N-Methylene-C-linked nitropyrazoles and 1,2,4-triazol-3-one: thermally stable energetic materials with reduced sensitivity

Recently, there has been a surge in research focusing on triazolone-based energetic materials, propelled by their remarkable properties such as good detonation performance as well as acceptable thermal and physical stability. In this work, a novel combination of the triazolone framework with dinitropyrazoles has been attained using the N-methylene-C-linked approach. Different substituents (NH2, NO2, N3, OH) were utilized on the dinitropyrazole moiety to obtain neutral energetic compounds 3-5 and 8. Furthermore, the hydroxy derivative (compound 8) facilitates the formation of energetic salts 9-13 to fine-tune the overall properties further. All the novel compounds 3-13 were thoroughly characterized by IR, multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. Compounds 3, 4, 8, and 10 were further confirmed via15N NMR spectroscopy. The structure of compounds 3 and 8 was also confirmed through single-crystal X-ray diffraction studies. The majority of synthesized compounds showed good thermal stability as well as insensitivity toward external stimuli. Computational studies, including analyses such as Hirshfeld surface, non-covalent interaction, electrostatic potential surface, and HOMO-LUMO analysis, were conducted to examine the influence of substitution at the 4th position on the overall stability of compounds 3, 4, and 8.

Construction of Highly Thermostable and Insensitive Three-Dimensional Energetic Salts Based on [1,2,5]Oxadiazolo[3,4-d]pyrimidine

A novel method for accessing energetic salts of a fused-ring skeleton based on [1,2,5]oxadiazolo[3,4-d]pyrimidine and three alkali metals, sodium (Na), potassium (K), and cesium (Cs), was developed. All three compounds were fully characterized, and their structures were confirmed by single-crystal X-ray analysis. They were highly thermally stable (>290 °C) and had high density, good detonation properties, and insensitive properties, which suggested possible heat-resistant explosive applications.

From Nitro- to Heterocycle-Functionalized 1,2,4-Triazol-3-one Derivatives: Achieving High-Performance Insensitive Energetic Compounds

5-Nitro-1,2,4-triazol-3-one, a nitro-functionalized 1,2,4-triazol-3-one (TO) derivative, shows excellent energetic properties and promising application potential. However, the use of the TO skeleton as an energetic material is still largely underexplored both theoretically and practically. We report here a mild and efficient method for obtaining the TO skeleton via a reaction of aminocarbohydrazide with BrCN. Two energetic compounds (2 and 5) were synthesized and fully characterized by ¹⁵N nuclear magnetic resonance, two-dimensional ¹H-¹⁵N heteronuclear multiple-bond correlation, and single-crystal X-ray diffraction. The reaction mechanism was also studied with the aid of quantum calculations. Compound 2 shows promising properties as a high-performance insensitive energetic material.

Properties and Promise of Catenated Nitrogen Systems As High-Energy-Density Materials

The properties of catenated nitrogen molecules, molecules containing internal chains of bonded nitrogen atoms, is of fundamental scientific interest in chemical structure and bonding, as nitrogen is uniquely situated in the periodic table to form kinetically stable compounds often with chemically stable N-N bonds but which are thermodynamically unstable in that the formation of stable multiply bonded N₂ is usually thermodynamically preferable. This unique placement in the periodic table makes catenated nitrogen compounds of interest for development of high-energy-density materials, including explosives for defense and construction purposes, as well as propellants for missile propulsion and for space exploration. This review, designed for a chemical audience, describes foundational subjects, methods, and metrics relevant to the energetic materials community and provides an overview of important classes of catenated nitrogen compounds ranging from theoretical investigation of hypothetical molecules to the practical application of real-world energetic materials. The review is intended to provide detailed chemical insight into the synthesis and decomposition of such materials as well as foundational knowledge of energetic science new to most chemists.

3D solvent-free energetic metal–organic framework (EMOF) achieved by removing inclusion molecules from a new coordination polymer

The reaction of CuCl and NaN₃ with 4,4′-azo-1,2,4-triazol-5-one (H₂ZTO) under solvothermal conditions produced a new 3D heteronuclear Cu(i)-Na(i) energetic metal–organic framework (EMOF), [Cu₃Na(ZTO)₂]_n·nCH₃CN (1).

Theoretical study of a series of 4,4'-azo-1H-1,2,4-triazol-5-one based nitrogen-rich salts as potential energetic compounds

Density function theory has been employed to systemically study 4,4'-azo-1H-1,2,4-triazol-5-one (ZTO) and its six nitrogen-rich salts at two different calculated levels (B3LYP/6-31G(d,p) and B3PW91/6-31G(d,p)). Their optimized geometries, electronic structures and molecular electrostatic potentials were further studied. Based on the two computed methods, the results of the optimized geometries show that the calculated structure of each compound adopted at the two different levels are rather similar except salt 7 with some differences. The values of the energy gaps indicate that compound 3 has the highest reactivity among salts 2-7. The crystal densities were corrected using the Politzer approach based on these two optimized levels. The density values with slight deviation indicate that the two calculated levels are applicable and the results are convincible. Based on the isodesmic reactions and Born-Haber energy cycle, the solid-phase heats of formation (HOFs) were predicted. Detonation parameters were evaluated using the Kamlet-Jacobs equations on the foundations of the calculated densities and HOFs. The results manifest that salt 2 exhibits the best detonation performance due to its highest density (1.819 g cm^-3), followed by salt 6. Moreover, impact sensitivities of compounds 1-7 were assessed using the calculated Q values to correlate with h ₅₀. Combining the detonation performance with safety, 1-7 exhibit good comprehensive properties and might be screened as a composition of modern nitrogen-rich energetic compounds.

The novel compound dimethylamine-5,5′-bistetrazole-1,1′-diolate: crystal structure, thermal investigation, safety evaluation and theoretical studies

The crystal of DMA-BTO, one unknown intermediate in the production of famous high energy insensitive explosive TKX-50, was easily prepared and characterized. Its thermal behaviors, safety parameters and theoretical studies were performed.

Structures and properties of energetic cations in energetic salts

Energetic cations play important roles in energetic performance, which may attribute to the diverse backbones and substituted groups of energetic cations. This review emphasizes the roles of backbones and substituted groups in the energetic performance of energetic salts.

Alkali and alkaline earth metal salts of tetrazolone: structurally interesting and excellently thermostable

Alkali and alkaline earth metal salts of tetrazolone were first reported and may be promising potential candidates of new green insensitive energetic materials.

Molecular dynamics simulations for 5,5′-bistetrazole-1,1′-diolate (TKX-50) and its PBXs

Molecular dynamics has been carried out to study the mechanical properties, moldability, binding energies, and detonation properties of TKX-50 and TKX-50 based polymer bonded explosives (PBXs) with four commonly used polymer binders.

Ag(i)-based high-energy metal organic frameworks (HE-MOFs) incorporating coordinated moieties in channels: synthesis, structure and physicochemical properties

A new Ag(i)-based HE-MOFs exhibited a compact 3D structure with channels containing coordinated NO₃⁻ and CH₃COO⁻ ions. The superior density, thermostability, insensitiveness and detonation properties indicated it can be used as potential explosive.

1,2,4,5-Dioxadiazine-functionalized [N–NO2]− furazan energetic salts

1,2,4,5-Dioxadiazine is identified as a key bridge to improve the density and detonation performance of energetic materials.