N′-(3,4-Dihydroxybenzylidene)acetohydrazide monohydrate

In the title compound, C9H10N2O3·H2O, the Schiff base molecule is approximately planar, the dihedral angle between the benzene and acetohydrazide planes being 5.40 (7)°. An intramolecular O—H⋯O hydrogen bond is observed. In the crystal, molecules are linked into a two-dimensional network parallel to (100) by O—H⋯O, N—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds, and by π–π interactions between symmetry-related benzene rings [centroid–centroid distance = 3.543 (2) Å].

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.  (Cimerman et al., 1997). They are also important ligands, which have been reported to have mild bacteriostatic activity and as potential oral iron-chelating drugs for genetic disorders such as thalassemia (Offe et al., 1952;Richardson et al., 1988). Metal complexes based on Schiff bases have received considerable attention because they can be utilized as model compounds of active centres in various complexes (Tamboura et al., 2009). We report here the crystal structure of the title compound ( Fig. 1).

Structure Reports Online
In the Schiff base molecule, the acetohydrazide group is planar and it forms a dihedral angle of 5.40 (7)° with the benzene ring. The molecule adopts a trans configuration with respect to the C═N bond. Bond lengths and angles are comparable to those observed for N'-[1-(4-methoxyphenyl)ethylidene]acetohydrazide (Li et al., 2008). An intramolecular O1-H1···O2 hydrogen bond is observed.
In the crystal, the Schiff base and water molecules are linked into a two-dimensional network by O-H···O, N-H···O, O-H···N and C-H···O hydrogen bonds (Table 1). In the network, an intermolecular π-π interaction is also observed between the benzene rings of the molecules at (x, y, z) and (1-x, 1-y, -z), with a centroid-to-centroid distance of 3.543 (2) Å.
Experimental 3,4-Dihydroxybenzaldehyde (1.38 g, 0.01 mol) and acetohydrazide (0.74 g, 0.01 mol) were dissolved in stirred methanol (15 ml) and left for 2.5 h at room temperature. The resulting solid was filtered off and recrystallized from ethanol to give the title compound in 95% yield. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution at room temperature (m.p. 460-462 K).

Refinement
H atoms of the water molecule were located in a difference map and were refined freely. All other H atoms were positioned geometrically (N-H = 0.86 Å, O-H = 0.82Å and C-H = 0.93 or 0.96Å) and refined using a riding model, with U iso (H) =1.2U eq (C,N) and 1.5U eq (C methyl ). Fig. 1

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.