3-{[(4Z)-1,2-Dimethyl-5-oxoimidazol-4-ylidene]methyl}-4-hydroxybenzonitrile

In the title compound, C13H11N3O2, an intramolecular O—H⋯N hydrogen bond generates an S(7) ring. The dihedral angle between the mean plane of the benzene ring and the imidazolidinone ring is 3.05 (2)°. In the crystal, inversion-related molecules are linked by dual C—H⋯Ocarbonyl hydrogen bonds to form a dimer with an R 2 2(14) graph-set motif. A C—H⋯Ohydroxy interaction links pairs of molecules into another type of cyclic dimer with an R 2 2(18) motif. The molecules are further linked by C—H⋯N interactions to form layers parallel to (001). Offset π–π stacking [3.3877 (8) Å] is observed in the crystal structure, with an interplanar spacing between the planes of neighboring benzene rings of 3.444 (1) Å.

In the title compound, C 13 H 11 N 3 O 2 , an intramolecular O-HÁ Á ÁN hydrogen bond generates an S(7) ring. The dihedral angle between the mean plane of the benzene ring and the imidazolidinone ring is 3.05 (2) . In the crystal, inversionrelated molecules are linked by dual C-HÁ Á ÁO carbonyl hydrogen bonds to form a dimer with an R 2 2 (14) graph-set motif. A C-HÁ Á ÁO hydroxy interaction links pairs of molecules into another type of cyclic dimer with an R 2 2 (18) motif. The molecules are further linked by C-HÁ Á ÁN interactions to form layers parallel to (001). Offsetstacking [3.3877 (8) Å ] is observed in the crystal structure, with an interplanar spacing between the planes of neighboring benzene rings of 3.444 (1) Å .

Comment
The excited-state intramolecular proton transfer (ESIPT) reaction of the title compound has been investigated recently (Chuang et al., 2011), which incorporates transfer of a hydroxy proton to the imine nitrogen through an intramolecular seven-membered-ring hydrogen-bonding system. The proton transfer dyes have found many important applications.
The molecular structure of the title compound is shown in Fig. 1. As expected, the molecule possesses an intramolecular O-H···N hydrogen bond, which generates an S(7) ring (Chen et al., 2007). The dihedral angle between the mean plane of the benzene ring and the imidazolidinone ring is 3.05 (2)°. In the crystal (Fig. 2), inversion-related molecules are linked by pairs of C12-H12···O1 hydrogen bonds, forming a cyclic dimer with an R 2 2 (14) graph-set motif, Fig. 2 ( Bernstein et al., 1995). In addition, the C5-H5C···O2 interaction links a pair of molecules into another type of cyclic dimer with an R 2 2 (18) graph-set motif. Molecules are further stabilized by intermolecular C-H···N interactions involving the methyl groups of C4 and C5 to form layers parallel to (001). See Table 1 for numerical details of the hdrogen bonds and symmetry operators. Offset π-π stacking is observed in the crystal structure with an interplanar spacing between planes of neighboring benzene rings of 3.444 (1) Å. The closest centroid-centroid distance [symmetry code: x, -1 + y, z] is 4.8350 (12) Å (Cg1 and Cg2 are the centroids of the N1/N2/C1-C3 and C7-C12 rings, respectively).

Experimental
The title compound was synthesized according to the literature (Chuang et al., 2011). Yellow needle-shaped crystals suitable for the crystallographic studies reported here were isolated over a period of six weeks by slow evaporation from a chloroform solution.

Refinement
H atoms bonded to O and C atoms were located in a difference electron density map. In the final model, H atoms were repositioned geometrically and refined using a riding model [C-H = 0.93 Å for C sp2 H atoms, 0.96 for C sp3 H atoms, 0.82 Å for hydroxy H atoms and U iso (H) = 1.2 (C sp2 ) or 1.5 (C sp3 , O) U eq (C/O)]. The hydroxy H atoms and C sp3 H atoms were allowed to rotate but not to tip to best fit the experimental electron density.

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.

Figure 2
A section of the crystal packing of the title compound, viewed down the c axis. Green dashed lines denote the intermolecular C12-H12···O1 hydrogen bonds [symmetry code: -x + 1, -y + 1, -z + 1]. 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.