Nitrogen-Rich Bis-1,2,4-triazoles-A Comparative Study of Structural and Energetic Properties

Single Step Synthesis of gem-Dinitro Methyl-1,2,4-triazole and Its Hydroxylamine Salt: An Alternative to the FOX-7 and Other Benchmark Explosives

gem-Dinitro methyl based high-energy-density material 5-(dinitromethylene)-4,5-dihydro-1H-1,2,4-triazole (2) and its hydroxylamine salt (4) were synthesized for the first time in a single step and characterized. Further, the structure of 2 was confirmed by single-crystal X-ray diffraction (SCXRD) studies. Interestengly, both the compounds show excellent density (> 1.83 g cm-3), detonation velocity (> 8700 m s-1), pressure (> 30 GPa) and are insensitive toward mechanical stimuli such as impact and friction sensitivity. Considering their synthetic fesibility and balanced energetic performance, compounds 2 and 4 show future prospects as potential next-generation energetic materials for the replacenent of many presently used benchmark high energy density materials such as RDX, FOX-7 and highly insensitive H-FOX.

Exploring a Fused Triazole-Tetrazine Binary CN Material for a Promising Initiating Substance

The pursuit of binary carbon-nitrogen (CN) materials with high density and good thermal stability presents a significant challenge due to the inherent trade-off between high-energy storage and low bond dissociation energy. In this study, we designed and synthesized (S)-1,2-bis(3-azido-1H-1,2,4-triazol-1-yl)diazene (BAzTD) and 2,9-diazidobis([1,2,4]-triazolo)[1,5-d:5',1'-f][1,2,3,4]tetrazine (DAzTT) through a straightforward reaction. Remarkably, DAzTT demonstrated a high density of 1.816 g·cm-3 (at 298 K) and a considerable thermal decomposition temperature of 216.86 °C. These properties outperform those of previously reported binary heterocyclic CN compounds and polyazido heterocyclic compounds. The quantum-chemical methods further substantiated the integral role of aromaticity as the driving force behind this difference. Additionally, the initiation capability of DAzTT was evaluated by a notably low minimum primary charge (MPC = 40 mg), surpassing conventional organic primary explosives, such as commercial 2-diazo-4,6-dinitrophenol (DDNP, MPC = 70 mg). The exceptional priming ability highlights the potential as an environmentally friendly replacement for toxic lead azide. DAzTT sets a new standard for binary CN compounds and provides a valuable precursor for high-nitrogen carbon nitride materials.

Azo-Bridged Triazole Macrocycles: Computational Design, Energy Content, Performance, and Stability Assessment

Oxadiazole and triazole are extensively investigated heterocyclic scaffolds in the development of energetic materials. New energetic molecules were designed by replacing 1,2,5-oxadiazole with 2H-1,2,3-triazole in the reported conjugated macrocyclic systems to assess the influence on the energetic properties and stability. In addition, nitro groups were introduced in triazole units (N-functionalization) to improve the energetic performance. Energetic properties, including heat of formation, oxygen balance, density, detonation pressure and velocity, and impact sensitivity, were estimated for these triazole-based macrocycles. The replacement of 1,2,5-oxadiazole with 2H-1,2,3-triazole and 2-nitro-1,2,3-triazole significantly enhances the energy content, detonation performance, and noncovalent interactions. The theoretically computed energetic properties of triazole-based macrocycles reveal high positive heats of formation (1507-2761 kJ/mol), oxygen balance (-88.8 to -22.8%), high densities (1.87-1.90 g/cm3), superior detonation velocities (8.41-9.52 km/s), pressures (26.64-40.55 GPa), acceptable impact sensitivity (27-40 cm), and safety factor (51-290). The overall energetic assessment highlights triazole-based macrocycles as a potential framework that will be useful for developing advanced energetic materials.

Synthesis of Advanced Pyrazole and N-N-Bridged Bistriazole-Based Secondary High-Energy Materials

In this work, we have synthesized 3,5-dihydrazinyl-4-nitro-1H-pyrazole (2), 9-nitro-1H-pyrazolo[3,2-c:5,1-c']bis([1,2,4]triazole)-3,6-diamine (3), and N-N-bonded N,N'-{[4,4'-bi(1,2,4-triazole)]-3,3'-diyl}dinitramide (5) and its stable nitrogen-rich energetic salts in one and two steps in quantitative yields from commercially available inexpensive starting material 4,6-dichloro-5-nitropyrimidine (1). Along with characterization via nuclear magnetic resonance, infrared, differential scanning calorimetry, and elemental analysis, the structures of 2 and 4-8 were confirmed by single-crystal X-ray diffraction. Interestingly, 5-8 show excellent thermal stability (242, 221, 250, and 242 °C, respectively) compared to that of RDX (210 °C). Detonation velocities of 2, 4, 6, and 7 range from 8992 to 9069 m s-1, which are better than that of RDX (8878 m s-1) and close to that of HMX (9221 m s-1). All of these compounds are insensitive to impact (10-35 J) and friction (360 N) sensitivity. These excellent energetic performances, stabilities, and synthetic feasibilities make compounds 2, 4, 6, and 7 promising candidates as secondary explosives and potential replacements for the presently used benchmark explosives RDX and HMX.

Enhanced thermal, safety and anti-hygroscopicity performance of core-shell ammonium perchlorate with a double coating layer

A new core-shell structure AP/Cu-DABT/Cu(Pa)2 (10 wt% each) (AP = ammonium perchlorate, DABT = 3,3'-diamino-5,5'-bis(1H-1,2,4-triazole), Pa = palmitic acid) with two coating layers was synthesized through two self-assembly reactions to improve the thermal decomposition performance, safety performance and moisture absorption resistance of AP. The results show that the surface of AP particles is uniformly and densely covered by Cu-DABT and Cu(Pa)2 coatings successively. Compared with pure AP, the HTD (high-temperature decomposition) peak temperature and activation energy of the AP/Cu-DABT/Cu(Pa)2 (10 wt% each) composite material were reduced by 74.7 °C and 117.67 kJ mol-1, respectively, and the heat release increased by 1421.02 J g-1. In addition, the burning rate and maximum flame temperature of the propellant containing the AP/Cu-DABT/Cu(Pa)2 (10 wt% each) composite were increased by 8.7 mm s-1 and 815.8 °C, respectively, compared with the propellant containing pure AP. Moreover, compared with pure AP, the contact angle of the AP/Cu-DABT/Cu(Pa)2 (10 wt% each) composite with water increased by 89.15°, and the water content decreased by 0.38 wt%. The impact sensitivity and friction sensitivity of the composite material were reduced by 16.9 cm and 96%, respectively. Analysis shows that the Cu-DABT coating plays a major role in improving the thermal properties of the composite material, the burning rate and flame temperature of the propellant, while the Cu(Pa)2 coating plays a major role in improving the hygroscopic performance and safety performance of the composite material. The composite material has good thermal decomposition properties, anti-hygroscopic properties and safety properties, so the composite material is very promising as a potential additive for solid propellants.

Dipole field in nitrogen-enriched carbon nitride with external forces to boost the artificial photosynthesis of hydrogen peroxide

Artificial photosynthesis is a promising strategy for efficient hydrogen peroxide production, but the poor directional charge transfer from bulk to active sites restricts the overall photocatalytic efficiency. To address this, a new process of dipole field-driven spontaneous polarization in nitrogen-rich triazole-based carbon nitride (C3N5) to harness photogenerated charge kinetics for hydrogen peroxide production is constructed. Here, C3N5 achieves a hydrogen peroxide photosynthesis rate of 3809.5 µmol g-1 h-1 and a 2e- transfer selectivity of 92% under simulated sunlight and ultrasonic forces. This high performance is attributed to the introduction of rich nitrogen active sites of the triazole ring in C3N5, which brings a dipole field. This dipole field induces a spontaneous polarization field to accelerate a rapid directional electron transfer process to nitrogen active sites and therefore induces Pauling-type adsorption of oxygen through an indirect 2e- transfer pathway to form hydrogen peroxide. This innovative concept using a dipole field to harness the migration and transport of photogenerated carriers provides a new route to improve photosynthesis efficiency via structural engineering.

Thermal stability of azole-rich energetic compounds: their structure, density, enthalpy of formation and energetic properties

Energetic compounds, as a type of special material, are widely used in the fields of national defense, aerospace and exploration. Their research and production have received growing attention. Thermal stability is a crucial factor for the safety of energetic materials. Azole-rich energetic compounds have emerged as a research hotspot in recent years owing to their excellent properties. Due to the aromaticity of unsaturated azoles, many azole-rich energetic compounds have significant thermal stability, which is one of the properties that researchers focus on. This review presents a comprehensive summary of the physicochemical and energetic properties of various energetic materials, highlighting the relationship between thermal stability and the structural, physicochemical, and energetic properties of azole-rich energetic compounds. To improve the thermal stability of compounds, five aspects can be considered, including functional group modification, bridging, preparation of energetic salts, energetic metal-organic frameworks (EMOFs) and co-crystals. It was demonstrated that increasing the strength and number of hydrogen bonds of azoles and expanding the π-π stacking area are the key factors to improve thermal stability, which provides a valuable way to develop energetic materials with higher energy and thermal stability.

Chemical Descriptors for a Large-Scale Study on Drop-Weight Impact Sensitivity of High Explosives

The drop-weight impact test is an experiment that has been used for nearly 80 years to evaluate handling sensitivity of high explosives. Although the results of this test are known to have large statistical uncertainties, it is one of the most common tests due to its accessibility and modest material requirements. In this paper, we compile a large data set of drop-weight impact sensitivity test results (mainly performed at Los Alamos National Laboratory), along with a compendium of molecular and chemical descriptors for the explosives under test. These data consist of over 500 unique explosives, over 1000 repeat tests, and over 100 descriptors, for a total of about 1500 observations. We use random forest methods to estimate a model of explosive handling sensitivity as a function of chemical and molecular properties of the explosives under test. Our model predicts well across a wide range of explosive types, spanning a broad range of explosive performance and sensitivity. We find that properties related to explosive performance, such as heat of explosion, oxygen balance, and functional group, are highly predictive of explosive handling sensitivity. Yet, models that omit many of these properties still perform well. Our results suggest that there is not one or even several factors that explain explosive handling sensitivity, but that there are many complex, interrelated effects at play.

Thermal stability of emerging N6-type energetic materials: kinetic modeling of simultaneous thermal analysis data to explain sensitivity trends

A number of new high-performing energetic materials possess explosophoric functionalities, high nitrogen content, and fused heterocyclic blocks. Two representatives of these materials have been synthesized recently, namely, 1,2,9,10-tetranitrodipyrazolo[1,5-d:5',1'-f][1,2,3,4]-tetrazine (1) and 2,9-dinitrobis([1,2,4]triazolo)[1,5-d:5',1'-f][1,2,3,4]tetrazine (2). The thermal stability of these energetic materials bearing the N-N-N = N-N-N fragment and three closely related compounds has been investigated for the first time. The thermal decomposition process of analyzed compounds was complicated by the appearance of the liquid phase, sublimation of the material, and autocatalysis by reaction products. In contrast to the traditional approach to the kinetic modeling based on data from either TGA or DSC, we use both signals' data measured at the same time and perform the joint kinetic analysis using the model-fitting technique to obtain the pertinent kinetic description of the process. Of the analyzed materials, 1 and 2 show the lowest thermal stability in melt with a characteristic rate constant of 2.6 × 10^-3 s^-1 at 250 °C. The kinetic parameters and calculated detonation performance data were used in the model to describe the mechanical sensitivity. The model output and the experimental friction sensitivity data show a respectable agreement, but more data are required to draw firm conclusions. In general, the provided thermal stability and kinetic data can be used for thermal response and storage modeling of these new N6-type energetic materials. The developed thermokinetic approach, joint model-fitting of several thermal analysis signals, can be applied to other complex thermally induced processes to increase the value and credibility of the kinetic findings.

Intramolecular Assembly of Nitrobiazoles and an Ether Bridge: Toward Energetic Materials with Enhanced Energy and Safety

Recently, the construction of novel fused-ring frameworks has become one of the most significant innovative approaches to access high-energy and thermostable energetic molecules. In this work, an ether bridge was utilized as a building block to construct energetic fused-ring skeletons for the first time. Two new [5,7,5]-tricyclic N-heterocycle-based backbones, ditriazole-1,3,6-oxadiazepine and pyrazole-triazole-1,3,6-oxadiazepine, were synthesized via a straightforward one-step synthetic route and the energetic performances of their derivatives were further evaluated. Containing an additional oxygen atom, high-density pyrazole-triazole backbone, and high crystal packing coefficient, the asymmetric molecule 2,10,11-trinitro-5H,7H-pyrazolo[1,5-c][1,2,4]triazolo[5,1-e][1,3,6]oxadiazepine (NOB-3) features a high crystal density of 1.825 g cm^-3, much superior to those of the symmetrical analogues 2,10-dinitro-5H,7H-bis([1,2,4]triazolo)[1,5-c:5',1'-e][1,3,6]oxadiazepine (NOB-4, d = 1.758 g cm^-3) and D (d = 1.634 g cm^-3). Meanwhile, the compounds NOB-3 and NOB-4 exhibit better thermal stability than the parent molecule DNBT (T_d = 251 °C), and their decomposition temperatures reach up to 303 and 294 °C, respectively. The remarkable overall performance of NOB-3 and NOB-4 strongly suggests them as appropriate candidates for heat-resistant explosives. Our study may give new insights into the close correlation of the structural properties of energetic fused-ring frameworks, and the universality of the asymmetric heterocycles combination strategy for designing advanced high-energy density materials (HEDMs) was emphasized again.

Promising Thermally Stable Energetic Materials with the Combination of Pyrazole-1,3,4-Oxadiazole and Pyrazole-1,2,4-Triazole Backbones: Facile Synthesis and Energetic Performance

Thermally stable energetic materials have broad applications in the deep mining, oil and natural exploration, and aerospace industries. The quest for thermally stable (heat-resistant) energetic materials with high energy output and low sensitivity has fascinated many researchers worldwide. In this study, two different series of thermally stable energetic materials and salts based on pyrazole-oxadiazole and pyrazole-triazole (3-23) with different explosophoric groups have been synthesized in a simple and straightforward manner. All the newly synthesized compounds were fully characterized by IR, ESI-MS, multinuclear NMR spectroscopy, elemental analysis, and thermogravimetric analysis-differential scanning calorimetry measurements. The structures of 3, 7, and 22 were supported by single-crystal X-ray diffraction studies. The density, heat of formation, and energetic properties (detonation velocity and detonation pressure) of all the compounds range between 1.75 and 1.94 g cm-3, 0.73 to 2.44 kJ g-1, 7689 to 9139 m s-1, and 23.3 to 31.5 GPa, respectively. All the compounds are insensitive to impact (>30 J) and friction (>360 N). In addition, compounds 4, 6, 10, 14, 17, 21, 22, and 23 show high onset decomposition temperature (Td between 238 and 397 °C) than the benchmark energetic materials RDX (Td = 210 °C), HMX (279 °C), and thermally stable HNS (318 °C). It is noteworthy that the pyrazole-oxadiazole and pyrazole-triazole backbones greatly influence their physicochemical and energetic properties. Overall, this study offers a perspective on insensitive and thermally stable nitrogen-rich materials and explores the relationship between the structure and performance.

C-C bonded bis-5,6 fused triazole-triazine compound: an advanced heat-resistant explosive with high energy and low sensitivity

It is still an urgent problem in the field of energetic materials to explore the synthesis of heat-resistant compounds with balanced energy and thermal stability through simple synthetic routes. Recently, fused compounds are considered to provide a promising framework for the construction of ideal heat-resistant compounds. In this study, three novel C-C bonded bis-5,6 fused triazole-triazine compounds, 3,3'-dinitro-[7,7'-bi[1,2,4]triazolo[5,1-c][1,2,4]triazine]-4,4'-diamine (2), 4,4'-diamino-[7,7'-bi[1,2,4]triazolo[5,1-c][1,2,4]triazine]-3,3'-dicarbonitrile (3), and 3,3'-di(1H-tetrazol-5-yl)-[7,7'-bi[1,2,4]triazolo[5,1-c][1,2,4]triazine]-4,4'-diamine (4), were synthesized by a simple method. Compound 2 exhibited an approaching detonation velocity of 8837 m s^-1 compared with that of the traditional high energy explosive RDX velocity of 8795 m s^-1, while its thermal stability (T_d = 327 °C) was comparable to that of the heat-resistant explosive HNS (T_d = 318 °C). At the same time, the double fused compound 2 also realized high density (1.90 g cm^-3) and extremely low sensitivity (FS > 360 N, IS > 40 J). The above good comprehensive properties prove that compound 2 can be used as a potential insensitive high-energy heat-resistant explosive. In addition, the effects of the crystal structure on the sensitivity and thermal stability were studied using the quantum chemical methods. These results imply that the formation of double fused ring compounds by the ring closing reaction at symmetrical positions is an ideal strategy for the development of advanced heat-resistant explosives.

Two 1D Anderson-Type Polyoxometalate-Based Metal-Organic Complexes as Bifunctional Heterogeneous Catalysts for CO2 Photoreduction and Sulfur Oxidation

Sulfur oxides from the combustion of petrol and excessive emissions of carbon dioxide (CO₂) are currently the main causes of environmental pollution. Considerable interest has been paid to solving the challenge, and catalytic reactions seem to be the desired choice. Due to the high density of Lewis acid active sites, polyoxometalates are considered to be the ideal choice for these catalytic reactions. Herein, two captivating polyoxometalate-based metal-organic complexes, formulated as [Co(H₂O)₂DABT]₂[CrMo₆(OH)₅O₁₉] ({Co-CrMo₆}) and [Zn(H₂O)₂DABT]₂[CrMo₆(OH)₅O₁₉] ({Zn-CrMo₆}) (DABT = 3,3'-diamino-5,5'-bis(1H-1,2,4-triazole)) were successfully obtained under hydrothermal conditions. The structural analysis demonstrates that {Co-CrMo₆} and {Zn-CrMo₆} are isostructural with two different transition metal (Co/Zn) ions based on quadridentate Anderson-type [CrMo₆(OH)₅O₁₉]^4- polyanions. A fan-shaped unit of {Co-CrMo₆}/{Zn-CrMo₆} is linked to generate a one-dimensional (1D) ladder-like structure. Intriguingly, benefitting from rich Co centers with a suitable energy band structure, {Co-CrMo₆} displays better photocatalytic activity than {Zn-CrMo₆} for converting CO₂ into CO, endowing the CO formation of 1935.3 μmol g^-1 h^-1 with high selectivity. Meanwhile, {Co-CrMo₆} also exhibits a satisfactory removal rate of 99% for oxidizing dibenzothiophene at 50 °C, which suggests that {Co-CrMo₆} may be utilized as a potential dual functional material with immense prospects in photocatalytic CO₂ reduction and sulfur oxidation for the first time.

Polynitro-Functionalized Azopyrazole with High Performance and Low Sensitivity as Novel Energetic Materials

The development of energetic materials is still facing a huge challenge because the relationship between energy and sensitivity is usually contradictory: high energy is always accompanied with low sensitivity. Here, a high-energy, low-sensitivity energetic polynitro-functionalized azopyrazole (TNAP) and its energetic salts have been synthesized. The structural characterization of these compounds was analyzed by elemental analysis, ¹H and ¹³C NMR spectroscopies, and infrared spectroscopy. The single-crystal structure of compounds K₂TNAP, TNAP, 5, and 6 was obtained by X-ray diffraction, and K₂TNAP is a novel energetic metal-organic framework. The calculated detonation properties of TNAP (9040 m s^-1 and 36.0 GPa) are superior to that of RDX (8796 m s^-1 and 33.6 GPa). In addition, TNAP also has lower mechanical sensitivity (IS > 40 J, FS = 244 N) and higher decomposition temperature (T_d = 221 °C) than RDX (IS = 7.4 J, FS = 120 N, and T_d = 204 °C). These experimental results suggest that TNAP may become a new candidate for secondary explosives.

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.

Synthesis of nitrogen-rich and thermostable energetic materials based on hetarenecarboxylic acids

Two series of both nitrogen-rich and thermostable energetic materials as well as their energetic salts based on hetarenecarboxylic acids are now described. Among these new compounds, neutral compounds 3 and 10 have higher nitrogen contents (69.66% and 63.05%) than their energetic salts, which suggests that they could be used as green energetic materials. In addition, compound 3 shows a good decomposition temperature (T_d = 281 °C), which is close to that of TNT (T_d = 295 °C). Nitrogen-rich salt 6 exhibits better integrated energetic-properties (D = 8913 m s^-1, IS = 24 J, FS = 320 N) than RDX (D = 8795 m s^-1, IS = 7.5 J, FS = 120 N).

Heterocyclic Nitrilimines and Their Use in the Synthesis of Complex High-Nitrogen Materials

We show the ability of a nitrilimine prepared from 3-amino-5-nitro-1,2,4-triazole to undergo various cyclization and rearrangement reactions, giving a beautiful diversity of nitrogen-rich heterocyclic products. This chemistry includes the first cyclization of a nitrilimine with a diazonium species, giving a tetrazole, a previously unknown transformation, as well as leading to the creation of several new energetic materials with backbones not available by traditional techniques. New materials prepared were characterized both chemically (multinuclear NMR, IR, mass spectrometry, and elemental analysis) and energetically, with sensitivities and performances reported.

Development and Evolution of Energetic Cocrystals

In spite of the importance of energetic materials to a broad range of military (munitions, missiles) and civilian (mining, space exploration) technologies, the introduction of new chemical entities in the field occurs at a very slow pace. This situation is understandable considering the stringent requirements for cost and safety that must be met for new chemical entities to be fielded. If existing manufacturing infrastructure could be leveraged, then this would offer a fundamental shift in the discovery paradigm. Cocrystallization is an approach poised to realize this goal because it can use existing materials and make new chemical compositions through the assembly of multiple unique components in the solid state. This account describes early proof-of-principle studies with widely used energetics in the field, including 2,4,6-trinitrotoluene (TNT) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), forming cocrystals with nonenergetic coformers that alter key properties such as density, sensitivity, and morphology. The evolution of these studies to produce cocrystals between two energetic components is detailed, including those exploiting new intermolecular interaction motifs that drive assembly such as halogen bonding. Implications of cocrystallization for performance, sensitivity to external stimuli, and manufacturability are explored at each stage. The derivation of many of these cocrystals from energetic materials in common use satisfies the goal of using materials already demonstrated to be cost-effective at scale and with well-understood safety profiles. The account concludes with a discussion of cocrystallizing molecules having excess of oxidizing power with those that are oxygen-deficient to push the limits of explosive performance to unprecedented levels. The purposeful production of an arbitrary combination of two solid components into a cocrystal is far from certain, but the studies described motivate the continued exploration of novel materials and the development of predictive models for identifying crystallization partners. When such cocrystals form, many of their most important properties cannot be predicted, pointing to another challenge for the purposeful development of energetic materials based on cocrystallization.

Introduction of the acylamino group to bridged bis(nitroamino-1,2,4-triazole): a strategy for tuning the sensitivity of energetic materials

Introduction of the acylamino group into energetic material compounds will contribute to balancing the sensitivity and the energy.

Facile and direct halogenation of 1,2,3-triazoles promoted by a KX–oxone system under transition metal free conditions

A convenient and efficient oxidative halogenation of 4-aryl 1,2,3-triazoles is realized at ambient temperature under transition metal free conditions.

Very thermostable energetic materials based on a fused-triazole: 3,6-diamino-1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole

The fused-triazole backbone 1H-[1,2,4]triazolo[4,3-b][1,2,4]triazole with two C-amino groups gave a highly thermally energetic compound.

A new 3D Ag(i)-based high-energy metal organic frameworks (HE-MOFs): synthesis, crystal structure and explosive performance

A new 3D HE-MOF, [Ag₂(TABT)(NO₃)₂]_n, where TABT represents 4,4′,5,5′-tetraamine-3,3′-bis-1,2,4-triazole, was synthesized by hydrothermal method, exhibiting high density, good thermostability, insensitivity and relative high detonation performance.

Crystalline Peroxosolvates: Nature of the Coformer, Hydrogen-Bonded Networks and Clusters, Intermolecular Interactions

Despite the technological importance of urea perhydrate (percarbamide) and sodium percarbonate, and the growing technological attention to solid forms of peroxide, fewer than 45 peroxosolvates were known by 2000. However, recent advances in X-ray diffractometers more than tripled the number of structurally characterized peroxosolvates over the last 20 years, and even more so, allowed energetic interpretation and gleaning deeper insight into peroxosolvate stability. To date, 134 crystalline peroxosolvates have been structurally resolved providing sufficient insight to justify a first review article on the subject. In the first chapter of the review, a comprehensive analysis of the structural databases is carried out revealing the nature of the co-former in crystalline peroxosolvates. In the majority of cases, the coformers can be classified into three groups: (1) salts of inorganic and carboxylic acids; (2) amino acids, peptides, and related zwitterions; and (3) molecular compounds with a lone electron pair on nitrogen and/or oxygen atoms. The second chapter of the review is devoted to H-bonding in peroxosolvates. The database search and energy statistics revealed the importance of intermolecular hydrogen bonds (H-bonds) which play a structure-directing role in the considered crystals. H2O2 always forms two H-bonds as a proton donor, the energy of which is higher than the energy of analogous H-bonds existing in isostructural crystalline hydrates. This phenomenon is due to the higher acidity of H2O2 compared to water and the conformational mobility of H2O2. The dihedral angle H-O-O-H varies from 20 to 180° in crystalline peroxosolvates. As a result, infinite H-bonded 1D chain clusters are formed, consisting of H2O2 molecules, H2O2 and water molecules, and H2O2 and halogen anions. H2O2 can form up to four H-bonds as a proton acceptor. The third chapter of the review is devoted to energetic computations and in particular density functional theory with periodic boundary conditions. The approaches are considered in detail, allowing one to obtain the H-bond energies in crystals. DFT computations provide deeper insight into the stability of peroxosolvates and explain why percarbamide and sodium percarbonate are stable to H2O2/H2O isomorphic transformations. The review ends with a description of the main modern trends in the synthesis of crystalline peroxosolvates, in particular, the production of peroxosolvates of high-energy compounds and mixed pharmaceutical forms with antiseptic and analgesic effects.

Density Functional Theory (DFT) Study on the Structures and Energetic Properties of Isomers of Tetranitro-bis-1,2,4-triazoles

A series of isomers of tetranitro-bis-1,2,4-triazoles were designed, and their electronic structures, heats of formation, densities, detonation performances, thermal stabilities, and impact sensitivities were investigated by density functional theory (DFT). The structure and energetic properties of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were also calculated at the same level. On comparing with the detonation velocity and pressure and bond dissociation energy (BDE) of HMX, it was found that four isomers (BT2, BT5, BT6, BT7) have higher detonation performances than HMX and three isomers (BT5, BT6, BT7) have better thermal stabilities than HMX. The calculated results of impact sensitivities indicated that all of the designed isomers have more sensitivity than HMX. The calculated results of energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) indicated that all of the designed isomers were more easily excited than HMX in the chemical reaction process. In particular, 3,3',5,5'-tetranitro-1,1'-bis-1,2,4-triazoles (BT5) exhibited excellent detonation performances (9464 m s^-1, 39.44 GPa) and good thermal stability (BDE 256.81 kJ mol^-1). The results indicated that the isomerization of tetranitro-bis-1,2,4-triazoles could improve their detonation performance or thermal stability and might lead to a promising isomer possessing both good performance and high thermal stability.

3,4-Bis(3-tetrazolylfuroxan-4-yl)furoxan: A Linear C-C Bonded Pentaheterocyclic Energetic Material with High Heat of Formation and Superior Performance

The design and preparation of new nitrogen-rich heterocyclic compounds are of considerable significance for the development of high-performing energetic materials. By combining nitrogen-rich tetrazole and oxygen-rich furoxan, a linear C-C bonded pentaheterocyclic energetic compound, 3,4-bis(3-tetrazolylfuroxan-4-yl) furoxan (BTTFO), was synthesized using a facile and straightforward method. Comprehensive X-ray analysis reveals the key role of hydrogen bonds, π-π interactions, and short contacts in the formation of dense packing of BTTFO and explains why a long chain-shaped molecule has a high density. This multicyclic structure incorporating three furoxan and two tetrazole moieties results in an exceptionally high heat of formation (1290.8 kJ mol^-1) and favorable calculated detonation performances (v _D, 8621 m s^-1, P, 31.5 GPa). The interesting structure and fascinating properties demonstrated the feasibility of a linear multicyclic approach as a high-energy-density skeleton. Additionally, the thermodynamic parameters, electrostatic potential (ESP), and frontier molecular orbitals were also studied to get a better understanding of structure-property correlations.

Thermochemistry and Initial Decomposition Pathways of Triazole Energetic Materials

A thorough investigation of the initial decomposition pathways of triazoles and their nitro-substituted derivatives has been conducted using the MP2 method for optimization and DLPNO-CCSD(T) method for energy. Different initial thermolysis mechanisms are proposed for 1,2,4-triazole and 1,2,3-triazole, the two kinds of triazoles. The higher energy barrier of the primary decomposition path of 1,2,4-triazole (H-transfer path, ∼52 kcal/mol) compared with that of 1,2,3-triazole (ring-open path, ∼45 kcal/mol) shows that 1,2,4-triazole is more stable, consistent with experimental observations. For nitro-substituted triazoles, more dissociation channels associated with the nitro group have been obtained and found to be competitive with the primary decomposition paths of the triazole skeleton in some cases. Besides, the effect of the nitro group on the decomposition pattern of the triazole skeleton has been explored, and it has been found that the electron-withdrawing nitro group has an opposite effect on the primary dissociation channels of 1,2,4-triazole derivatives and 1,2,3-triazole derivatives.

1,3,4-Oxadiazole based thermostable energetic materials: synthesis and structure–property relationship

A combination of 1,3,4-oxadiazole and pyrazole produces a series of new compounds with satisfactory energetic properties.

Modification of crystalline energetic salts through polymorphic transition: enhanced crystal density and energy performance

We presented a detailed investigation of polymorphic transition of energetic salts and explored a new path for modifying crystalline energetic salts.

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.

A novel energetic framework combining the advantages of furazan and triazole: a design for high-performance insensitive explosives

Combining energetic furazan and triazole rings to achieve a series of high performance and insensitive energetic compounds.

Tetrazolyl and dinitromethyl groups with 1,2,3-triazole lead to polyazole energetic materials

A class of polyazole energetic compounds (combination of tetrazolyl, dinitromethyl and triazole) was obtained from 4,5-dicyanotriazole.

1,2,4-Oxadiazole-derived polynitro energetic compounds with sensitivity reduced by a methylene bridge

This is a new family of energetic compounds combining a high-energy polynitro group with an insensitive methylene linkage and thermostable 1,2,4-oxadiazole skeleton.

Synthesis and performance study of methylene-bridged bis(nitramino-1,2,4-oxadiazole) and its energetic salts

A series of new energetic compounds based on methylene-bridged bis(nitramino-1,2,4-oxadiazole) was synthesized through a simple, safe and efficient route and fully characterized.

Synthesis of high-performance insensitive energetic materials based on nitropyrazole and 1,2,4-triazole

A new family of symmetric nitropyrazole and 1,2,4-triazole derivatives and its energetic salts were obtained. The positive effect of ternary hydrogen bonds improve the performances of target compounds.