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The dominance of nitro pyrazole-based explosives in the recently reported high-performing energetic materials motivated us to comprehensively investigate the energy–stability correlation among different compounds based on 3,5-dinitro pyrazoles employing various computational methods. We also explored the energetic and physicochemical properties of the overlooked 3,5-dinitro pyrazole-based compound 3,5-dinitropyrazole-4-carboxylic acid (CDNP). This study revealed that CDNPexhibits the highest thermal stability among 4-substituted-3,5-dinitropyrazoles, combined with an acceptable energetic performance. These characteristics are attributed to its layered packing, strong intermolecular interactions, and the stability of its carbonyl bonds. Furthermore, the dicationic energetic salt formation of CDNPfurther allowed us to fine-tune the overall performance and stability. The dihydroxylammonium salt (5) of CDNPshows the best energetic performance, comparable to well-known traditional explosive TATB, with good thermal stability and low sensitivity toward impact and friction.

Two novel nitrogen-rich green energetic compounds were synthesized for the first time from readily available and cost-effective pyrazine starting materials. All newly synthesized molecules were comprehensively characterized, including infrared spectroscopy, nuclear magnetic resonance, elemental analysis, mass spectrometry, and thermogravimetric analysis–differential scanning calorimetry. All compounds have additionally been validated by single-crystal X-ray diffraction analysis. The physicochemical properties of compounds 2, 4, and 5were thoroughly investigated. Notably, all compounds exhibit remarkable performance, such as a high density (>1.84 g cm–3), excellent detonation properties (VOD > 8582 m s–1, and DP > 31.3 GPa), outstanding thermostability (>205 °C), and high insensitivity (IS > 35 J, and FS = 360 N). These attributes are quite comparable to those of secondary benchmark explosives such as TATB, RDX, LLM-105, and FOX-7. This tuned performance evidences that the incorporation of hydrazine, nitro, and aminotetrazole into the pyrazine framework fosters robust nonbonded interactions, ultimately enhancing thermal stability and reducing sensitivity. The findings of this study not only signify that compounds 2and 5have excellent detonation properties and stability but also prove that the strategy of replacing amino groups with hydrazine and aminotetrazole is a practical means of developing new insensitive energetic materials.

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 2was 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 2and 4show 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.

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 2and 4–8were confirmed by single-crystal X-ray diffraction. Interestingly, 5–8show excellent thermal stability (242, 221, 250, and 242 °C, respectively) compared to that of RDX (210 °C). Detonation velocities of 2, 4, 6, and 7range 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 7promising candidates as secondary explosives and potential replacements for the presently used benchmark explosives RDX and HMX.

High energetic 2-(1-hydroxy-2,2-dinitrovinyl)guanidine and guanidinium dinitromethanide (GDNM) salt were synthesized in one and two steps using a simple and cost-effective methodology from commercially available inexpensive starting materials with a high yield. NMR, IR spectroscopy, elemental analysis, and differential scanning calorimetry studies were used to characterize compound 2aand GDNMsalt. Single-crystal XRD, Hirshfeld surface analysis, and SEM analysis were used to study the crystal structure, hydrogen-bonding/noncovalent interactions, and morphology of the GDNMsalt, respectively. The physicochemical and energetic properties of compound 2aand GDNMsalt reveal their good energetic performance, specific impulse, and high mechanical insensitivity, which are better than that of propellants such as ADN and AP and close to that of the benchmark explosives such as RDX and FOX-7.

Density functional theory (DFT) methods were used to design a series of energetic dinitro-tris(triazole) isomers by altering the triazole rings and −NO2groups. The impact of three nitrogen atoms’ position in the tris(triazole) scaffold on energy content, performance, and stability was discussed. Based on computed heats of formation and densities, the detonation properties were predicted using the thermochemical EXPLO5 (v6.06) code. Using the bond dissociation energy of the longest C–NO2bond, the thermal stability was investigated. The mechanical sensitivities were estimated and correlated with RDX and HMX using maximum heats of detonation (Q), free void (ΔV) in the lattice of the crystalline compound, and total −NO2group charge. Among the designed series, compounds O4, R1, R3, and R4 display high heats of formation (>450 kJ/mol), high densities (>1.92 g/cm3), good detonation performances (D> 8.76 km/s and P> 32.0 GPa), and low sensitivities. Our findings suggest that the isomeric tricyclic triazole backbone could be a promising platform for developing new high-performing and thermostable energy materials.

Four novel energetic cocrystals of 5-nitropyrimidine-2,4,6(1H,3H,5H)-trione/nitro barbituric acid (NBA) with energetic coformers 1H-tetrazol-5-amine (AmTz), 5-(4-nitro-1H-pyrazol-3-yl)-4H-1,2,4-triazol-3-amine (NPTA), 1,3-diaminoguanidinehydrochloride (DAG), and 7H-[1,2,4]triazolo[4,3-b][1,2,4]triazole-3,6,7-triamine (TATOT) were synthesized for the first time and confirmed by single-crystal X-ray diffraction. Three cocrystals, NBA:AmTz, NBA:NPTA, and NBA:DAG, were obtained in a stoichiometry of 1:1, while NBA:TATOT was obtained with 1:2 stoichiometry. All the presented molecules were synthesized from commercially available inexpensive starting materials in one or two steps. All the cocrystals possess high densities (1.71–1.80 g cm–3), excellent thermal stability (222–310 °C), and low impact and friction sensitivity (>40 J and >360 N), which suggest that they are a better replacement for TNT as a core explosive and are close to RDX and HMX as a formulating energetic material. The strong stabilizing hydrogen bonding and vdW interactions are preserved among all the components of cocrystals. These interactions also play a significant role in cocrystal formation. These cocrystals combine the stability of AmTz, NPTA, DAG, and TATOT with the energetic performance of NBA into a homogeneous energetic material.

Graphical abstract:

Various energetic salts (3a–f) were obtained from 1,3,5-tris[(2H-tetrazol-5-yl)methyl]isocyanurate (3), while N2,N4,N6-tri(1H-tetrazol-5-yl)-1,3,5-triazine-2,4,6-triamine (5) and N,N′-{6-[(1H-tetrazol-5-yl)amino]-1,3,5-triazine-2,4-diyl}bis[N-(1H-tetrazol-5-yl)nitramide] (6) were obtained from cyanuric chloride via a simple, efficient two-step synthetic route from inexpensive starting materials. Compounds 3a–fand 6show excellent detonation properties (VOD = 7876–8832 m s–1, and DP = 20.73–30.0 GPa), a high nitrogen content (>62%), and high positive heats of formation (205.2–1888.9 kJ mol–1) with excellent thermostability and remarkable insensitivity.

Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal–organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N′-([4,4′-bi(1,2,4-triazole)]-3,3′-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n(K-MOF) and sodium [Na2BDNBT]n(Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm–3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557–9724 m/s, detonation pressure (DP) of 30.41–36.97 GPa, positive heat of formation of 122.52–242.25 kJ mol–1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30–40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2–and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20.

The pursuit of heat-resistant energetic materials featuring high thermostability and energy has gained keen interest in recent years owing to their use in coal mining and aerospace domains. In this study, we synthesized 4-((4,6-diamino-1,3,5-triazin-2-yl) amino)-1H-1,2,3-triazole-5-carbonitrile (6) and its perchlorate and nitrate energetic salts (6aand 6b) by incorporating amino bridging (−NH−) using the Dimroth rearrangement (DR) from inexpensive starting materials as a heat-resistant energetic materials. All of the compounds were thoroughly characterized by infrared (IR), NMR, elemental analysis (EA), high-resolution mass spectrometry (HRMS), and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) studies. Compounds 6aand 6bshowed good densities (1.81 and 1.80 g cm–3), detonation performance (VOD = 7505 and 8257 m s–1, DP = 23.47 and 24.41 GPa), insensitivity to mechanical stimuli (IS = 40 J and FS = >360 N), and excellent thermal stability (Td= 307 and 334 °C), surpassing presently used heat-resistant explosive HNS (318 °C). The molecular electrostatic potentials and noncovalent interactions were pursued to understand possible interaction sites and structure-directing interactions in these salts. Their facile synthetic approach, good energetic performance, and outstanding thermal stability indicate that they are the ideal combination for replacing current benchmark heat-resistant explosive HNS. Additionally, this study highlights the use of classical DR for making new energetic materials with fine-tuned properties.

Various types of materials have been explored in the pursuit of high energy density materials (HEDMs) that have balanced energy and stability. Among them, energetic salts show numerous advantages, such as lower vapor pressures, high physical stabilities, and the opportunity for favorable tuning by careful selection of cations/anions. Nitrogen-rich bases are generally used as cations for energetic salt formation. While the synthesis of salts with larger cations lowers the sensitivity, smaller cations aid better energetic performance. A combination of both in the same ionic moieties might help in the formation of a superior explosive. In this work, a facile route for the synthesis of mixed dicationic energetic salts based on 1-((1H-tetrazol-5-yl)methyl)-3,5-dinitro-1H-pyrazol-4-ol (compound 1) has been explored by various combinations of bigger and smaller cations (compounds 4–10). All the synthesized energetic salts showed high positive heats of formation, energetic performance comparable to TATB, excellent stability towards impact and friction, and acceptable thermal stabilities. This improved technique will provide an additional option for fine-tuning the energetic properties of HEDMs and will facilitate in exploring the role of various cations in the overall performance of the energetic compounds.

A novel fused-ring compound, 5-azido-6-oxo-6,7-dihydro-[1,2,5]oxadiazolo[3,4-b]pyrazine 1-oxide (3a), was synthesized for the first time with simple two-step process and characterized using various spectroscopic techniques such NMR, IR, EA and HRMS. Two polymorphs (α-3aand β-3a) identified by SCXRD differ in crystal packing and noncovalent interactions, demonstrating high density, substantial heat of formation, and superior detonation properties with reduced mechanical sensitivity compared to TNT, TATB, and close to RDX, suggesting their potential as environmentally friendly high energy density materials.

A systematic computational study on the structural, electronic, bonding, and optical properties of orthorhombic ammonium azide (NH4 N3 ) has been performed using planewave pseudopotential (PW-PP) method based on density functional theory (DFT). Semiempirical dispersion correction schemes have been used to account for non-bonded interactions in molecular crystalline NH4 N3 . The ground state lattice parameters and fractional co-ordinates obtained using the dispersion correction schemes are in excellent agreement with experimental results. We calculated the single crystal elastic constants of NH4 N3 and its sensitivity is interpreted through the observed ordering of the elastic constants (C33 > C11 > C22 ). The electronic structure and optical properties were calculated using full potential linearized augmented plane wave (FP-LAPW) approach with recently developed functional of Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The TB-mBJ electronic structure shows that NH4 N3 is a direct band gap insulator with a band gap of 5.08 eV, while the calculated band gap with standard generalized gradient approximation is found to be 4.10 eV. The optical anisotropy is analyzed through the calcu- lated optical constants namely dielectric function and refractive index along three different crystallographic axes. The absorption spectra reveal that NH4 N3 is sensitive to ultraviolet (UV) light. Further, we also analyzed the detonation characteristics of the NH4 N3 using the reported heat of formation and density. NH4 N3 is found to have a detonation velocity of 6.45 km/s and a detonation pressure about 15.16 GPa computed by Kamlet-Jacobs empirical equations.

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 22were 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 23show high onset decomposition temperature (Tdbetween 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.

Nitrogen‐rich polyazole derivatives were designed and synthesized from the commercially available 4,5‐dicyano‐2‐aminoimidazole. The relatively simple synthesis of multiple azole rings in desired compounds with good yields allows for an efficient scale‐up. All synthesized compounds were characterized by NMR and vibrational spectroscopy, elemental analysis, and DSC studies. The impact and friction sensitivities were measured by the BAM apparatus. The energy content of the target compounds was predicted by using density functional methods. Performing cautious characterization point out that these compounds offer a good combination of high nitrogen‐ and energy‐content with insensitivity towards friction and impact stimuli. These results indicate the superior potential of these nitrogen‐rich polyazole derivatives for enthalpy enhancement, gas generant, and cationic components in energetic salts. Nitrogen‐rich compounds with multiple tetrazoles, oxadiazole, and imidazole rings were synthesized conveniently using the 4,5‐dicyano‐2‐aminoimidazole. All the target compounds possess high nitrogen content (49 to 71%) and have high positive energy content than those of RDX and HMX, owing to the enormous N−N/C−N bonds in the backbone. DSC‐TGA and BAM sensitivity tests indicate that all the compounds are thermally stable and insensitive towards impact and friction. The synthesized nitrogen‐rich compounds are potential candidates for enthalpy enhancement, gas generators, and source of cation moiety in energetic salts.

Background: The synthesis of small organic molecules based Hg2+ ions receptors have gained considerable attention because it is one of the most prevalent toxic metals which is continuously discharged into the environment by different natural and industrial activities. 1,4-Disubstituted 1,2,3-triazoles have been reported as good chemosensors for the detection of various metal ions including Hg2+ ions. Methods: The synthesis of 1,2,3-triazoles (4a-4c) was achieved by Cu(I)-catalyzed azide-alkyne cycloaddition, and their binding affinity towards various metal ions and anions were studied by UVVisible titration experiments. The perchlorate salts of metal ions and tetrabutylammonium salts of anions were utilized for the UV-Visible experiments. DFT studies were performed to understand the binding and mechanism on the sensing of 4a toward Hg2+ using the B3LYP/6-311G(d,p) method for 4a and B3LYP/LANL2DZ for 4a-Hg2+ species on the Gaussian 09W program. Results: The UV-visible experiments indicated that the compounds 4a-4c show a selective response towards Hg2+ ion in UV-Visible spectra, while other ions did not display such changes in the absorption spectra. The binding stoichiometry was evaluated by Job’s plot which indicated the 1:1 binding stoichiometry between receptors (4a-4c) and Hg2+ ion. The detection limit of 4a, 4b and 4c for the Hg2+ ions was found to be 29.1 nM, 3.5 μM and 1.34 μM, respectively. Conclusion: Some 1,2,3-triazole derivatives were synthesized (4a-4c) exhibiting high selectively and sensitivity towards Hg2+ ions in preference to other ions. Compound 4a has a low detection limit of 29.1 nM and the binding constant of 2.3x106 M-1. Similarly, 4b and 4c also showed selective sensing towards Hg2+ ions in the μM range. The observed experimental results were corroborated by density functional theory (DFT) calculations.

In the quest to synthesize high-performing insensitive high-energy density materials (HEDMs), the main challenge is establishing an equilibrium between energy and stability. For this purpose, we explored 4-hydroxy-3,5-dinitropyrazole- and tetrazole-based energetic scaffolds connected via a N-methylene-C bridge. The hydroxy functionality between nitro groups on the pyrazole ring promotes physical stability via inter- and intramolecular hydrogen bonding and contributes to oxygen balance, supporting better energetic performance. Due to two acidic sites (OHand NH) with different reactivities, a series of monocationic and dicationic salts were synthesized, and their overall performance was compared. All compounds synthesized in this study have high physical stability with impact sensitivity >40 J and friction sensitivity >360 N. Monocationic salts were generally found to have better thermal stability with respect to their corresponding dicationic energetic salts, which showed better energetic performance. The salt formation strategy effectively improved the thermal stability of 2(Td= 168 °C), where most energetic salts have decomposition temperatures higher than 220 °C. All of the compounds were characterized through IR, multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. The structure–property relationship was studied using Hirshfeld surface analysis, noncovalent interaction (NCI) analysis, and electrostatic potential studies.

Poly tetrazole-containing thermally stable and insensitive alkali metal-based 3D energetic metal–organic frameworks (EMOFs) are promising high energy density materials to balance the sensitivity, stability, and detonation performance of explosives in defense, space, and civilian applications. Herein, the self-assembly of L3–ligand with alkali metals Na(I) and K(I) was prepared at ambient conditions, introducing two new EMOFs, [Na3(L)3(H2O)6]n(1) and [K3(L)3(H2O)3]n(2). Single crystal analysis reveals that Na-MOF (1)exhibited a 3D wave-like supramolecular structure with significant hydrogen bonding among the layers, while K-MOF (2)also featured a 3D framework. Both EMOFs were thoroughly characterized by NMR, IR, PXRD, and TGA/DSC analyses. Compounds 1and 2show excellent thermal decomposition Td= 344 and 337 °C, respectively, compared to the presently used benchmark explosives RDX (210 °C), HMX (279 °C), and HNS (318 °C), which is attributed to structural reinforcement induced by extensive coordination. They also show remarkable detonation performance (VOD = 8500 m s–1, 7320 m s–1, DP = 26.74 GPa, 20 GPa for 1and 2, respectively) and insensitivity toward impact and friction (IS ≥ 40 J, FS ≥ 360 N for 1; IS ≥ 40 J, FS ≥ 360 N for 2). Their excellent synthetic feasibility and energetic performance suggest that they are the perfect blend for the replacement of present benchmark explosives such as HNS, RDX, and HMX.

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.

This work describes a new route to thermally stable energetic materials by connecting different types of energetic moieties (nitropyrazole and polynitrobenzene) with C−C bonds, where the first step involves a Suzuki cross‐coupling reaction between 4‐bromo‐3,5‐dinitro‐1H‐pyrazole and 4‐chlorophenylboronic acid. Further nitration, amination, oxidation, and salt formation reactions on the resulting C−C coupled framework resulted in various thermally stable energetic materials. All the compounds were fully characterized using IR, NMR [1H, 13C{1H}], differential scanning calorimetry (DSC), elemental analysis, and HRMS studies. Compounds 7and 9were further characterized by 15N NMR, and compounds 3and 6were characterized by single‐crystal X‐ray diffraction studies. Theoretical heats of formation and energetic performance for all the energetic compounds were calculated using Gaussian 09 and EXPLO5 v6.06 programs, respectively. This research introduces a novel method for synthesizing C−C coupled energetic materials that are not accessible by any other routes. This work demonstrates the synthesis and characterization of heat‐resistant explosives using Suzuki Cross‐Coupling reactions.

An attractive synthetic route was devaluped for making N‐(4‐(1,2,4‐oxadiazol‐3‐yl)‐1,2,5‐oxadiazol‐3‐yl) formamide (4) and di(1,2,4‐oxadiazol‐3‐yl) methanone O‐(nitrodi(1,2,4‐oxadiazol‐3‐yl)methyl) oxime (6) from commercially available inexpensive malononitrile starting material with easy purification, short experimental time and high yields at room temperature. The chemical structures of 4and 6were identified by NMR, IR, EA and verified by single‐crystal X‐ray studies. A plausible mechanism is proposed for the conversion of 4to 6. Furthermore, both compounds have been evaluated for energetic applications. Based on their insensitive nature and good detonation performance, they are potential energetic materials. The unexpected synthesisof N‐(4‐(1,2,4‐oxadiazol‐3‐yl)‐1,2,5‐oxadiazol‐3‐yl) formamide (4) and di(1,2,4‐oxadiazol‐3‐yl)methanone O‐(nitrodi(1,2,4‐oxadiazol‐3‐yl)methyl) oxime (6) in a simple and straightforward manner is reported. Compound 6exhibits high positive heat of formation, high nitrogen content, and good density, and may find use in energetic material applications.

1,2,3-Triazole and 1,2,4-triazole have been vigorously used in energetic materials research. Among these two, 1,2,4-triazole has been a widely used backbone in designing new energetic materials with improved performance. This study showed the synthesis of nitrogen-enriched dianionic energetic salts (3–6) based on methylene bridged 3,4-diamino-1,2,4-triazole combined with nitrate, perchlorate, picrate, and azide anions. Structures of 5,5′-methylenedi(4H-1,2,4-triazole-3,4-diamine) and its salts 4and 5were confirmed by single-crystal X-ray diffraction studies, showing a strong hydrogen-bonding network owing to the presence of –NH2groups, numerous oxygen and nitrogen atoms in the structure. The DSC results indicate acceptable thermal stabilities with the observed decomposition temperatures over 180 °C. All the compounds are dense (1.70–1.86 g/cm3) and exhibit reasonable detonation velocities (7.49–8.99 km/s) and pressures (21.9–28.2 GPa). Interestingly, salt 6possess detonation velocity comparable to that of RDX. These properties illustrate that incorporating a methylene bridge in a 3,4-diamino-1,2,4-triazole ring can effectively support the progress of mechanically insensitive and thermally stable energetic compounds in future research.

In this work, 110 energetic salts were designed and studied for their applications in energetic materials. Density functional theory methods were used to predict the heats of formation (HOFs), electronic structure, and energetic properties of a series of triazine-based ionic and nonionic compounds. It is observed that the −N3group, triazole, tetrazole, triazine, and tetrazine are effective structural units for increasing the HOFs in the designed compounds. The HOFs of cations and anions and the lattice energies of the salts were calculated separately to obtain the HOFs of the salts based on the Born–Haber cycle. The combination of three cations within the same framework is very useful for improving the HOFs of energetic salts. Similarly, the presence of the −NO2and −NHNO2groups in the same structure were found to be helpful in improving densities through strong inter- and intramolecular hydrogen bonding. The detonation velocities and detonation pressures of the salts were predicted by the Kamlet–Jacobs equations using calculated densities and HOFs. The calculated energetic properties indicate that the combination of suitable anion and cation species is useful for modifying detonation properties and oxygen balances (OB). The predicted results reveal that most of the compounds outperform hexahydro-1,3,5-trinitro-1,3,5-triazine and 2,4,6-trinitro-1,3,5-triaminobenzene and may be considered as potential candidates for high-energy materials. These results provide basic information for molecular design of novel high- energy salts.

A systematic computational study on the structural, electronic, bonding, and optical properties of orthorhombic ammonium azide (NH4N3) has been performed using planewave pseudopotential (PW-PP) method based on density functional theory (DFT). Semiempirical dispersion correction schemes have been used to account for nonbonded interactions in molecular crystalline NH4N3. The ground state lattice parameters, and fractional coordinates obtained using the dispersion correction schemes are in excellent agreement with experimental results. We calculated the single crystal elastic constants of NH4N3, and its sensitivity is interpreted through the observed ordering of the elastic constants (C33> C11> C22). The electronic structure and optical properties were calculated using full potential linearized augmented plane wave (FP-LAPW) approach with recently developed functional of Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. The TB-mBJ electronic structure shows that NH4N3is a direct band gap insulator with a band gap of 5.08 eV, while the calculated band gap with standard generalized gradient approximation is found to be 4.10 eV. The optical anisotropy is analyzed through the calculated optical constants, namely, dielectric function and refractive index along three different crystallographic axes. The absorption spectra reveal that NH4N3is sensitive to ultraviolet (UV) light. Further, we also analyzed the detonation characteristics of the NH4N3using the reported heat of formation and calculated density. NH4N3is found to have a detonation velocity of 6.45 km/s and a detonation pressure about 15.16 GPa computed by Kamlet–Jacobs empirical equations.

In this work, we report an approach for designing a series of energetic compounds derived from nitrogen-rich tris(1,2,4,5-tetrazin-3-yl)amine backbone. Based on available synthetic method, nitrogen content (70.8%), heat of formation (1371 ​kJ·mol-1), density (1.67 ​g·cm-3), detonation parameters (7.75 ​km·s-1, 24.30 ​GPa), and experimentally reported high decomposition temperature (231 ​°C), less sensitivity to accidental impact (42 ​J) and friction (360 ​N) data, tris(1,2,4,5-tetrazin-3-yl)amine found to be an efficient building block for designing energetic materials. The explosophoric functional groups –NO2, –NH2, –ONO2, –NHNO2, and N3were introduced in the tris(1,2,4,5-tetrazin-3-yl)amine framework to further improve energetic properties. All tris(1,2,4,5-tetrazin-3-yl)amine derivatives have a much higher heat of formation than TNT (2,4,6-trinitrotoluene) and RDX (1,3,5-trinitro-1,3,5-triazinane). Crucially, higher detonation velocities (>9.10 ​km·s-1) and detonation pressures (>35.20 ​GPa) were calculated for –NO2, –ONO2, and –NHNO2substituted compounds compared to RDX. Considering the experimental and computed stability of tris(1,2,4,5-tetrazin-3-yl)amine towards high temperatures and mechanical stimuli, the entire designed molecules are expected to be less sensitive and stable for energetic applications. These advantages make tris(1,2,4,5-tetrazin-3-yl)amine an effective building block. There is no denying that the insertion of energetic functional groups will undoubtedly benefit the development of secondary explosives and propellants.