(E)-Methyl N′-[(1H-indol-3-yl)methylidene]hydrazinecarboxylate 0.25-hydrate

The asymmetric unit of the title compound, C11H11N3O2·0.25H2O, contains two independent organic molecules and a water molecule, which lies on a twofold rotation axis. The side chains of the two molecules have slightly different orientations, the C=N—N—C torsion angle being −163.03 (15)° in one and −177.52 (14)° in the other, with each adopting a trans configuration with respect to the C=N bond. In the crystal, molecules are linked into chains extending along b by N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds and in addition, four intermolecular C—H⋯π interactions are present.

The asymmetric unit of the title compound, C 11 H 11 N 3 O 2 Á-0.25H 2 O, contains two independent organic molecules and a water molecule, which lies on a twofold rotation axis. The side chains of the two molecules have slightly different orientations, the C N-N-C torsion angle being À163.03 (15) in one and À177.52 (14) in the other, with each adopting a trans configuration with respect to the C N bond. In the crystal, molecules are linked into chains extending along b by N-HÁ Á ÁO, O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds and in addition, four intermolecular C-HÁ Á Á interactions are present.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Schiff bases have attracted much attention due to their potential analytical applications (Cimerman et al., 1997). They are also important ligands, which have been reported to have mild bacteriostatic activity and are used 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 C 11 H 11 N 3 O 2 . 0.25H 2 O.

Experimental
1H-Indole-3-carbaldehyde (1.45 g, 0.01 mol) and methyl hydrazinecarboxylate (0.90g, 0.01 mol) were dissolved in stirred methanol (15 ml) and left for 3.5 h at room temperature. The resulting solid was filtered off and recrystallized from ethanol to give the title compound in 93% yield. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution at room temperature (m.p. 465-467 K).

Refinement
The water H atom was located in a difference Fourier and both positional and isotropic displacement parameters were refined. Other H atoms were positioned geometrically (N-H = 0.86 Å and C-H = 0.93 or 0.96 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C,N) and 1.5U eq (C methyl ). A rotating group model was used for the methyl H atoms. Fig. 1. The molecular conformation and atom numbering scheme for the two independent organic molecules and the water molecule of solvation in the asymmetric unit of the title compound. The water molecule lies on a twofold rotation axis and the hydrogen bond is shown as a dashed line. Displacement ellipsoids are drawn at the 30% probability level.

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.