Interaction of Nitrogen-Rich Cations with Azotriazolone Anions through Ion Exchange Results in the Formation of Energetically Stable and Insensitive Compounds.

In our pursuit of promoting the green development of energetic materials and harnessing their functional benefits, we strive to address the inherent contradiction between energy and low sensitivity. In this regard, we have successfully constructed an azotriazole framework via environmentally friendly electrochemistry with a satisfactory yield of 62.3%. Through a simple ion-exchange process, we then synthesized nitrogen-rich salt derivatives of azotriazolone. These nitrogen-rich salts exhibit a wide range of nitrogen contents, ranging from 32.16 to 68.80%. Remarkably, crystallographic analysis of these green energy-containing salts reveals substantial advantages in terms of thermodynamic stability and low sensitivity. Experimental investigations have demonstrated a positive relationship between the nitrogen content and the pyrothermal performance of the azotriazolone derivatives. Of particular significance is compound 5, a triaminoguanidine salt, which exhibits an exceptionally high nitrogen content of 68.80%. It displays a detonation pressure of 28.2 GPa and a detonation velocity of 7939.4 m s-1. Moreover, the derivatives of azotriazolone salts demonstrate the formation of nitrogen-rich compounds, characterized by insensitive properties, attributed to the hydrogen-bonded network structures resulting from anion-cation interactions. With the exception of compound 5, which exhibits a friction sensitivity of 252 N, the remaining derivatives show a similar value of approximately 360 N. This suggests that azotriazolone serves as a promising material possessing both stabilizing properties and better detonation performance, thereby providing a favorable platform for the synthesis of novel compounds with advantageous properties.

Fabrication of CL-20/HMX Cocrystal@Melamine-Formaldehyde Resin Core-Shell Composites Featuring Enhanced Thermal and Safety Performance via In Situ Polymerization.

Safety concerns remain a bottleneck for the application of 2,4,6,8,10,12-hexanitro- 2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)/1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) cocrystal. Melamine-formaldehyde (MF) resin was chosen to fabricate CL-20/HMX cocrystal-based core-shell composites (CH@MF composites) via a facile in situ polymerization method. The resulted CH@MF composites were comprehensively characterized, and a compact core-shell structure was confirmed. The effects of the shell content on the properties of the composites were explored as well. As a result, we found that, except for CH@MF-2 with a 1% shell content, the increase in shell content led to a rougher surface morphology and more close-packed structure. The thermal decomposition peak temperature improved by 5.3 °C for the cocrystal enabled in 1.0 wt% MF resin. Regarding the sensitivity, the CH@MF composites exhibited a significantly reduced impact and friction sensitivity with negligible energy loss compared with the raw cocrystal and physical mixtures due to the cushioning and insulation effects of the MF coating. The formation mechanism of the core-shell micro-composites was further clarified. Overall, this work provides a green, facile and industrially potential strategy for the desensitization of energetic cocrystals. The CH@MF composites with high thermal stability and low sensitivity are promising to be applied in propellants and polymer-bonded explosive (PBX) formulations.

Comparative Thermal Research on Energetic Molecular Perovskite Structures.

Molecular perovskites are promising practicable energetic materials with easy access and outstanding performances. Herein, we reported the first comparative thermal research on energetic molecular perovskite structures of (C6H14N2)[NH4(ClO4)3], (C6H14N2)[Na(ClO4)3], and (C6H14ON2)[NH4(ClO4)3] through both calculation and experimental methods with different heating rates such as 2, 5, 10, and 20 °C/min. The peak temperature of thermal decompositions of (C6H14ON2)[NH4(ClO4)3] and (C6H14N2) [Na(ClO4)3] were 384 and 354 °C at the heating rate of 10 °C/min, which are lower than that of (C6H14N2)[NH4(ClO4)3] (401 °C). The choice of organic component with larger molecular volume, as well as the replacement of ammonium cation by alkali cation weakened the cubic cage skeletons; meanwhile, corresponding kinetic parameters were calculated with thermokinetics software. The synergistic catalysis thermal decomposition mechanisms of the molecular perovskites were also investigated based on condensed-phase thermolysis/Fourier-transform infrared spectroscopy method and DSC-TG-FTIR-MS quadruple technology at different temperatures.

5-Nitrotetrazol and 1,2,4-Oxadiazole Methylene-Bridged Energetic Compounds: Synthesis, Crystal Structures and Performances.

A new structural type for melt cast materials was designed by linking nitrotetrazole ring with 1,2,4-oxadiazole through a N-CH2-C bridge for the first time. Three N-CH2-C linkage bridged energetic compounds, including 3-((5-nitro-2H-tetrazol-2-yl) methyl)-1,2,4-oxadiazole (NTOM), 3-((5-nitro-2H-tetrazol-2-yl)methyl)-5-(trifluoromethyl)-1,2,4 -oxadiazole (NTOF) and 3-((5-nitro-2H-tetrazol-2-yl)methyl)-5-amine-1,2,4-oxadiazole (NTOA), were designed and synthesized through a two-step reaction by using 2-(5-nitro-2H-tetrazole -2-yl)acetonitrile as the starting material. The synthesized compounds were fully characterized by NMR (1H, 13C), IR spectroscopy and elemental analysis. The single crystals of NTOM, NTOF and NTOA were successfully obtained and investigated by single-crystal X-ray diffraction. The thermal stabilities of these compounds were evaluated by DSC-TG measurements, and their apparent activation energies were calculated by Kissinger and Ozawa methods. The crystal densities of the three compounds were between 1.66 g/cm3 (NTOA) and 1.87 g/cm3 (NTOF). The impact and friction sensitivities were measured by standard BAM fall-hammer techniques, and their detonation performances were computed using the EXPLO 5 (v. 6.04) program. The detonation velocities of the three compounds are between 7271 m/s (NTOF) and 7909 m/s (NTOM). The impact sensitivities are >40 J, and the friction sensitivities are >360 N. NTOM, NTOF and NTOA are thermally stable, with decomposition points > 240 °C. The melting points of NTOM and NTOF are 82.6 °C and 71.7 °C, respectively. Hence, they possess potential to be used as melt cast materials with good thermal stabilities and better detonation performances than TNT.

Synthesis of Energetic 7-Nitro-3,5-dihydro-4H-pyrazolo[4,3-d][1,2,3]triazin-4-one Based on a Novel Hofmann-Type Rearrangement.

Rearrangement reactions are efficient strategies in organic synthesis and contribute enormously to the development of energetic materials. Here, we report on the preparation of a fused energetic structure of 7-nitro-3,5-dihydro-4H-pyrazolo[4,3-d][1,2,3]triazin-4-one (NPTO) based on a novel Hofmann-type rearrangement. The 1,2,3-triazine unit was introduced into the fused bicyclic skeleton from a pyrazole unit for the first time. The new compound of NPTO was fully characterized using multinuclear NMR and IR spectroscopy, elemental analysis as well as X-ray diffraction studies. The thermal behaviors and detonation properties of NPTO were investigated through a differential scanning calorimetry (DSC-TG) approach and EXPLO5 program-based calculations, respectively. The calculation results showed similar detonation performances between NPTO and the energetic materials of DNPP and ANPP, indicating that NPTO has a good application perspective in insensitive explosives and propellants.

The Art of Framework Construction: Core-Shell Structured Micro-Energetic Materials.

Weak interfacial interactions remain a bottleneck for composite materials due to their weakened performance and restricted applications. The development of core-shell engineering shed light on the preparation of compact and intact composites with improved interfacial interactions. This review addresses how core-shell engineering has been applied to energetic materials, with emphasis upon how micro-energetic materials, the most widely used particles in the military field, can be generated in a rational way. The preparation methods of core-shell structured explosives (CSEs) developed in the past few decades are summarized herein. Case studies on polymer-, explosive- and novel materials-based CSEs are presented in terms of their compositions and physical properties (e.g., thermal stability, mechanical properties and sensitivity). The mechanisms behind the dramatic and divergent properties of CSEs are also clarified. A glimpse of the future in this area is given to show the potential for CSEs and some suggestions regarding the future research directions are proposed.

Comparative Studies on Thermal Decompositions of Dinitropyrazole-Based Energetic Materials.

Dinitropyrazole is an important structure for the design and synthesis of energetic materials. In this work, we reported the first comparative thermal studies of two representative dinitropyrazole-based energetic materials, 4-amino-3,5-dinitropyrazole (LLM-116) and its novel trimer derivative (LLM-226). Both the experimental and theoretical results proved the active aromatic N-H moiety would cause incredible variations in the physicochemical characteristics of the obtained energetic materials. Thermal behaviors and kinetic studies of the two related dinitropyrazole-based energetic structures showed that impressive thermal stabilization could be achieved after the trimerization, but also would result in a less concentrated heat-release process. Detailed analysis of condensed-phase systems and the gaseous products during the thermal decomposition processes, and simulation studies based on ReaxFF force field, indicated that the ring opening of LLM-116 was triggered by hydrogen transfer of the active aromatic N-H moiety. In contrast, the initial decomposition of LLM-226 was caused by the rupture of carbon-nitrogen bonds at the diazo moiety.

Comparative Theoretical Studies on a Series of Novel Energetic Salts Composed of 4,8-Dihydrodifurazano[3,4-b,e]pyrazine-based Anions and Ammonium-based Cations.

4,8-Dihydrodifurazano[3,4-b,e]pyrazine (DFP) is one kind of parent compound for the synthesis of various promising difurazanopyrazine derivatives. In this paper, eleven series of energetic salts composed of 4,8-dihydrodifurazano[3,4-b,e]pyrazine-based anions and ammonium-based cations were designed. Their densities, heats of formation, energetic properties, impact sensitivity, and thermodynamics of formation were studied and compared based on density functional theory and volume-based thermodynamics method. Results show that ammonium and hydroxylammonium salts exhibit higher densities and more excellent detonation performance than guanidinium and triaminoguanidinium salts. Therein, the substitution with electron-withdrawing groups (-NO2, -CH2NF2, -CH2ONO2, -C(NO2)3, -CH2N3) contributes to enhancing the densities, heats of formation, and detonation properties of the title salts, and the substitution of -C(NO2)3 features the best performance. Incorporating N-O oxidation bond to difurazano[3,4-b,e]pyrazine anion gives a rise to the detonation performance of the title salts, while increasing their impact sensitivity meanwhile. Importantly, triaminoguanidinium 4,8-dihydrodifurazano[3,4-b,e]pyrazine (J4) has been successfully synthesized. The experimentally determined density and H50 value of J4 are 1.602 g/cm3 and higher than 112 cm, which are consistent with theoretical values, supporting the reliability of calculation methods. J4 proves to be a thermally stable and energetic explosive with decomposition peak temperature of 216.7 °C, detonation velocity 7732 m/s, and detonation pressure 25.42 GPa, respectively. These results confirm that the derivative work in furazanopyrazine compounds is an effective strategy to design and screen out potential candidates for high-performance energetic salts.

Association between Unsaturated Fatty Acid-Type Diet and Systemic Lupus Erythematosus: A Systematic Review with Meta-Analyses.

BACKGROUND: Systemic lupus erythematosus (SLE) is a complex autoimmune disorder that affects multiple organ systems, with a higher prevalence among women in their reproductive years. The disease's multifactorial etiology involves genetic, environmental, and hormonal components. Recent studies have highlighted the potential impact of dietary factors, particularly unsaturated fatty acids, on the modulation of SLE due to their anti-inflammatory properties. This meta-analysis aims to evaluate the association between unsaturated fatty acid consumption and the risk, progression, and clinical manifestations of SLE, providing evidence-based guidance for dietary management. METHODS: We conducted a comprehensive search across major medical databases up to January 2024, focusing on studies that examined the intake of unsaturated fatty acids and the impact of such intake on SLE. Using the PICOS (population, intervention, comparator, outcomes, study design) framework, we included randomized controlled trials and case-control studies, assessing outcomes such as SLE activity, measured by SLE Disease Activity Index (SLEDAI) or the British Isles Lupus Assessment Group (BILAG) index, inflammation biomarkers. Studies were analyzed using either a fixed- or random-effects model based on heterogeneity (I2 statistic), with sensitivity analyses performed to assess the robustness of the findings. RESULTS: Our search included 10 studies, encompassing a wide variety of designs and populations. The meta-analysis showed that a diet rich in unsaturated fatty acids is significantly associated with a reduction in SLEDAI scores (pooled SMD) of -0.36, 95% CI: -0.61 to -0.11, p = 0.007, indicating a beneficial effect on disease activity. Additionally, we found that unsaturated fatty acid intake has a significant impact on HDL levels, suggesting a positive effect on lipid profiles. However, no significant effects were observed on levels of the inflammatory marker IL-6 or other lipid components (LDL and cholesterol). With minimal heterogeneity among studies (I2 ≤ 15%), sensitivity analysis confirmed the stability and reliability of these results, highlighting the potential role of unsaturated fatty acids in SLE management. CONCLUSIONS: This meta-analysis suggests that dietary intake of unsaturated fatty acids may play a positive role in reducing SLE activity and may significantly affect HDL levels without having significant effects on inflammation markers or other lipid profiles. These findings support the inclusion of unsaturated fatty acids in the dietary management of SLE patients, although further research is required to refine dietary recommendations and explore the mechanisms underlying these associations.

Application and prospects of EMOFs in the fields of explosives and propellants.

Energetic Metal-Organic Framework (EMOF) compounds have gained significant attention in recent years as a hot research topic in the fields of explosives and propellants. This article provides an overview of the latest research progress of EMOFs in various areas, including heat-resistant explosives, burning rate catalysts and initiating explosives. It discusses the recent development trends of high-energy EMOFs, such as high-dimensional and solvent-free structural design, simplified and scalable synthesis conditions, environmentally friendly manufacturing processes with tunable structures, high-energy, low-sensitivity and multifunctional target products. The challenges and issues faced by EMOFs in heat-resistant explosives, burning rate catalysts and initiating explosives are presented. Furthermore, the key research directions for future applications of EMOFs in the fields of explosives and propellants are discussed, including solvent-free high-dimensional EMOFs design and synthesis, precise modulation of EMOFs molecular composition and pore structure, improvement of accurate prediction methods for physicochemical properties of high-energy EMOFs, low-cost large-scale production and development of multifunctional composite EMOFs as energetic materials, exploration of influencing factors, and comprehensive study on the application of novel and high-performance multifunctional EMOFs.

Mechanisms and risk assessments on the N-nitration of N-acetylhexahydro-s-triazines: understanding the preparation of RDX (2).

Although the N-nitration by nitric acid is widely used to synthesize nitramines in biological, medical, and explosive industries, little is known about the microscopic behavior when the nitrated substrates are tertiary amines. Hexahydro-1,3,5-triacetyl-s-triazine (TRAT) nitrated into hexahydro-1,3,5-trinitro-s-triazine (RDX) was theoretically investigated at the MP2/cc-PVDZ level. An O-to-N transnitration mechanism was put forward for the N-nitration of N-acetyl tertiary amines, including the formation of diverse complexes R'N(COCH3)RNO2(+) and deacetylate. The electron transfer results in the complex formation, and the acetyl-to-nitro electrophilic displacement leads to deacetylate. Presumably, the carbonyl groups (C═O) in N-acetyl tertiary amines serve as the hinged joint in the electron transfer. Three successive N-nitrations transform TRAT into RDX; their electron transfers are strongly exothermic by -21.1, -19.5, and -15.4 kcal/mol relative to TRAT + 3NO2(+), repectively, and their electrophilic displacements possess low activation Gibbs free energies of 9.0, 6.8, and 7.5 kcal/mol relative to the σ-complexes 6, 11, and 14, respectively. The rate constants of the single electron transfer (SET) and the acetyl-to-nitro displacement were estimated roughly by Marcus and transition-state (TS) theories, respectively, indicating that they are both fast with the strong exothermicity. The available experimental phenomena were well interpreted by the computational results.

Carbamo-yl(di-amino-methyl-idene)aza-nium 3-nitro-5-oxo-4,5-di-hydro-1H-1,2,4-triazol-4-ide.

In the anion of the title salt, C2H7N4O(+)·C2HN4O3 (-), the negative charge resides formally on the N(3) atom of the triazole ring. In the crystal, the N(3) and exocyclic O atoms are hydrogen-bond acceptors with respect to the formally double-bond iminium and amido N atoms of the cation. The cation and anion are almost planar (r.m.s. deviations = 0.012 and 0.051 Å, respectively), but they are slightly bent with respect to each other [dihedral angle = 12.6 (1)°]. In the crystal, adjacent anions and cations are linked by extensive N-H⋯N and N-H⋯O hydrogen bonds, generating a ribbon running along the b-axis direction.

Dehydrogenative Syntheses of Biazoles via a "Pre-Join" Approach.

The structural motif of biazoles is the predominant substructure of many natural products, pharmaceuticals, and organic materials. Considerable efforts have focused on synthesizing these compounds; however, a limited number of processes have been reported for the efficient formation of biazoles. Herein, we report a "pre-join" approach for the dehydrogenative synthesis of biazoles, which are challenging to prepare using conventional methods. A bench-stable and easily synthesized pyrazine-based group is critical for this transformation. This strategy enables the homocoupling of biazoles and the heterocoupling of two different azoles. Due to the broad substrate scope, this strategy exhibits potential for use in other fields, such as medicine, materials, and natural product chemistry.

An environment friendly electrochemical synthesis of 1,1,4,4-tetramethyl-2-tetrazene energetic materials from undimethylhydrazine.

As a prospective alternative liquid propellant, 1,4,4-tetramethyl-2-tetrazene (TMTZ) possesses high enthalpy of formation and environment friendly decomposition products, and shows a promising application prospect in aerospace, munitions manufacturing, etc. An environment friendly and convenient synthesis of TMTZ through electrochemical oxidative coupling of undimethylhydrazine (UDMH) on commercially procured electrodes was carried out under mild conditions, in which the purity is up to 98.5% with a yield of over 45%. It is a simple, clean and suitable method for industrial production in contrast with the previously reported conventional chemical oxidation syntheses.

Performance enhancement strategy for tetrazoles based on nitrogen-boron bonds.

Based on N-B bonds, a novel strategy was developed for improving the energetic performance of tetrazoles. By employing the amino neighboring group participation, the azolyl borane compound 7 was selectively constructed, which exhibited excellent stability in water and air. This strategy solved the acidity problem of tetrazole as well as increasing the heat of detonation and combustion by 25% and 36%, respectively. Through laser ignition experiments, it also improved the combustion performance of tetrazoles. In DSC experiments, thermal decomposition temperatures of N-B covalent compounds were elevated as well. In an electrostatic potential calculation and sensitivity test, N-B covalent compounds exhibited good sensitivity (IS > 40 J and FS > 360 N). Through TG-DSC-FTIR-MS and in situ IR experiments, decomposition products were investigated to determine the next optimization stage for heat of detonation. It offered a significant potential for development to incorporate the N-B bond into nitrogen-rich compounds.

4,9,12,15-Tetra-oxa-3,5,8,10,14,16-hexa-aza-tetra-cyclo-[11.3.0.0.0]hexa-deca-1(16),2,5,7,10,13-hexaen-3-ium-3-olate monohydrate.

The organic mol-ecule in the title monohydrate, C(6)N(6)O(5)·H(2)O, presents an almost planar configuration, the greatest deviation from the least-squares plane through the atoms being 0.061 (1) Šfor the O atom within the seven-membered ring. Each water H atom is bifurcated, one forming two O-H⋯N hydrogen bonds and the other forming O-H⋯N,O hydrogen bonds. The result of the hydrogen bonding is the formation of supra-molecular layers with a zigzag topology that stack along [001].

Diethyl 2,2'-bis-(hy-droxy-imino)-3,3'-(hydrazinediyl-idene)dibutano-ate.

Each mol-ecule of the title compound, C(12)H(18)N(4)O(6), is located on an inversion centre at the mid-point of the central N-N bond. The azo groups C=N of the Schiff base group have an E conformation and the azo groups in the oxime C=N-O groups have a Z conformation. O-H⋯O hydrogen bonds link neighbouring mol-ecules into infinite monolayers perpendicular to the a axis.

2-tert-Butyl-1-(4-nitro-amino-1,2,5-oxadiazol-3-yl)diazene 1-oxide.

In the title compound, C(6)H(10)N(6)O(4), the nitro-amine -NHNO(2) substituent and the C-N=N(→ O) unit of the other substituent of the oxadiazole ring are nearly coplanar with the five-membered ring [dihedral angles = 5.7 (1) and 3.0 (1)°]. The amino group of the -NHNO(2) substituent is a hydrogen-bond donor to the two-coordinate N atom of the C-N=N(→ O) unit.

4-[4-(4-Amino-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazol-3-yl]-1,2,5-oxadiazol-3-amine.

The complete molecule of the compound, C(6)H(4)N(8)O(3), is generated by a crystallographic twofold rotation axis that runs through the central ring. The flanking ring is twisted by 20.2 (1)° with respect to the central ring. One of the amino H atoms forms an intra-molecular N-H⋯N hydrogen bond; adjacent mol-ecules are linked by N-H⋯N hydrogen bonds forming a chain running along [10-2].

Synthetic Strategies Toward Nitrogen-Rich Energetic Compounds Via the Reaction Characteristics of Cyanofurazan/Furoxan.

The structural units of amino-/cyano-substituted furazans and furoxans played significant roles in the synthesis of nitrogen-rich energetic compounds. This account focused on the synthetic strategies toward nitrogen-rich energetic compounds through the transformations based on cyanofurazan/furoxan structures, including 3-amino-4-cyanofurazan, 4-amino-3-cyano furoxan, 3,4-dicyanofurazan, and 3,4-dicyanofuroxan. The synthetic strategies toward seven kinds of nitrogen-rich energetic compounds, such as azo (azoxy)-bridged, ether-bridged, methylene-bridged, hybrid furazan/furoxan-tetrazole-based, tandem furoxan-based, hybrid furazan-isofurazan-based, hybrid furoxan-isoxazole-based and fused framework-based energetic compounds were fully reviewed, with the corresponding reaction mechanisms toward the nitrogen-rich aromatic frameworks and examples of using the frameworks to create high energetic substances highlighted and discussed. The energetic properties of typical nitrogen-rich energetic compounds had also been compared and summarized.