Bis([1,2,4]triazolo)[1,5-b:5′,1′-e][1,2,4,5]tetrazine: Reconsideration of an advanced energetic fused heterocycle and synthesis of azo derivatives as ultrahigh-temperature heat-resistant energetic materials

• Two azo-coupled energetic compounds, ABATC and ABNTC, were synthesized, exhibiting a well-balanced combination of high energy density, thermal stability, and insensitivity. • The actual structure of DATC, bis([1,2,4]triazolo)[1,5- b :1′,5′- e ][1,2,4,5]tetrazine-2,7-diamine, was first determined by single crystal X-ray diffraction analysis. • The symmetrical planar conjugated tricyclic molecular framework imparts excellent high-temperature heat-resistance to the compound series. Bis([1,2,4]triazolo)[1,5- b :1′,5′- e ][1,2,4,5]tetrazine-2,7-diamine (DATC) was synthesized via thermal polycyclization in polyphosphoric acid and confirmed by single crystal X-ray diffraction, and its azo-coupled derivatives ABATC ( 4 ) and ABNTC ( 5 ) were subsequently obtained through oxidation and azo coupling reactions. Computational analysis of reaction energy barriers and 15 N NMR chemical shifts provides strong support for the two-step cyclization mechanism while ruling out the existence of the structural isomer. The thermal decomposition temperature of 4 is up to 427 °C, demonstrating an exceptional thermal stability under ultrahigh-temperature conditions. Compound 5 exhibits superior detonation performance (D: 8851.6 m/s, P: 31.72 GPa) compared to RDX and outstanding insensitivity (IS > 50 J; FS > 360 N), representing a rare combination of high energy density, thermal stability, and insensitivity. Density functional theory-based calculations clearly reveal the significant contributions of hydrogen bonding, π-π stacking, and delocalized conjugation effects to the thermal stability of these energetic compounds. Comparative analysis of the structural features and performance profiles across this series not only elucidates their intrinsic structure-property relationships, but also establishes a rational foundation for subsequent molecular design of novel high-temperature heat-resistant energetic materials. This series of energetic compounds have significant potential applications in specialized blasting, hypersonic weapon systems, and ultra-deep drilling technologies.