Synthesis and detonation performance of novel tetrazolyl–triazine nitrogen-rich energetic materials

Abstract

The properties of energetic materials (EMs) are significantly influenced by specific features of their components and including multiple nitrogen-rich (N-rich) heterocycles within a single rigid framework is perhaps one of the most impactful and modern techniques employed in the design and development of novel high-performing explosives. In this regard, coupling tetrazole and s-triazine moieties is an attractive approach given their high nitrogen content and heats of formation resulting from the multiple N–N and/or C–N bonds in their frameworks. With this in mind, herein we report the synthesis of 2,4,6-tris(1H-tetrazol-5-yl)-1,3,5-triazine (H₃TTT, 1), a new N-rich (73.7%) EM, along with a series of its salts (3–7). All compounds were physically characterized by IR, multinuclear (¹H, ¹³C) NMR spectroscopy, gas pycnometry, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The molecular structure of the TTT³⁻ moiety was confirmed through single-crystal X-ray diffraction (SCXRD) analysis of the triethylammonium (TEA) salt (2). Key energetic parameters were assessed, revealing neutral H₃TTT (1) exhibits excellent thermal stability over 247 °C as confirmed through DSC studies, while the decomposition temperatures of the energetic salts (3–7) were found to be lower than the parent material 1 (T_dec ranges from 144 °C (7) to 217 °C (3)). In terms of detonation performance, the highest values were observed for 4 (P_det = 24.8 GPa, V_det = 8061 m s⁻¹) and 5 (P_det = 24.6 GPa, V_det = 7984 m s⁻¹), as well as for 1 (P_det = 22.4 GPa, V_det = 7430 m s⁻¹), where all three outperform TNT (P_det = 19.5 GPa; V_det = 6881 m s⁻¹). The results of the thermochemical calculations indicate that H₃TTT (1) and its salts 4 and 5 are characterized by ballistic parameters comparable to those of the commonly used JA-2 propellant. By using this simple and straightforward approach to EM development, we have generated a series of materials that may be employed as green alternatives to TNT secondary explosives and low-erosion, environmentally benign high-nitrogen ingredients for gun-propellants.