Energetic Materials Based on 5,5′-Diamino-4,4′-dinitramino-3,3′-bi-1,2,4-triazole

Zwitterionic Energetic Materials: Synthesis, Structural Diversity and Energetic Properties

Zwitterionic compounds are an emergent class of energetic materials and have gained synthetic interest of many in the recent years. Due to their better packing efficiencies and strong inter/intramolecular electrostatic interactions, they often ensue superior energetic properties than their salt analogues. A systematic review from the perspective of design, synthesis, and physicochemical properties evaluation of the zwitterionic energetic materials is presented. Depending on the parent ring(s) used for the synthesis and the type of moieties bearing positive and negative charges, different classes of energetic materials, such as primary explosives, secondary explosives, heat resistant explosives, oxidizers, etc., may result. The properties of some of the energetic zwitterionic compounds are also compared with analogous energetic salts. This review will encourage readers to explore the possibility of designing new zwitterionic energetic materials.

Theoretical study of a series of 1,2-diazete based trinitromethyl derivatives as potential energetic compounds

CONTEXT

Explosive properties of novel potential high energy density materials of a series of 1,2-diazete-based molecules with trinitromethyl functional group were investigated computationally. All the sixty seven molecules were optimised to obtain their molecular geometries and electronic structures. Electrostatic potential analysis was also carried out in the determination of different parameters. The calculations indicate that the majority of the compounds have high positive heat of formations, high density and good detonation performance greater than that of traditional energetic materials like RDX and HMX. They are also having comparable values of impact sensitivity. These features promise their potential to be used as energetic materials for future applications. Most of the designed molecules are having high positive oxygen balance values so that the study of these molecules can also be extended as potential candidates for oxidisers in solid propellants.

METHODS

Optimisation and vibrational frequency analysis of the studied molecules were done with density functional theory using B3LYP/aug-cc-pVDZ as the basis set to zero imaginary frequencies using Gaussian 09. Electrostatic potential analysis were carried using the Multiwfn program.

Nitrification Progress of Nitrogen-Rich Heterocyclic Energetic Compounds: A Review

As a momentous energetic group, a nitro group widely exists in high-energy-density materials (HEDMs), such as trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), etc. The nitro group has a significant effect on improving the oxygen balance and detonation performances of energetic materials (EMs). Moreover, the nitro group is a strong electron-withdrawing group, and it can increase the acidity of the acidic hydrogen-containing nitrogen-rich energetic compounds to facilitate the construction of energetic ionic salts. Thus, it is possible to design nitro-nitrogen-rich energetic compounds with adjustable properties. In this paper, the nitration methods of azoles, including imidazole, pyrazole, triazole, tetrazole, and oxadiazole, as well as azines, including pyrazine, pyridazine, triazine, and tetrazine, have been concluded. Furthermore, the prospect of the future development of nitrogen-rich heterocyclic energetic compounds has been stated, so as to provide references for researchers who are engaged in the synthesis of EMs.

Nucleophilic Catalyzed Structural Binary Cleavage of a Fused [5,5]-Bicyclic Compound

Structural binary cleavage of 3,7-diamino-2,6-dinitro-1H,5H-pyrazolo-[1,2-a]pyrazole-1,5-dione 3, under nucleophilic conditions, leads to the formation of a monocyclic pyrazole unit of 5-amino-4-nitro-1,2-dihydro-3H-pyrazol-3-one, 4. Additionally, various salts of the pyrazole ring were synthesized and fully characterized. Detonation properties and mechanical sensitivities of 4 and other new compounds are remarkably improved compared to 3. This simple and efficient strategy is highly desirable for future studies on the development of insensitive and high performing materials.

Cu-Enabled [3 + 2] Annulation of In Situ Formed Nitrile Ylides with Aryldiazonium Salts: Access to 5-Cyano-1,2,4-Triazoles

The unified construction of cyano-substituted 1,2,4-triazoles, particularly the 5-cyano counterparts, remains underdeveloped. Herein we describe a three-component method to access a wide range of 1-aryl 5-cyano-1,2,4-triazoles using readily available 2-diazoacetonitriles, nitriles, and aryldiazonium salts. This regiospecific synthesis relies on the dipolar [3 + 2] annulation of the in situ formed nitrile ylides with aryldiazonium salts. Furthermore, this protocol can be amendable to gram-scale synthesis, chemical transformations of the nitrile moieties, and access to chiral bis(cyano-triazole)-1,1'-naphthalene, which would all be likely applicable in the synthesis of structurally diverse bioactive compounds and novel bidentate ligands for asymmetric catalysis.

Synthesis, crystal structure, and properties of energetic copper(II) compound based on 3,5-dinitrobenzoic acid and imidazole

Energetic copper(II) compound was synthesized based on 3,5-dinitrobenzoic acid (HDNBA) and imidazole (IMI), and characterized by elemental analysis and FTIR characterization. Single-crystal X-ray diffraction analysis revealed that [Cu(IMI)2(DNBA)2] (1) belongs to monoclinic, pertains to P21/c space group, β= 96.195(2) and Dc= 1.742 g cm–3. Cu(II) ion was coordinated to a plane tetragon, by two oxygen atoms and two nitrogen atoms from different DNBA ions and IMI ligands, which of them present typical monodentate coordination mode. Differential scanning calorimetry (DSC) was applied to assess the thermal decomposition behavior of 1. The non-isothermal kinetics parameters were calculated by the Kissinger’s method, Ozawa’s method and Starink’s method, respectively. Impact sensitivity and friction Sensitivity were also determined by standard method. In the end, the catalytic effects on the decomposition of ammonium perchlorate (AP), HMX and RDX of 1 were studied by DSC. All results supported the potential applications of the energetic complex 1 as additive of solid rocket propellant.

Synthesis and properties of azamonocyclic energetic materials with geminal explosophores

Diversity-oriented synthesis of energetic pyrimidine structures with geminal explosophoric groups of geminal dinitro and azido-nitro groups via a novel reductive cleavage and oxidative coupling strategy is reported. Fluorine has also been introduced for the first time based on the nucleophilic coupling process. The obtained energetic pyrimidines are investigated via X-ray diffraction and theoretical techniques of electrostatic potential and proton affinity calculations. Both experimental and calculation results showed impressive detonation performances and good application prospects of the energetic pyrimidine structures. Among them, DNNC exhibited great promise as a green oxidant in solid propellant formulations to replace ammonium perchlorate (AP). TNHA (ρ = 1.79 g cm-3, D = 8537 m s-1, P = 32.69 Gpa) and TNHF (ρ = 1.85 g cm-3, D = 8517 m s-1, P = 32.64 Gpa) proved to be ideal candidates for high explosives due to their high densities and detonation properties. Moreover, TNHA could also be applied as a potential underwater explosive owing to its great heat of formation.

Sandwich-like low-sensitive nitroamine explosives stabilized by hydrogen bonds and π–π stacking interactions

Sandwich-like low-sensitive nitroamine explosives were developed which expand the structural category of low-sensitive energetic materials and could give references to the design of new low-sensitive energetic materials.

Computational study of energetic derivatives of 3,3′-bridged ditriazoles

A series of energetic bridged ditriazole was designed by incorporating different bridges and substituents into 4H-1,2,4-triazole ring. The geometrical structures, heats of formation, detonation properties, electronic structures, thermodynamic properties, free spaces, impact sensitivities, and thermal stabilities of the designed compounds were evaluated by employing density functional theory. The results elucidate that the –N3 substituent and –N=N– bridge can sufficiently increase their heats of formation. The calculated values of detonation properties show that –NF2, –ONO2, –O–, and –N=N(O)– are useful structural fragments to improve their detonation performance. The incorporation of the oxy (–O–) bridge increases their HOMO–LUMO energy gaps. An analysis of h50 values indicate that most of the designed compounds are less sensitive. The N(ring)-NO2 bond in the majority of the derivatives may be a possible trigger bond in thermal decomposition process. The incorporation of –CH2–CH2– and –O– is helpful to enhance their thermal stabilities. Based on appropriate thermal stabilities and superb detonation properties, six compounds were screened as promising high energy density compounds.

A facile synthesis of energetic salts based on fully nitroamino-functionalized [1,2,4]triazolo[4,3-b][1,2,4]triazole

Promising high-energy-density materials: energetic salts based on fully nitroamino-functionalized [1,2,4]triazolo[4,3-b][1,2,4]triazole.

New Strategy for Enhancing Energetic Properties by Regulating Trifuroxan Configuration: 3,4-Bis(3-nitrofuroxan-4-yl)furoxan

It is of current development to construct high-performance energetic compounds by aggregation of energetic groups with dense arrangement. In this study, a hydrogen-free high-density energetic 3,4-bis(3-nitrofuroxan-4-yl)furoxan (BNTFO-I) was designed and synthesized in a simple, and straightforward manner. Its isomer, 3,4-bis(4-nitrofuroxan-3-yl)furoxan (BNTFO-IV), was also obtained by isomerization. The structures of BNTFO-I and BNTFO-IV were confirmed by single-crystal X-ray analysis for the first time. Surprisingly, BNTFO-I has a remarkable calculated crystal density of 1983 g cm-3 at 296 K, which is distinctly higher than BNTFO-IV (1.936 g cm-3, 296 K), and ranks highest among azole-based CNO compounds yet reported. It is noteworthy that BNTFO-I exhibits excellent calculated detonation properties (vD, 9867 m s-1, P, 45.0 GPa). The interesting configuration differences of BNTFO-I and BNTFO-IV provide insight into the design of new advanced energetic materials.

New green energetic materials based on unsymmetrically substituted pyrazole-tetrazines and their hydroperchlorates

Some novel metal-free energetic materials were synthesized. Structural diversification of substituted tetrazines affects their physical and explosive properties making them have potential applications as green energetic materials.

C8N12O10: a promising energetic compound with excellent detonation performance and desirable sensitivity

A promising energetic molecule bis(4-nitro-1,2,5-oxadiazole-2-oxid-3-yl)-azo-1,2,4-oxadiazole was synthesized and characterized. It has high density, acceptable thermal stability, high heat of formation, outstanding detonation properties and desirable mechanical properties.

Energetic furazan–triazoles with high thermal stability and low sensitivity: facile synthesis, crystal structures and energetic properties

Mononitroamino-diamino and dinitramino-monoamino furazan–triazoles were designed and synthesized by a flexible method and showed excellent stability and high performance, respectively.

Synthesis of 3,5-ditetrazolyl-1,2,4-triazole-based complexes: a strategy for developing C–N-linked triheterocyclic energetic compounds

Two complexes based on the novel C–N-linked triheterocyclic compound 3,5-ditetrazolyl-1,2,4-triazole (DTT) were reported for the first time. The present study has contributed to the field of C–N-linked polyheterocyclic systems and has provided a new insight into the design and synthesis of new energetic materials.

Isomers of Dinitropyrazoles: Synthesis, Comparison and Tuning of their Physicochemical Properties

Three isomeric dinitropyrazoles (DNPs) were synthesized starting from readily available 1H-pyrazole by slightly improved methods than described in the literature. 3,4-Dinitropyrazole (3), 1,3-dinitropyrazole (4), and 3,5-dinitropyrazole (5) were obtained and compared to each other with respect to thermal stability, crystallography, sensitivity and energetic performance. Two isomers (3 and 4) show high densities (1.79 and 1.76 g cm^-3 ) and interesting thermal behavior as melt-castable materials (3: T_melt. =71 °C, T_dec. =285 °C; 5: T_melt. = 68 °C, T_dec. =171 °C). Furthermore, eight salts (sodium, potassium, ammonium, hydrazinium, hydroxylammonium, guanidinium, aminoguanidinium and 3,6,7-triamino-[1,2,4]triazolo[4,3-b][1,2,4]triazole (TATOT) of 3 and 5 were synthesized in order to tune performance and sensitivity values. These compounds were characterized using ¹ H, ¹³ C, ¹⁴ N, ¹⁵ N NMR and IR spectroscopy as well as mass spectrometry, elemental analysis and thermal analysis through differential scanning calorimetry. Crystal structures of 14 compounds were obtained (3-7, 10-12 and 15-20) by low-temperature single crystal X-ray diffraction. Impact, friction and electrostatic discharge (ESD) values were also determined by standard methods. The sensitivity values range between 8.5 and 40 J for impact and 240 N and 360 N for friction and show mainly insensitive character. The energetic performances were determined using recalculated X-ray densities, heats of formation and the EXPLO5 code and support the energetic character of the title compounds. The calculated energetic performances (V_D : 6245-8610 m s^-1 ; p_CJ : 14.1-30.8 GPa) were compared to RDX ((O₂ NNCH₂ )₃ ).

Design and Synthesis of Energetic Materials towards Versatile Applications by N-trinitromethyl and N-nitromethyl Functionalization of Nitroimidazoles

Modifying the properties of energetic materials is important not only for gaining insight into the relationship between structures and properties but also for multiple applications. A new family of energetic compounds, polynitroimidazoles featuring trinitromethyl, nitromethyl and methyl acetate moieties at the nitrogen position of heterocyclic rings were synthesized. The high-energy oxidizers 2-nitro and 4-nitro-1-(trinitromethyl)-1H-imidazoles were obtained by nitration of 1-acetonylpolynitroimidazoles in fuming HNO₃ and concentrated H₂ SO₄ . 4,5-Dinitro-1-(nitromethyl)-1H-imidazole and 4,5-dinitro-1-(acetate methyl)-1H-imidazole were afforded by using 68 % HNO₃ and concentrated H₂ SO₄ through controllable synthesis. All the intermediates and the target compounds were confirmed by X-ray diffraction. It is noteworthy that one of the N-trinitromethyl nitroimidazole derivatives showed high density (ρ: 1.88 g cm^-3 ), attractive positive oxygen balance (Ω: +18.3 %) and good detonation performance (D: 9003 m s^-1 ) exceeding those of ADN, while N-nitromethyl derivative behaved higher thermal stability and lower sensitivity in contrast to those of NG. N-acetate methyl derivative gave an interesting melt-castable property (T_m.p .: 86 ^o C, T_d : 224 ^o C), acceptable detonation performance as well as low sensitivity towards impact and friction (IS>40 J, FS>360 N), making it a competitive replacement for DNAN. These chemical and physical properties indicate that these novel materials show promising energetic performance towards future applications.

Formation of trinitromethyl functionalized 1,2,4-triazole-based energetic ionic salts and a zwitterionic salt directed by an intermolecular and intramolecular metathesis strategy

Energetic trinitromethyl bistriazole and its ionic salts, as well as an unexpected energetic-zwitterion featuring trinitromethyl and diazonium moieties, were synthesized via an intermolecular and intramolecular metathesis strategy.

Synthesis and properties of 5,5′-dinitramino-3,3′-bi(1,2,4-oxadiazole) and its energetic salts

In order to develop high energy density materials, 5,5′-dinitramino-3,3′-bi(1,2,4-oxadiazole) (3, DNABO), a new heterocyclic energetic compound, was synthesized by the simple nitration of 5,5′-diamino-3,3′-bi(1,2,4-oxadiazole) (2) with 95% fuming nitric acid.

A Strontium- and Chlorine-Free Pyrotechnic Illuminant of High Color Purity

The development of a red-light-emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community owing to potential regulations by the United States Environmental Protection Agency (U.S. EPA) regarding the use of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium-based red-light-emitting pyrotechnic compositions of high purity and color quality is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non-hygroscopic dilithium nitrogen-rich salt that serves as both oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military pyrotechnics communities for further development as they both have a vested interest in the development of environmentally conscious formulations.

Cooperative enhancement of the nonlinear optical response in conjugated energetic materials: A TD-DFT study

Conjugated energetic molecules (CEMs) are a class of explosives with high nitrogen content that posses both enhanced safety and energetic performance properties and are ideal for direct optical initiation. As isolated molecules, they absorb within the range of conventional lasers. Crystalline CEMs are used in practice, however, and their properties can differ due to intermolecular interaction. Herein, time-dependent density functional theory was used to investigate one-photon absorption (OPA) and two-photon absorption (TPA) of monomers and dimers obtained from experimentally determined crystal structures of CEMs. OPA scales linearly with the number of chromophore units, while TPA scales nonlinearly, where a more than 3-fold enhancement in peak intensity, per chromophore unit, is calculated. Cooperative enhancement depends on electronic delocalization spanning both chromophore units. An increase in sensitivity to nonlinear laser initiation makes these materials suitable for practical use. This is the first study predicting a cooperative enhancement of the nonlinear optical response in energetic materials composed of relatively small molecules. The proposed model quantum chemistry is validated by comparison to crystal structure geometries and the optical absorption of these materials dissolved in solution.

5,6-Di(2-fluoro-2,2-dinitroethoxy)furazano[3,4-b]pyrazine: a high performance melt-cast energetic material and its polycrystalline properties

A new high-energetic and insensitive melt-cast material was synthesized, and its polycrystalline properties were characterized and theoretically investigated.