2-{[(4-{[(2-Hydroxyphenyl)(phenyl)methylidene]amino}butyl)imino](phenyl)methyl}phenol

The asymmetric unit of the title compound, C30H28N2O2, comprises half of a potential tetradentate Schiff base ligand; an inversion centre is situtated at the center of the butanediamine spacer. The central methylene segment of the diamine spacer is disordered over two positions with a refined site-occupancy ratio of 0.651 (7):0.349 (7). The phenyl ring and the hydroxy-substituted benzene ring are almost perpendicular to each other, with a dihedral angle of 87.90 (8) Å. Intramolecular O—H⋯N hydrogen bonds make S(6) ring motifs.

The asymmetric unit of the title compound, C 30 H 28 N 2 O 2 , comprises half of a potential tetradentate Schiff base ligand; an inversion centre is situtated at the center of the butanediamine spacer. The central methylene segment of the diamine spacer is disordered over two positions with a refined siteoccupancy ratio of 0.651 (7):0.349 (7). The phenyl ring and the hydroxy-substituted benzene ring are almost perpendicular to each other, with a dihedral angle of 87.90 (8) Å . Intramolecular O-HÁ Á ÁN hydrogen bonds make S(6) ring motifs.

Comment
Schiff base ligands are one of the most prevalent systems in coordination chemistry (Granovski et al., 1993;Kargar et al., 2009). As part of a general study of potential tetradenate Schiff bases (Kargar et al., 2009), we have synthesized the title compound and report herein on its crystal structure.
The asymmetric unit of the title compound, Fig. 1, comprises half of a potential tetradentate Schiff base ligand. The inversion centre is situtated at the center of the butanediamine spacer. The bond lengths (Allen et al., 1987) and angles are within the normal ranges and are comparable to those reported for a related structure (Friscic et al., 1998).
There are intramolecular O-H···N hydrogen bonds (Table 1) making S(6) ring motifs (Bernstein et al., 1995). The phenyl ring and the hydroxy-substituted benzene ring are almost perpendicular to each other with a dihedral angle of 87.90 (8)Å.
The central methylene segment (C15) of the diamine spacer was disordered over two positions with a refined site occupancy ratio of 0.651 (7)/0.349 (7).

Experimental
The title compound was synthesized by adding 2-hydroxybenzophenone (2 mmol) to a solution of 1,4-butylenediamine (1 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for 30 min. The resultant solution was filtered. Yellow single crystals of the title compound, suitable for X-ray structure determination, were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days. The sample was hygroscopic and for the data collection it was sealed in fine glass cappilary under an inert atmosphere.

Refinement
The OH and C-bound H-atoms were included in calculated positions and treated as riding atoms: O-H = 0.82 Å, C-H = 0.93 and 0.97 Å for CH and CH 2 H-atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for OH, and k = 1.2 for all other H-atoms. The methylene segment (C15) of the diamine spacer was disordered over two positions with a refined site occupancy ratio 0.651 (7)/0.349 (7).

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 supplementary materials sup-3 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 > 2sigma(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.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )