One-Pot Synthesis, Crystal Structure, and Thermal Decomposition Behavior of 1,1ʹ-Diamino-4,4ʹ,5,5ʹ-Tetranitro-2,2ʹ-Biimidazole

Abstract

ABSTRACT1,1ʹ-Diamino-4,4ʹ,5,5ʹ-tetranitro-2,2ʹ-biimidazole (DATNBI) was synthesized, by employing one-pot facile method, from 4,4ʹ,5,5ʹ-tetranitro-2,2ʹ-biimidazole. The crystal structure was determined by X-ray diffraction for the first time. DATNBI crystallized in monoclinic system P21/c, with a crystal density of 1.934 g cm−3 at 293(2) K and 2.019 g cm−3 at 130(2) K, respectively. Its crystal parameters at 293 K are a = 4.8833(15) Å, b = 6.960(2) Å, c = 6.928(4) Å, α = γ = 90°, β = 93.418(6)°, V = 591.1(3) Ǻ3, Z = 2, μ = 0.178 mm−1, and F(000) = 348. The thermal stability and non-isothermal kinetics of DATNBI were studied by differential scanning calorimeter (DSC) with heating rates of 5, 10, 15, and 20 K min−1. The apparent activation energy (Ea) at the first decomposition peak calculated by Kissinger, Ozawa, and Starink equations were 85.50, 89.67, and 86.10 kJ mol−1, respectively. For the second peak, these were 116.49, 119.82, and 117.45 kJ mol−1, respectively, with individual pre-exponential factors lnA = 18.40 s−1 and lnA = 25.11 s−1. The thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) analysis of thermal decomposition products reveals that the main decomposition gas products are H2O, N2O, CO2, and NO2. Based on the new crystalline densities, the detonation velocity and pressure predicted by EXPLO5 are 9062 m s−1 and 36.4 GPa, respectively.