N′-[(E)-2-Methoxybenzylidene]pyrazine-2-carbohydrazide

In the title compound, C13H12N4O2, all the non-H atoms lie on a crystallographic mirror plane and an intramolecular N—H⋯N hydrogen bond generates an S(5) ring; the conformation about the imine bond [1.280 (3) Å] is E. In the crystal, molecules assemble into a two-dimensional array via C—H⋯O(carbonyl) and C—H⋯N(pyrazine) contacts. Layers stack along the b-axis direction via weak π–π interactions between pyrazine rings [ring centroid distance = 3.8028 (8) Å].

In the title compound, C 13 H 12 N 4 O 2 , all the non-H atoms lie on a crystallographic mirror plane and an intramolecular N-HÁ Á ÁN hydrogen bond generates an S(5) ring; the conformation about the imine bond [1.280 (3) Å ] is E. In the crystal, molecules assemble into a two-dimensional array via C-HÁ Á ÁO(carbonyl) and C-HÁ Á ÁN(pyrazine) contacts. Layers stack along the b-axis direction via weakinteractions between pyrazine rings [ring centroid distance = 3.8028 (8) Å ].
The use of the EPSRC X-ray crystallographic service at the University of Southampton, England, and the valuable assistance of the staff there is gratefully acknowledged. JLW acknowledges support from CAPES (Brazil).

Comment
Pyrazinamide has well known anti-mycobacterial activity and it is the one of the most important drugs used in tuberculosis treatment (Chaisson et al., 2002;Gordin et al., 2000;de Souza, 2006). Various derivatives have been prepared and their anti-tuberculosis properties studied (Pinheiro et al., 2007). Among the reported crystal structures of pyrazinamide derivatives are those of pyrazinecarbonylhydrazones (Baddeley et al., 2009;Howie et al. 2010aHowie et al. , 2010b. In continuation of previous work, we now wish to report on the crystal structure of the title compound, (I).
All non-hydrogen atoms in (I) lie on a crystallographic mirror plane, Fig. 1 (3) Å] is E. The most prominent contacts in the crystal packing are of the type C-H···O and C-H···N, Table   1. The C-H···O contacts lead to chains along the a direction and involve the bifurcated carbonyl-O1 atom. Chains are linked in the c direction by C-H···N2(pyrazinyl) contacts with the result that a two-dimensional array is formed in the ac plane, Fig. 2. Layers stack along the b direction stabilized by weak π-π interactions formed between pyrazinyl rings [ring Fig. 3.
The N-bound atom was refined with N-H = 0.88±0.01 Å, and with U iso (H) = 1.2U eq (N). One reflection, i.e. (011), was omitted from the final refinement owing to poor agreement. Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 50% probability level. Fig. 2. View of the supramolecular array in the ac plane in the crystal structure of (I). The C-H···O and C-H···N contacts are shown as orange and blue dashed lines, respectively.  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 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.