(2E)-N′-[(E)-Benzylidene]-3-phenylprop-2-enohydrazide from synchrotron radiation

In the title compound, C16H14N2O, the dihedral angle between the phenyl rings is 25.48 (12)°. An E conformation is found for each of the imine [1.269 (3) Å] and ethylene [1.313 (3) Å] bonds. In the crystal, molecules are linked by N—H⋯O hydrogen bonds, leading to zigzag chains along [010]. Supramolecular layers in the ab plane are formed, whereby the chains are linked by C—H⋯N and C—H⋯π interactions.

In the title compound, C 16 H 14 N 2 O, the dihedral angle between the phenyl rings is 25.48 (12) . An E conformation is found for each of the imine [1.269 (3) Å ] and ethylene [1.313 (3) Å ] bonds. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds, leading to zigzag chains along [010]. Supramolecular layers in the ab plane are formed, whereby the chains are linked by C-HÁ Á ÁN and C-HÁ Á Á interactions.

Wardell and Edward R. T. Tiekink
Comment (E)-Cinnamoylhydrazone derivatives have recently been shown to be agents against Chagas′ disease (CD) (Carvalho et al., 2012b), caused by the parasite Trypanosoma cruzi. CD is the major cause of infectious cardiopathy and represents an important public health problem. It affects approximately eight million people in Latin America (Rassi et al., 2010).
Neither the two established drugs, Nifurtimox and Benznidazole, is ideal because they present variable results depending on the phase of the disease, the dose and duration of the treatment, the patient's age and endemic region, as well as showing undesirable secondary side-effects (Soeiro & de Castro, 2011). The ArCH═ CHCONHN═CHAr′ compounds used in the trypanocidal study (Carvalho et al., 2012b) indicated considerable biological potential. Following on from our structural studies on (E)-PhCH═CH-CONHNHPh (Carvalho et al., 2009), (E)-4-O 2 NC 6 H 4 CH═CH-CONHNHCOPh (Carvalho et al., 2010a) and (E)-PhCH═CH-CONHN═ CHC 6 H 4 Cl-4.monohydrate (Carvalho et al., 2010b), we now wish to report the crystal structure of one of the compounds from the trypanocidal study, namely the title compound, (I).
In (I), Fig. 1, there is a twist in the molecule as seen in the dihedral angle between the phenyl rings of 25.48 (12) (Carvalho et al., 2010b), a decidedly more planar arrangement was noted (r.m.s. deviation of the 20 non-H atoms = 0.172 Å). However, a more twisted arrangement was found in the 2-hydroxyl derivative (Carvalho et al., 2012a) where the dihedral angle between the benzene rings is 16.67 (8)°.
In the crystal of (I), the molecules are linked by N-H···O hydrogen bonds (Table 1), resulting in zigzag chains along the b axis. The chains are linked into a supramolecular layer in the ab plane by C-H···N and C-H···π interactions, Fig.   3 and Table 1; the layers inter-digitate along the c axis, Fig. 4.

Experimental
The title compound was prepared as reported (Carvalho et al., 2012b). The sample used in the crystallographic study was grown from its EtOH solution in the form of small colourless needles.

Figure 1
The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.     Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.