2,2′-{[(1E,1′E)-(Cyclohexane-1,4-diyl)bis(azanylylidene)]bis(ethan-1-yl-1-ylidene)}diphenol

The title compound, C22H26N2O2, crystallizes with three independent molecules, two of which are situated on inversion centers, so the asymmetric unit contains two independent half-molecules and one molecule in a general position. The two hydroxy groups in each molecule are involved in intramolecular O—H⋯N hydrogen bonds, which generate S(6) rings. In the crystal, weak intermolecular C—H⋯π interactions link the molecules into two crystallographically independent columns propagating along [001]; one column consists of molecules in general positions, while the other column is built from alternating independent centrosymmetric molecules.

The title compound, C 22 H 26 N 2 O 2 , crystallizes with three independent molecules, two of which are situated on inversion centers, so the asymmetric unit contains two independent halfmolecules and one molecule in a general position. The two hydroxy groups in each molecule are involved in intramolecular O-HÁ Á ÁN hydrogen bonds, which generate S(6) rings. In the crystal, weak intermolecular C-HÁ Á Á interactions link the molecules into two crystallographically independent columns propagating along [001]; one column consists of molecules in general positions, while the other column is built from alternating independent centrosymmetric molecules.  Table 1 Hydrogen-bond geometry (Å , ).

Comment
The research field dealing with Schiff base coordination chemistry has expanded enormously (Chu et al., 2008;Gao et al., 2002;Hamil et al., 2012); the presence of a lone pair of electrons in an sp 2 hybridized orbital of nitrogen atom of the azomethine group is of considerable chemical and biological importance (More et al., 2001). Because of the relative easiness of preparation, synthetic flexibility, and the special property of C=N group, Schiff bases are generally excellent chelating agents (Vigato et al., 2004). In azomethine derivatives, the C=N linkage is essential for biological activity, several azomethines were reported to possess remarkable antibacterial, antifungal, anticancer and diuretic activities.
Herewith we present the crystal structure of the title compound.
The title compound crystallizes with two half-molecules situated on inversion centers and one molecule in general position ( Fig. 1). Two hydroxy groups in each molecule are involved in intramolecular O-H···N hydrogen bonds (Table   1), which generate S(6) rings. In the crystal, weak intermolecular C-H···π interactions (Table 1) link the molecules into two crystallographically independent columns propagated in [001] -one column consists from the molecules in general positions, while another column is built from the alternating independent centrosymmetric molecules.

Experimental
The title compound was prepared by treating trans1, 4-diamino cyclohexane with 2-hydroxy acetophenone in the stoichiometric ratio in the ethanolic solution and refluxed for 5 h. The reaction mixture was then cooled slowly to room temperature; a yellow crystalline product was obtained and further washed with cold ethanol respectively (Huang et al., 2008). It was then recrystallized from chloroform. The yellow like single-crystal of the title compound used in X-ray diffraction studies were grown in a chloroform solution by slow evaporation of the solvent at room temperature.

Refinement
All hydrogen atoms were fixed geometrically (C-H 0.93-0.98 Å) and refined as riding, with U iso (H) = 1.2-1.5 U eq (C). Three crystallographically independent molecules showing the atomic numbering and 30% probability displacement

Computing details
H atoms omitted for clarity.

2,2′-{[(1E,1′E)-(Cyclohexane-1,4-diyl)bis(azanylylidene)]bis(ethan-1-yl-1-ylidene)}diphenol
Crystal data Hall symbol: -P 1 a = 9.0299 (6)   Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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 Rfactors based on ALL data will be even larger.