(E)-N'-(3,4-Dichloro-benzyl-idene)nicotino-hydrazide monohydrate.

In the title compound, C(13)H(9)Cl(2)N(3)O·H(2)O, the 3,4-dichloro-benzene ring is nearly coplanar with the pyridine ring, making a dihedral angle of 4.78 (8)°. Inter-molecular O-H⋯O, O-H⋯N, N-H⋯O and weak C-H⋯O hydrogen bonding is present in the crystal structure.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: XU2600).

Comment
The chemistry of Schiff bases has attracted a great deal of interest in recent years. These compounds play an important role in the development of various proteins and enzymes (Kahwa et al., 1986;Santos et al., 2001). As part of our interest in the coordination chemistry of Schiff bases, we have synthesized the title compound and report here its crystal structure.
The title molecule crystallizes in the E conformation ( Fig. 1), with the N2-N1-C7-C6 torsion angle of 179.81 (15)°. The molecule structure is nearly planar, the dihedral angle between the 3,4-dichlorobenzene ring and the pyridine ring

Experimental
Nicotinohydrazide (1 mmol, 0.137 g) was dissolved in ethanol (15 ml). The solution was stirred for several minitutes at 351 K, then the 3,4-dichlorobenzaldehyde (1 mmol, 0.175 g) in ethanol (8 ml) was added dropwise, and the mixture was stirred at refluxing temperature for 2 h. The solid product was isolated and recrystallized from methanol-water solution.
Colourless single crystals were obtained after 3 d.

Refinement
H atoms of water molecule are located in a difference Fourier map and refined isotropically, with O-H and H···H distances restrained to 0.85 (2) and 1.37 (2) Å. Other H atoms were positioned geometrically and refined as riding with C-H = 0.93 (aromatic) and N-H = 0.86 Å, U iso (H) = 1.2U eq (C,N). Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 Rfactors(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.