Image1_The ionic salts with super oxidizing ions O2+ and N5+: Potential candidates for high-energy oxidants.TIF

As an important component of energetic materials, high-energy oxidant is one of the key materials to improve their energy. The oxidizability of oxidant directly determines the intensity of combustion or explosion reaction. It is generally believed that when the nature of reductant is certain, the stronger the oxidizability, the more intense the reaction. Dioxygenyl cation (O2+) and pentazenium cation (N5+) are two kinds of super oxidizing ions, which oxidizability are comparable to that of fluorine. A series of high energetic ionic salts with O2+, N5+ and various anions as active components are designed, and the results show that: 1) Most ionic salts have appropriate thermodynamic stability, high density (up to 2.201 g/cm3), high enthalpy of formation (up to 1863.234 kJ/mol) and excellent detonation properties (up to 10.83 km/s, 45.9 GPa); 2) The detonation velocity value of O2 (nitrotetrazole-N-oxides) and O2B(N3)4 exceed 10.0 km/s, and the detonation pressure exceed 45.0 GPa because of the O2+ salts have higher crystal density (g/cm3) and oxygen balance than that of N5+salts; 3) With a higher nitrogen content than O2+, the N5+ salts have higher enthalpy of formation, which exceed 330 kJ/mol than that of O2+ salts; 4) The linear spatial structure of N5+ leads the salts to reduce their density. Encouragingly, this study proves that these super oxidizing ions have the potential to become high-energy oxidants, which could be a theoretical reference for the design of new high energetic materials.</p

Can Catenated Nitrogen Compounds with Amine-like Structures Become Candidates for High-Energy-Density Compounds?

The worthwhile idea of whether amine-like catenated nitrogen compounds are stable enough to be used as high-energy materials was proposed and answered. Abstracting the NH3 structure into NR3 (R is the substituent) yields a new class of amine-like catenated nitrogen compounds. Most of the azole ring structures have a high nitrogen content and stability. Inspired by this idea, a series of new amine-like catenated nitrogen compounds (A1 to H5) were designed, and their basic energetic properties were calculated. The results showed that (1) amine-like molecular structures are often characterized by low density; however, the density of these compounds increases as the number of nitrogens in the azole ring increases; (2) these catenated nitrogen compounds generally have extremely high enthalpies of formation (882.91–2652.03 kJ/mol), and the detonation velocity of some compounds exceeds 9254.00 m/s; (3) the detonation performance of amine-like catenated nitrogen compounds designed based on imidazole and pyrazole rings is poor due to their low nitrogen content; and (4) the bond dissociation enthalpy of trigger bonds of most compounds is higher than 84 kJ/mol, indicating that these compounds have a certain thermodynamic stability. In summary, amine-like catenated nitrogen compounds have the potential to become energetic compounds with excellent detonation properties and should be considered to be synthesized by experimental chemists

The Highly Effective Hydrogenolysis-Based Debenzylation of Tetraacetyl-Dibenzyl-Hexaazaisowurtzitane (TADBIW) Using a Palladium/DOWEX Catalyst Having a Synergistic Effect

<p>A Pd/resin catalyst system was prepared using a simple process and it exhibited excellent performance during the catalytic hydrogenolysis-based debenzylation of tetraacetyl-dibenzyl-hexaazaisowurtzitane (TADBIW) to 2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (TAIW). Employing this system, the palladium concentration could be reduced from 1% to 0.4% while improving the yield from 92% to 98% under mild reaction conditions. These outstanding results can be attributed to a synergistic effect between the palladium and the acidic resin. A possible reaction mechanism is proposed for the acid-assisted removal of N-benzyl from TADBIW in the presence of this catalyst.</p

MOESM1 of Thermogravimetric analysis, kinetic study, and pyrolysis–GC/MS analysis of 1,1ʹ-azobis-1,2,3-triazole and 4,4ʹ-azobis-1,2,4-triazole

Additional file 1. The purity of the title compounds

Highly Selective Nitroamino Isomerization Guided by Proton Transport Dynamics: Full-Nitroamino Imidazole[4,5‑<i>d</i>]pyridazine Fused-Ring System

Due to the advantage of the hydrogen bond system formed by nitroamino isomerization, by the calculations of hydrogen transfer in reported nitroamino explosives, the proton transport dynamics was first proposed to predict the nitroamino isomerization of energetic materials. With the calculated results of zero-point energy, the full-nitroamino fused energetic materials, 2,4-nitroamino-7-nitroimino-1,5-dihydro-4H-imidazolo[4,5-d]pyridazine (FNPI-1) and 2,2′,7,7′-tetranitromino-4,4′-azo-imidazolo[4,5-d]pyridazine (FNPI-2) were designed and successfully synthesized. The highly selective nitroamino isomerization of neutral compound FNPI-1 is shown by X-ray diffraction. After the hydrogen transfer occurs, the intermolecular hydrogen bonds will greatly promote tight stacking, which enhances the density and thus a series of comprehensive properties of energetic materials. The theoretical calculations of zero-point energy explain perfectly the selectivity of hydrogen transfer between the nitroamino groups and the fused-ring skeleton for FNPI-1. The hydrogen atom transfer and selective isomerization of nitroamino energetic materials can be accurately predicted following proton transport dynamics, which provides computational bases and new ideas for the efficient design of fully nitroamino-based explosives

Highly Selective Nitroamino Isomerization Guided by Proton Transport Dynamics: Full-Nitroamino Imidazole[4,5‑<i>d</i>]pyridazine Fused-Ring System

Due to the advantage of the hydrogen bond system formed by nitroamino isomerization, by the calculations of hydrogen transfer in reported nitroamino explosives, the proton transport dynamics was first proposed to predict the nitroamino isomerization of energetic materials. With the calculated results of zero-point energy, the full-nitroamino fused energetic materials, 2,4-nitroamino-7-nitroimino-1,5-dihydro-4H-imidazolo[4,5-d]pyridazine (FNPI-1) and 2,2′,7,7′-tetranitromino-4,4′-azo-imidazolo[4,5-d]pyridazine (FNPI-2) were designed and successfully synthesized. The highly selective nitroamino isomerization of neutral compound FNPI-1 is shown by X-ray diffraction. After the hydrogen transfer occurs, the intermolecular hydrogen bonds will greatly promote tight stacking, which enhances the density and thus a series of comprehensive properties of energetic materials. The theoretical calculations of zero-point energy explain perfectly the selectivity of hydrogen transfer between the nitroamino groups and the fused-ring skeleton for FNPI-1. The hydrogen atom transfer and selective isomerization of nitroamino energetic materials can be accurately predicted following proton transport dynamics, which provides computational bases and new ideas for the efficient design of fully nitroamino-based explosives

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications

Backbone Isomerization to Enhance Thermal Stability and Decrease Mechanical Sensitivities of 10 Nitro-Substituted Bipyrazoles

The development of novel, environmentally friendly, and high-energy oxidizers remains interesting and challenging for replacing halogen-containing ammonium perchloride (AP). The trinitromethyl moiety is one of the most promising substituents for designing high-energy density oxidizers. In this study, a backbone isomerization strategy was utilized to manipulate the properties of 10 nitro group-substituted bipyrazoles containing the largest number of nitro groups among the bis-azole backbones so far. Another advanced high-energy density oxidizer, 3,3′,5,5′-tetranitro-1,1′-bis­(trinitromethyl)-1H,1′H-4,4′-bipyrazole (3), was designed and synthesized. Compared to the isomer 4,4′,5,5′-tetranitro-2,2′-bis­(trinitromethyl)-2H,2′H-3,3′-bipyrazole (4) (Td = 125 °C), 3 possesses better thermostability (Td = 156 °C), which is close to that of ammonium dinitramide (ADN) (Td = 159 °C), and it possesses better mechanical sensitivity (impact sensitivity (IS) = 13 J and friction sensitivity (FS) = 240 N) than that of 4 (IS = 9 J and FS = 215 N), thereby demonstrating a promising perspective for practical applications