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

The asymmetric unit of the title molecular salt, C10H16N+·C10H5N4O7 − (trivial name: N,N-diethylanilinium 2,4-dinitrophenylbarbiturate), comprises two anion–cation units. In the anions, the dinitrophenyl ring and the mean plane of the barbiturate ring [planar to within 0.011 (2) and 0.023 (2) Å in the two anions] are inclined to one another by 41.47 (9) and 45.12 (9)°. In the crystal, the anions are linked via strong N—H⋯O hydrogen bonds, forming chains propagating along [10-1]. Within the chains, adjacent inversion-related anionic barbiturate entities are joined through R 2 2(8) ring motifs. The cations are linked to the chains via N—H⋯O hydrogen bonds. The chains are linked via a number of C—H⋯O interactions, forming a three-dimensional structure.

In the crystal of (II), the anions are linked via N-H···O hydrogen bonds (Table 1 and Fig. 2), forming chains along direction [1 0 -1]. This linkage and the R 2 2 (8) ring motifs formed between inversion-related barbiturate residues contributes considerably to the extraordinary stability of the title molecular salt. The cations are linked to the chains via N-H···O hydrogen bonds (Table 1 and Fig. 2). There are C-H···O interactions present (Table 1) but no π-π stacking interactions between the N,N-diethylaniline and 2,4-dinitrophenyl ring moieties.
As barbiturates are employed in the treatment of neurological disorders (Hueso et al., 2003;Kalaivani et al., 2008;Tripathi, 2009;Kalaivani & Buvaneswari, 2010), the non-bonding interactions of the present investigation may help to understand the mechanistic aspects of the physiological action of barbiturates.

Experimental
Analytical grade 1-chloro-2,4-dinitrobenzene (2.02 g, 0.01 mol) was dissolved in 20 ml of absolute alcohol. Barbituric acid (1.28 g, 0.01 mol) was also dissolved in 30 ml of absolute alcohol separately. These two solutions were then mixed well. To this mixture, ca. 4 ml of N,N-diethylaniine (0.03 mol) was added and shaken well for 5-6 hrs. The slightly turbid solution obtained was filtered and kept as such at room temperature. After a period of four weeks, dark shiny maroon red coloured crystals of the title salt crystallized out from this solution. The crystals were filtered and washed well with 30 ml of dry ether. The crystals were then powdered and washed with 5 ml of absolute alcohol to remove the unreacted reactants and finally with 25 ml of dry ether. The pure powder was then recrystallized from hot ethanol (M.p: 481 K; yield: 80%). Good quality single crystals, suitable for X-ray diffraction studies, were obtained by slow evaporation of a solution in ethanol at room temperature. The crystals obtained were non-hygroscopic and extraordinarily stable at room supplementary materials sup-2 . E69, o3-o4 temperature.

Refinement
The N-bound H atoms were located in a difference electron density map and refind with a N-H distance restraint of 0.90 (2) Å. The C-bound hydrogen atoms were placed in calculated positions and refined as riding atoms: C-H = 0.93, 0.97 and 0.96 Å for CH, CH 2 and CH 3 H atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for methyl H atoms and = 1.2 for other H atoms.   A partial view of the crystal packing of the title compound with the N-H···O hydrogen bonds shown as dashed lines (see Table 1 for details).

N,N-Diethylanilinium 5-(2,4-dinitrophenyl)-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-olate
Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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 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.