N,N-Diethylanilinium 2,4-dioxo-5-(2,4,6-trinitrophenyl)-1,2,3,4-tetrahydropyrimidin-6-olate

In the crystal structure of the title molecular salt, C10H16N+·C10H4N5O9 −, the components are linked through a N—H⋯O hydrogen bonds. R 2 2(8) ring motifs are formed between inversion-related barbiturate residues. Two intramoleculer N—H⋯O hydrogen bonds are observed in the anion. The dihedral angle between 2,4,6-trinitrophenyl and barbiturate rings is 53.6 (2)°. The N,N-diethylamine substituent is disordered and was modeled as two geometrically equivalent conformers with occupancies of 0.737 (2) and 0.273 (2).

Data collection: APEX2 (Bruker, 2004); cell refinement: APEX2 and SAINT (Bruker, 2004); data reduction: SAINT and XPREP (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97. N,N-Diethylanilinium 2,4-dioxo-5-(2,4,6-trinitrophenyl)-1,2,3,4-tetrahydropyrimidin-6-olate M. Buvaneswari and D. Kalaivani Comment N,N-Dialkylaniline (aromatic amine) usually forms donor-acceptor adducts with electron-deficient nitro aromatics (Radha et al., 1987, Rizk et al., 1993. In the present investigation, it forms a different type of molecular salt (scheme) with the electron-deficient nitro aromatic compound, 1-chloro-2,4,6-trinitrobenzene (picryl chloride) in the presence of barbituric acid. We have already reported molecular salts of a similar type obtained from chlorine containing nitro aromatic compounds, barbituric acid and aliphatic amines (Kalaivani et al., 2008, Kalaivani & Malarvizhi, 2009, Kalaivani & Buvaneswari, 2010, Buvaneswari & Kalaivani, 2011. As noticed in other barbiturates, ring motifs are observed in the crystal structure of the title molecule. The protonated nitrogen atom of N,N-diethylaniline forms a hydrogen bond with the oxygen atom of the barbiturate anion and this may probably be the driving force for the formation of the title molecular salt.The negative charge on the oxygen atom of olate is delocalized over the nitro groups of the trinitrophenyl moiety and due to this extended conjugation the salt appears bright maroon red in colour.The title molecular salt is obtained with high purity in good yield (90%). Fig.1and 2 represent the ORTEP and packing view of the title molecule.

Experimental
Picryl chloride(1.3.g, 0.005 mol) was dissolved in 15 ml absolute alcohol. Barbituric acid (0.6 g, 0.005 mol)was dissolved in 30 ml of absolute alcohol. These two solutions were mixed and heated to 50°C.To this hot mixture, 4 ml of N,N-diethylaniline (0.03 mol) was added and shaken well for 3hrs. The crystals obtained were filtered, washed with 50 ml of dry ether and recrystallized from absolute alcohol (yield of pure crystals 90%, m.p.> 573 K). Maroon red block-like single crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of an ethanolic solution of the title compound at room temperature.

Refinement
H atoms bonded to C atoms were placed in their geometrically calculated positions and refined using the riding model, with

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.
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 > 2sigma(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.