Alkaline metal and alkaline earth metal salts of di(1H-tetrazol-5-yl)methanone (DTO): energetic catalysts for ammonium perchlorate decomposition

Abstract

To explore novel coordination complexes for promising energetic materials, alkaline metal (Na⁺ (1), Na⁺ (2), K⁺ (3), and Rb⁺ (4)) and alkaline earth metal (Mg²⁺ (5), Ca²⁺ (6), and Sr²⁺ (7)) salts of di(1H-tetrazol-5-yl)methanone (DTO) were synthesized via a mild route. These energetic salts were characterized by single-crystal X-ray diffraction, FTIR spectroscopy, and elemental analysis. DTO showed various coordination modes in these compounds. The thermal behaviors and sensitivities of the energetic salts were measured by the differential scanning calorimetry (DSC) and BAM methods. Na⁺ (1), Na⁺ (2), Mg²⁺ (5), Ca²⁺ (6), and Sr²⁺ (7) salts exhibited two slow exothermic processes in their DSC curves, while K⁺ (3) and Rb⁺ (4) salts had sharp exothermic peaks at 222.8 °C and 242.3 °C, respectively. In addition, their catalytic performances with respect to ammonium perchlorate (AP) thermal decomposition were studied by DSC. Mg²⁺ (5) and Ca²⁺ (6) demonstrated good catalytic properties for ammonium perchlorate (AP) decomposition, allowing for high-temperature decomposition at temperatures 63.9 °C and 54.8 °C higher than pure AP, respectively. The apparent activation energy (E_O) of AP + 5 and AP + 6 were calculated using the Kissinger and Ozawa equations. Considering that the calculated values are lower than that of pure AP, the complexes can be employed as combustion catalysts for composite propellants.