(E)-N′-(2-Hydroxy-3,5-diiodobenzylidene)nicotinohydrazide acetonitrile monosolvate

In the hydrazone molecule of the title compound, C13H9I2N3O2·CH3CN, the aromatic rings form a dihedral angle of 9.4 (3)°. In the crystal structure, intermolecular I⋯N interactions [3.099 (4) Å] link hydrogen-bonded aggregates of the hydrozone and solvent molecules related by translation along the b axis into chains. An intramolecular O—H⋯N hydrogen bond forms an S(6) ring.

In the hydrazone molecule of the title compound, C 13 H 9 I 2 N 3 O 2 ÁCH 3 CN, the aromatic rings form a dihedral angle of 9.4 (3) . In the crystal structure, intermolecular IÁ Á ÁN interactions [3.099 (4) Å ] link hydrogen-bonded aggregates of the hydrozone and solvent molecules related by translation along the b axis into chains. An intramolecular O-HÁ Á ÁN hydrogen bond forms an S(6) ring.

Comment
In continuation of our structural studies of hydrazone derivatives (Liu & You, 2010a,b,c;Liu & Wang, 2010a,b;2011), we present here the title compound (I).

Experimental
The title compound was prepared by the condensation reaction of 2-hydroxy-3,5-diiodobenzaldehyde (1.0 mmol, 0.374 g) and nicotinohydrazide (1.0 mmol, 0.137 g) in acetonitrile (50 ml) at ambient temperature. Colourless block-shaped single crystals suitable for X-ray structural determination were obtained by slow evaporation of the solution for a few days.

Refinement
H2 was located from a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å.
The remaining H atoms were positioned geometrically and constrained to ride on their parent atoms, with C-H distances of 0.93-0.96 Å, O-H distance of 0.82 Å, and with U iso (H) = 1.2-1.5U eq of the parent atom. Fig. 1. The molecular structure of (I). Displacement ellipsoids are drawn at the 30% probability level. H atoms are shown as spheres of arbitrary radius and the hydrogen bonds are drawn as dashed lines.

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.