Copper Azide-based Complexes without Repulsive Steric Clashes between Azides for Advanced Primary Explosives

Primary explosives are essential energy transfer materials in explosive systems. At present, heavy metal-containing materials, such as lead azide (LA), are still the most widely used primary explosives. Copper azide (CA)-based primary explosives are considered as promising replacements for LA. However, there has little advancement in the high initiation performance and high safety of CA-based primary explosives because of the absence of the relevant theories and structural models. Herein, we report [Cu(N₃)(2-bmttz)]_n 1 with the exceptionally remarkable initiating capability and high safety. Performance tests indicated only 5 mg of 1 can successfully ignite the commercial secondary explosive RDX, as 1/6 priming charge of LA, demonstrating 1 is possibly the most efficient primary explosive known to date. Moreover, 1 possesses the rarely low impact sensitivity (IS = 2.5 J), which is comparable to that of LA and better than most of reported CA-based candidates. Both experimental and theoretical studies have shown that passivation of high-energy primary explosives can be achieved through the coordination between functional ligands and azide ions, in which azide ions without repulsive steric clashes only act as energetic building blocks. This work offers a new insight for designing high performance primary explosives for applications in advanced explosive systems.