2-Amino-3-[(E)-(2-hydroxy-3-methylbenzylidene)amino]but-2-enedinitrile

The title compound, C12H10N4O, is a Schiff base obtained from the condensation of diaminomaleonitrile and 2-hydroxy-3-methylbenzaldehyde. The molecule is roughly planar, with an r.m.s. deviation of 0.0354 Å, and adopts the phenol–imine tautomeric form. An intramolecular O—H⋯N hydrogen bond involving the O—H group and the azomethine N atom generates an S(6) ring. In the crystal, there are two N—H⋯N hydrogen bonds.

The title compound, C 12 H 10 N 4 O, is a Schiff base obtained from the condensation of diaminomaleonitrile and 2-hydroxy-3methylbenzaldehyde. The molecule is roughly planar, with an r.m.s. deviation of 0.0354 Å , and adopts the phenol-imine tautomeric form. An intramolecular O-HÁ Á ÁN hydrogen bond involving the O-H group and the azomethine N atom generates an S(6) ring. In the crystal, there are two N-HÁ Á ÁN hydrogen bonds.

2-Amino-3-[(E)-(2-hydroxy-3-methylbenzylidene)amino]but-2-enedinitrile Elham S. Aazam and Orhan Büyükgüngör Comment
Tetrameric HCN (diaminomaleonitrile, DAMN) is one of the most versatile reagents in organic chemistry. It has been used as a precursor for producing nucleotides and for synthesizing a wide variety of heterocyclic compounds. These compounds are important as synthetic intermediates and they are also used in pharmacology (Da Silva et al., 2011;Rivera et al., 2006). Schiff bases derived from DAMN have also been used as versatile ligands in coordination chemistry (Aazam et al., 2011;Kargar et al., 2009;Yeap et al., 2009). There are two types of intra-molecular hydrogen bonds in Schiff bases, which may be stabilized either in keto-amine (N-H···O hydrogen bond) (Hökelek et al., 2000) or phenol-imine (N···H-O hydrogen bond) tautomeric forms (Odabaşoǧlu et al., 2005;Aazam & Büyükgüngör, 2010). The present X-ray investigation shows that the title compound is a Schiff base and exists in the phenol-imine form in the solid-state.
The molecular structure of the title compound is shown in Figure 1. An intramolecular O1-H1···N1 hydrogen bond, a characteristic hydrogen bond for Schiff bases, leads to the formation of a S(6) six-membered ring ( Figure 1) (Bernstein et al., 1995).

Refinement
The H atoms bonded to oxygen and nitrogen atoms were located in Fourier map and refined isotropically. Other hydrogen atoms were positioned geometrically and treated using a riding model, fixing bond lengths at 0.93 and 0.96 Å for CH (aromatic) and CH 3 , respectively. The displacement parameters of the H atoms were constrained with U iso (H) = 1.2U eq (aromatic and methyl C). SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).  The molecular structure of the title compound, showing 50% probability displacement ellipsoids and atomic numbering.

Figure 2
Part of the crystal structure of the title compound, showing the formation of C(5) chains parallel to the b axis (i; -x, y -1/2, -z + 1/2). Hydrogen bonds are indicated by dashed lines.   Table 1) 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 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.