Crystal structure of (E,E)-2′,4′-dihydroxyacetophenone azine dimethylformamide disolvate

The approximately planar (E,E)-2′,4′-dihydroxyacetophenone azine molecule is located on an inversion centre and linked with dimethylformamide solvent molecules via O—H⋯O hydrogen bonds.


Chemical context
Hydrazones are important compounds due to their possible applications in material and coordination chemistry. Fluorescence properties of hydrazones have been reported (Qin et al., 2009). Many organometallic compounds containing acylhydrazone ligands have also been synthesized for their potential magneto-chemical properties (Guo et al., 2010). In particular, they have received increasing interest for their biological activity as antioxidants (Kitaev et al., 1970), and their antimicrobial (Ramamohan et al., 1995) and antiviral properties (El-Tabl et al., 2008;Rollas & Kü çü kgü zel, 2007).
Although 2 0 ,4 0 -dihydroxyacetophenone azine has been prepared and studied as a fluorescent probe, its structure has not been reported. As a part of our studies on synthesis and structural peculiarities of Schiff base ligands derived from 2 0 ,4 0 -dihydroxyacetophenone and hydrazine, we determined the structure of the title compound, (E,E)-2 0 ,4 0 -dihydroxyacetophenone azine dimethylformamide disolvate, (I).

Structural commentary
The molecular structure of the title compound is depicted in Fig. 1. The asymmetric unit contains one half-molecule of (E,E)-2 0 ,4 0 -dihydroxyacetophenone azine and one dimethylformamide (DMF) molecule. The complete azine molecule is centrosymmetric and exists in an E,E configuration with respect to the two C N bonds. The N1-C2 bond length of 1.301 (3) (Chantrapromma et al., 2011;Tai et al., 2008). All the non-H atoms of the azine molecule are approximately coplanar. The nine atoms (i.e. N1, C1 and C2, and the six C atoms in the benzene ring) are essentially planar, with a mean deviation of 0.0024 Å . Each hydroxy group is nearly coplanar with its attached benzene ring; the r.m.s. deviation is 0.0045 Å for the seven non-H atoms. Intramolecular O-HÁ Á ÁN hydrogen bonds exist in the azine molecule (Table 1).

Supramolecular features
In the crystal of (I), intermolecular O-HÁ Á ÁO hydrogen bonds exist between azine molecules and DMF molecules (Table 1 and Fig. 2).

4,4′-[1,1′-(Hydrazinediylidene)bis(ethan-1-yl-1-ylidene)]bis(benzene-1,3-diol)
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.28 e Å −3 Δρ min = −0.25 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.17 (2) 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.