Insensitive High Energy Density Materials Research Articles

Controlling the Energetic Properties of N-Methylene-C-Linked 4-Hydroxy-3,5-dinitropyrazole- and Tetrazole-Based Compounds via a Selective Mono- and Dicationic Salt Formation Strategy.

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 (OH and 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.

Insensitive High-Energy Density Materials Based on Azazole-Rich Rings: 1,2,4-Triazole N-Oxide Derivatives Containing Isomerized Nitro and Amino Groups.

It is an arduous and meaningful challenge to design and develop new energetic materials with lower sensitivity and higher energy. How to skillfully combine the characteristics of low sensitivity and high energy is the key problem in designing new insensitive high-energy materials. Taking a triazole ring as a framework, a strategy of N-oxide derivatives containing isomerized nitro and amino groups was proposed to answer this question. Based on this strategy, some 1,2,4-triazole N-oxide derivatives (NATNOs) were designed and explored. The electronic structure calculation showed that the stable existence of these triazole derivatives was due to the intramolecular hydrogen bond and other interactions. The impact sensitivity and the dissociation enthalpy of trigger bonds directly indicated that some compounds could exist stably. The crystal densities of all NATNOs were larger than 1.80 g/cm3, which met the requirement of high-energetic materials for crystal density. Some NATNOs (9748 m/s for NATNO, 9841 m/s for NATNO-1, 9818 m/s for NATNO-2, 9906 m/s for NATNO-3, and 9592 m/s for NATNO-4) were potential high detonation velocity energy materials. These study results not only indicate that the NATNOs have relatively stable properties and excellent detonation properties but also prove that the strategy of nitro amino position isomerization coupled with N-oxide is an effective means to develop new energetic materials.

Bis-3,5-Diamino-1,2,4-Triazolyl-1,2,4,5-Tetrazine: From Insensitive High Energy Density Materials to Small Molecule Organic Semiconductors

Besides the well-known pyrotechnic applications of insensitive high energy compounds such as s-tetrazine, they are promising materials for relevant applications (e.g., electrochemical energy storage, photocatalysis). Bis-3,5-diamino-1,2,4-triazolyl-1,2,4,5-tetrazine (BDTT) is a nitrogen-rich conjugated heterocyclic compound (nitrogen ≈ 71 wt %), inert to ignition and mechanical stimuli and thermally stable up to 370 °C. The solvent-free crystalline structure of this high energy density compound (named IEF-12 for IMDEA energy framework) is reported here for the first time using the high resolution powder X-ray diffraction (PXRD) and 1H, 13C, and 15N solid state nuclear magnetic resonance (NMR) spectroscopy. We demonstrate that IEF-12 has features of a small molecule organic semiconductor, namely, lamellar π-stacked crystal packing in the solid state, a low energy optical bandgap Egopt = 2.27 eV, and a relatively high value of dielectric constant εr = 4.86. Overall, we demonstrated on IEF-12 that insensitive high energy density materials (HEDM) may open an avenue for nonclassically structured organic semiconductors, paving the way for optoelectronic and photovoltaic applications.

Efficient synthesis of N-methyltetranitropyrrole: A stable, insensitive and high energy melt-castable material

1-Methyl-2,3,4,5-tetranitropyrrole is the first pyrrole based stable and insensitive high energy density material at par or slightly better than RDX.

Triaminotrinitrobenzene Isomers - A DFT Treatment

1,3,5-triamino-2,4,6-trinitrobenzene known as TATB is an insensitive high energy density material. It has two more constitutional isomers. The present study deals with all these triaminotrinitrobenzene isomers within the constraints of density functional theory at the levels of RB3LYP/6-31G(d,p) and UB3LYP/6-31G(d). Some geometrical and quantum chemical properties have been obtained and compared. The calculated IR and UV-VIS spectra are produced. Additionally the NICS values have been collected by calculating absolute NMR shielding values at the ring centers, NICS(0), and aromaticity of these isomers are compared. UB3LYP/6-31+G(d) level of calculations revealed that monoionic forms of these isomeric compounds are stable.

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.

Crystal structure of 1,10-phenanthrolinium 3-hy-droxy-2,4,6-tri-nitro-phenolate.

In the title molecular salt, C12H9N2 (+)·C6H2N3O8 (-), the cation and anion are connected by an N-H⋯O hydrogen bond. In the anion, an intra-molecular O-H⋯O hydrogen bond with an S(6) ring motif is observed. The planes of two of the nitro groups are approximately parallel to the plane of the benzene ring, making dihedral angles of 3.9 (2) and 15.3 (2)°, while the third nitro group is almost perpendicular to the benzene ring, with a dihedral angle of 78.6 (3)°. In the crystal, cation-anion pairs related by an n-glide plane are connected by C-H⋯O hydrogen bonds, forming a chain structure along [101]. Sensitivity tests and thermal testing indicate that the title salt is an insensitive high-energy-density material (IHEDM).

Synthesis of a new class of carbon-bonded anionic sigma complexes with 1,3-dimethyl-2,6-dioxo-5-(2,4,6-trinitrophenyl)-1,2,3,6-tetrahydropyrimidin-4-olate moiety as insensitive high energy density materials -- implications from impact sensitivity and thermal testings.

BackgroundPoly nitro aromatic compounds are high energy density materials. Carbon–bonded anionic sigma complexes derived from them have remarkable thermal stability. At present there is a strong requirement for thermally stable insensitive high energy density materials (IHEDMs) in the energetic field which necessitates the present investigation.ResultsThree new carbon–bonded anionic sigma complexes were synthesized from 2-chloro-1,3,5-trinitrobenzene, 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (1,3-dimethylbarbituric acid) and bases such as triethanolamine, pyridine and N,N-diethylaniline, characterized by UV–VIS, IR, 1H NMR, 13C NMR and elemental analysis data. Their molecular structures were further ascertained through single crystal X-ray diffraction studies. TGA/DTA testings were undertaken at four different heating rates (5, 10, 20 and 40 K/min) and energy of activation was determined employing Ozawa and Kissinger plots.ConclusionsThe reported carbon–bonded anionic sigma complexes were prepared through single pot synthesis in good yield with high purity. These complexes are molecular salts comprise of cation and anion moieties. Because of the salt–like nature, they are highly stable upto 300°C and decompose in two stages on further heating. They are stable towards impact of 2 kg mass hammer upto height limit (160 cm) of the instrument. The delocalization of the negative charge and various hydrogen bonds noticed in their crystals are the added factors of their thermal stability. The new insensitive high energy density materials of the present findings may receive attention in the field of energetics in future.Graphical A new class of carbon-bonded anionic sigma complexes as insensitive high energy density materials

Synthesis, characterization, thermal behaviour and single crystal X-ray analysis of two new insensitive high energy density materials [8-hydroxyquinolinium 5-(2,4,6-trinitrophenyl)barbiturate (I) and 8-hydroxyquinolinium 5-(5-chloro-2,4-dinitrophenyl)-1,3-dimethyl barbiturate (II)

Barbiturates I and II have been synthesized as maroon red and red orange coloured solids by mixing the ethanolic solutions of 2-chloro-1,3,5-trinitrobenzene (TNCB), pyrimidine-2,4,6(1H,3H,5H)-trione [barbituric acid (BA)] and 8-hydroxyquinoline and 1,3-dichloro-4,6-dinitrobenzene (DCDNB), 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione(1,3-dimethylbarbituric acid) and 8-hydroxyquinoline respectively. The structures of these two barbiturates have been predicted from the spectral studies (UV-VIS, IR, 1H NMR, 13C NMR, mass) and elemental analysis. Qualitative tests have been carried out to infer the presence of nitrogen and nitro groups and also chlorine atom in barbiturate II. Slow evaporation of ethanol-dimethylsulphoxide/ethanol solutions of barbiturate I/barbiturate II at 293 K yielded good for X-Ray diffraction crystals. Single crystal X-ray diffraction studies of the crystals further confirm the putative structures of the barbiturates. The asymmetric unit of the barbiturate I comprises of 8-hydroxyquinolinium cation, 5-(2,4,6-trinitrophenyl) barbiturate anion and a molecule of dimethylsulphoxide (DMSO), which is used as a recrystallizing solvent. It crystallizes in the triclinic system with space group \(P\bar 1\) (centrosymmetric). Barbiturate II crystallizes in the orthorhombic system with space group P212121 (non-centrosymmetric). Barbiturates I and II are stable towards an impact sensitivity test, when a weight of 2 kg mass hammer is dropped from a height of 160 cm of the instrument. TGA/DTA analyses at four different heating rates (5, 10, 20, and 40 K/min) imply that they undergo exothermic decomposition (∼85%) in three different stages between 273 and 873 K. Activation energies for these decomposition processes have been calculated by employing Kissinger and Ozawa plots. Impact sensitivity test and activation energies have revealed that the titled barbiturates are insensitive high energy density materials (IHEDMS).

New Molecular Salts from Chloronitroaromatic Compounds, 1,3-Disubstituted pyrimidine-2,4,6(1H,3H,5H)-trione and Amines: Synthesis, Characterization, Thermal Behavior and Crystal Structure

New molecular salts have been synthesized from chloronitroaromatic compounds, 1,3-disubstituted pyrimidine-2,4,6(1H,3H,5H)-trione and amines. Structures of these molecular salts have been established by elemental analysis and spectroscopic techniques (UV–Vis, FT-IR, 1H NMR and 13C NMR). The structures of all these molecular salts have also been ascertained through single crystal X-ray diffraction studies. They crystallize either in the monoclinic or triclinic system. A number of O–H⋯O, N–H⋯O and C–H⋯O hydrogen bonds stabilize the crystal lattice. Disorder has been observed in the cation moiety of these molecular salts. TGA/DTA studies of these molecular salts have also been undertaken at four different heating rates (5, 10, 20 and 40 K/min) and energy of activation has been determined by employing Ozawa and Kissinger plots. Impact sensitivity test and activation energies imply that the synthesized molecular salts are insensitive high energy density materials. Essence of the paper: The article focuses on the formation of new molecular salts with good thermal stability which may be used as the insensitive high energy density materials (IHEDMS). A figure of the most important structure:

Structure and detonation performance of a novel HMX/LLM‐105 cocrystal explosive

Intermolecular interactions and properties of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐ tetrazocine (HMX) / 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) cocrystal were studied by using the dispersion‐corrected density functionals (ωB97XD, B97D) and meta‐hybrid functional (M062x) methods. Binding energies, heats of formation, thermodynamic properties, atoms in molecules, and natural bond orbital analysis were performed to investigate HMX/LLM‐105 complexes. Results show that the main intermolecular interactions between HMX and LLM‐105 are CH…O, NH…O, N…O, and O…O interactions. In addition, Monte Carlo simulation was employed to predict the crystal structure of HMX/LLM‐105 cocrystal. The HMX/LLM‐105 cocrystal is most likely to crystallize inC2/c space group, and its corresponding cell parameters are Z = 8, a = 41.63 Å, b = 6.77 Å, c = 45.63 Å, ß = 164.55°, and ρ = 1.99 g/cm3. Detonation velocity and pressure of HMX/LLM‐105 cocrystal are 8.95 km/s, 37.69GPa, a little lower than those of HMX (9.10 km/s, 37.76GPa). However, according to the net charges of nitro group, HMX/LLM‐105 cocrystal exhibits less sensitive than HMX. Finally, bond dissociation energy calculation shows that HMX/LLM‐105 complexes are thermally stable. Considering thermal stability, sensitivity, and detonation performance, HMX/LLM‐105 cocrystal meets the requirements of insensitive high energy density materials. Copyright © 2013 John Wiley & Sons, Ltd.

Decomposition Mechanisms and Kinetics of Novel Energetic Molecules BNFF-1 and ANFF-1: Quantum-Chemical Modeling

Decomposition mechanisms, activation barriers, Arrhenius parameters, and reaction kinetics of the novel explosive compounds, 3,4-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole (BNFF-1), and 3-(4-amino-1,2,5-oxadiazol-3-yl)-4-(4-nitro-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole (ANFF-1) were explored by means of density functional theory with a range of functionals combined with variational transition state theory. BNFF-1 and ANFF-1 were recently suggested to be good candidates for insensitive high energy density materials. Our modeling reveals that the decomposition initiation in both BNFF-1 and ANFF-1 molecules is triggered by ring cleavage reactions while the further process is defined by a competition between two major pathways, the fast C-NO2 homolysis and slow nitro-nitrite isomerization releasing NO. We discuss insights on design of new energetic materials with targeted properties gained from our modeling.

First principles prediction of an insensitive high energy density material

A new high performance yet insensitive explosive is proposed, based on an extensive computational study of tris(tetrazolyl)amine in the solid state and in the gas phase. The calculations for the solid state employ the PBE density functional with empirical dispersion correction while the gas phase calculations use the higher level of B3LYP and MP2. Two stable crystalline structures of tris(tertrazolyl)amine were located belonging to P1 and P21 space groups. The crystal structures obtained reveal that solid tris(tertrazolyl)amine is organized in layers with a very small interlayer spacing, due to π stacking, as well as significant inter and intra-molecular hydrogen bonding. Application of these results to the calculation of the detonation velocity and pressure indicate high performance for both phases, especially the P21 phase. At the same time the small value found for the interlayer spacing and the significant hydrogen bonding suggest relatively high stability. These results point to a promising new explosive material with a balance between high performance and insensitivity.

Synthesis, Spectral Characterization, Crystal Structure and Thermal Behavior of Tert-butyl 2,2-bis(2,4-dinitrophenyl)ethanoate

Tert-butyl 2,2-bis(2,4-dinitrophenyl)ethanoate was prepared from the ethanolic solution of 1-chloro-2,4-dinitrobenzene, tert-butyl 3-oxobutanoate and triethylamine. Acetyl group in tert-butyl 3-oxobutanoate has cleaved off during the formation of the title molecule. UV–VIS, IR, 1H NMR, 13C NMR, Proton–Proton COSY data and single crystal XRD results support the proposed structure. Flammability test, impact sensitivity test and TG/DTA studies at different heating rates on the synthesized molecule imply that it is an insensitive high energy density material. Article covers synthetic method, spectral characterization, crystal structure and thermal behavior of tert-butyl 2,2-bis(2,4-dinitrophenyl)ethanoate .