A Smart Access to the Dinitramide Anion - The Use of Dinitraminic Acid for the Preparation of Nitrogen-Rich Energetic Copper(II) Complexes

Dinitraminic acid (HN(NO₂)₂, HDN) was prepared by ion exchange chromatography and acid‐base reaction with basic copper(II) carbonate allowed the in  situ preparation of copper(II) dinitramide, which was reacted with twelve nitrogen‐rich ligands, for example, 4‐amino‐1,2,4‐triazole, 1‐methyl‐5H‐tetrazole, di(5H‐tetrazolyl)‐methane/‐ethane/‐propane/‐butane. Nine of the complexes were investigated by low‐temperature X‐ray diffraction. In addition, all compounds were investigated by infrared spectroscopy (IR), differential thermal analysis (DTA), elemental analysis (EA) and thermogravimetric analysis (TGA) for selected compounds. Furthermore, investigations of the materials were carried out regarding their sensitivity toward impact (IS), friction (FS), ball drop impact (BDIS) and electrostatic discharge (ESD). In addition, hot plate and hot needle tests were performed. Complex [Cu(AMT)₄(H₂O)](DN)₂, based on 1‐amino‐5‐methyltetrazole (AMT), is most outstanding for its detonative behavior and thus also capable of initiating PETN in classical initiation experiments. Laser ignition experiments at a wavelength of 915 nm were performed for all substances and solid‐state UV‐Vis spectra were recorded to apprehend the ignition mechanism.

Azo- and methylene-bridged mixed azoles for stable and insensitive energetic applications

A simple synthetic strategy for the preparation of high nitrogen content azo- and methylene bridged mixed energetic azoles was used.

Stability and performance of gun propellants incorporating 3,6-dihydrazino-s-tetrazine and 5-aminotetrazolium nitrate

The addition of either 3,6-dihydrazino-s-tetrazine (DHT) or 5-aminotetrazolium nitrate (HAT-NO₃) to nitrocellulose-based propellants were investigated. At 25% (m/m) concentration, DHT and HAT-NO3 had significant impact on the burning rate of the propellant, up to 80% higher than that of the reference propellant. DHT was found to have very poor compatibility with nitrocellulose and the nitrated esters used in the formulation despite the presence of stabilizer. This lead to a rapid autocatalytic decomposition reaction resulting in a deflagration. HAT-NO₃ also had poor compatibility with the same materials. On the contrary, non-ionic tetrazoles were found to be fully compatible with nitrocellulose and nitrated esters based propellants. Most nitrogen-rich energetic molecules have been studied for their explosive characteristics. This study shed light on the potential use of these materials as burning rate modifiers for gun propellant applications, for which very little is known. Moreover, it investigates the stability of the formulations incorporating nitrogen-rich molecules, as a means of assessing the safe use of these novel propellants.

Proposed Proton-Transfer Mechanism for the Initial Decomposition Steps of BTATz

The first steps in the gas-phase decomposition mechanism of N3,N6-bis (1 H-tetrazol-5-yl)-1,2,4,5-tetrazine-3,6-diamine, BTATz, anions and the kinetic isotope effects in these processes were studied using combined multistage mass spectrometry (MS/MS) and computational techniques. Two major fragmentation processes, the exergonic loss of nitrogen molecules and the endergonic loss of hydrazoic acid, were identified. The observation of a primary isotope effect supported by calculations suggests that the loss of a nitrogen molecule from the tetrazole ring involves proton migration, either to or within the terazole ring, as a rate-determining step. The fragmentation of a hydrazoic acid occurs through an asymmetrical retro-pericyclic reaction. Calculations show the relevance of these mechanisms to neutral BTATz. Our findings may contribute to the understanding of decomposition routes in these nitrogen-rich energetic materials and allow tailoring their reactivity and decomposition pathways for better control of performance.

A novel facile transformation to 1,2-bis(3-nitro-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-yl)hydrazine salts

A facile and unique conversion from NN group to HN–NH group was discovered, by which 1,2-bis(3-nitro-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-yl)hydrazine and its energetic salts have been readily prepared as high-energy-density materials.

Computational study of the structure and properties of bicyclo[3.1.1]heptane derivatives for new high-energy density compounds with low impact sensitivity

To design new high-energy density compounds (HEDCs), a series of new bicyclo[2.2.1]heptane derivatives containing an aza nitrogen atom and nitro substituent were designed and studied theoretically. The density, heat of sublimation and impact sensitivity were estimated by electrostatic potential analysis of the molecular surface. Based on the designed isodesmic reaction, and the reliable heat of formation (HOF) of the reference compounds, HOFs were calculated and compared at B3LYP/6-311G(d,p) and B3P86/6-311G(d,p), respectively. The detonation performances, bond dissociation energies (BDE) and impact sensitivity were calculated to evaluate the designed compounds. The calculated results show that the number of aza nitrogen atoms and NO₂ groups are two important factors for improving HOF, density and detonation properties. Thermal stability generally decreases with increasing nitro groups. And the N-NO₂ bond is the trigger bond for all designed compounds except B8, whose trigger bond is C-NO₂. Importantly, the BDE values are between 86.95 and 179.71 kJ mol^-1 and meet the requirement for HEDCs. Detonation velocity and detonation pressure were found to be 5.77-9.65 km s^-1 and 12.30-43.64 GPa, respectively. After comprehensive consideration of thermal stability, impact sensitivity and detonation properties, A7, A8, B8, C8, D7, E7, F7 and G6 may be considered as potential HEDCs. Especially, A8, B8, C8, and D7 have better detonation properties than the famous caged nitramine CL-20 (D = 9.40 km/s, P = 42.00GPa). Besides, all the designed potential HEDCs have reasonable impact sensitivity. Graphical abstract New high-energy density compounds (HEDCs) with low impact sensitivity (A8, B8, C8 and D7 have better detonation properties than CL-20).

N-oxide 1,2,4,5-tetrazine-based high-performance energetic materials

One route to high density and high performance energetic materials based on 1,2,4,5-tetrazine is the introduction of 2,4-di-N-oxide functionalities. Based on several examples and through theoretical analysis, the strategy of regioselective introduction of these moieties into 1,2,4,5-tetrazines has been developed. Using this methodology, various new tetrazine structures containing the N-oxide functionality were synthesized and fully characterized using IR, NMR, and mass spectroscopy, elemental analysis, and single-crystal X-ray analysis. Hydrogen peroxide (50 %) was used very effectively in lieu of the usual 90 % peroxide in this system to generate N-oxide tetrazine compounds successfully. Comparison of the experimental densities of N-oxide 1,2,4,5-tetrazine compounds with their 1,2,4,5-tetrazine precursors shows that introducing the N-oxide functionality is a highly effective and feasible method to enhance the density of these materials. The heats of formation for all compounds were calculated with Gaussian 03 (revision D.01) and these values were combined with measured densities to calculate detonation pressures (P) and velocities (νD ) of these energetic materials (Explo 5.0 v. 6.01). The new oxygen-containing tetrazines exhibit high density, good thermal stability, acceptable oxygen balance, positive heat of formation, and excellent detonation properties, which, in some cases, are superior to those of 1,3,5-tritnitrotoluene (TNT), 1,3,5-trinitrotriazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX).

High-pressure characterization of nitrogen-rich bis-triaminoguanidinium azotetrazolate (TAGzT) by in situ Raman spectroscopy

Compounds rich in nitrogen are attracting significant interest not only because of their high energy content but also because they are potentially more environmentally benign in comparison to conventional energetic materials. Given this interest, it is desirable to understand their molecular composition and structural variations with pressure to derive their stability and determine the conditions in which they transform physically or chemically. In this study, we examine the room-temperature isothermal compression behavior of bis-triaminoguanidinium azotetrazolate (TAGzT) by in situ Raman spectroscopy to pressures near 17 GPa. We assign the characteristic vibrational bands and report the effects of pressure on band intensity, line width, and frequency shift. Two prominent peaks near 1370 and 1470 cm(-1) arise from the C-N and N═N symmetric stretches, respectively. Overall, the intensity of these bands and others diminishes with pressure, and their spectral linewidths increase monotonically upon compression. The vibrational frequency modes blue shift linearly upon compression, indicating a generalized stiffening of the bonds as the pressure increases. These results, together with micro Raman spectroscopic analyses of the recovered, decompressed samples, suggest that TAGzT does not undergo any phase transitions within this pressure range. We estimate and report the C-N and N═N intermolecular bond lengths under compression.