The Ingenious Synthesis of a Nitro-Free Insensitive High-Energy Material Featuring Face-to-Face and Edge-to-Face π-Interactions

Synthetic Strategies Toward Nitrogen-Rich Energetic Compounds Via the Reaction Characteristics of Cyanofurazan/Furoxan

The structural units of amino-/cyano-substituted furazans and furoxans played significant roles in the synthesis of nitrogen-rich energetic compounds. This account focused on the synthetic strategies toward nitrogen-rich energetic compounds through the transformations based on cyanofurazan/furoxan structures, including 3-amino-4-cyanofurazan, 4-amino-3-cyano furoxan, 3,4-dicyanofurazan, and 3,4-dicyanofuroxan. The synthetic strategies toward seven kinds of nitrogen-rich energetic compounds, such as azo (azoxy)-bridged, ether-bridged, methylene-bridged, hybrid furazan/furoxan-tetrazole–based, tandem furoxan–based, hybrid furazan-isofurazan–based, hybrid furoxan-isoxazole–based and fused framework–based energetic compounds were fully reviewed, with the corresponding reaction mechanisms toward the nitrogen-rich aromatic frameworks and examples of using the frameworks to create high energetic substances highlighted and discussed. The energetic properties of typical nitrogen-rich energetic compounds had also been compared and summarized.

Design and properties of a new family of wing-like and propeller-like multi-tetrazole molecules as potential high-energy density compounds

Density functional theory (DFT) methods were employed to design a new family of wing-like and propeller-like multi-tetrazole molecules based on the combination of N-center multi-tetrazole and various energetic groups. The optimized geometry, electronic properties, and thermodynamics were calculated for investigating the molecular stability and chemical reactivity. Their energetic parameters including density, heats of formation, detonation properties, and impact sensitivity were extensively evaluated, and the effects of energetic groups were investigated as well. These newly designed wing-like and propeller-like multi-tetrazole molecules exhibit acceptable oxygen balance, moderate impact sensitivities, high density, excellent heats of formation, and good detonation performance. Especially, B3, B4, B5, and B6 are very helpful for enhancing their detonation performance (D ≥ 9500 m·s^-1, P ≥ 41 GPa) are promising candidates for new environmentally friendly HEDMs.

Theoretical study of effects of introducing varying linkages into bis-triazoles on energetic performance

A series of novel bis-triazole compounds was designed by combining high-energy functionalities (nitro and nitramino groups) as substituents with each triazole and incorporating of varying linkages into the bis-triazoles. Then, their heats of formation (HOFs), energetic properties, HOMO-LUMO, electrostatic potential, and impact sensitivity were studied theoretically to facilitate further developments. In general, all the designed compounds possess much higher HOFs than RDX, -CH₂-CH₂-, -N=N-, or -NH-NH- linkages contribute to increase the HOFs, while incorporation of the bridge group -O-CH₂-CH₂-O- shows negative effect on HOFs. Detonation properties of most of the designed compounds can be comparable with or even better than ones of RDX, suggesting that designing the bridged bis-triazoles-based derivatives with energy-rich substituents is an efficient method to obtain potential energetic compounds. Considering the detonation performance and impact sensitivity, -NH-(I), -N=N- (V), and -NH-NH- (VI) are favorable bridged groups between energetic moieties for designing efficient energetic materials (EMs).

A Family of Energetic Materials Based on 1,2,4-Oxadiazole and 1,2,5-Oxadiazole Backbones With Low Insensitivity and Good Detonation Performance

Design and synthesis of new compounds with both high detonation performances and good safety properties have always been a formidable task in the field of energetic materials. By introducing -ONO₂ and -NHNO₂ moieties into 1,2,4-oxadiazole- and 1,2,5-oxadiazole-based backbones, a new family of energetic materials, including ammonium 3-nitramino-4-(5-hydroxymethyl-1,2,4-oxadiazol-3-yl)-furazan (4), 3,3′-bis[5-nitroxymethyl-1,2,4-oxadiazol-3-yl]-4,4′-azofuroxan (6), [3-(4-nitroamino-1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazol-5-yl]-methylene nitrate (8), and its energetic ionic salts (10–12), were synthesized and fully characterized. The energetic and physical properties of the materials were investigated through theoretical calculations and experimental determination. The results show that the oxadiazole-based compounds exhibit high enthalpy of formations, good detonation performances, and extraordinary insensitivities. In particular, the hydrazinium salt (11) shows the best energetic properties (11: d = 1.821 g cm⁻³; P = 35.1 GPa, v_D = 8,822 m s⁻¹, IS = 40 J, FS > 360N). The ESP and Hirshfeld surface analysis indicated that a large number of hydrogen bonds as well as π-π stacking interactions within molecules might be the key reason for their low sensitivities and high energy-density levels.

5,6-Fused bicyclic tetrazolo-pyridazine energetic materials

Two 5,6-fused tetrazolo-pyridazine compounds were synthesized and characterized, which exhibited high thermal stability, excellent energetic properties and low mechanical sensitivity.

Energetic N-azidomethyl derivatives of polynitro hexaazaisowurtzitanes series: CL-20 analogues having the highest enthalpy

Novel energetic components for rocket propellants, based on polynitro hexaazaisowurtzitanes, have been prepared with high enthalpies of formation that significantly exceed that of CL-20.