Tetranitro-bimidazole/pyrazole represent a class of energetic scaffolds featuring high nitrogen-oxygen content and positive heat of formation. In this work, two series of energetic derivatives based on tetranitro-bimidazole/pyrazole were designed and synthesized: azo-bridged compounds (2a, 3a) and MDO-based (2,4,6-triamino-1,3,5-triazine-1,3-dioxide) energetic salts (2b, 3b). The target compounds can be efficiently obtained via selective amination/oxidative coupling and salt formation/ion-exchange reactions. Remarkably, all compounds exhibit moderate thermal stability and insensitive characteristics (IS > 30 J, FS > 360 N). Among them, azo-bridged compound 2a possesses a high positive heat of formation (up to 1370 kJ kg⁻¹) and outstanding detonation performance (D = 9161 m s⁻¹). All compounds were characterized by NMR, IR, and elemental analysis, and the structures of 2a and 3a were unambiguously confirmed by single-crystal X-ray diffraction. This work demonstrates that azo-bridging or pairing MDO cations with tetranitro-bimidazole/pyrazole frameworks is an effective strategy for developing novel insensitive high-energy density materials.

A scalable synthetic method for metallic pentazolate via commercially available ferrous salt-catalyzed one-pot [3+2] cyclization/C–N dearylation is reported. Through mechanistic studies, a stable aryl-pentazole intermediate was identified and a plausible mechanism was established. Reaction conditions were screened based on quantitative determination via NMR and ion chromatography (IC), achieving up to 48% IC yield of sodium pentazolate and 33% isolated yield of cobalt pentazolate under mild conditions. The safety of the reaction was evaluated using a reaction calorimeter (RC1e), indicating a relatively safe thermal profile. Scaling up was verified by a hundred-gram-scale synthesis of cobalt pentazolate at -10 °C on a 30 L jacketed reactor.

The strategic introduction of ring strain into high-energy-density materials (HEDMs) presents a powerful yet underutilized pathway to augment detonation performance and stability. However, most research focus on planar five- and six-membered structures, with few studies introducing larger rings with increased ring strain, which often require alkylene as a linkage between azoles, resulting in higher stability by sacrificing detonation properties. Here, we report a new fused [5,7,5] tricyclic energetic scaffold by the construction of robust NH-CO-NH and NH-CH2-NH bridges and successfully incorporate a strained seven-membered ring toward tricyclic architectures. The oxygen balance was further modified by the installation of multiple nitro groups on the novel fused skeleton, which suppresses carbonaceous residue formation and contributes to its clean and efficient energy release. Notably, a hexanitro-substituted polycyclic structure was obtained, which exhibits a calculated detonation velocity of 9084 m s-1 and a detonation pressure of 35.8 GPa with favorable sensitivity and stability, and the ignition and flame propagation experiments demonstrate that the hexanitro-substituted tricyclic energetic material exhibits a much shorter ignition delay time and brighter flame compared to HMX and RDX, indicating an enhanced ignition and combustion performance.

Polynitromethyl explosives exhibit outstanding detonation performance, yet their application is significantly hindered by safety concerns. Thus, enhancing the stability of polynitromethyl high-energy density materials (HEDMs) while maintaining high energy levels is of urgent importance. In this study, a novel tricyclic scaffold combining furoxan and 1,2,4-oxadiazole was successfully constructed. Two new HEDMs, 3,4-bis(5-fluorodinitromethyl-1,2,4-oxadiazol-3-yl)furoxan (BOFN-4) and 3,4-bis(5-trinitromethyl-1,2,4-oxadiazol-3-yl)furoxan (BOTN-6), were designed and synthesized by introducing a polynitromethyl energetic group for the first time. Experimental tests and theoretical calculations revealed that BOFN-4 possesses a higher thermal decomposition temperature (Td peak: 193 °C) and lower mechanical sensitivity (IS: 8 J, FS:252 N) compared to most reported fluorodinitromethyl-functionalized energetic compounds, while also exhibiting high density (ρ: 1.92 g·cm−3, 296 K). As a zero-oxygen balance explosive, BOTN-6 demonstrated 1.3 times the destructive performance of octogen (HMX) in plasma initiation experiments. These results indicate that the introduction of a tricyclic furoxan-isofurazan scaffold is an effective strategy to overcome the thermal stability and sensitivity limitations of polynitromethyl HEDMs, without compromising their energy levels.

A series of energetic ionic salts derived from a bis(5-aminotetrazolyl)borane scaffold was synthesized to investigate the influence of oxygen-rich explosophores. Among them, the perchlorate derivative (compound 9) crystallized with a high density (1.77 g center dot cm- 3) and demonstrated an outstanding detonation velocity of 8994 m center dot s-1. The presence of the oxygen-rich anion further optimized the energy-release dynamics, affording an exceptionally short combustion duration of only 68 ms. The oxidizing capability of compound 9 was assessed through theoretical HTPB-based propellant formulations, where partial substitution of ammonium perchlorate (50 wt%) resulted in an 8.9 % increase in specific impulse, reaching 2633.9 N center dot s center dot kg- 1. These results underscore the effectiveness of incorporating oxygen-rich anions as a strategy to simultaneously enhance detonation performance and regulate combustion behavior in boron-azole energetic frameworks.

High energy, low sensitivity, and easy preparation have long been the core objectives in the synthesis of energetic materials. Herein, a novel strategy for constructing furazan-isofurazan-tetrazole energetic skeletons was developed using low-cost and readily available 3-amino-4-aminooximofurazan (AAOF) as the starting material. Based on the reactivity of amino and hydroxyl groups in AAOF, a series of nitrogen-rich and low-sensitivity energetic compounds were synthesized for the first time, including nitro-, azido-and hydroxytetrazol-substituted compounds. The chemical structures and energetic properties of all it-conjugated compounds were fully characterized and evaluated by NMR, IR, single-crystal X-ray diffraction (XRD), differential scanning calorimetry (DSC), etc. Several compounds achieved a favorable balance between energy performance and safety sensitivity, endowing them with promising application prospects in liquid plasticizers and melt-cast explosives.

Two-step antisolvent method for MPECs.

A series of novel energetic compounds bearing nitrogen-containing aromatic rings, synthesized through energetic methylene bridging, were prepared for the first time. By tuning the bonding sites, the energy levels of these energetic compounds were enhanced while their stability was maintained-their densities range from 1.80 g·cm⁻ 3 to 1.89 g·cm⁻ 3 , and their detonation velocities range from 8000 m·s -1 to 8800 m·s -1 . The resultant energetic materials were fully characterized by Fourier transform infrared (FTIR) spectroscopy, NMR, and X-ray diffraction (XRD). Distinctive properties were observed in crystal structure analysis and differential scanning calorimetry (DSC) tests. Moreover, the energy levels and sensitivity of these compounds were comprehensively evaluated. These novel materials exhibit excellent performance, suggesting potential applications in propellants and composite explosives.

The design and synthesis of insensitive high-energy materials remain a critical challenge in the field of energetic compounds. In this work, a series of energetic compounds based on the 3-dinitromethyl-1,2,4-oxadiazole scaffold were synthesized via a concise and efficient route starting from 1,1-diamino-2,2-dinitroethylene (FOX-7). The potassium salt 3 was obtained through cyclization with triethyl orthoformate, and subsequent ion metathesis reactions afforded four nitrogen-rich ionic salts 3a-d. Fluorination of 3 using XeF2 or Selectfluor (R) yielded the liquid derivative 4, which exhibits pronounced supercooling behavior with a melting point of -2.2 degrees C and remains liquid after storage at -16 degrees C for 48 h. All compounds were fully characterized by NMR, IR, elemental analysis, and single-crystal X-ray diffraction. Hirshfeld surface analyses revealed that intermolecular hydrogen bonding and coordination interactions play a dominant role in crystal packing, contributing to their low sensitivity. Thermal behavior was investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG), and decomposition kinetics were analyzed using model-free methods. Detonation performances were calculated using EXPLO5 based on experimental densities and computed heats of formation. The non-metal salts 3b-d show excellent insensitivity (IS >= 39 J, FS = 360 N) and detonation velocities up to 8872 m & centerdot;s(-1) (for 3d), comparable to RDX. The liquid compound 4 exhibits a promising combination of safety (IS > 40 J, FS > 360 N) and calculated detonation parameters (V-det = 7898 m & centerdot;s(-1), P-cj = 25.9 GPa) compared to traditional energetic plasticizers such as N-Butyl-N-(2-nitroxy-ethyl)-nitramine (Bu-NENA) and nitroglycerin (NG). This work provides a new family of insensitive energetic materials and suggests that fluorinated dinitromethyl-1,2,4-oxadiazoles represent a structural motif worthy of further exploration as energetic plasticizers.

Hydrazine salt of 5-aminotetrazole (HAT) is an excellent material for use in gas generator solid propellants due to its extremely high amount of nitrogen. Combustion performance is an important indicator of solid propellant. The investigation of thermal behaviors could offer insights into enhancing combustion performance through the strategic addition of catalysts. However, discovering highly effective catalysts is challenging. So, for this purpose, we investigated the catalytic activity of catalysts at three different categories and scales (metal oxide microFe2O3, nano-Fe2O3, and liquid metal-organic compound ferrocene-based derivative catocene) on the thermal decomposition behaviors of HAT. The thermal decomposition process of HAT is performed at temperatures ranging from 50 to 550 degrees C employing a combined DSC-TG-FTIR-MS technique. The most probable thermal decomposition route of HAT was inferred by capturing the released gas products. The thermal activation energy is evaluated using Friedman isoconversional method. The results reveal that the activation energy is the highest in stage II of the thermal decomposition process, indicating that the catalytic effect of the catalyst is primarily manifested in stage II. The Criado with model-fitting method is used to identify the possible thermal decomposition reaction models. The findings indicate that the thermolysis model is not guided in any particular model, rather it is consistent with the Fn model. The catalytic activity of the catalysts was also analyzed based on frontier molecular orbitals theory. The findings indicate that the incorporation of the liquid metal-organic compound catocene is an effective way to accelerate its thermal decomposition rate. This suggests that the particle size dominates the catalytic effect, but the molecular orbitals also have some influence on the catalytic performance. The conclusion of this study is beneficial for optimizing, managing, and applying the combustion performance of HAT-based solid propellants.

The skeleton structures of azine (including diazine, triazine and tetrazine) are widely used as important candidate for building good performance energetic materials due to their uniform electron distribution, planar aromaticity, multi reactive sites and low ring tension. Introducing N-oxide coordination bonds into azine framework turns out to be an important and highly rewarding protocol for the construction of energetic compounds with balanced performances. A variety of energetic compounds with good comprehensive performances have been designed and synthesized by introducing N-O coordination bonds to azine skeletons. In this work, a review of recent research in the synthesis and physicochemical properties of N-oxides energetic compounds based on diazine, triazine and tetrazine skeleton is presented. And the application research progress of typical N-oxides energetic compounds are introduced.

Two series of energetic salts with nitrogen and oxygen-rich skeleton, hydroxytetrazole, and detonation units were synthesized by convenient routes via available commercial reagents. The obtained energetic materials were investigated via IR, NMR and X-ray diffraction. Meanwhile, the electrostatic potential, detonation performance, along with DSC-TG-IR-MS analysis, were comprehensively investigated. The synthesized energetic salts exhibit convincing physical-chemical and detonation properties (Densities range from 1.70 g cm-3 to 1.92 g cm-3. Detonation velocities up to 9500 m & sdot;s-1). The obtained materials display a decent thermal and mechanical stability. The decomposition temperatures of most of salts are close to 200 degrees C. The impact and friction sensitivities can surpass 40 J and 360 N, respectively. Also the thermal decomposition mechanism was clarified. In general, novel series of energetic materials with promising performance are synthesized, which make their great application in the propellant field possible.

Diazidoglyoxime (DAzG), a pivotal intermediate in the synthesis of dihydroxylammonium 5,5′-bis-tetrazole-1,1′-diolate (TKX-50)—a high-energy-density explosive with growing applications in defense and aerospace—was comprehensively investigated to elucidate its thermal decomposition behavior and assess safety risks during synthesis. Differential scanning calorimetry (DSC) analyses were conducted on both the precursor dichloroglyoxime (DCG) and product diazidoglyoxime (DAzG), revealing distinct thermal degradation profiles. The onset decomposition temperatures were determined to be 197.8 °C for DCG and 156.9 °C for DAzG, highlighting DAzG’s lower thermal stability. Reaction calorimetry (RC1) studies under varied synthesis conditions further quantified the thermal dynamics of the azidation step, identifying a maximum temperature of the synthesis reaction (MTSR) of 4.9 °C. To evaluate secondary decomposition hazards, accelerating rate calorimetry (ARC) was employed, measuring a TD24 (the temperature at which the time-to-maximum rate under adiabatic conditions, TMRad, reaches 24 h) of 20.4 °C for the reaction residue. This low TD24 value indicates a high propensity for thermal runaway at near-ambient temperatures, necessitating stringent thermal control protocols. Based on Francis Stoessel’s thermal risk classification framework, the thermal risk of DAzG is classified as class 2, signifying moderate but manageable thermal risks during synthesis and handling. The findings emphasize the critical need for real-time temperature monitoring, controlled cooling systems, and hazard mitigation strategies in industrial-scale DAzG production. This study not only advances the understanding of DAzG’s thermal behavior but also provides actionable guidelines for enhancing safety in the manufacturing of advanced energetic materials like TKX-50.

To modify the sensitivity and melting point of the casting of DNTF, a eutectic system of insensitive explosive 3,5,5-trinitro-1,3-oxazinane (TNTON) and DNTF was prepared through a new method. The melting and liquefaction processes of TNTON/DNTF at different ratios were investigated, and a T-x phase diagram was established. The melting and decomposition processes of TNTON, DNTF, and TNTON/DNTF eutectic at different heating rates were compared, while the sensitivity tests were conducted to study the desensitizing effect of TNTON on DNTF. Using EXPLO-5 software, the detonation performance of the TNTON/DNTF eutectic was calculated. The experimental results show that the stoichiometric composition of the TNTON/DNTF eutectic is 58.26 : 41.74, with an average melting point of 69 degrees C. With the increase of heating rate, both the melting and decomposition reactions are delayed. According to the activation energy (Ea) curve, the thermal decomposition is through an autocatalytic process. The impact and friction sensitivity of the TNTON/DNTF eutectic are 38 J and 252 N, respectively. Theoretical density of the TNTON/DNTF eutectic is 1.906 g cm-3, and the calculated detonation velocity is 8921 m s-1. The TNTON/DNTF eutectic exhibits good thermal stability and can significantly reduce the sensitivity of DNTF while maintaining its high energy level. The detonation performance of TNTON/DNTF low eutectic cast explosive is better than that of TNT based cast explosive.

Two novel energetic compounds, 3-nitroxymethyl-5-(4-nitro-furazan-3-yl)-1,2,4-oxadiazole (4) and 3-nitroxymethyl-5-(4-azido-furazan-3-yl)-1,2,4-oxadiazole (5), were synthesized. Both of them were fully characterized, and the structure of 4 was further confirmed by X-ray single crystal diffraction. The thermal behaviors, detonation performances and the sensitivities of 4 and 5 were also investigated by differential scanning calorimetry (DSC), EXPLO5 program and BAM standard techniques. In addition, the electrostatic potential energy surface (ESP) was studied by Multiwfn program and density functional theory at B3LPY/6-31G (d, p). Both compounds have low melt-point, good energetic performance and mechanical sensitivity, which endow them with promising properties as plasticizing ingredients in propellant formulations.

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.

3-叠氮基-1,3-二硝基氮杂环丁烷(AzDNAZ)是一种含偕叠氮硝基基团的低熔点含能化合物.AzDNAZ结构与性能研究对于新型含能化合物的设计合成具有重要的借鉴意义.采用1-叔丁基-3-硝基-3-羟甲基氮杂环丁烷盐酸盐(TNHAC)为原料,经氧化-叠氮化、中和以及硝化等反应制备了AzDNAZ,改进了合成工艺,总收率达到70％(文献中收率为37％).采用红外光谱、1HNMR、13CNMR及元素分析等对中间体及目标化合物进行了结构表征.首次培养出了AzDNAZ的单晶.晶体结构属三斜晶系;空间群为P-1,a=0.6120(6)nm,b=0.6345(6)nm,c=1.0190(9)nm,V=0.368(6)nm3,Z=2,Dc=1.695g/cm3,F(000)=192,R1=0.0321,R2=0.0372.采用Hirshfeld表面分析方法研究了晶体分子内的相互作用,O…H和N…H的作用点占比达到51％,占主导地位.对比计算了AzDNAZ和1,3,3-三硝基氮杂环丁烷(TNAZ)的键离解能,AzDNAZ的C—NO2和N—NO2键离解能分别较TNAZ高9.63kJ/mol和4.87kJ/mol;实测AzDNAZ的撞击感度大于40J.采用EXPLO5程序预估了AzDNAZ的爆轰性能:爆速为8421m/s;爆压为29.60Gpa.与TNAZ相比,AzDNAZ的能量性能略低.但是,丰富的分子间氢键作用以及较高的键离解能使得AzDNAZ的机械感度较低,安全性提升.

A novel energetic potassium salt 2,3,5,6-tetranitro-4H,9H-dipyrazolo [1,5-a:5',1'-d][1,3,5] triazinane (KTNDPT) was synthesized using sodium 4-amino-3,5-dinitropyrazolate as raw material, and structurally characterized by elemental analysis, IR spectra, 1 H NMR, 13 C NMR. The single crystal of KTNDPT was obtained and analyzed by single-crystal X-ray diffraction. The thermal behavior of KTNDPT was studied by DSC-TG method. Solid phase formation heat and density were calculated by Gaussian 09 program and Trouton′s rule, and the physicochemical detonation properties of AFTF were predicted by means of EXPLO5 detonation software. The results show that the crystal of KTNDPT·H2O belongs to a monoclinic system and space group P21/n with cell parameters:a=8.330(15), b=9.869(17), c=16.61(3)?,β=102.04(3)°, V=1335(4) ?3, Z=4, Dc=1.966 g/cm3, F(000)= 792,μ=0.480 mm-1, S=1.040, the final R=0.1541 and wR(I> 2σ(I))=0.3779. DSC-TG analysis shows that the decomposition peak temperature of KTNDPT is 241.6 ℃.The heat of formation is 331.6 kJ/mol, detonation velocity is 8647 m·s-1 and detonation pressure is 32.0 GPa. As an energetic ion potassium salt, KT-NDPT with excellent detonation performance is expected to use in high energy propellants.

Two energetic bicyclic scaffolds (furazan-isoxazole and furazan-1,3,4-oxadiazole) were constructed via different cyclization reactions. Based on the energetic bicyclic scaffolds, the energetic compounds, 3-(4-nitraminofurazan-3-ly)-isoxazole-5-methylnitrate 1c and 5-(4-nitraminofurazan-3-ly)-1,3,4-oxadiazole-2-methylnitrate 2c, were designed and synthesized in good yields. Because of the acidity of nitramine, the corresponding energetic ionic salts, ammonium 3-(4-nitraminofurazan-3-ly)isoxazole-5-methylnitrate 1d and ammonium 5-(4-nitraminofurazan-3-ly)-1,3,4-oxadiazole-2-methylnitrate 2e, were also obtained and well characterized, their structures were further determined by X-ray single crystal diffraction. To have a better understanding of the structure-property relationships of furazan-bicyclic scaffolds and nitrate groups, their thermal behaviors, detonation performances and the sensitivities were investigated via differential scanning calorimetry (DSC), ESP analysis, Hirshfeld surfaces calculation, EXPLO5 program and BAM standard techniques. Compared with those of ammonium 5-(4-nitraminofurazan-3-ly)-1,2,4-oxadiazole-2-methylnitrate 3e, the results show that all these methyl nitrate energetic compounds based on bicyclic scaffolds of furazan-isofurazan exhibit good detonation performances and extraordinary insensitivities. As supported by experimental and theoretical data, the formation of energetic ionic salts causes an increase of the weak interactions, significantly improving the thermal performance over 110 °C.

1,1,4,4-Tetramethyl-2-tetrazene (TMTZ), a potential candidate for replacing 1,1-dimethylhydrazine (UDMH), has excellent properties including a high specific impulse, non-toxicity and non-volatility. However, most synthetic methods depicted in the literature use stoichiometric oxidative coupling, and the oxidizing agents are usually heavy metals or halogens, leading to low synthetic efficiency and high environmental pollution. In order to overcome these problems, it is necessary to explore more environmentally friendly and catalytic synthetic methods. In this paper, a method of photocatalytic oxidative coupling for the preparation of TMTZ was reported for the first time. By using an organic photocatalyst Eosin Y, TMTZ was synthesized rapidly and efficiently. The thermal decomposition properties of TMTZ were studied, and different performance characteristics between TMTZ and UDMH were determined and analyzed, which provided a basis for the application of TMTZ based new liquid propellant.