(E)-N′-[3-(4-Chlorobenzoyloxy)benzylidene]pyridine-4-carbohydrazide acetic acid monosolvate monohydrate

In the Schiff base molecule of the title compound, C20H14ClN3O3·CH3COOH·H2O, the central benzene ring makes dihedral angles of 36.26 (7) and 27.59 (8)°, respectively, with the terminal chlorophenyl and pyridine rings. In the crystal, the three components are linked by O—H⋯O, N—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds into a double-tape structure along the a axis.

In the Schiff base molecule of the title compound, C 20 H 14 ClN 3 O 3 ÁCH 3 COOHÁH 2 O, the central benzene ring makes dihedral angles of 36.26 (7) and 27.59 (8) , respectively, with the terminal chlorophenyl and pyridine rings. In the crystal, the three components are linked by O-HÁ Á ÁO, N-HÁ Á ÁO, O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds into a double-tape structure along the a axis.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: IS5118).  (Santos et al., 2001). Among the large number of the compounds, isonicotinohydrazide forms a variety of Schiff bases with aldehydes, and the synthesis and crystal structures of some of them have been reported (Wardell et al., 2005;Peralta et al., 2007;. In order to obtain more detailed information on the structural conformation of the molecule that may be of value in structure-activity analysis, we report here the synthesis and structure of the title compound, (I), as part of our study of isonicotinoylhydrazones (Diao et al., 2007).

Experimental
An anhydrous ethanol solution (50 ml) of 3-formylphenyl 4-chlorobenzoate (2.61 g, 10 mmol) was added to an anhydrous ethanol solution (50 ml) of isonicotinohydrazide (1.37 g, 10 mmol) and the mixture stirred at 350 K for 5 h under N 2 , giving a white precipitate. The product was isolated, recrystallized from ethanol, and then dried in a vacuum to give pure compound (I) in 72% yield. Colorless single crystals of (I) suitable for X-ray analysis were obtained by slow evaporation of a solution of ethanol and acetic acid (80:20 v/v).

Refinement
The H atoms of the water molecules were located in a difference Fourier map and refined, with distance restraints of O-H = 0.85 (1) and H···H = 1.45 (1) Å, and with U iso (H) = 1.5U eq (O). Other H atoms were included in calculated positions and refined using a riding model approximation.

Figure 1
The structure of the title compound with displacement ellipsoids for non-H atoms drawn at the 50% probability level.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.17 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0070 (17) 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 > 2σ(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.