Combination Multinitrogen with Good Oxygen Balance: Molecule and Synthesis Design of Polynitro-Substituted Tetrazolotriazine-Based Energetic Compounds

Design and selection of high energy materials based on 4,8-dihydrodifurazano[3,4-b,e]pyrazine

In order to search for high energy density materials, various 4,8-dihydrodifurazano[3,4-b,e]pyrazine based energetic materials were designed. Density functional theory was employed to investigate the relationships between the structures and properties. The calculated results indicated that the properties of these designed compounds were influenced by the energetic groups and heterocyclic substituents. The -N3 energetic group was found to be the most effective substituent to improve the heats of formation of the designed compounds while the tetrazole ring/-C(NO2)3 group contributed much to the values of detonation properties. The analysis of bond orders and bond dissociation energies showed that the addition of -NHNH2, -NHNO2, -CH(NO2)3 and -C(NO2)3 groups would decrease the bond dissociation energies remarkably. Compounds A8, B8, C8, D8, E8, and F8 were finally screened as the potential candidates for high energy density materials since these compounds possess excellent detonation properties and acceptable thermal stabilities. Additionally, the electronic structures of the screened compounds were calculated.

Molecular design of energetic tetrazine-triazole derivatives

Nitrogen-rich compounds are promising candidates for preparing high energetic density materials (HEDMs) and show the potential in the application of propellants, explosives, and pyrotechnics. Two kinds of typical nitrogen-rich compounds, such as tetrazine and triazole, have attracted the attentions in recent years owing to their high densities, good thermal stabilities, and excellent energetic performances. In this work, four series of innovative energetic compounds based on the conjugates of tetrazine and triazole bearing various substituents (-NH₂, -NO₂, and -NHNO₂) were designed. The optimized structures, crystal densities, heats of formation (HOFs) in gas phase and in condensed phase, detonation properties, bond dissociation energies (BDEs), and impact sensitivity (h₅₀) of these compounds were studied systematically via density functional theory (DFT) method. The detonation velocities of four series of compounds are in the range between 7.03 and 8.59 km s^-1 and their detonation pressures are in the range between 20.6 and 33.1 GPa. Results indicated that the linkage of -N=N- bond contributed significantly to HOFs and energy density of the energetic molecules, and 1,2,3-triazole showed better performances than 1,2,4-triazole slightly. As for the same series compounds with different substituents, the compounds with -NHNO₂ possessed the highest HOFs (such as A6, B6, C6, D6). In terms of the energetic properties (D and P), four compounds (A7, B7, C7, and D7) exhibited the comparable performance with the widely used hexa-hydro-1,3,5-trinitro-1,3,5-triazine (RDX) and in the meanwhile displayed superior thermal stability and sensitivity to RDX, which indicated their potential application in the insensitive energetic materials.

A new oxygen-rich energetic salt dihydrazine tetranitroethide: a promising explosive alternative with high density and good performance

A novel high-energy salt with good oxygen balance, dihydrazine tetranitroethide (5), has been synthesized and characterized by FT-IR spectroscopy, NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction. Compound 5 exhibits high crystal density (1.81 g cm-3) and impressive detonation velocity (9508 m s-1) and detonation pressure (37.9 GPa), showing potential applications as a high performance explosive and a promising additive of propellants.

Molecular and Crystal Features of Thermostable Energetic Materials: Guidelines for Architecture of "Bridged" Compounds

Extensive density functional theory (DFT) calculation and data analysis on molecular and crystal level features of 60 reported energetic materials (EMs) allowed us to define key descriptors that are characteristics of these compounds' thermostability. We see these descriptors as reminiscent of "Lipinski's rule of 5", which revolutionized the design of new orally active pharmaceutical molecules. The proposed descriptors for thermostable EMs are of a type of molecular design, location and type of the weakest bond in the energetic molecule, as well as specific ranges of oxygen balance, crystal packing coefficient, Hirshfeld surface hydrogen bonding, and crystal lattice energy. On this basis, we designed three new thermostable EMs containing bridged, 3,5-dinitropyrazole moieties, HL3, HL7, and HL9, which were synthesized, characterized, and evaluated in small-scale field detonation experiments. The best overall performing compound HL7 exhibited an onset decomposition temperature of 341 °C and has a density of 1.865 g cm-3, and the calculated velocity of detonation and maximum detonation pressure were 8517 m s-1 and 30.6 GPa, respectively. Considering HL7's impressive safety parameters [impact sensitivity (IS) = 22 J; friction sensitivity (FS) = 352; and electrostatic discharge sensitivity (ESD) = 1.05 J] and the results of small-scale field detonation experiments, the proposed guidelines should further promote the rational design of novel thermostable EMs, suitable for deep well drilling, space exploration, and other high-value defense and civil applications.

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.

Trends of the macroscopic behaviors of energetic compounds: insights from first-principles calculations

Understanding the structure-property relationships of energetic compounds is challenging. Herein, by including the experimental data, we systematically evaluated the microscopic characteristics of a series of transition metal carbohydrazide perchlorate (TMCP) complexes (MnCP, FeCP, CoCP, NiCP, ZnCP, and CdCP) by first-principles calculations. The calculated properties, i.e., lattice enthalpy, bulk modulus, and electronic structures, were correlated with their thermal decomposition temperatures and impact sensitivities, which indicated that the stability and sensitivity of the TMCP complexes were greatly changed through coordination with different metal ions. The trend was that a large lattice enthalpy indicated a better thermal stability. Complexes with a high impact sensitivity tended to have a smaller bulk modulus and pseudo-gap. The ultra-high impact sensitivity of FeCP may have been related to the unstable spin state with respect to the volume change in the lattice. The calculated bond order and bond dissociation energy did not fully reflect the impact and friction sensitivities in this study. In addition, the combination of crystal properties and local bond information may better describe the sensitivity trend for the TMCP energetic compounds. This analysis can be applied to other energetic compounds and may provide clues for the synthesis and assessment of novel energetic compounds.

Dimethoxycarbonyl Groups Surrounding a Symmetric Diaminobistetrazole Ring: Exploring New Green Energetic Materials

A novel oxygen-containing dimethoxycarbonyl diaminobistetrazole (1) was synthesized via a facile strategy. The sodium salt (2) based on this ligand was prepared and these two compounds were fully characterized by using elemental analysis, IR and mass spectrometry and single-crystal X-ray diffraction. Their density, heats of formation, thermal stability and sensitivity, as well as the energetic properties from EXPLO5 code were investigated. These newly synthesized compounds possess high positive heats of formation and detonation heats. Compound 1 exhibits good detonation performance and acceptable stability, and might be a potential eco-friendly alternative of lead azide. The present study contributes to the development of tetrazole derivatives as new energetic materials.

DFT studies on nitrogen-rich pyrazino [2, 3-e] [1, 2, 3, 4] tetrazine-based high-energy density compounds

By using the density functional theory method, we investigated the heats of formation (HOFs), electronic structure, detonation properties, thermal stability and sensitivity for a set of pyrazino [2, 3-e] [1, 2, 3, 4] tetrazine derivatives with different substituents and different numbers of N-oxides. Our findings reveal that the HOFs of the derivatives decrease dramatically with the increasing number of N-oxides. The effects of the substituents on the HOMO-LUMO gaps are coupled with those of the N-oxides. The calculated detonation properties point out that -NF₂, -ONO₂ and an increasing number of N-oxides are very helpful for improving the detonation performance of the designed derivatives. The bond dissociation energies of the weakest bonds indicate that a majority of our designed compounds have better thermal stability. The -NH₂ group is very useful to decrease the free space value. Most of the derivatives have higher h₅₀ values compared with parent molecules. Considering the sensitivity, thermal stability and detonation performance, four compounds could be considered as potential candidates of high-energy density compounds.

Molecular design and selection of 1,2,5-oxadiazole derivatives as high-energy-density materials

A family of 1,2,5-oxadiazole-based energetic compounds were designed and their properties were investigated fully by density functional theory.

Energetic transition metal salts of 5,5′-dinitramino-3,3′-methylene-1H-1,2,4-bistriazole: syntheses, structures and properties

Five energetic transition metal salts based on H₂DNAMT were synthesized. Meanwhile, H₂DNAMT was oxidized to H₂BNATO due to Fe³⁺ in [Fe(BNATO)(H₂O)₄]·2H₂O. All of the metal salts exhibit comparable thermal stability and insensitivity.

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.

Exploration of High-Energy-Density Materials: Computational Insight into Energetic Derivatives Based on 1,2,4,5-Tetrahydro-1,2,4,5-tetrazine

Density functional theory was employed to investigate ten 1,2,4,5-tetrahydro-1,2,4,5-tetrazine-based energetic materials. The heats of formation and detonation properties were calculated by isodesmic reactions and Kamlet-Jacobs equations. The thermal stabilities and impact sensitivities were also estimated to give a better understanding of their decomposition mechanism. The results indicate that all of the designed compounds have high positive heats of formation ranging from 525.1 to 1639.1 kJ mol-1, moderate detonation properties (heats of detonation of 536.6 to 2187.6 cal g-1, theoretical densities of 1.48 to 2.32 g cm-3, detonation velocities of 7.02 to 12.18 km s-1, and detonation pressures of 19.8 to 75.1 GPa), and acceptable stabilities (bond dissociation energies of 0.8 to 104.9 kJ mol-1). Taking both the detonation properties and the stabilities into consideration, compounds A4 and B4 were finally selected as promising candidates of high-energy-density materials, as their detonation properties and impact sensitivities were superior to those of HMX. Additionally, the frontier molecular orbitals, electronic densities, electrostatic potentials, and thermal dynamic parameters of compounds A4 and B4 were also investigated.

Assessment of two new nitrogen-rich tetrazine derivatives as high performance and safe energetic compounds

This work introduces two novel nitrogen-rich derivatives of tetrazine, i.e. 1,2-bis (6-nitro-1,2,4,5-tetrazin-3-yl)diazene and 1,2-bis(6-nitro-1,2,4,5-tetrazin-3-yl)hydrazine, as high performance and safe energetic compounds.