4-Methyl-N-(4-nitrobenzylidene)piperazin-1-amine

In the title compound, C12H16N4O2, the piperazine ring is in a slightly distorted chair conformation. In the molecule, the mean plane of the nitro group is twisted by 8.0 (3)° from that of the benzene ring. Also, the mean plane of the 2-nitrobenzyl ring is twisted slightly from that of the piperazine ring, with an N—N=C—C torsion angle of −176.24 (11)°. In the crystal, pairs of weak C—H⋯O interactions link the molecules into dimers approximately along [010].

In the title compound, C 12 H 16 N 4 O 2 , the piperazine ring is in a slightly distorted chair conformation. In the molecule, the mean plane of the nitro group is twisted by 8.0 (3) from that of the benzene ring. Also, the mean plane of the 2-nitrobenzyl ring is twisted slightly from that of the piperazine ring, with an N-N C-C torsion angle of À176.24 (11) . In the crystal, pairs of weak C-HÁ Á ÁO interactions link the molecules into dimers approximately along [010].
CNK thanks University of Mysore for research facilities and is also grateful to the Principal, Maharani's Science College for Women, Mysore, for giving permission to undertake research. JPJ acknowledges the NSF-MRI program (grant No. CHE-1039027) for funds to purchase the X-ray diffractometer. Schiff base ligands derived from 1-amino-4-methylpiperazine have attracted interest due to diverse biological activities associated with the piperazine moiety. Schiff base piperazine derivatives have been designed to study their antimicrobial (Savaliya et al., 2010;Kharb et al., 2012)) and antibacterial activity (Xu et al., 2012). In addition, many drugs contain a piperazine ring as part of their molecular structure (Cai et al., 2009). Piperazines are among the most important building blocks in today's drug discovery and are found in biologically active compounds across a number of different therapeutic areas (Brockunier et al., 2004;Bogatcheva et al., 2006) such as antifungal (Upadhayaya et al., 2004), anti-bacterial, antimalarial activity and as in antipsychotic agents (Choudhary et al., 2006). A review on the current pharmacological and toxicological information for piperazine derivatives has been recently presented (Elliott, 2011). The synthesis of related piperazine compounds and their medicinal and pharmaceutical activity have also been reported (Contreras et al., 2001;Capuano et al., 2002). The crystal structures of some related compounds, viz., 2-[(4-methylpiperazin-1-yl)iminomethyl]phenol (Guo, 2007) (Xu et al., 2009), 2-methoxy-4-[(4-methylpiperazin-1-yl)-iminomethyl]phenol (Zhou et al., 2011) and 2,4-dibromo-6-[(4-methylpiperazin-1yl)iminomethyl]phenol (Ming-Lin et al., 2007) have been reported. In view of the above importance of N-piperazinyl Schiff bases, the title compound, (I), C 12 H 16 N 4 O 2 has been synthesized and the crystal structure is reported herin.
In the title compound, (I), the piperazine ring is in a slightly distorted chair conformation with puckering parameters Q, θ, and φ = 0.5646Å, 170.8 (5)° and 187.961 (8)° (Cremer & Pople, 1975) (Fig. 1). In the molecule, the mean plane of the nitro group is twisted by 8.0 (3)° from that of the phenyl ring. Also, the mean plane of the 2-nitrobenzyl ring is twisted slightly from that of the piperazine ring with an N1/N2/C5/C6 torsion angle of -176.24 (11)°. Bond lengths are in normal ranges (Allen et al., 1987). Weak C-H···O intermolecular interactions are observed which lead to formation of dimers approximately along [010] and influence crystal packing (Fig. 2).

Experimental
To a solution of o-nitrobenzaldehyde (0.75 g, 0.005 mol) in 10 ml of methanol, an equimolar amount of (1-amino-4methyl)piperazine (0.57 g, 0.005 mol) is added dropwise with constant stirring. The mixture was refluxed for 8 hours to obtain an orange solution. The solution was evaporated to a small volume at room temperature and allowed to stand.
Yellow crystals were formed in one day (m.p.: 358-360 K) and were used as such for x-ray diffraction studies.

Refinement
All of the H atoms were placed in their calculated positions and then refined using the riding model with Atom-H lengths of 0.95Å (CH), 0.99Å (CH 2 ) or 0.98Å (CH 3 ). Isotropic displacement parameters for these atoms were set to 1.2 (CH, CH 2 ) or 1.5 (CH 3 ) times U eq of the parent atom. Idealised Me were refined as rotating groups.  (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.