Synthesis and Characterization of 2,2'-Dinitramino-5,5'-bi(1-oxa-3,4-diazole) and Derivatives as Economic and Highly Dense Energetic Materials

Fabrication, Characterization, and Performance Evaluation of Thermally Stable [5,6]-Fused Bicyclic Energetic Materials

In recent decades, there has been considerable interest in investigating advanced energetic materials characterized by high stability and favorable energetic properties. Nevertheless, reconciling the conflicting balance between high energy and the insensitivity of such materials through traditional approaches, which involve integrating fuel frameworks and oxidizing groups into an organic molecule, presents significant challenges. In this study, we employed a promising method to fabricate high-energy-density materials (HEDMs) through the intermolecular assembly of variously substituted purines with a high-energy oxidant. Purines are abundant in nature and are readily available. A series of advanced energetic materials with a good balance between energy and sensitivity were prepared by the simple and effective self-assembly of purines with high-energy oxidants. Notably, these compounds exhibit incredibly improved crystal densities (1.80-2.00 g·cm-3) and good detonation performance (D: 7072-8358 m·s-1; P: 19.82-34.56 GPa). In comparison to RDX, these self-assembled energetic materials exhibit reduced mechanical sensitivities and enhanced thermal stabilities. Compounds 1-5 demonstrate both high energy and low sensitivity, indicating that self-assembly represents a straightforward and effective approach for developing advanced energetic materials with a balanced combination of energy and safety. Moreover, this study offers an avenue for synthesizing energetic materials based on naturally occurring compounds assembled through intermolecular attractions, thereby achieving a balance between energy and sensitivity along with versatile functionality.

Energetic derivatives substituted with trinitrophenyl: improving the sensitivity of explosives

The incorporation of trinitrophenyl-modified 1,3,4-oxadiazole fragments is commonly observed in high-energy molecules with heat-resistant properties. This study explores the strategy of developing heat-resistant energetic materials by incorporating trinitrophenyl and an azo group into 1,3,4-oxadiazole, which involved the synthesis and characterization of (E)-1,2-bis(5-(2,4,6-trinitrophenyl)-1,3,4-oxadiazol-2-yl)diazene (2), N-(5-(2,4,6-trinitrophenyl)-1,3,4-oxadiazol-2-yl)nitramide (3), and the energetic salts of 3. Characterization techniques employed included 1H and 13C NMR, IR and elemental analysis. Additionally, the structures of 2 and 3 were validated using single crystal X-ray analysis. To further understand the physical and chemical characteristics of these novel energetic compounds, various calculations and measurements were performed. Compound 2 exhibits excellent thermostability (Td = 294 °C), which is comparable to that of traditional heat-resistant explosive HNS (Td = 318 °C). But 2 is insensitive towards impact (>40 J) and friction (>360 N), surpassing HNS (5 J, 240 N), suggesting that compound 2 deserves further investigation as a potential heat-resistant explosive.

First-principle calculations of the electronic, vibrational, and thermodynamic properties of nitrogen-rich salt of 3,6-dinitramino-1,2,4,5-tetrazine [(NH4)2(DNAT)]

CONTEXT

Energy-containing materials such as explosives have attracted considerable interest recently. In the field of high-energy materials, tetrazine and its derivatives can largely meet the requirements of high nitrogen content and oxygen balance. Nitrogen-rich energetic salts are important research subjects. Nitrogen-rich salt of 3,6-dinitramino-1,2,4,5-tetrazine is a high-energy nitrogen-rich material, but there are few related studies. This paper systematically studies the crystal structure and electronic, vibrational, and thermodynamic properties of (NH4)2(DNAT). The lattice parameters of (NH4)2(DNAT) are observed to align well with the experimental values. The properties of electrons are analyzed by band structure and density of states (DOS). The phonon dispersion curves indicate that the compound is dynamically stable. The vibrational modes of bonds and chemical groups are described in detail, and the peaks in the Raman and infrared spectra are assigned to different vibration modes. Based on the vibration characteristics, thermodynamic properties such as enthalpy (H), Helmholtz free energy (F), entropy (S), Gibbs free energy (G), constant volume heat capacity (CV), and Debye temperature (Θ) are analyzed. This article can pave the way for subsequent work or provide data support to other researchers, promoting further research.

METHODS

In this study, we utilized the density functional theory (DFT) for our calculations. The exchange-correlation potential and van der Waals interactions were characterized based on the GGA-PBE + G function calculation. We obtained Brillouin zone integrals using Monkhorst-Pack k-point grids, with the k-point of the Brillouin zone set to a 2 × 2 × 2 grid. During the self-consistent field operation, we set the total energy convergence tolerance to 5 × 10-6 eV per atom. The cut-off energy for the calculation was established at 830 eV. Additionally, the states of H (1s1), C (2s2 2p2), N (2s2 2p3), and O (2s2 2p4) were treated as valence electrons in our study.

Site-Selective Oxidative Coupling Reaction of Diamines toward Aminoazo Compounds

A selective oxidative coupling reaction of a diamine containing both C- and N-NH₂ was achieved using acidic potassium permanganate as the coupling reagent. The reaction conditions were optimized, and the reaction selectivity was illustrated by quantum calculations. Furthermore, the azo-coupled product was derivatized to four nitroamine energetic materials with excellent detonation performances.

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.

Regulation of external electric field on sensitivity of ICM energetic materials

CONTEXT

[2,2'-Bi(1,3,4-oxadiazole)]-5,5'-dinitramide (ICM-101), 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102), and 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) are excellent China-made explosives, but their performance under external electric fields (EEF) has never been explored, especially sensitivity. To study the induction effect of EEF on it, the chemical reactivity, electron localization function (ELF), spectrum, and other parameters were calculated by density functional theory. The results show that the increasing EEF can weaken the △E_HOMO-LUMO (△E_HOMO-LUMO = E_HOMO-E_LUMO) materials, making the stability worse and the sensitivity higher. The proportion of the positive electrostatic surface potential area is also smaller under the increasing EEF, indicating that ICM molecules are becoming more and more unstable. The ELF and localized orbital locator (LOL) decrease with the increase of EEF strength, which suggests that the trigger bond length increases, the E_BDE decreases, and the molecular sensitivity increases. When the intensity of EEF increases, the absorption peak of the molecular spectrum gradually redshifts, and even a weak new absorption peak appears, indicating that the color of the material may change. Finally, EEF strength affects electron density, nitro charge, and chemical reactivity parameters.

METHODS

Gaussian 16 software was used for calculation. The calculation levels are B3LYP/6-311G+ (d, p) and B3LYP/Def2-TZVPP. The optimized structure has a local true minimum energy on the potential energy surface and no imaginary frequency. Multiwfn 3.8 and VMD 1.9.3 were used in this work to analyze the ICM series of energetic material wave functions. The strength range of EEF is 0.000-0.016 a.u., and the increasing gradient is 0.002 a.u.

Synthesis, Crystal Structure, and Characterization of Energetic Salts Based on 3,5-Diamino-4H-Pyrazol-4-One Oxime

In order to broaden the study of energetic cations, a cation 3,5-diamino-4H-pyrazol-4-one oxime (DAPO) with good thermal stability was proposed, and its three salts were synthesized by a simple and efficient method. The structures of the three salts were verified by infrared spectroscopy, mass spectrometry, elemental analysis, and single crystal X-ray diffraction. The thermal stabilities of the three salts were verified by differential scanning calorimetry and thermos-gravimetric analysis. DAPO-based energetic salts are analysed using a variety of theoretical techniques, such as 2D fingerprint, Hirshfeld surface, and non-covalent interaction. Among them, the energy properties of perchlorate (DAPOP) and picrate (DAPOT) were determined by EXPLO5 program combined with the measured density and enthalpy of formation. These compounds have high density, acceptable detonation performance, good thermal stability, and satisfactory sensitivity. The intermolecular interactions of the four compounds were studied by Hirshfeld surface and non-covalent interactions, indicating that hydrogen bonds and π-π stacking interactions are the reasons for the extracellular properties of perchlorate (DAPOP) and picrate (DAPOT), indicating that DAPO is an optional nitrogen-rich cation for the design and synthesis of novel energetic materials with excellent properties.

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.

Energetic isomers of bridged oxadiazole nitramines: the effect of asymmetric heterocyclics on stability and energetic properties

Energetic isomers often exhibit different properties. To understand the effect of arrangement and connection of isomers on energetic properties and sensitivity, in this study, we designed and synthesized a series of oxadiazole nitramine compounds including N-(5-(5-(nitramino)-1,3,4-oxadiazol-2-yl)-1,2,4-oxadiazol-3-yl)nitramide (NOON) and its ionic derivatives. NOON exhibits comparable performance (D = 8888 m s^-1, P = 34.1 GPa) to highly explosive RDX. A comparative study of detonation properties, sensitivity, and thermal stability of the three oxadiazole nitramine isomers (NOON, ICM-101, and DNBO) is carried out. The results show that due to the proton transformation, strong intramolecular hydrogen bonding interaction, and formation of six-membered ring conformation, the 2-nitramino-1,3,4-oxadiazole building block exhibits better detonation properties and higher thermal stability than its isomer 2-nitramino-1,2,4-oxadiazole.

Kinetics and mechanism of decomposition induced by solvent evolution in ICM-101 solvates: solvent-evolution-induced low-temperature decomposition

[2,2'-Bi(1,3,4-oxadiazole)]-5,5'-dinitramide (ICM-101), a high-energy-density material, was reported in recent years. ICM-101 is the first energetic material with the 2,2'-bi(1,3,4-oxadiazole) structure as the main ring structure. The molecular structure of ICM-101 shows excellent planar characteristics, providing a new option for the design of high-energy-density materials. However, during crystal preparation, ICM-101 easily interacts with solvents and forms the corresponding solvates. Interestingly, during thermal decomposition, when the solvent escapes from ICM-101 solvates, it induces the decomposition of ICM-101. In this study, the decomposition of ICM-101 induced by solvent evolution was evaluated in detail, and the decomposition kinetic equation was established. The mechanism of solvent-evolution-induced decomposition in ICM-101 solvates was further studied, and it was found that solvent evolution might produce defects in the crystals of ICM-101 solvates, and induce the decomposition of ICM-101 on the defects.

A facile synthesis of energetic salts based on fully nitroamino-functionalized [1,2,4]triazolo[4,3-b][1,2,4]triazole

Promising high-energy-density materials: energetic salts based on fully nitroamino-functionalized [1,2,4]triazolo[4,3-b][1,2,4]triazole.

Nitramino-furazan-functionalized fused high-nitrogen backbones as energetic materials with high detonation performance and good molecular stabilities

A promising fused energetic compound is investigated through the cooperation between nitramino-1,2,5-oxadiazole and fused high-nitrogen backbone.

Amino-tetrazole functionalized fused triazolo-triazine and tetrazolo-triazine energetic materials

In this study, two insensitive energetic compounds using fused triazolo-triazine and tetrazolo-triazine as the framework, one amino and one tetrazole as functional groups, were prepared through a two-step reaction.

QTAIM Assessment of the Intra- and Intermolecular Bonding in a Bis(nitramido-oxadiazolate) Energetic Ionic Salt at 20 K

Accurate experimental determination of the electron density distribution for the energetic ionic salt bis(ammonium) 2,2'-dinitramido-5,5'-bis(1-oxa-3,4-diazolate) dihydrate (1) is obtained from multipole modeling of single-crystal X-ray diffraction data collected at 20 K. The intra- and intermolecular bonding is assessed in terms of the quantum theory of atoms in molecules (QTAIM) with a view to better understanding the physicochemical properties in relation to chemical bonding. Topological analysis reveals stronger bonding for the N-NO₂ bond relative to energetic nitramines RDX and HMX and the indication of a trend between this and impact sensitivity of nitro-containing energetic materials is noted. The intermolecular bonding of 1 is dominated by classical H-bonds but includes multiple π-bonding interactions and interactions between H-bond donor and acceptor atoms where bond paths are deflected by H atoms. There also exists a weak O···O interaction between end-on nitro groups, as well as an intramolecular ring-forming 1,5-type interaction. An anharmonic description of thermal motion was required to obtain the best fitting model, despite the low temperature of the study. The experimental study was complemented by periodic boundary DFT calculations at the experimental geometry as well as gas phase calculations on the isolated dianion.

Optimizing the oxygen balance by changing the A-site cations in molecular perovskite high-energetic materials

Two new members of molecular perovskite high-energetic materials exhibit optimized oxygen balances by changing the A-site cations.

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.