C⋯O = 3.3297 (18) Å] are also apparent. The closest centroid–centroid distance between two aromatic systems is 4.9186 (9) Å.

The title compound, C 14 H 12 O 4 , is an asymmetric substitution product of benzophenone. Both hydroxy groups are orientated towards the O atom of the keto group. Intramolecular as well as intermolecular O-HÁ Á ÁO hydrogen bonds can be observed in the crystal structure, with the latter connecting the molecules into chains along the crystallographic b axis. C-HÁ Á ÁO contacts [CÁ Á ÁO = 3.3297 (18) Å ] are also apparent. The closest centroid-centroid distance between two aromatic systems is 4.9186 (9) 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 an asymmetric substitution product of benzophenone. Both aromatic moieties adopt a conformation in which its hydroxyl group is orientated towards the central oxygen atom. The least-squares planes defined by the respective carbon atoms of both aromatic rings intersect at an angle of 42.11 (6) °. Intracyclic C-C-C angles hardly deviate from the ideal value of 120 °. The methoxy group is nearly in plane with its resident aromatic system, the respective C-O-C-C torsional angle is found at 4.9 (2) ° ( Fig. 1).
In the crystal structure, intra-as well as intermolecular hydrogen bonds are observed. While the intramolecular hydrogen bonds are apparent between the hydroxyl groups as donors and the double-bonded oxygen atom as acceptor, the intermolecular hydrogen bond stems from the hydroxyl group on the otherwise unsubstituted phenyl ring and has the etheric oxygen atom as acceptor (Fig. 2). The latter hydrogen bond thus shows bifurcation. In addition, a C-H···O contact whose range falls by more than 0.1 Å below the sum of van-der-Waals radii is present in the crystal structure. The latter one is supported by one of the CH groups in ortho-position to the methoxy substituent and has the keto group's oxygen atom as acceptor. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the hydrogen bonding system based on the hydroxyl groups on the unitary level is S(6)S(6)C(10) while the C-H···O contacts necessitate a C (6) descriptor on the same level. In total, the molecules are connected to undulated chains along the crystallographic b axis. The shortest intercentroid distance between two aromatic systems was measured to be at 4.9186 (9) Å and is apparent between the two different aromatic moieties.
The molecular 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.
supplementary materials sup-2 Refinement Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic carbon atoms) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C). The H atoms of the methyl group were allowed to rotate with a fixed angle around their respective C-O bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite (Sheldrick, 2008)), with U(H) set to 1.5U eq (C) and C-H set to 0.98 Å. The H atoms of the hydroxyl groups were allowed to rotate with a fixed angle around their respective C-O bond to best fit the experimental electron density (HFIX 147 in the SHELX program suite (Sheldrick, 2008)), with U(H) set to 1.5U eq (O) and O-H set to 0.84 Å. Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level). dashed lines C-H···O contacts. Symmetry operators: i -x + 2, y + 1/2, -z + 1/2; ii -x + 2, y -1/ 2, -z + 1/2.