Synthesis, Structure and Property of 5‐Aminotetrazolate Room‐Temperature Ionic Liquids

Abstract

AbstractEight 5‐aminotetrazolate (AT) salts based on the 1,2,3‐trimethylimidazolium (1), 1,3‐dimethylimidazolium (2), 1‐ethyl‐3‐methylimidazolium (3), 1‐butyl‐3‐methylimidazolium (4), 1‐isobutyl‐3‐methylimidazolium (5), 1‐(3′‐methylbutyl)‐3‐methylimidazolium (6), 1‐hexyl‐3‐methylimidazolium (7) and 1‐methyl‐3‐octylimidazolium (8) cations have been synthesized in high yields and fully characterized by IR and NMR spectroscopy and elemental analysis. White plate crystals of 1 were isolated in methanol/diethyl ether and crystallized. Both the AT anion and the 1,2,3‐trimethylimidazolium cation in 1 were delocalized. Differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests were used to assess the thermal stabilities of the AT salts. These salts decomposed within the temperature range 230 °C–262 °C. Salts 3–8 are very fluent room‐temperature ionic liquids, whose glass transition temperatures are low. Their viscosities at 30 °C are in the range from 92 cP to 208 cP. A correlation between the viscosity and temperature was found, and the ionic liquids to do not display an Arrhenius temperature behaviour. In addition, the standard enthalpies of formation of salts 1–8 were investigated and analyzed by the theoretical methods. Salt 2 with the 1,3‐dimethylimidazolium cation gave the highest positive enthalpy of formation. For the assessment of the energetic character of the AT salts, impact sensitivities and friction sensitivities were recorded. These AT salts are insensitive to impact (>40 J) and friction (>360 N) confirmed by UN standards. The reactions of these AT salts with 100 % HNO3 were also determined.