Design and Synthesis of Energetic Materials towards Versatile Applications by N-trinitromethyl and N-nitromethyl Functionalization of Nitroimidazoles

Modifying the properties of energetic materials is important not only for gaining insight into the relationship between structures and properties but also for multiple applications. A new family of energetic compounds, polynitroimidazoles featuring trinitromethyl, nitromethyl and methyl acetate moieties at the nitrogen position of heterocyclic rings were synthesized. The high-energy oxidizers 2-nitro and 4-nitro-1-(trinitromethyl)-1H-imidazoles were obtained by nitration of 1-acetonylpolynitroimidazoles in fuming HNO₃ and concentrated H₂SO₄. 4,5-Dinitro-1-(nitromethyl)-1H-imidazole and 4,5-dinitro-1-(acetate methyl)-1H-imidazole were afforded by using 68 % HNO₃ and concentrated H₂SO₄ through controllable synthesis. All the intermediates and the target compounds were confirmed by X-ray diffraction. It is noteworthy that one of the N-trinitromethyl nitroimidazole derivatives showed high density (ρ: 1.88 g cm⁻³), attractive positive oxygen balance (Ω: +18.3 %) and good detonation performance (D: 9003 m s⁻¹) exceeding those of ADN, while N-nitromethyl derivative behaved higher thermal stability and lower sensitivity in contrast to those of NG. N-acetate methyl derivative gave an interesting melt-castable property (T_m.p.: 86 ^oC, T_d: 224 ^oC), acceptable detonation performance as well as low sensitivity towards impact and friction (IS>40 J, FS>360 N), making it a competitive replacement for DNAN. These chemical and physical properties indicate that these novel materials show promising energetic performance towards future applications.