3,3′-Dinitroamino-4,4′-azoxyfurazan and Its Derivatives: An Assembly of Diverse N–O Building Blocks for High-Performance Energetic Materials

Theoretical study of a series of 4,4'-azo-1H-1,2,4-triazol-5-one based nitrogen-rich salts as potential energetic compounds

Density function theory has been employed to systemically study 4,4'-azo-1H-1,2,4-triazol-5-one (ZTO) and its six nitrogen-rich salts at two different calculated levels (B3LYP/6-31G(d,p) and B3PW91/6-31G(d,p)). Their optimized geometries, electronic structures and molecular electrostatic potentials were further studied. Based on the two computed methods, the results of the optimized geometries show that the calculated structure of each compound adopted at the two different levels are rather similar except salt 7 with some differences. The values of the energy gaps indicate that compound 3 has the highest reactivity among salts 2-7. The crystal densities were corrected using the Politzer approach based on these two optimized levels. The density values with slight deviation indicate that the two calculated levels are applicable and the results are convincible. Based on the isodesmic reactions and Born-Haber energy cycle, the solid-phase heats of formation (HOFs) were predicted. Detonation parameters were evaluated using the Kamlet-Jacobs equations on the foundations of the calculated densities and HOFs. The results manifest that salt 2 exhibits the best detonation performance due to its highest density (1.819 g cm^-3), followed by salt 6. Moreover, impact sensitivities of compounds 1-7 were assessed using the calculated Q values to correlate with h ₅₀. Combining the detonation performance with safety, 1-7 exhibit good comprehensive properties and might be screened as a composition of modern nitrogen-rich energetic compounds.

Stability, Elastic Properties, and Deformation of LiBN2: A Potential High-Energy Material

Searching for high-energy-density materials is of great interest in scientific research and for industrial applications. Using an unbiased structure prediction method and first-principles calculations, we investigated the phase stability of LiBN₂ from 0 to100 GPa. Two new structures with space groups P4̅2₁ m and Pnma were discovered. The theoretical calculations revealed that Pnma LiBN₂ is stable with respect to a mixture of ¹/₃Li₃N, BN, and ¹/₃N₂ above 22 GPa. The electronic band structure revealed that Pnma LiBN₂ has an indirect band gap of 2.3 eV, which shows a nonmetallic feature. The Pnma phase has a high calculated bulk modulus and shear modulus, indicating its incompressible nature. The microscopic mechanism of the structural deformation was demonstrated by ideal tensile shear strength calculations. It is worth mentioning that Pnma LiBN₂ is dynamically stable under ambient conditions. The decomposition of this phase is exothermic, releasing an energy of approximately 1.23 kJ/g at the PBE level. The results provide new thoughts for designing and synthesizing novel high-energy compounds in ternary systems.

Novel catenated N6 energetic compounds based on substituted 1,2,4-triazoles: synthesis, structures and properties

1-Amino-3,5-dinitro-1,2,4-triazole (ADNT) was prepared using an efficient N-amination process. Three novel catenated N6 energetic derivatives of ADNT, which contain 1,1'-azobis(3,5-dinitro-1,2,4-triazole) (ABDNT), 1,1'-azobis(3-chloro-5-nitro-1,2,4-triazole) (ABCNT) and 1,1'-azobis(3,5-diazido-1,2,4-triazole) (ABDAT), were synthesized from N-amino oxidative-coupling reactions of ADNT. All compounds were fully characterized by 1H and 13C nuclear magnetic resonance spectroscopies, infrared spectroscopy, elemental analysis, mass spectrum, as well as differential scanning calorimetry (DSC). The crystal structure of compound ABCNT was confirmed by single-crystal X-ray diffraction showing an extensive conjugated structure. The densities of energetic derivatives ranged from 1.71 to 1.93 g cm-3, and all compounds have positive heats of formation in the range of 774.8 to 2150.8 kJ mol-1. Based on the measured densities and calculated heats of formation, theoretical performance calculations, including detonation pressures (29.6-42.4 GPa) and detonation velocities (8.22-9.49 km s-1) were carried out using the Gaussian 09 program and Kamlet-Jacobs equations, and they compared favorably with those of TNT and RDX. These properties make them potentially competitive as new high energy-density compounds.

Mild Synthesis of Substituted 1,2,5-Oxadiazoles Using 1,1'-Carbonyldiimidazole as a Dehydrating Agent

1,1'-Carbonyldiimidazole was found to induce the formation of a variety of 3,4-disubstituted 1,2,5-oxadiazoles (furazans) from the corresponding bisoximes at ambient temperature. This method enables these inherently energetic compounds to be prepared at temperatures well below their decomposition points and with improved functional group compatibility relative to prior methods. Conditions were developed that allowed for the first high-yielding synthesis of chlorofurazans from their amino counterparts, enabling the mild synthetic manipulation of these heterocycles.

Nitramino-functionalized tetracyclic oxadiazoles as energetic materials with high performance and high stability: crystal structures and energetic properties

The combination of 1,2,4-oxadiazole and nitramino-1,2,5-oxadiazole is a promising strategy for designing energetic materials with high performance and high stability.

Formation of trinitromethyl functionalized 1,2,4-triazole-based energetic ionic salts and a zwitterionic salt directed by an intermolecular and intramolecular metathesis strategy

Energetic trinitromethyl bistriazole and its ionic salts, as well as an unexpected energetic-zwitterion featuring trinitromethyl and diazonium moieties, were synthesized via an intermolecular and intramolecular metathesis strategy.

Self-assembled energetic 3D metal–organic framework [Na8(N5)8(H2O)3]n based on cyclo-N5–

A new 3D zeolite-like MOF [Na₈(N₅)₈(H₂O)₃]_n with an enhanced stability has been successfully synthesized by the self-assembly of Na⁺ with cyclo-N₅⁻ ligands.

N,N′-Methylenebis(N-(1,2,5-oxadiazol-3-yl)nitramide) derivatives as metal-free green primary explosives

Metal-free green primary explosives with excellent detonation properties and acceptable sensitivities were synthesized and fully characterized.

A novel method to synthesize stable nitrogen-rich polynitrobenzenes with π-stacking for high-energy-density energetic materials

A larger multi-nitro, multi-azide and multi-oxidized furazan ring compound with π–π stacking is herein reported. The coupling reaction of a NN bond and an azido was an efficient method to synthesize benzotriazole.

Theoretical design and prediction of properties for dinitromethyl, fluorodinitromethyl, and (difluoroamino)dinitromethyl derivatives of triazole and tetrazole

Twelve series of –CH(NO₂)₂, –CF(NO₂)₂and –C(NF₂)(NO₂)₂substituted derivatives of triazole and tetrazole were designed, some physicochemical or detonation properties of them were calculated.

Theoretical investigations on azole-fused tricyclic 1,2,3,4-tetrazine-2-oxides

Fused compounds, a unique class of large conjugate structures, have emerged as prime candidates over traditional nitrogen-rich mono-ring or poly-ring materials. Meanwhile, compounds containing catenated nitrogen chains have also attracted attention from scientists due to their high heats of formation. On the other hand, the azoxy [–N Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N(O)–] moiety has been found to increase density effectively in the molecular structure of compounds. Therefore, combining fused heterocyclic organic skeletons with the azoxy moiety can be regarded as an effective method for increasing the density and heat of formation, which results in substantial increase in detonation properties. Based on the above-mentioned considerations, in this study, a series of new non-hydrogen-containing 5/6/5 fused ring molecules with azoxy moiety structures are designed. Furthermore, their properties as potential high-energy-density materials, including their density, heats of formation, detonation properties, and impact sensitivity, have been extensively evaluated using thermodynamic calculations and density functional theory. Among the investigated compounds, 1,3,8,10-tetranitrodiimidazo[1,5-d:5′,1′-f][1,2,3,4]tetrazine 5-oxide (B), 1,10-dinitrobis([1,2,3]triazolo)[1,5-d:5′,1′-f][1,2,3,4]tetrazine 5-oxide (C) and 2,9-dinitrobis([1,2,4]triazolo)[1,5-d:5′,1′-f][1,2,3,4]tetrazine 5-oxide (D) display remarkable stabilities and are predicted to be high-performance energetic materials due to their high density (>1.94 g cm⁻³), detonation velocity (>9616 m s⁻¹), and detonation pressure (>41.1 GPa). In addition, our design strategy, which combines the azoxy moiety and fused tricyclic skeleton to construct nitrogen-rich molecular structures with high density and positive heat of formation, is a valuable approach for developing novel high-energy-density materials with excellent performance and stability.

In this work, a series of novel non-hydrogen-containing 5/6/5 fused ring molecules with azoxy moiety were designed, some physicochemical or detonation properties of them were calculated.

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

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

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

N-Fluoro functionalization of heterocyclic azoles: a new strategy towards insensitive high energy density materials

The finding of this study shows the introduction of a highly dense –F group instead of hydrogen atoms by N-functionalization, which is a very effective method for increasing the densities and detonation properties and decreasing the sensitivities of energetic molecules.

5-Amino-1H-1,2,4-triazole-3-carbohydrazide and its applications in the synthesis of energetic salts: a new strategy for constructing the nitrogen-rich cation based on the energetic moiety combination

A new strategy for constructing a nitrogen-rich cation through energetic moiety (energetic “gene”) combination was presented and its derivatives were synthesized.

Amino-nitramino functionalized triazolotriazines: a good balance between high energy and low sensitivity

Amino-nitramino functionalized triazolotriazines with high-energy content and low sensitivity are reported, presenting a potential design concept for high-performance insensitive energetic materials.

Axial substitution of a precursor resulted in two high-energy copper(ii) complexes with superior detonation performances

The design and synthesis of explosives with high performance, good thermal stability, and low sensitivity is an important subject for the development of energetic materials. Energetic complexes have recently emerged as a promising energetic material form. As one of the representatives, [Cu(Htztr)₂(H₂O)₂]_n (H₂tztr = 3-(1H-tetrazol-5-yl)-1H-triazole) was previously reported with good energetic performance, outstanding thermostability (T_dec = 345 °C) and low sensitivity to impact and friction stimuli. However, due to the existence of water molecules, its effective energy density is remarkably decreased, resulting in a diminished detonation performance. In order to further improve the detonation performance, using [Cu(Htztr)₂(H₂O)₂]_n as a precursor, {[Cu(Htztr)(H₂O)]NO₃}_n (1) and [Cu(H₂tztr)₂(HCOO)₂]_n (2) were synthesized by the axial substitution reaction with NO₃^- and HCOO^-. The structures of 1 and 2 were characterized by single crystal X-ray diffraction. Both of them exhibit high thermal stabilities and insensitivities to impact and friction. Moreover, the same DFT calculation methodology shows that the heat of detonation of 2 (3.5663 kcal g^-1) is significantly higher than that of the precursor [Cu(Htztr)₂(H₂O)₂]_n (2.1281 kcal g^-1). Meanwhile, the empirical Kamlet-Jacobs equations were used to theoretically predict the detonation properties of the title complexes, and the results show that 1 and 2 have excellent detonation velocity (D) and detonation pressure (P).

Explosives in the Cage: Metal-Organic Frameworks for High-Energy Materials Sensing and Desensitization

An overview of the current status of coordination polymers and metal-organic frameworks (MOFs) pertaining to the field of energetic materials is provided. The explosive applications of MOFs are discussed from two aspects: one for detection of explosives, and the other for explosive desensitization. By virtue of their adjustable pore/cage sizes, high surface area, tunable functional sites, and rich host-guest chemistry, MOFs have emerged as promising candidates for both explosive sensing and desensitization. The challenges and perspectives in these two areas are thoroughly discussed, and the processing methods for practical applications are also discussed briefly.

A promising high-energy-density material

High-energy density materials represent a significant class of advanced materials and have been the focus of energetic materials community. The main challenge in this field is to design and synthesize energetic compounds with a highest possible density and a maximum possible chemical stability. Here we show an energetic compound, [2,2'-bi(1,3,4-oxadiazole)]-5,5'-dinitramide, is synthesized through a two-step reaction from commercially available reagents. It exhibits a surprisingly high density (1.99 g cm^-3 at 298 K), poor solubility in water and most organic solvents, decent thermal stability, a positive heat of formation and excellent detonation properties. The solid-state structural features of the synthesized compound are also investigated via X-ray diffraction and several theoretical techniques. The energetic and sensitivity properties of the explosive compound are similar to those of 2, 4, 6, 8, 10, 12-(hexanitrohexaaza)cyclododecane (CL-20), and the developed compound shows a great promise for potential applications as a high-energy density material.High energy density materials are of interest, but density is the limiting factor for many organic compounds. Here the authors show the formation of a high density energetic compound from a two-step reaction between commercially available compounds that exhibit good heat thermal stability and detonation properties.

New concept for the design of zero-hydrogen energetic materials with high energy and low sensitivity: achieving a good balance among parent compounds, nitro groups, and N-oxides

A new powerful zero-hydrogen energetic compound DNDOBTT (2,7-dinitro-4N,9N-dioxide-bis[1,2,4]-triazolo)[1,5-b:1′,5′e][1,2,4,5] tetrazine) was produced by a new design concept of achieving a balance among the parent compound, nitro groups, and N-oxides. Its structure and properties was studied by the density functional theory. The breaking of N–N bond in the tetrazine ring is an initial decomposition step of DNDOBTT, and the energy barrier was predicted to be 175 kJ·mol−1. DNDOBTT has comparable detonation performance with some CHNO energetic compounds, including the most powerful ONC (octanitrocubane), whereas its sensitivity and thermal stability are obviously lower and better than those of ONC, respectively, indicating that DNDOBTT has both the high energy and reduced sensitivity and may be a valuable candidate for experiments. Therefore, a new novel energetic material DNDOBTT with good overall performance has been obtained successfully by the new design concept, and it may be applied to design and develop other novel improved zero-hydrogen energetic materials.

A single molecular fluorescent probe for selective and sensitive detection of nitroaromatic explosives: A new strategy for the mask-free discrimination of TNT and TNP within same sample

A simple naphthalene based fluorescent probe was first time reported as dual sensing of 2,4,6-trinitrotolune (TNT) and 2,4,6-trinitrophenol (TNP) by distinguishable changes in both solution color change and fluorescence within same sample without any mask agent. Upon addition of TNT and TNP, the strong emission quenching at 412nm and a new emission band at 530nm was observed, respectively. In addition, the sensing mechanism was evaluated by DFT calculations by Gaussian 09 software.

5,6-Di(2-fluoro-2,2-dinitroethoxy)furazano[3,4-b]pyrazine: a high performance melt-cast energetic material and its polycrystalline properties

A new high-energetic and insensitive melt-cast material was synthesized, and its polycrystalline properties were characterized and theoretically investigated.

Energetic π-conjugated vinyl bridged triazoles: a thermally stable and insensitive heterocyclic cation

A new family of vinyl bridged energetic nitrogen-rich salts with diversiform crystal-packing, good thermal stabilities, detonation performance and insensitive properties were synthesized and fully characterized.

Materials with good energetic properties resulting from the smart combination of nitramino and dinitromethyl group with furazan

The combination of nitramino and dinitromethyl group with furazan gave novel energetic materials with good energetic properties.

Structures and properties of energetic cations in energetic salts

Energetic cations play important roles in energetic performance, which may attribute to the diverse backbones and substituted groups of energetic cations. This review emphasizes the roles of backbones and substituted groups in the energetic performance of energetic salts.

Bottom-up design of high-energy-density molecules (N2CO)n (n = 2–8)

A bottom-up strategy from an HEDM seed (i.e., cyc-N₂CO) to novel oligomeric HEDMs was propsed.

Ionization and separation as a strategy for significantly enhancing the thermal stability of an instable system: a case for hydroxylamine-based salts relative to that for pure hydroxylamine

Energetic ionic salts (EISs) are attracting extensive attention because of their ready preparation and some excellent properties and performances that are comparable to those of common explosives with neutral molecules.

A facile method to prepare energetic materials (EMs)

A facile method to synthesise two powerful yet safe energetic materials (EMs) with high yield is reported.