2-[N-(4-{4-[(E)-(2-Hydroxybenzylidene)amino]phenoxy}phenyl)carboximidoyl]phenol

The molecular structure of the title Schiff base compound, C26H20N2O3, shows that respective methylidene residues are almost coplanar with the adjacent terminal benzene ring owing to the presence of intramolecular O—H⋯N hydrogen bonds [the N—C—C—C torsion angles are −6.6 (7) and −6.7 (7)°]. However, twists are exhibited about each methylidene and respective benzene ring connected to the central O atom; the dihedral angles formed between the two inner and two outer benzene rings are 54.6 (2) and 45.6 (3)°, respectively. The conformation about each of the C=N bonds [1.285 (5) and 1.295 (5) Å] is E. In the crystal, extensive C—H⋯π contacts involving all benzene rings results in the formation of layers in the ac plane.

The molecular structure of the title Schiff base compound, C 26 H 20 N 2 O 3 , shows that respective methylidene residues are almost coplanar with the adjacent terminal benzene ring owing to the presence of intramolecular O-HÁ Á ÁN hydrogen bonds [the N-C-C-C torsion angles are À6.6 (7) and À6.7 (7) ]. However, twists are exhibited about each methylidene and respective benzene ring connected to the central O atom; the dihedral angles formed between the two inner and two outer benzene rings are 54.6 (2) and 45.6 (3) , respectively. The conformation about each of the C N bonds [1.285 (5) and 1.295 (5) Å ] is E. In the crystal, extensive C-HÁ Á Á contacts involving all benzene rings results in the formation of layers in the ac plane.
Tabriz Azad University is gratefully acknowledged for the support of this work.

Comment
In continuation of structural studies of Schiff base ligands (Prasath et al., 2010), attention is now directed to evaluating the structures of flexible derivatives (Chu & Huang, 2007;Xu et al., 2008) which have been shown, for example, to lead to helical coordination polymers (Chu & Huang, 2007). In this context the title compound (I) was prepared and characterized crystallographically.
The molecule of (I) is twisted at both the central O atom, and about each of the methylidene residues. Thus, the dihedral angle formed between the least-squares planes through the benzene rings directly connected to the central O atom is 54.6 (2) °. Similarly, the dihedral angles formed between the terminal benzene ring and the adjacent benzene ring are 51.6 (2) °f or each of C1-C6/C8-C13 and C14-C19/C21-C26. Finally, the dihedral angle formed between the terminal benzene rings is 45.6 (3) °. The conformation about each of the C═N bonds [N1═C7 is 1.285 (5) Å and N2═C20 is 1.295 (5) The presence of intramolecular O-H···N hydrogen bonds, Table 1, ensures co-planarity between the respective terminal benzene rings and methylidene residues as reflected in the C1-C2-C7-N1 and N2-C20-C21-C22 torsion angles of -6.6 (7) and -6.7 (7) °. respectively.
The crystal packing is dominated by C-H···π interactions, Table 1, whereby each of the four benzene rings accepts two such contacts. The result is the formation of layers in the ac plane, Fig. 2.

Experimental
A solution of 4,4'-diaminodiphenyl ether (10 mmol) in ethanol (50 ml) was added drop wise to a solution of salicylaldehyde (20 mmol) in ethanol (50 ml). The mixture was stirred for 6 h. The resulting solution was filtered to obtain a Schiff base which was dried. Crystals of the title compound were obtained by using the branched tube method (Harrowfield et al., 1996) where the Schiff base (5 mmol) was placed in the arm to be heated. Methanol was carefully added to fill both arms, and then the arm to be heated was placed in a bath at 333 K. After 2 days, yellow crystals were deposited in the cooler arm, which were filtered, washed with water and air dried.