Insensitive energetic 5-nitroaminotetrazolate ionic liquids

Abstract

Five energetic ionic liquids of 5-nitroaminotetrazolate anion (NAT) combined with 1,3-dimethylimidazolium (1), 1-ethyl-3-methylimidazolium (2), 1-butyl-3-methylimidazolium (3), 1-hexyl-3-methylimidazolium (4), and 1-methyl-3-octylimidazolium (5) cations were synthesized in high yields and fully characterized by IR, NMR and elemental analysis. Colorless block crystals of 1 were isolated in methanol/ethanol and crystallized in the orthorhombic system Fdd2(43) (a = 49.337(3) Å, b = 20.9073(12) Å, c = 3.6993(2) Å, V = 3815.84(38) ų, Z = 16). The ionic liquids 1–5 are thermally stable at temperatures higher than 200 °C. Among them, 2–5 are found to be room temperature ionic liquids. The heats of formation of 1–5 obtained by both experimental and theoretical methods are all positive. 1 possesses the highest value of 194.6 kJ mol⁻¹ and 0.86 kJ g⁻¹. These novel NAT energetic ionic liquids contain only C, H, N and O elements. The CHNO type ionic liquids 1–5 are insensitive towards impact (>40 J) and friction (>360 N). They showed good combustion characteristics after being ignited by a flame. They are of interest as liquid energetic materials with modestly high energy, high thermal stability, and good insensitivity to impact and friction, as well as environmentally friendly decomposition gases.