Pushing the Limit of Nitro Groups on a Pyrazole Ring with Energy-Stability Balance

Abstract

Polynitro compounds exhibit high density and good oxygen balance, which are desirable for energetic material applications, but their syntheses are often very challenging. Now, the design and syntheses of a new three-dimensional (3D) energetic metal–organic framework (EMOF) and high-energy-density materials (HEDMs) with good thermal stabilities and detonation properties based on a polynitro pyrazole are reported. Dipotassium 3,5-bis­(dinitromethyl)-4-nitro-1H-pyrazole (5) exhibits a 3D EMOF structure with good thermal stability (202 °C), a high density of 2.15 g cm–3 at 100 K (2.10 g cm–3 at 298 K) in combination with superior detonation performance (D v = 7965 m s–1, P = 29.3 GPa). Dihydrazinium 3,5-bis­(dinitromethyl)-4-nitro-1H-pyrazole (7) exhibits a good density of 1.88 g cm–3 at 100 K (1.83 g cm–3 at 298 K) and superior thermal stability (218 °C), owing to the presence of 3D hydrogen-bonding networks. Its detonation velocity (8931 m s–1) and detonation pressure (35.9 GPa) are considerably superior to those of 1,3,5-trinitro-1,3,5-triazine (RDX). The results highlight the syntheses of a 3D EMOF (5) and HEDM (7) with five nitro groups as potential energetic materials.

Energetic Salts of Sensitive N,N′-(3,5-Dinitropyrazine-2,6-diyl)dinitramide Stabilized through Three-Dimensional Intermolecular Interactions

“… a Density at 25 °C (gas pycnometer). b Calculated density. c Crystal density. d Detonation velocity. e Detonation pressure. f Calculated enthalpy of formation. g Decomposition temp. (onset). h Impact sensitivity. i Friction sensitivity. j Oxygen balance. k Figure a, ref . l Figure b, Ref . m Figure c, Ref . n Ref . …”

“…Recently, various research groups disclosed the preparation of EMOFs based on nitro (NO 2 ) or nitramide (NHNO 2 )-substituted azole rings. , However, these EMOFs show a decrease in stability with the increase in explosophore units, and only a few show balance between performance and stability (Figure ). − Recently, several EMOFs were disclosed based on nitrogen-rich five-membered rings . In contrast, there are only a few reports of EMOFs based on planar six-membered azines …”

Nitrogen-rich ion salts of 1-hydroxytetrazole-5-hydrazide: a new series of energetic compounds that combine good stability and high energy performance

“…Azoles and oxazines rich in C-N and N-N bonds in their structures are the main building blocks for the design and preparation of nitrogen-rich materials due to their high thermal stability, high heats of formation and large ring tension. [1][2][3][4] Tetrazole is a highly stable heterocyclic structure with an extremely high nitrogen content and heats of formation. These structural characteristics endow tetrazole-based energetic compounds with a high energy level, low signature and environmentally friendly properties.…”

“…[5][6][7][8][9] Hydroxytetrazole compounds not only eliminate the environmental pollution caused by the nitration reaction, but also meet the demand for oxygen atoms in CHON-explosives during energy release. 10 However, the N-O bond on the tetrazole ring also brings great drawbacks, namely high acidity and high sensitivity to external stimuli (including mechanical and thermal stimuli). For example, 5-amino-1H-tetrazol-1-ol (5-ATO), 5,5′-(diazene-1,2-diyl)bis(1H-tetrazol-1-ol) (AZBTO), 1H-tetrazol-1-ol (TO) and 1H,1′H-[5,5′-bitetrazole]-1,1′-diol (BTO) all show excellent detonation performance, but they do not show satisfactory thermal stability or sensitivity.…”

Insensitive nitrogen-rich compounds with a planar 2D configuration based on an imidazole–tetrazole

“…Energetic materials have played a positive role in the development of human society since they were discovered. [1][2][3][4][5][6] With the continuous development of the fields of national defense and aerospace, as well as people's continuous attention to environmental issues, the development of energetic compounds is advancing in the direction of high nitrogen content with the characteristics of being "environmentally friendly". [7][8][9][10] In this process, heterocyclic azole structures have received great attention due to their high nitrogen content and positive heat of formation.…”