Structural and thermal behavior of imidazolium N,N′-dinitrourea

The structural and thermal behavior of energetic salts based on N,N′-dinitrourea (DNU) should be fully investigated for their further applications. In the present paper, the crystal structure and vibrational spectrum of imidazolium N,N′-dinitrourea ([IMI][DNU]) were investigated in detail. A slight twist or torsion was found in the cation and anion because of their interactions. These interactions also formed a stabilized hydrogen bond network. The vibrations of the functional groups were mainly exhibited in an infrared (IR) spectrum, and the skeletal stretching vibrations mainly appeared in a Raman spectrum. The non-isothermal kinetics of the title compound and its mixture with polyethylene glycol 10000 (PEG10000) were investigated with the methods of Kissinger and Ozawa. In situ IR analysis, mass spectral fragmentation, and bond dissociation enthalpy calculations showed that the initial decomposition step of [IMI][DNU] was the breakage of the NN bond in the anion. The in situ IR of gaseous phase products and mass spectral fragmentation indicated that the main final products of [IMI][DNU] decomposition were N2O and imidazole.

► Crystal structure of imidazolium N,N′-dinitrourea ([IMI][DNU]) has been investigated.
► IR and Raman spectrum were investigated specifically by experimental and DFT methods.
► In situ IR and mass spectroscopy confirmed the final decomposition products of [IMI][DNU].
► The possible decomposition pathway was proposed by combining with BDE analysis.