Energetic transition metal complexes based on methyl carbazate and picric acid: syntheses, structures, physicochemical properties and catalysis on the thermal decomposition of ammonium perchlorate

Abstract

New energetic transition metal complexes based on methyl carbazate (MCZ) and picric acid (PA), [M(MCZ)₂(H₂O)₂]PA₂ (M = Mn²⁺ (1), Fe²⁺ (2), Co²⁺ (3), Ni²⁺ (4), Cu²⁺ (5), Zn²⁺ (6)) and [Cd(MCZ)₂(H₂O)₃]PA₂·4H₂O (7), were synthesized by a facile strategy, and characterized by FT-IR and elemental analysis. Their crystal structures were determined by single crystal X-ray diffraction. Thermal stability of the seven complexes was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Decomposition onset temperatures of 1 to 7 rise in the following order: 2 < 5 < 3 < 4 < 7 < 6 < 1. The apparent activation energy (E_a) of the thermal decomposition processes of these compounds is in the range of 112.3 to 232.9 kJ mol⁻¹, which illustrates their moderate activity of thermo-kinetics. Sensitivity tests reveal that these compounds are insensitive to friction (>360N), and the impact sensitivities of these compounds fall within the range of 2.75 (complex 7) to 40 J (complex 1). Furthermore, these compounds were examined for use as additives to promote the thermal decomposition of ammonium perchlorate. Results from DSC reveal that all of them exhibit excellent catalytic performance. Notably, when compound 5 is added to AP, there is only one exothermic peak with a peak temperature of 240 °C in its decomposition process; the endothermic crystal transformation of AP disappeared, which shows the outstanding catalytic effect of compound 5.