Abstract:

Abstract:

Abstract:In the early stage, studies on pentazole chemistry are mainly focused on the substituent effect and stability of aryl pentazole compounds, but the successful preparation of room-temperature stable pentazole ionic compounds has not been achieved. Until to 2017, for the first time, the Chinese scientists reported their successful preparation of isolated and stable cyclo-N₅^- compounds through an oxidative cleavage strategy at low temperature. Subsequently, a variety of cyclo-N₅^- based salts with different structures were synthesized, attracting a wide of attention in the fields of energetic materials. Up to now, full-nitrogen pentazole materials have achieved a series of breakthroughs and various full-nitrogen pentazole salts have also been prepared with the de composition temperatures mostly higher than 100 ℃. The ionic salts based on cyclo-N₅^- anion and nitrogen-rich cations will open a new avenue to develop cyclo-N₅^- based energetic materials. This work reviews the theoretical calculations, organic syntheses, structural characterization, and the perspectives on pentazole compounds, which aims to provide guidance for the researchers working in the field of polynitrogen materials.

Abstract:Nitrogen-rich fused-ring energetic materials are a kind of energetic compounds with incorporating nitro and other energetic functional groups into the nitrogen-rich fused-ring heterocycle skeletons. Due to the excellent properties including high detonation properties, low sensitivity and high decomposition temperature, these nitrogen-rich fused-ring energetic materials have attracted wide research interest in the domestic and foreign scholars of energetic materials. The studies reveal that the stability of fused-ring skeleton has been significantly increased owing to the delocalization and resonance of π-electrons in nitrogen-rich fused-ring skeletons. For example, the detonation properties of 4-amino-3, 7-dinitrotriazolo-[5, 1-c][1, 2, 4] triazine 4-oxide (DPX-27)is comparable to RDX with detonation velocity and detonation pressure of 8.97 km·s^-1 and 35.4 GPa, respectively. But its impact and fraction sensitivities are 10 J and 258 N, respectively, obviously lower than those of RDX. For 1, 2, 9, 10-tetranitrodipyrazolo [1, 5-d: 5′, 1′-f][1, 2, 3, 4]-tetrazine(TNDPT), its detonation velocity and detonation pressure are separately 9.63 km·s^-1 and 44.0 GPa, as high as those of CL-20. Moreover, its mechanical sensitivities(IS:10 J, FS:240 N)are obviously lower than CL-20. We can find that, as a new generation of energetic materials, nitrogen-rich fused-ring energetic materials can well balance the conflict between high stability and high detonation performance, showing great scientific and applied potentials. In this paper, the authors review the synthesis, detonation properties, stability and outlook of nitrogen-rich fused-ring energetic materials, which will provide some references for the subsequent study.

Abstract:Energetic salts as a unique class of energetic materials arereadily modified to improve their detonation properties through the appropriate combination of different cations and anions.In this review, a brief introduction to the latest developments in the field of energetic salts synthesis over the past few years.These energetic salts generally exhibit desirable properties and per-formance, which in some cases are superior to those of the common energetic materials HMX, RDX, TNT and TATB. Furthermore, the development direction and trend of synthetic research of the energetic salts are discussed.

Abstract:The instantaneous thermal effect from the explosion of traditional explosives cannot effectively kill biological agents carried by biological weapons. Iodine-rich compounds can not only release energy, but also efficiently kill biological agents. Therefore, iodine-rich compounds has been thought as the most promising "energetic biocidal agent"compounds. This paper reviews the synthesis and properties of covalent, ionic and co-crystal iodine-rich compounds, and presents bactericidal ability of part"energetic biocidal agent"compounds. Combined with the structure-function relationship, this review points out that developing new iodine-richcompounds with good thermostability, high density, high iodine and high bactericidal activity, will be a research focus on"energetic biocidal agent"compounds. Moreover, on the premise of good bactericidal ability, constantly increasing the energy density and spraying range of"energetic biocidal agent"compounds is another development trend of anti-biological agent research.

Abstract:Seven metal salts based on the 1-(1H-1, 2, 4-triazole-3-yl) -1H-tetrazole were synthesized firstly by using the reaction with related hydroxide or carbonate. They are characterized by using EA, IR, NMR technologies. And X-ray single crystals of five metal salts were obtained. The thermal stability of the metal salts was studied by DSC. Most of them have good thermal stability after the water molecular was lost, and the decomposition temperature of lithium salts is highest with a value of 258 ℃. The enthalpy of formation was calculated by the isometric reaction method. The enthalpy of formation of two metal salts are higher than 1000 kJ·mol^-1. The detonation performance was estimated by using EXPLO5 software, and the impact sensitivity and friction sensitivity were tested. The results show that these metal salt are insensitive energetic materials.

Abstract:N-(2-fluoro-2, 2-dinitroethyl) -1, 5-diaminotetrazole-1H was synthesized by a one-step Mannich reaction under mild conditions using 1, 5-diaminotetrazole-1H and 2, 2-fluorodinitroethanol as starting materials. Its molecular structure was deter- mined by X-ray single crystal diffraction analysis. It crystallizes in orthorhombic system, space group Pca2₁, with a crystal densi- ty of 1.77 g·cm^-3 at 173 K. The different interactions in crystal were analyzed by Hirshfeld surface. In the analysis, the dominant intermolecular interactions in the crystal and their distributions were (R is a proportional abbreviation):R_O…H/H…O=27.0%, R_N…H/H…N=21.5%, R_{F…O/O…F/F…H/H…F/N…F/F…N}=15.9%, mainly hydrogen bonding and halogen bonding interactions. The thermal stability was studied by thermogravimetry and differential scanning calorimetry(TG-DSC). At a heating rate of 5 ℃·min^-1, there was only one sharp decomposition peak with the temperature at 177.32 ℃, and the mass loss was 92.53% demonstrating a nearly complete decomposition at such temperature. Its activation energy were calculated by using Kissinger method and Ozawa method as 213.228 kJ·mol^-1, 209.984 kJ·mol^-1 respectively, which were shown. A spatial reticulated porous structure were observed according to the field emission-scanning electron microscopy(FE-SEM)analyses.

Abstract:Based on energetic ligands 3, 5-dinitro-1-H-1, 2, 4-triazole and 3, 4-bis (1H-5-tetrazolyl) furoxan, two solvent-free ener-getic Ag(Ⅰ)-MOFs, [Ag₂(2-ntz)₂]_n(1) and [Ag₂(BTOF)]_n(2) have been prepared under hydrothermal conditions. Single-crys-tal X-ray analysis reveals that the Ag⁺ centersin both Ag(Ⅰ)-MOFs are three-coordinated. Compound 1 features a 3D framework (ρ₁=2.805 g·cm^-3) constructed by 2-ntz^- ligands bridging metal ions with a μ₃-1, 2, 4 mode. Compound 2 presents a 2D folded layer structure (ρ₂=3.101 g·cm^-3) formed by BTOF^2- ligands linking metal ions with aquinquedentatechelating-bridging coordina-tionmode. TG-DSC curves demonstrate that both compounds 1 and 2 keep stable until 240 ℃, exhibiting high thermal stability. The heats of combustion of 1 and 2 are determined by oxygen-bomb calorimeter, and the corresponding standard molar enthal-pies of formationare determined to be (1375.74±1.27)kJ·mol^-1 and (1647.42±1.46)kJ·mol^-1, respectively. The detonation and safety performance analyses show that the heat of detonation, detonation velocityand detonationpressureof compounds 1 and 2 are, respectively calculated as 5.55 kJ·g^-1 and 3.78 kJ·g^-1, 8.97 km·s^-1 and 7.69 km·s^-1, as well as 44.87 GPa and 34.37 GPa. Both compounds 1 and 2 are insensitive to impact and friction, and are good high energy yet low sensitivity materials.

Abstract:To develop novel hypergolic propellant fuels with high density, low viscosity, wide liquid temperature range, high specific impulse, and high decomposition temperature, a series of N-alkyltriazole cyanoborane complexes were prepared in a straight forward way by treating N-substituted triazoles hydrogen chloride salts and NaBH₃CN. The synthesized compounds were characterized by IR, NMR and HRMS for their structures, and measured by differential scanning calorimetry (DSC), densimeter and viscometer for their thermostability, density, viscosity and ID. On the other hand, Gaussian 09 was used to optimize the crystal structure and calculate the formation enthalpy, based on which Explo5 v6.02 was employed to predict the theoretical specific impulse. Four out of five compounds were found to be liquid at room temperature and proved to be hypergolic with white fuming nitric acid (WFNA) by the droplet test. Especially, N-Propyl-1, 2, 3-triazole cyanoborane complex (3) demonstrated attractive properties such as short ID time (12 ms), high density (1.024 g∙cm⁻³), good thermostability (T_d=233 ℃, onset), good I_sp (201.7 s) and ρI_sp (357 s∙g∙cm⁻³), super low viscosity (16 mPa∙s) and wide liquid range (T_m < -70 ℃), showing the promising application potential as a propellant fuel candidate.

Abstract:Sodium pentazole salt was prepared by treating 2, 6-dimethyl-4-(2H-pentazol-2-yl) phenolate with m-chloroperbenzoic acid (m-CPBA) and ferrous bisglycinate [Fe(Gly)₂] under low-temperature conditions, thereinto, m-CPBA and Fe(Gly)₂ were oxidizer and catalyst, respectively. The synthetic conditions were optimized, as following:the molar ratio between arylpentazole, Fe(Gly)₂ and m-CPBA was 1:3:4.5, the reaction time was 24 h and the reaction temperature was-45 ℃(crude yield of 28%). The effect of different oxidizing cleavage reagents on the yield of sodium pentazole salt was studied and the reason for the low yield of sodium pentazole salt was analyzed. In addition, sodium pentazole salt and the reaction by-product (2, 6-dimethylcyclohexa-2, 5-diene-1, 4-dione) were characterized by X-ray single crystal diffractometer (XRD), NMR (¹⁵NMR and ¹H NMR), FT-IR, mass spectrometry and elemental analysis. Based on these results, the mechanism of oxidizing cleavage of the C─N bond in arylpentazole by m-CPBA and Fe(Gly)₂ was speculated.

Abstract:Using 3-amino-4-(tert-butyl-NNO-azoxy) furazan (ABAoF) as starting material, 1-hydroxy-1H[-1, 2, 3] triazolo [4, 5-e] [1, 2, 3, 4] tetrazine 5, 7-dioxide (HTTDO) was synthesized by 5-steps reactions including diazotization, oximation, oxidation, amination and nitration cyclization, with a total yield of 24.1%. HTTDO and the associate dintermediates were characterized by FT-IR, NMR, mass spectrometry and elementary analysis. Further, the reaction mechanisms of amination and nitration cyclization were clarified. In this work, the single crystal of HTTDO·4.5H₂O was cultivated for the first time, and the crystal structure of which was determined by X-ray diffraction analysis, demonstrating that HTTDO·4.5H₂O crystallized in the orthorhombic space group Pna2(1). The physico-chemistry and detonation properties of HTTDO were calculated by Gaussian 09 program and Kam let-Jacobs formula. The detonation velocity of HTTDO was 9393 m·s^-1, and the detonation pressure was 41.9 GPa and the detonation heat was 8010 J·g^-1. In addition, the thermal behaviors of HTTDO were studied by differential scanning calorimetry (DSC). During the exothermic thermal decomposition process of HTTDO, a sharp peak occurred at 194.5 ℃.

Abstract:Using 5, 5′-dinitroamino-2, 2′-bi (1, 3, 4-oxadiazole) as starting material, a serials of energetic salts were synthesized. All compounds were characterized by FT-IR, multinuclear NMR spectroscopy and elemental analysis. The structures of di (3-amino-1, 2, 4-triazolium) 5, 5′-dinitroamino-2, 2′-bi (1, 3, 4-oxadiazolate)·2H₂O(9·2H₂O) and di (4-amino-1, 2, 4-triazolium) 5, 5′-dinitroamino-2, 2′-bi (1, 3, 4-oxadiazolate)(10) were further confirmed by single crystal X-ray diffraction. Their thermal stabilities were determined by differential scanning calorimetry (DSC). The detonation performance was calculated with Explo5 v6.02 software. The results show that the temperature of the thermal decomposition reaction is in the range of 146.8-239.9 ℃. The calculated detonation velocity and pressure are higher than 7693 m·s^-1 and 21.3 GPa, respectively. Their densities are from 1.683 to 1.941 g·cm^-3. The measured impact sensitivities are between 10 J and 28 J and friction sensitivities are between 160 N and 360 N, which indicated that most salts of 5, 5′-dinitroamino-2, 2′-bi (1, 3, 4-oxadiazole) are high energy-density materials with good properties.

Abstract:The development of new energetic materials with high energy, low sensitivity, and high thermal stability is always desirable. In this study, a series of tetrazole-linked 4, 8-dihydrodifurazano [3, 4-b, e] pyrazine (DFP) based energetic salts have been synthesized and fully characterized. The as-synthesized energetic salts exhibited excellent comprehensive performances in terms of high decomposition temperature (T_d > 260 ℃), low mechanical sensitivity (IS≥20 J and FS≥360 N), and high detonation velocity (D > 8800 m·s^-1). Notably, the thermal decomposition temperature of di (aminoguanidinium)-4, 8-di (1H-tetrazol-5-yl)-difurazano [3, 4-b, e] pyrazine (compound 4e) is up to 314 ℃, while its detonation velocity and impact sensitivity are highly desirable with the values of 9005 m·s^-1 and 25 J, respectively. Overall, these novel energetic compounds have shown their great-potential as insensitive high-energy-density materials.