Highly energetic N-cyano-substituted CL-20 analogues: challenging the stability limits of polynitro hexaazaisowurtzitanes.

To design high-energy-density materials of a new level, it is necessary to develop methods for the functionalization of energetic scaffolds, which will make it possible to tune their physicochemical and energetic properties. For this reason, we have elaborated an approach for synthesizing a new series of energetic cage compounds with advanced properties by introducing the N-cyano group into the polynitro hexaazaisowurtzitane framework. The structures of the obtained substances were fully characterized with a combination of methods, including multinuclear (1H, 13C{1H}, 14N, and 15N{1H}) NMR and IR spectroscopy, high-resolution mass spectrometry, X-ray diffraction analysis, electron microscopy and quantum chemical calculations. For the resulting compounds, thermal stability and safety tests were carried out, calorimetric and pycnometric measurements were performed, and the energetic potential was determined by high-temperature chemical equilibrium thermodynamic calculations. The new cyano derivatives have an acceptable density (up to 1.92 g cm-3) and a high enthalpy of formation (up to 2 MJ kg-1), which is 2 times that of the benchmark CL-20. The resistance of the target compounds to friction (up to 220 N) is the highest compared to CL-20 and its known analogues. 4,10-Dicyano-2,6,8,12-tetranitro-2,4,6,8,10,12-hexaazaisowurtzitane of the new series is the most thermally stable (a Tdec of 238 °C) among the known energetic polynitro hexaazaisowurtzitanes and is the first derivative of this family to surpass CL-20 in heat resistance. Moreover, the specific impulse for the novel materials showed an improvement of 6.5-13 s over CL-20.

Correction: [(3-Nitro-1H-1,2,4-triazol-1-yl)-NNO-azoxy]furazans: energetic materials containing an N(O)[double bond, length as m-dash]N-N fragment.

[This corrects the article DOI: 10.1039/D1RA03919A.].

[(3-Nitro-1H-1,2,4-triazol-1-yl)-NNO-azoxy]furazans: energetic materials containing an N(O)[double bond, length as m-dash]N-N fragment.

The strategy for the synthesis of substituted [(3-nitro-1H-1,2,4-triazol-1-yl)-NNO-azoxy]furazans 4-7, in which the distal nitrogen of the azoxy group is bonded to the nitrogen atom of the azole ring, includes, firstly, the reaction of 1-amino-3-nitro-1H-1,2,4-triazole with 2,2,2-trifluoro-N-(4-nitrosofurazan-3-yl)acetamide in the presence of dibromisocyanuric acid followed by removing of the trifluoroacetyl protecting group to afford aminofurazan (4). Transformation of the amino group in the latter made it possible to synthesize the corresponding nitro (5), azo (6), and methylene dinitramine (7) substituted furazans. The compounds synthesized are thermally stable (decomposition onset temperatures 147-228 °C), exhibit acceptable densities (1.77-1.80 g cm-3) and optimal oxygen balance (the oxidizer excess coefficients α = 0.42-0.71). Their standard enthalpies of formation (576-747 kcal kg-1) were determined experimentally by combustion calorimetry and these compounds have been estimated as potential components of solid composite propellants. In terms of the specific impulse level, model solid composite propellant formulations based on nitro and methylene dinitramine substituted furazans 5 and 7 outperform similar formulations based on CL-20 by 1-4 s, and formulations based on HMX and RDX by 5-8 s.

Synthesis and Characterization of 3-(5-(Fluorodinitromethyl)-1H-1,2,4-triazol-3-yl)-4-nitrofurazan: A Novel Promising Energetic Component of Boron-based Fuels for Rocket Ramjet Engines.

The synthesis of a new energetic 1,2,4-triazole compound bearing nitrofurazanyl and fluorodinitromethyl units, which may find use as a component for rocket ramjet engines (RRE), is described. The target product was prepared in a four-step process applying oxidation/nitration/decarboxylation/fluorination reactions and is fully characterized. Its density and structural features were uniquely determined by X-ray analysis. It is shown that replacing HMX with the compound of this study in boron-based fuels gives an increase in energy.

Assembly of Nitrofurazan and Nitrofuroxan Frameworks for High-Performance Energetic Materials.

The design of novel energetic materials with improved performance, optimized parameters, and environmental compatibility remains a challenging task. In this study, new high-energy materials based on isomeric dinitrobi-1,2,5-oxadiazole structures comprising nitrofurazan and nitrofuroxan subunits were synthesized. Due to planarity and strong noncovalent interactions, these materials display high density values as determined by single-crystal X-ray diffraction. The thermal, impact, and friction sensitivities of both isomers are similar to that of nitroesters. Their high detonation performance along with the combined benefits of high density, high heat of formation, and good oxygen balance make the synthesized compounds promising as explosives and highly-energetic oxidizers.