N,N′-Bis(2-iodobenzylidene)ethane-1,2-diamine

The molecule of the title Schiff base compound, C16H14I2N2, lies across a crystallographic inversion centre. An intramolecular C—H⋯I hydrogen bond forms a five-membered ring, producing an S(5) ring motif. The C=N bond is coplanar with the benzene ring and adopts a trans configuration. Within the molecule, the planar units are parallel, but extend in opposite directions from the dimethylene bridge. An interesting feature of the crystal structure is the short I⋯N [3.2096 (15) Å] interaction, which is significantly shorter than the sum of the van der Waals radii of these atoms. In the crystal structure, molecules are linked into one-dimensional extended chains along the c axis and also into one-dimensional extended chains along the b axis through short intermolecular I⋯N interactions, forming two-dimensional networks parallel to the bc plane.

The molecule of the title Schiff base compound, C 16 H 14 I 2 N 2 , lies across a crystallographic inversion centre. An intramolecular C-HÁ Á ÁI hydrogen bond forms a five-membered ring, producing an S(5) ring motif. The C N bond is coplanar with the benzene ring and adopts a trans configuration. Within the molecule, the planar units are parallel, but extend in opposite directions from the dimethylene bridge. An interesting feature of the crystal structure is the short IÁ Á ÁN [3.2096 (15) Å ] interaction, which is significantly shorter than the sum of the van der Waals radii of these atoms. In the crystal structure, molecules are linked into one-dimensional extended chains along the c axis and also into one-dimensional extended chains along the b axis through short intermolecular IÁ Á ÁN interactions, forming two-dimensional networks parallel to the bc plane.

Comment
Schiff bases are one of most prevalent mixed-donor ligands in the field of coordination chemistry. Schiff bases have been used widely as ligands in the formation of transition metal complexes. Many such complexes have been structurally characterized, but only a relatively small number of free Schiff base ligands have been characterized (Calligaris & Randaccio, 1987). There has been growing interest in Schiff base ligands, mainly because of their wide application in the field of biochemistry, synthesis, and catalysis (Pal et al., 2005;Hou et al., 2001;Ren et al., 2002). The molecule of the title compound, (I), (Fig. 1), lies across a crystallographic inversion centre. The bond lengths and angles are within normal ranges (Allen et al.,1987). An intramolecular C-H···I hydrogen bond (Brammer et al. 2001) forms a five-membered ring, producing an S(5) ring motif (Bernstein et al., 1995) (Table 1). The asymmetric unit of the compound is composed of one-half of the molecule. The C═N bond is coplanar with the benzene ring and adopts a trans configuration. Within the molecule, the planar units are parallel, but extend in opposite directions from the methylene bridge.
The interesting feature of the crystal structure is the short I···N [3.2096 (15) Å] interactions (Lommerse et al. 1996), which is significantly shorter than the sum of the van der Waals radii of the relevant atoms. In the crystal structure, molecules are linked into 1-D extended chains along the c axis and are also into 1-D extended chains along the b axis through short intermolecular I···N interactions forming 2-D networks (Fig. 2 & 3) which are parallel to the bc plane.

Experimental
The synthetic method has been described earlier (Fun, Kia & Kargar et al., 2008). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

Refinement
All of the H atoms were located from the difference Fourier map and freely refined. The highest peak is located 0.61 Å from C5 and the deepest hole is located 0.63 Å from I1. Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms [symmetry code for A: -x, 1 -y, -z].  Geometric parameters (Å, °)