4-[(2E)-2-(4-Chlorobenzylidene)hydrazinylidene]-1-methyl-1,4-dihydropyridine monohydrate

In the title compound, C13H12ClN3·H2O, the organic molecule is almost planar, with a dihedral angle of 3.22 (10)° between the benzene and pyridine rings. The crystal structure is stabilized by O—H⋯N and C—H⋯O hydrogen bonding and π–π stacking interactions [centroid–centroid distances = 3.630 (1) and 3.701 (1) Å].

We have also carried out the quantum mechanical calculations using the CNDO (Pople et al., 1970) approximation.
The spatial view of the single molecule considered in a vacuum, is shown in Fig.3. According to the theoretical CNDO and experimental X-rays results, the values of the geometric parameters of (I) are closely comparable within the observed experimental errors. The calculated dipole moment of (I) is about 11.481 Debye. The HOMO and LUMO energy levels are -8.3484 and 1.3565 eV, respectively.

Refinement
The H atoms of the water molecule were found from a difference Fourier map and their isotropic thermal parameters were refined by using a riding model with U iso (H) = 1.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and tor-

sion angles
Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.