Jiaheng Zhang

Energetic Salts with π-Stacking and Hydrogen-Bonding Interactions Lead the Way to Future Energetic Materials

Among energetic materials, there are two significant challenges facing researchers: 1) to develop ionic CHNO explosives with higher densities than their parent nonionic molecules and (2) to achieve a fine balance between high detonation performance and low sensitivity. We report a surprising energetic salt, hydroxylammonium 3-dinitromethanide-1,2,4-triazolone, that exhibits exceptional properties, viz., higher density, superior detonation performance, and improved thermal, impact, and friction stabilities, then those of its precursor, 3-dinitromethyl-1,2,4-triazolone. The solid-state structure features of the new energetic salt were investigated with X-ray diffraction which showed π-stacking and hydrogen-bonding interactions that contribute to closer packing and higher density. According to the experimental results and theoretical analysis, the newly designed energetic salt also gives rise to a workable compromise in high detonation properties and desirable stabilities. These findings will enhance the future prospects for rational energetic materials design and commence a new chapter in this field.

Energetic Salts Based on 3,5-Bis(dinitromethyl)-1,2,4-triazole Monoanion and Dianion: Controllable Preparation, Characterization, and High Performance

Molecular modification of known explosives is considered to be an efficient route to design new energetic materials. A new family of energetic salts based on the 3,5-bis(dinitromethyl)-1,2,4-triazole monoanion and dianion were controllably synthesized by using 1-diamino-2,2-dinitroethene as a precursor. X-ray structure determination of monohydrazinium 3,5-bis(dinitromethyl)-1,2,4-triazolate (5) and monoammonium (6) and diammonium 3,5-bis(dinitromethyl)-1,2,4-triazolate hydrate (8·H2O) further confirmed the structures of these anions. In addition, as supported by X-ray data, in the monoanion system, the roving proton on the ring nitrogen rather than on the gem-dinitro carbon results in extensive hydrogen-bonding interactions and higher packing coefficients. Interestingly, 5 and 6 possess the highest calculated crystal densities, 1.965 and 1.957 g cm(-3) at 150 K, for hydrazinium and ammonium energetic salts, respectively. Energetic evaluation indicates that 5 (detonation velocity vD = 9086 m s(-1); detonation pressure P = 38.7 GPa) and 6 (vD, 9271 m s(-1); P = 41.0 GPa) exhibit great detonation properties, superior to those of current highly explosive benchmarks, such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX).

Combination of 1,2,4‐Oxadiazole and 1,2,5‐Oxadiazole Moieties for the Generation of High‐Performance Energetic Materials

Salts generated from linked 1,2,4-oxadiazole/1,2,5-oxadiazole precursors exhibit good to excellent thermal stability, density, and, in some cases, energetic performance. The design of these compounds was based on the assumption that by the combination of varying oxadiazole rings, it would be possible to profit from the positive aspects of each of the components. All of the new compounds were fully characterized by elemental analysis, IR spectroscopy, (1)H, (13)C, and (in some cases) (15)N NMR spectroscopy, and thermal analysis (DSC). The structures of 2-3 and 5-1⋅5 H2O were confirmed by single-crystal X-ray analysis. Theoretical performance calculations were carried out by using Gaussian 03 (Revision D.01). Compound 2-3, with its good density (1.85 g cm(-3)), acceptable sensitivity (14 J, 160 N), and superior detonation pressure (37.4 GPa) and velocity (9046 m s(-1)), exhibits performance properties superior to those of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX).

Energetic N-Trinitroethyl-Substituted Mono-, Di-, and Triaminotetrazoles

A series of dense energetic N-trinitroethyl-substituted mono-, bis-, and tri-5-aminotetrazoles were obtained by reacting primary amines with in situ generated cyanogen azide, followed by the trinitroethyl functionalization that involves a condensation of a hydroxymethyl intermediate (prepared by a reaction with formaldehyde) with trinitromethane. These compounds were fully characterized by using multinuclear NMR spectroscopy, IR, elemental analysis, differential scanning calorimetry (DSC), and, in one case with 9, with single-crystal XRD analysis. The heats of formation for all compounds were calculated with Gaussian 03 and then combined with experimental densities to determine the detonation pressures (P) and velocities (D(v)) of the energetic materials. Interestingly, most of them exhibited high density, good thermal stability, acceptable oxygen balance, positive heat of formation, low impact sensitivity, and excellent detonation properties, which highlighted their practical application potentials as a fascinating class of highly energetic materials.

Taming of 3,4-Di(nitramino)furazan

Highly energetic 3,4-di(nitramino)furazan (1, DNAF) was synthesized and confirmed structurally by using single-crystal X-ray diffraction. Its highly sensitive nature can be attributed to the shortage of hydrogen-bonding interactions and an interactive nitro chain in the crystal structure. In order to stabilize this structure, a series of corresponding nitrogen-rich salts (3-10) has been prepared and fully characterized. Among these energetic materials, dihydrazinium 3,4-dinitraminofurazanate (5) exhibits a very promising detonation performance (νD = 9849 m s(-1); P = 40.9 GPa) and is one of the most powerful explosives to date. To ensure the practical applications of 5, rather than preparing the salts of 1 through acid-base reactions, an alternative route through the nitration of N-ethoxycarbonyl-protected 3,4-diaminofurazan and aqueous alkaline workup was developed.

Polynitro-substituted pyrazoles and triazoles as potential energetic materials and oxidizers

N-Trinitroethylamino energetic derivatives were obtained from carbon and nitrogen functionalization of nitropyrazoles and nitrotriazoles. N-Trinitroethylamino nitroazoles and N-amino nitroazoles were fully characterized by IR, multinuclear NMR spectra, and elemental analyses. Compounds 10, 11 and 15 were further confirmed by single crystal X-ray structuring. N-Functionalized nitroazoles have moderate to excellent thermal stabilities with good densities. Data based on impact and friction tests show these compounds range from very sensitive to insensitive. Theoretical calculations carried out using Gaussian 03 demonstrate good to excellent detonation pressures and velocities, as well as high specific impulse.

1,2,3-Triazolo(4,5,-e)furazano(3,4,-b)pyrazine 6-Oxide—A Fused Heterocycle with a Roving Hydrogen Forms a New Class of Insensitive Energetic Materials

The straightforward synthesis and energetic properties of a new class of energetic materials, 1,2,3-triazolo- [4,5-e]furazano[3,4-b]pyrazine 6-oxide and its energetic salts are described. They were characterized by IR and multinuclear NMR spectroscopy, elemental analysis, differential scanning calorimetry, and single-crystal X-ray diffraction are given. The X-ray structures show that in the title compound, the hydrogen atom is bonded to the nitrogen in the pyrazine ring; however, in the salts, the negative charge is associated with the triazole nitrogen. Heats of formation for all compounds were calculated with the G2 method and then combined with experimentally determined densities to obtain detonation pressures (P) and velocities (D) by using EXPLO5 program. These new materials exhibit good densities and thermal stabilities, high heats of formation, acceptable detonation properties, and are insensitive to impact.

N-Trinitroethylamino functionalization of nitroimidazoles: a new strategy for high performance energetic materials

An N-functionalized strategy, including N-amination and N-trinitroethylamination, was utilized for the synthesis of nitroimidazole-based energetic materials, giving rise to a new family of highly insensitive N-aminonitroimidazoles and oxygen-rich N-trinitroethylaminonitroimidazoles with good to excellent properties. These new energetic materials were fully characterized by IR, 1H, and 13C NMR, elemental analysis, and some high performance compounds were further confirmed by 15N NMR (4a, 4d, 6a, 6b, and 6d), as well as single crystal X-ray diffraction (6a and 6b). N-Functionalization of nitroimidazoles not only gives rise to the N-aminonitroimidazoles as impact insensitive and thermally stable materials (IS > 40 J; Td: 144–308 °C), but also provides a series of N-trinitroethylaminoimidazoles, which have favorable densities (1.75–1.84 g cm−3), good detonation properties (P: 27.6–35.9 GPa; vD: 7815–8659 m s−1), and moderate thermal stabilities (136–172 °C). These properties are better than some known energetic compounds, such as TNT (P: 19.5 GPa; vD: 6881 m s−1) and TATB (P: 31.2 GPa; vD: 8114 m s−1), and are comparable to RDX (P: 35.0 GPa; vD: 8762 m s−1).

New Roles for 1,1-Diamino-2,2-dinitroethene (FOX-7): Halogenated FOX-7 and Azo-bis(diahaloFOX) as Energetic Materials and Oxidizers

The syntheses and full characterization of two new halogenated 1,1-diamino-2,2-dinitroethene (FOX-7) compounds and three halogenated azo-bridged FOX-7 derivatives are described. Some of these new structures demonstrate properties that approach those of the commonly used secondary explosive RDX (cyclo-1,3,5-trimethylene-2,4,6-trinitramine). All the compounds display hypergolic properties with common hydrazine-based fuels and primary aliphatic amines (ignition delay times of 2-53 ms). This is a new role that has yet to be reported for FOX-7 and its derivatives. Their physical and energetic properties have been investigated. All compounds were characterized by single-crystal X-ray crystallography, elemental analysis, infrared spectra, and differential scanning calorimetry. These new molecules as energetic materials and hypergolic oxidizers contribute to the expansion of the chemistry of FOX-7.

4-Chloro-3,5-dinitropyrazole: a precursor for promising insensitive energetic compounds

A series of 3,5-dinitropyrazole derivatives was prepared from 4-chloro-3,5-dinitropyrazole in good yields and characterized by IR, 1H, and 13C NMR (some cases 15N NMR) spectroscopy, elemental analysis, and DSC. The structures of 7 and 13 were confirmed by single crystal X-ray diffraction. The impact sensitivity was determined using a standard BAM method, and detonation properties were obtained using experimental densities and calculated heats of formation.