N′-{(E)-[5-(Hydroxymethyl)furan-2-yl]methylidene}pyridine-4-carbohydrazide dihydrate

In the title compound, C12H11N3O3·2H2O, the dihedral angle formed by the planes of the pyridine and the furan rings of the organic carbohydrazide molecule is 4.66 (7)°. In the crystal, these molecules form stacks along the b-axis direction, neighbouring molecules within each stack being related by inversion and the shortest distance between the centroids of the pyridine and furan rings being 3.714 (1) Å. Molecules from neighboring stacks are linked by pairs of N—H⋯O hydrogen bonds. The water molecules fill the channels between the stacks being linked by O—H⋯O hydrogen bonds into helices along [010]. Besides this, water molecules are involved in O—H⋯N and O—H⋯O hydrogen bonds with the carbohydrazide molecules, thus forming a three-dimensional network, augmented by weak C—H⋯O interactions.

In the title compound, C 12 H 11 N 3 O 3 Á2H 2 O, the dihedral angle formed by the planes of the pyridine and the furan rings of the organic carbohydrazide molecule is 4.66 (7) . In the crystal, these molecules form stacks along the b-axis direction, neighbouring molecules within each stack being related by inversion and the shortest distance between the centroids of the pyridine and furan rings being 3.714 (1) Å . Molecules from neighboring stacks are linked by pairs of N-HÁ Á ÁO hydrogen bonds. The water molecules fill the channels between the stacks being linked by O-HÁ Á ÁO hydrogen bonds into helices along [010]. Besides this, water molecules are involved in O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds with the carbohydrazide molecules, thus forming a three-dimensional network, augmented by weak C-HÁ Á ÁO interactions.

Experimental
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 2010); software used to prepare material for publication: SHELXL97 and publCIF (Westrip, 2010  Heterocyclic carbohydrazides are compounds with a wide spectrum of biological and analytical applications. They form stable metal chelates which find applications in molecular sensing (Bakir & Brown, 2002). The title compound is a derivative of isoniazid which is one of the first line drug used in the treatment of tuberculosis. A number of hydrazones derived from isoniazid were reported to be active antitubercular agents and were found to be less toxic than isoniazid (Rollas & Kucukguzel, 2007).

Experimental
The title compound was prepared by adapting a reported procedure (Sreeja & Kurup, 2005). To a warm methanolic solution of 5-(hydroxymethyl)furan-2-carbaldehyde (0.126 g, 1 mmol), a methanolic solution of pyridine-4carbohydrazide (0.137 g, 1 mmol) was added and the resulting solution was stirred well with slight heating for 75 minutes. A colorless compound formed was filtered off, washed with water, ethanol and finally with ether and dried.
Single crystals suitable for X-ray diffraction studies were obtained by recrystallization from a mixture of methanol, ethanol and DMF.

Refinement
All H atoms on C were placed in calculated positions, guided by difference maps, with C-H bond distances 0.93-0.97 Å.
H atoms were assigned as U iso (H)=1.2Ueq(carrier) or 1.5Ueq (methyl C). The H atoms of the water molecule were located from difference maps and restrained using DFIX and DANG instructions. Omitted owing to disagreement was the reflection (1 1 0).

Figure 1
View of the structure of the title compound, showing the atom-labelling scheme and displacement ellipsoids for the non-H atoms drawn at the 50% probability level.

Figure 2
Hydrogen bonding in the crystal of the title compound.  The π···π stacking interactions in the title compound.

Figure 4
A view of the unit cell along the b axis. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.23 e Å −3 Δρ min = −0.19 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0056 (14) Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 R-factors based on ALL data will be even larger.