4-Nitramino-3,5-dinitropyrazole-Based Energetic Salts

Synthetic manifestation of trinitro-pyrazolo-2H-1,2,3-triazoles (TNPT) as insensitive energetic materials

This study showcases the design and development of a facile method for synthesizing trinitro-pyrazolo-triazole (TNPT) and its derivatives. The synthesized compounds are analysed using multinuclear NMR [1H, 13C, and 15N] and HRMS analyses. Furthermore, X-ray diffraction studies confirm the structure of some TNPT derivatives. Notably, compounds 8, 9, 11, and 12 exhibit good thermal stability with a decomposition threshold above 250 °C, and show a high level of insensitivity towards impact and friction [impact sensitivity (IS) is more than 25 J and friction sensitivity (FS) is above 180 N]. Compound 12, in particular, displays excellent performance characteristics [density 1.76 g cc-1 (at 298 K), a high detonation velocity (Dv = 8550 m s-1), and good thermal stability (Td = 280 °C), with high insensitivity towards impact and friction (IS = 35 J; FS = 180 N)]. The Hirshfeld surface analysis study provides further insight into the sensitivity of the TNPT derivatives.

Synthesis and Energetic Properties of N-Substituted 3,4- and 3,5-Dinitropyrazoles

3,4- and 3,5-Dinitropyrazoles (DNPs) were substituted with acryl and allyl groups on the N1 nitrogen atom, resulting in three novel energetic materials. These compounds are all liquids at room temperature with melting points ranging from -60.2 to -38.6 °C and were fully characterized by high-resolution mass spectrometry, elemental analysis, proton and carbon nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. These materials were also tested for electrostatic discharge, friction, and impact sensitivities and then compared to DNP starting materials and to the explosive nitroglycerin (NG). These results indicate that the synthesized compounds are less sensitive to impact compared to NG and have higher thermal stabilities to decomposition.

Polynitro-N-aryl-C-nitro-pyrazole/imidazole Derivatives: Thermally Stable-Insensitive Energetic Materials

A wide array of methoxy-substituted-polynitro-aryl-pyrazole/imidazoles with readily oxidizable -NH₂/NO₂/NHNO₂/diazo functional groups is synthesized. Single crystal X-ray diffraction (XRD) analysis confirms the molecular structure of the compounds. Energetic properties of the synthesized compounds are determined by theoretical and experimental studies. Most of the compounds are thermally stable and insensitive to impact and friction. Some of the molecules possess better detonation velocity and detonation pressure over TNT.

Nitrification Progress of Nitrogen-Rich Heterocyclic Energetic Compounds: A Review

As a momentous energetic group, a nitro group widely exists in high-energy-density materials (HEDMs), such as trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), etc. The nitro group has a significant effect on improving the oxygen balance and detonation performances of energetic materials (EMs). Moreover, the nitro group is a strong electron-withdrawing group, and it can increase the acidity of the acidic hydrogen-containing nitrogen-rich energetic compounds to facilitate the construction of energetic ionic salts. Thus, it is possible to design nitro-nitrogen-rich energetic compounds with adjustable properties. In this paper, the nitration methods of azoles, including imidazole, pyrazole, triazole, tetrazole, and oxadiazole, as well as azines, including pyrazine, pyridazine, triazine, and tetrazine, have been concluded. Furthermore, the prospect of the future development of nitrogen-rich heterocyclic energetic compounds has been stated, so as to provide references for researchers who are engaged in the synthesis of EMs.

Recent Advances in Synthesis and Properties of Nitrated-Pyrazoles Based Energetic Compounds

Nitrated-pyrazole-based energetic compounds have attracted wide publicity in the field of energetic materials (EMs) due to their high heat of formation, high density, tailored thermal stability, and detonation performance. Many nitrated-pyrazole-based energetic compounds have been developed to meet the increasing demands of high power, low sensitivity, and eco-friendly environment, and they have good applications in explosives, propellants, and pyrotechnics. Continuous and growing efforts have been committed to promote the rapid development of nitrated-pyrazole-based EMs in the last decade, especially through large amounts of Chinese research. Some of the ultimate aims of nitrated-pyrazole-based materials are to develop potential candidates of castable explosives, explore novel insensitive high energy materials, search for low cost synthesis strategies, high efficiency, and green environmental protection, and further widen the applications of EMs. This review article aims to present the recent processes in the synthesis and physical and explosive performances of the nitrated-pyrazole-based Ems, including monopyrazoles with nitro, bispyrazoles with nitro, nitropyrazolo[4,3-c]pyrazoles, and their derivatives, and to comb the development trend of these compounds. This review intends to prompt fresh concepts for designing prominent high-performance nitropyrazole-based EMs.

Derivatives of 3,6-Bis(3-aminofurazan-4-ylamino)-1,2,4,5-tetrazine: Excellent Energetic Properties with Lower Sensitivities

To find a balance between energy and safety, a series of compounds based on azo-, azoxy-, 1,4,2,5-dioxadiazene-, and 3,6-diamino-1,2,4,5-tetrazine-bridged bis(aminofurazan) were designed and synthesized. These compounds were analyzed by nitro group charges (Q_nitro) and bond dissociation energy (BDE) calculations, which are related to sensitivity and stability. Based on the calculated results, derivatives of 3,6-bis(3-aminofurazan-4-ylamino)-1,2,4,5-tetrazine have the largest values for -Q_nitro and BDE of all of the bis(aminofurazan) compounds. This shows that compounds based on 3,6-bis(3-aminofurazan-4-ylamino)-1,2,4,5-tetrazine have the lowest sensitivities and best stabilities, which has been substantiated by experiments. Additionally, their explosive properties remain essentially competitive with compounds based on azo-, azoxy-, and 1,4,2,5-dioxadiazene-bridged bis(aminofurazan). Hirshfeld surface calculations were also performed to better understand the relationship between the molecular structure and stability/sensitivity. This work highlights the value of 3,6-diamino-1,2,4,5-tetrazine as a linker to achieve good balance between safety and energy.

New pyrazole energetic materials and their energetic salts: combining the dinitromethyl group with nitropyrazole

In this work, a series of pyrazole-derived energetic compounds were successfully synthesized. These energetic compounds were fully characterized by NMR spectroscopy, IR spectroscopy, and elemental analysis. The structures of compounds 5, 6, 7 and 7a were determined by single crystal X-ray diffraction. The physicochemical and energetic properties of all synthesized energetic compounds, including density, thermal stability and energetic performance, were investigated. The structure-property relationship was illustrated using two-dimensional fingerprint plots based on Hirshfeld surfaces, NCI plots and ESP of 7 and 7a. Among these energetic compounds, the hydroxylammonium salt 7b exhibited satisfactory calculated detonation performance (8700 m s-1), which was comparable to the commonly used highly explosive RDX (8748 m s-1). The potassium salt 5 was tested for its detonation ability by detonating RDX. The result indicates that compound 5 could be used as a potential green primary explosive.

Design, synthesis and investigations of a series of energetic salts through the variation of amines and concentration of picrate anions

Eight energetic salts combining N-bases with picrate ion were synthesized in high yields. The structures and energetic properties were regulated by the variation of N-base molecules and the concentration of the picric acid in the reaction mixture.

Versatile functionalization of 3,5-diamino-4-nitropyrazole for promising insensitive energetic compounds

Variation of functional groups offers an efficient approach for tuning properties of materials such as thermal stability, and detonation performance while improving sensitivities to mechanical stimuli. Now versatile functionalization of 3,5-diamino-4-nitropyrazole involving the introduction of a tetrazole ring, or a guanyl group, or ring expansion is described. All of the compounds were fully characterized and some of them (2, 9 and 13) were verified by single crystal X-ray diffraction. Based on their good thermal stabilities and high detonation performance as well as insensitive properties, they are potentially insensitive energetic compounds.

Facile and selective polynitrations at the 4-pyrazolyl dual backbone: straightforward access to a series of high-density energetic materials

Progressive nitro functionalization of 4,4′-bipyrazole yields insensitive and stable high explosives with excellent densities and detonation properties.

C8N12O10: a promising energetic compound with excellent detonation performance and desirable sensitivity

A promising energetic molecule bis(4-nitro-1,2,5-oxadiazole-2-oxid-3-yl)-azo-1,2,4-oxadiazole was synthesized and characterized. It has high density, acceptable thermal stability, high heat of formation, outstanding detonation properties and desirable mechanical properties.

Carbon-free energetic materials: computational study on nitro-substituted BN-cage molecules with high heat of detonation and stability

A new series of high-energy density materials (HEDMs) B₆N₆H_6−n(NO₂)_n (n = 1–6) are studied at the M06-2X/6-311++G**, ωB97XD/6-311++G** and B3LYP/6-311++G** levels. Analysis of the structural changes caused by substituting the NO₂ and the electronic structures, such as electron localization function (ELF), Wiberg bond index (WBI), charge transfer and bond dissociation energies (BDE), provide important insights into the essence of the chemical characteristics and stability. Moreover, the Born–Oppenheimer molecular dynamic (BOMD) simulation is performed to verify their stability, which suggests that only the BN-cage derivatives with one and two nitro groups bonding with boron atoms (NO₂-1-1 and NO₂-2-1) can remain stable under ambient conditions. To predict the detonation performance and sensitivity of these two stable BN-cage energetic molecules accurately, the density, gas phase enthalpy of formation, enthalpy of sublimation, detonation performance, impact sensitivity and BDE are calculated systematically. The calculation results show that both NO₂-1-1 and NO₂-2-1 have a higher heat of detonation, higher value of h₅₀, and larger BDE of trigger bonds than CL-20.

A new series of high-energy density materials were created by replacing the H atoms in the BN-cage with nitro groups.

Exploiting the energetic potential of 1,2,4-oxadiazole derivatives: combining the benefits of a 1,2,4-oxadiazole framework with various energetic functionalities

A series of 1,2,4-oxadiazole derived energetic compounds were synthesized and structurally characterized, some of which have the potential as melt-cast explosives or secondary explosives.

Electrophilic iodination: a gateway to high iodine compounds and energetic materials

Preparation of polyiodopyrazoles and subsequent highly oxygenated nitro compounds.

Curious cases of 3,6-dinitropyrazolo[4,3-c]pyrazole-based energetic cocrystals with high nitrogen content: an alternative to salt formation

Two structurally interesting 3,6-dinitropyrazolo[4,3-c]pyrazole-based energetic cocrystals were prepared and confirmed by single crystal X-ray diffraction. As novel energetic materials, these two unusual neutral acid-base complexes possess high nitrogen content, good detonation properties, and improved impact and friction sensitivities which highlight their potential energetic applications.

Amination of nitroazoles--a comparative study of structural and energetic properties

In this work, 3-nitro-1H-1,2,4-triazole (1) and 3,5-dinitro-1H-pyrazole (2) were C-aminated and N-aminated using different amination agents, yielding their respective C-amino and N-amino products. All compounds were fully characterized by NMR (¹H, ¹³C, ¹⁵N), IR spectroscopy, differential scanning calorimetry (DSC). X-ray crystallographic measurements were performed and delivered insight into structural characteristics as well as inter- and intramolecular interactions of the products. Their impact sensitivities were measured by using standard BAM fallhammer techniques and their explosive performances were computed using the EXPLO 5.05 program. A comparative study on the influence of those different amino substituents on the structural and energetic properties (such as density, stability, heat of formation, detonation performance) is presented. The results showed that the incorporation of an N-amino group into a nitroazole ring can improve nitrogen content, heat of formation and impact sensitivity, while the introduction of a C-amino group can enhance density, detonation velocity and pressure. The potential of N-amino and C-amino moieties for the design of next generation energetic materials is explored.

Synthesis and characterization of a new family of energetic salts based on guanidinium cation containing furoxanyl functionality

A new family of energetic salts based on a guanidinium cation containing furoxanyl functionality was synthesized and well characterized.