Crystal structure of (E)-4-hydroxy-N′-(3-methoxybenzylidene)benzohydrazide

The molecules of C15H14N2O3 are slightly twisted. N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds play an important role in the crystal packing, resulting in the formation of molecular sheets parallel to the bc plane.


Structural commentary
There are two crystallographically independent molecules, A and B, of the title benzohydrazide derivative, C 15 H 14 N 2 O 3 , in the asymmetric unit of (I). These differ in the orientation of the 3-methoxyphenyl ring with respect to the methylidenebenzohydrazide unit. The dihedral angles between the two benzene rings are 24.02 (10) and 29.30 (9) in molecules A and B, respectively. The molecules exist in the trans-conformation with respect to the C8 N2 bond [1.275 (2) Å in molecule A and 1.271 (2) Å in molecule B] and the torsion angle N1-N2-C8-C9 = À178.14 (16) in molecule A and À177.69 (16) in molecule B. Five atoms (O1, C7, N1, N2 and C8) of the central fragment are approximately coplanar, having r.m.s. deviations of 0.0179 (2) Å in molecule A and 0.0327 (2) Å in molecule B. The mean plane through this central fragment makes dihedral angles of 23.87 (11) and 0.20 (12) with the planes of the 4-hydroxyphenyl and 3-methoxyphenyl rings, respectively, in molecule A. The corresponding values are 22.58 (11) and 11.04 (11) in molecule B. In molecule A, the methoxy group is slightly twisted from the attached benzene ring [C15-O3-C11-C10 = 14.2 (3) ] whereas it is essentially coplanar in molecule B [where the corresponding torsion angle is À2.4 (3) ]. The bond distances agree with literature values and are comparable with those in related structures Horkaew et al., 2011;Rassem et al., 2012;Shi, 2009).

Database survey
A search of SciFinder (Scifinder, 2015) reveals a total of 719 related structures with benzohydrazides, and 52 related structure with 4-hydroxybenzohydrazides. Specific examples by Fun et al., 2011;Horkaew et al., 2011;Rassem et al., 2012;Shi, 2009) have been mentioned in the Chemical context section.

Synthesis and crystallization
A solution of 4-hydroxybenzohydrazide (2 mmol, 0.30 g) in ethanol (10 ml) and 3-methoxybenzaldehyde (2 mmol, 0.27 g) in ethanol (10 ml) were mixed, stirred and refluxed for 5 h. The resulting mixture was then cooled to room temperature. The white precipitate that formed was filtered. Colorless block-shaped single crystals of (I) suitable for X-ray structure determination were recrystallized from methanol by slow evaporation at room temperature over a period of several days, m.p. 478-479 K. The UV-Vis spectrum of (I) shows absorption bands of a benzohydrazide (212 and 302 nm). The IR spectrum of (I) shows the typical stretching of C N and amide C O functionalities at 1648 and 1607 cm À1 , respectively, which confirm the successful synthesis of the N 0 -benzylidenebenzohydrazide skeleton. In addition, the 1 H NMR spectrum of (I) also supports the formation of the N 0 -benzylidenebenzohydrazide skeleton by showing the characteristic signals of an amine (N CH) at 8.39 (s, 1H) and an amide (N-H) at 11.65 (s, 1H) p.p.m.

Spectroscopic studies and a-glucosidase inhibitory assay
The -glucosidase inhibitory assay was modified from the method of Kim et al. (2004). The result showed that (I) possesses weak activity with 7.30AE2.85% inhibition at a concentration of 100 mg/mL.

(E)-4-Hydroxy-N′-(3-methoxybenzylidene)benzohydrazide
Crystal data Extinction coefficient: 0.0036 (6) 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 > 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.