Piao He

Energetic Salts Based on Tetrazole N-Oxide

Energetic materials (explosives, propellants, and pyrotechnics) are used extensively for both civilian and military applications and the development of such materials, particularly in the case of energetic salts, is subject to continuous research efforts all over the world. This Review concerns recent advances in the syntheses, properties, and potential applications of ionic salts based on tetrazole N-oxide. Most of these salts exhibit excellent characteristics and can be classified as a new family of highly energetic materials with increased density and performance, alongside decreased mechanical sensitivity. Additionally, novel tetrazole N-oxide salts are proposed based on a diverse array of functional groups and ions pairs, which may be promising candidates for new energetic materials.

A 1D cadmium complex with 3,4-diamino-1,2,4-triazole as ligand: synthesis, molecular structure, characterization, and theoretical studies

An energetic complex, [Cd2(μ-Cl)4Cl2(DATr)2]n (1) (DATr = 3,4-diamino-1,2,4-triazole), was synthesized from DATr·HCl and cadmium(II) chloride. The product was characterized by Fourier transform infrared spectroscopy analysis, elemental analysis, X-ray diffraction analysis, and differential scanning calorimeter (DSC) analysis. The central cadmium(II) ions in 1 are six-coordinate twisted octahedral structures, which are made up of 1D chains linked by bridging chlorides. The results of the DSC analysis suggest the temperature of decomposition to be above 503.15 K. Furthermore, the kinetic properties of decomposition are studied by Kissinger’s and Ozawa–Doyle’s methods, and the calculated average activation is 166.5 kJ M−1, which means the complex is stable under normal conditions. In addition, the energy of combustion was measured by oxygen bomb calorimetry. The critical temperature of thermal explosion and parameters of thermodynamics of 1 were calculated. The periodic structure of 1 has been calculated based on the density functional theory. The theoretical results explain the electronic structure and thermal dynamic properties. Graphical abstract A new 1D Cd complex based on 3,4-diamino-1,2,4-triazole was synthesized and structurally characterized. Its thermal stability, non-isothermal kinetics analysis, and theoretical calculation were studied, and energy of combustion was also measured.

Design of New Bridge-Ring Energetic Compounds Obtained by Diels–Alder Reactions of Tetranitroethylene Dienophile

The density functional theory method was employed to calculate three-dimensional structures for a series of novel explosophores. The design of new molecules (DA1-DA12) was based on the bridge-ring structures that could be formed via Diels-Alder (DA) reaction of selected nitrogen-rich dienes and tetranitroethylene dienophile. The feasibility of the proposed DA reactions was predicted on the basis of the molecular orbital theory. The strong interactions between the HOMO of dienes, with electron-donating groups (Diene2, Diene6, and Diene8), and the LUMO of tetranitroethylene dienophile suggested thermodynamically favorable formation of the desired DA reaction products. In addition to molecular structures of the explored DA compounds, their physicochemical and energetic properties were also calculated in detail. Due to compact bridge-ring structures, new energetic molecules have highly positive heats of formation (up to 1124.90 kJ·mol-1) and high densities (up to 2.04 g·cm-3). Also, as a result of all-right ratios of nitrogen and oxygen, most of the new compounds possess high detonation velocities (8.28-10.02 km·s-1) and high detonation pressures (30.87-47.83 GPa). Energetic compounds DA1, DA4, and DA12 exhibit a superior detonation performance over widely used HMX explosive, and DA5, DA7, and DA10 could be comparable to the state-of-the-art CL-20 and ONC explosives. Our proposed designs and synthetic methodology should provide a platform for the development of novel energetic materials with superior performance.

A comparative theoretical study on energetic substituted 1,2,3- and 1,2,4-triazoles: the azido-cyclization mechanism and the effect of solvent

The hybrid DFT calculations with B3LYP/6-311G* level of theory have allowed us to gain insight into the azido-cyclization of 4,5-diazido-1,2,3-triazole and 3,5-diazido-1,2,4-triazole and the effect of solvent. The optimized geometry, charges and molecular electrostatic potential were calculated and the results indicate that the cyclization occurs mainly in the conversion azido → tetrazole, in which the molecular and electronic structures change more significantly. Further analysis of the energy parameters indicates that all possible reactions are endothermic and not spontaneous in the gas phase, but the first and second azido-cyclization of 3,5-diazido-1,2,4-triazole could be performed theoretically with energy barriers of 26 kcal mol−1 and 33 kcal mol−1. Again, the rate constants and the Arrhenius experience formula of azido-cyclization have been obtained between 200–1000 K temperature regions. In addition, the solvent effect on azido-cyclization was studied with acetone, trifluoroacetic acid and dimethylsulfoxide. The results show that the solvent effect can make the intermediates and products more stable than in the gas phase. The energy barriers for the first and second cyclization are lowered more or less especially in dimethylsulfoxide, and the influence on the azido-cyclization of 4,5-diazido-1,2,3-triazole is a little larger.