2,6-Diamino-3,5-dinitro-1,4-pyrazine dimethyl sulfoxide solvate

The title compound, C4H4N6O4.C2H6OS, crystallizes in the triclinic space gr oup P (1) over bar. It is a dimethyl sulfoxide (DMSO) solvate of the insens itive energetic compound 2,6-diamino-3,5-dinitro-1,4-pyrazine (ANPZ). The s tructure has been determined to obtain more accurate metrical parameters fo r the 2,6-diamino-3,5-dinitro-1,4-pyrazine moiety than those obtained from unsolvated crystals which are invariably twinned. The packing motif consist s of two formula units linked by strong complementary hydrogen bonds betwee n the ANPZ units with the two DMSO solvate molecules each linked by two bif urcated hydogen bonds to the two ANPZ units. This central motif is further linked into planar sheets by weaker interactions between the DMSO methyl H atoms and the O atoms from the nitro groups. This looser packing arrangemen t compared to ANPZ is reflected in a lower density (1.662 Mg m(-3) versus 1 .812 Mg m(-3) for ANPZ).