3-(4-Hydroxyphenylimino)indolin-2-one

In the title compound, C14H10N2O2, the dihedral angle between the indole and benzene rings is 61.63 (4)°. In the crystal structure, centrosymmetrically related molecules are linked into dimers by N—H⋯O hydrogen bonds, generating rings of graph-set motif R 2 2(8). The dimers are further connected into a three-dimensional network by O—H⋯O and C—H⋯O hydrogen bonds.

In the title compound, C 14 H 10 N 2 O 2 , the dihedral angle between the indole and benzene rings is 61.63 (4) . In the crystal structure, centrosymmetrically related molecules are linked into dimers by N-HÁ Á ÁO hydrogen bonds, generating rings of graph-set motif R 2 2 (8). The dimers are further connected into a three-dimensional network by O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds.
The X-ray structural analysis confirmed the assignment of the structure from spectroscopic data. The molecular structure is depicted in Fig. 1, and a packing diagram of is depicted in Fig. 2. Geometric parameters of the title compound are in the usual ranges. The dihedral angle between the indole and benzene rings is 61.63 (4)°. The C2-N2-C9 angle is 122.97 (12)°, and the C8-C2-N2-C9 torsion angle is -9.0 (3). In the crystal structure, centrosymmetrically related molecules are linked into dimers by N-H···O hydrogen bonds (Table 1) generating rings of graph set motif R 2 2 (8). The dimers are further connected into a three-dimensional network by O-H···O and C-H···O hydrogen bonds.

Experimental
Isatin (1 mmol) was dissolved in methanol (20 ml) and a methanol solution of 1.2 mmol 4-aminophenol (10 ml) was added dropwise, until the disappearance of isatin, as evidenced by thin-layer chromatography. The solvent was removed in vacuo and the residue was separated by column chromatography (silica gel, petroleum ether/ethyl acetate = 1:1 v/v), to give the title compound. Yellow single crystals of the title compound suitable for X-ray analysis were obtained on slow evaporation

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