Boosting intermolecular interactions of fused cyclic explosives: the way to thermostable and insensitive energetic materials with high density

Density is a crucial factor affecting the energetic performance of explosives. However, the method of increasing density by introducing sensitive high-energy substituents is at the expense of molecular stability. Here, the packing efficiency of energetic materials was enhanced by boosting the intermolecular hydrogen-bonding and pi-type interactions. Two fused cyclic tetrazine explosives with strong hydrogen bonds and edge-to-face stacking were successfully obtained via facile and effective nucleophilic substitution reaction and a series of their salts were also synthesized. All the compounds were fully characterized by IR, multinuclear NMR spectra, elemental analysis and differential scanning calorimetry (DSC). Four of them were also structurally characterized with single-crystal X-ray diffraction. The physicochemical properties of all the compounds were investigated. The results show that the strong intermolecular interactions give the neutral compounds high density while maintaining low mechanical sensitivity, high thermal stability and good detonation property. The hydroxylammonium and hydrazinium salts show comparable detonation velocities with RDX while exhibiting superior mechanical insensitivities. These findings demonstrate that boosting intermolecular interactions of fused cyclic explosives is promising in obtaining novel high density energetic materials.