(1E,1′E)-4,4′-[1,1′-(Hydrazine-1,2-diylidene)bis(ethan-1-yl-1-ylidene)]diphenol dihydrate

The asymmetric unit of the title compound, C16H16N2O2·2H2O, contains one half-molecule of diphenol and one water molecule. The complete diphenol molecule is generated by a crystallographic inversion centre. In the molecule, the central Cmethyl—C=N—N=C—Cmethyl plane makes a dihedral angle of 8.88 (6)° with its adjacent benzene ring. In the crystal, the components are linked by O—H⋯N and O—H⋯O hydrogen bonds into a three-dimensional network. The crystal structure is further stabilized by a weak C—H⋯π interaction.

The asymmetric unit of the title compound, C 16 H 16 N 2 O 2 Á-2H 2 O, contains one half-molecule of diphenol and one water molecule. The complete diphenol molecule is generated by a crystallographic inversion centre. In the molecule, the central C methyl -C N-N C-C methyl plane makes a dihedral angle of 8.88 (6) with its adjacent benzene ring. In the crystal, the components are linked by O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds into a three-dimensional network. The crystal structure is further stabilized by a weak C-HÁ Á Á interaction.

Comment
Hydrazones have been reported to possess fluorescence properties (Qin et al., 2009) and various biological activities such as to be used as insecticides, antitumor agents and antioxidants (Kitaev et al., 1970), as well as antimicrobial (Ramamohan et al., 1995) and antiviral properties (El-Tabl et al., 2008;Rollas & Küçükgüzel, 2007) and tyrosinase inhibitory activity (Bendre et al., 1998). With our on-going research on structural studies and properties of hydrazones Fun et al., 2010;Jansrisewangwong et al., 2010), the title compound (I) was synthesized. Our results show that (I) was inactive for tyrosinase inhibitory activity. Herein we report the synthesis and crystal structure of the title compound (I).
In the crystal structure (Fig. 2), the molecules are linked into three dimensional network by O-H···N and O-H···O hydrogen bonds (Table 1). C-H···π interaction was also also observed (Table 1).

Experimental
The title compound was synthesized by mixing a solution (1:2 molar ratio) of hydrazine hydrate (0.10 ml, 2 mmol) and 4-hydroxyacetophenone (0.54 g, 4 mmol) in ethanol (20 ml). The resulting solution was refluxed for 6 h, yielding the yellow solid. The resultant solid was filtered off and washed with methanol. Yellow block-shaped single crystals of the title compound suitable for x-ray structure determination were recrystalized from acetone by slow evaporation of the solvent at room temperature over several days, m.p. 377-379 K.

Refinement
The water hydrogen atoms were restrained to the ideal positions. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(O-H) = 0.86 Å, and d(C-H) = 0.93 Å for aromatic and 0.96 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 0.40 Å from H1W and the deepest hole is located at 0.35 Å from H1W. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Atoms with suffix A were generated by symmetry code 1 -x, 1 -y, 1 -z.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 120.0 (1) K. 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 Rfactors(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.