Nitrogen-Rich Salts Based on Energetic Nitroaminodiazido[1,3,5]triazine and Guanazine

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.

Detonation properties and impact sensitivities of trinitromethane derivatives of three-membered heterocyclic ring compounds

We have carried out the design and theoretical investigation of a series of trinitromethane derivatives of three-membered heterocyclic ring compounds - aziridine, 1H-azirine, diaziridine, 1H-diazirine, triaziridine, 1H-triazirene, oxaziridine, oxadiaziridine, dioxaziridine, oxirane, and dioxirane - in search for new high energy density materials (HEDM). We have estimated the properties relevant to HEDMs of the proposed molecules using Density Functional Theory (B3LYP/aug-cc-pVDZ). The results show that most of the molecules have a high value of solid-phase heat of formation, crystal density, detonation velocity and pressure with satisfying values for impact sensitivities. We have identified some of these molecules, 1-(triinitromethyl)diaziridine, 2-(trinitromethyl)-1-nitro-1H-azirine, and (2-(trinitromethyl)-3-nitrooxirane) are potential candidates of energetic molecules among the 60 molecules we investigated. As most of them are having a high positive oxygen balance, they can be recommended for use as oxidisers in solid propellants.

Phenol as a Modulator in the Chemical Reactivity of 2,4,6-Trichloro-1,3,5-triazine: Rules of the Game II

2,4,6-Trichloro-1,3,5-triazine (TCT) is a privileged core that has the capacity to undergo sequential nucleophilic substitution reactions. Three nucleophiles, namely phenol, thiol and amine, were studied and the preferential order of incorporation on TCT was found to be first phenol, second thiol and third amine. The introduction of phenol was achieved at −20°C. The incorporation of this nucleophile in TCT helped to replace the third ‘Cl’ at 35°C, which is compatible with a biological context. The atomic charges on ‘Cl’ calculated by theoretical approaches were consistent with the experimental findings.

Investigating Triorthogonal Chemoselectivity. Effect of Azide Substitution on the Triazine Core

An example of triorthogonal chemoselectivity is reported here for the first time. In this regard, a series of 43 reactions were performed using tridentate s-triazine as a model. In all of the possible cases, the three substitutions were carried out using different nucleophiles at a temperature compatible with biological systems.

Amino-tetrazole functionalized fused triazolo-triazine and tetrazolo-triazine energetic materials

In this study, two insensitive energetic compounds using fused triazolo-triazine and tetrazolo-triazine as the framework, one amino and one tetrazole as functional groups, were prepared through a two-step reaction.

Synthesis of energetic salts containing three heterocyclic anions by a one-pot condensation reaction

Energetic ionic salts 1 and 2 containing three heterocyclic anions were prepared in a one-pot reaction using 1,3,5-benzenetricarboxaldehyde, aminoguanidine salts, and organic energetic salts (5-nitrotetrazole and 3,5-dinitro-1,2,4-triazole ammonium salt).

Stabilization of an intramolecular hydrogen-bond block in an s-triazine insensitive high-energy material

A unique intramolecular hydrogen-bond block was stabilized in s-triazine insensitive high-energy materials with face-to-face stacking.

Density functional study of guanidine-azole salts as energetic materials

A series of guanidine cations and azole anions were designed for use as energetic salts. Their geometrical structures were optimized by the density functional theory (DFT) method. The counter ions were matched by the similar magnitude of the electron affinity (EA) of the cation and the ionization potential (IP) of the anion. The densities, heats of formation, detonation parameters, and impact sensitivity were predicted. The incorporation of guanidine cations and diazole anions are favorable to form thermal stable salts except cation A1. The diaminoguanidine cation has greater impact on the density and detonation properties of the salts than the triaminoguanidine cation. 2-Amino-3-nitroamino-4,5-nitro-dinitropyrazole is the best anion for advancing the detonation performance among all the anions. Incorporating the C=O bond into the guanidine cations enhances the density and detonation performance of the guanidine-azole salts. The salts containing III1–III4 anion have better detonation properties than HMX, indicating that these salts are potential energetic compounds. Compared with RDX or HMX, some salts with diaminoguanidine cation display lower impact sensitivity.

Computational study of azole salts as high-energy materials

The crystal densities, heats of formation (HOFs), detonation properties, and impact sensitivities of a series of azole salts were investigated by the density functional theory and volume-based thermodynamics calculations. The HOFs of cations and anions and lattice energies were obtained based on the Born–Haber energy cycles. The detonation parameters (Q, D, and P) of 18 energetic salts have been calculated by the Kamlet–Jacobs equations with the calculated density and HOFs. The outcomes reflected that the hydroxylammonium cation has greater impact on the density and detonation properties of the azole salts than the hydrazine cation. Among all of the series salts under investigation, 2-amino-3-nitroamino-4,5-dinitropyrazole and 3-nitroamino-4,5-dinitropyrazole anions have greater HOFs and better detonation performances than other anions. In summary, the incorporations of all the cations studied here with the 2-amino-3-nitroamino-4,5-dinitropyrazole or 3-nitroamino-4,5-dinitropyrazole anions can be considered as potential high-energy salts.

Strategy for designing stable and powerful nitrogen-rich high-energy materials by introducing boron atoms

One of the most important aims in the development of high-energy materials is to improve their stability and thus ensure that they are safe to manufacture and transport. In this work, we theoretically investigated open-chain N₄B₂ isomers using density functional theory in order to find the best way of stabilizing nitrogen-rich molecules. The results show that the boron atoms in these isomers are aligned linearly with their neighboring atoms, which facilitates close packing in the crystals of these materials. Upon comparing the energies of nine N₄B₂ isomers, we found that the structure with alternating N and B atoms had the lowest energy. Structures with more than one nitrogen atom between two boron atoms had higher energies. The energy of N₄B₂ increases by about 50 kcal/mol each time it is rearranged to include an extra nitrogen atom between the two boron atoms. More importantly, our results also show that boron atoms stabilize nitrogen-rich molecules more efficiently than carbon atoms do. Also, the combustion of any isomer of N₄B₂ releases more heat than the corresponding isomer of N₄C₂ does under well-oxygenated conditions. Our study suggests that the three most stable N₄B₂ isomers (BN13, BN24, and BN34) are good candidates for high-energy molecules, and it outlines a new strategy for designing stable boron-containing high-energy materials. Graphical abstract The structural characteristics, thermodynamic stabilities, and exothermic properties of nitrogen-rich N₄B₂ isomers were investigated by means of density functional theory.

13 C and 15 N NMR spectra of high-energy polyazidocyanopyridines

¹³ C and ¹⁵ N NMR spectra of high-energy 2,4,6-triazidopyridine-3,5-dicarbonitrile, 2,3,5,6-tetraazidopyridine-4-carbonitrile and 3,4,5,6-tetraazidopyridine-2-carbonitrile are reported. The assignment of signals in the spectra was performed on the basis of density functional theory calculations. The molecular geometries were optimized using the M06-2X functional with the 6-311+G(d,p) basis set. The magnetic shielding tensors were calculated by the gauge-independent atomic orbital method with the Tao-Perdew-Staroverov-Scuseria hybrid functional known as TPSSh. In all the calculations, a polarizable continuum model was used to simulate solvent effects. This approach provided accurate predictions of the ¹³ C and ¹⁵ N chemical shifts for all the three compounds despite complications arising due to non-coplanar arrangement of the azido groups in the molecules. It was found that the ¹⁵ N chemical shifts of the N_α atoms in the azido groups of 2,4,6-triazidopyridines correlate with the ¹³ C chemical shifts of the carbon atoms attached to these azido groups. Copyright © 2016 John Wiley & Sons, Ltd.

Materials with good energetic properties resulting from the smart combination of nitramino and dinitromethyl group with furazan

The combination of nitramino and dinitromethyl group with furazan gave novel energetic materials with good energetic properties.

Structures and properties of energetic cations in energetic salts

Energetic cations play important roles in energetic performance, which may attribute to the diverse backbones and substituted groups of energetic cations. This review emphasizes the roles of backbones and substituted groups in the energetic performance of energetic salts.

Novel trinitroethanol derivatives: high energetic 2-(2,2,2-trinitroethoxy)-1,3,5-triazines

The multicomponent reaction of 2,4,6-trichloro-1,3,5-triazine with potassium trinitromethane and trinitroethanol was exploited for the first synthesis of the hetaryl trinitroethyl ethers.

Structural Properties of High-Energy N12C6 Molecules: Cyclic Hexamers of NCN

Molecules with high nitrogen content are of interest for their potential as high-energy materials. However, many molecules with 100% nitrogen content are unstable and dissociate with low barriers, which limits practical applications. In the present study, cyclic hexamers of the basic unit NCN (70% nitrogen by mass) are studied to determine the structural features and bonding characteristics that lead to more stable molecules. Double- and triple-bonded NCN units are compared to determine which form of NCN contributes the greater stability. Theoretical calculations using density functional theory and couple-cluster theory are carried out on a series of N12C6 molecules to determine trends in stability. Energetic and structural trends, as well as differences between DFT and coupled-cluster theory, are calculated and discussed.

Tandem deprotonation/azide-tetrazole tautomerization of 4,6-diazido-N-nitro-1,3,5-triazin-2-amine in dimethylsulfoxide solutions: a theoretical study

4,6-Diazido-N-nitro-1,3,5-triazin-2-amine (2) is a new promising high-energy organic compound that isomerizes in dimethylsulfoxide (DMSO) solutions to form unknown products with interesting 13C and 15N NMR spectroscopic characteristics. To identify these products, the relative energies and the 13C and 15N chemical shifts were calculated for various prototropic and valence isomers of 2. It was found that this diazide in DMSO solutions exists in equilibrium with the deprotonated form of 5-azido-N-nitrotetrazolo[1,5-a][1,3,5]triazin-7-amine (8). The anion 8 is also observed in DMSO solutions of energetic salts derived from 2 and guanidines or 4H-1,2,4-triazol-4-amines. The tandem transformations of 2 in DMSO solutions found may be of interest from both theoretical and practical points of view, for instance, in the synthesis of new energetic materials, using the reactions of anion 8 with various electrophilic agents.

New thermally stable energetic materials: synthesis and characterization of guanylhydrazone substituted furoxan energetic derivatives

The synthesis and characterization of guanylhydrazone substituted furoxan energetic derivatives with good thermal stabilities and detonation performance are now reported.

Dense nitrogen-rich energetic materials: a study of 5,5'-bis(1H-tetrazolyl)amine [corrected]

5,5'-bis(1H-tetrazolyl)amine (BTA), a nitrogen rich molecular solid has been investigated under compression at room temperature [corrected]. Powder x-ray diffraction using synchrotron radiation and micro-Raman spectroscopy were carried out to pressures up to 12.9 GPa. BTA conserves the crystalline structure of its room condition phase up to the highest pressure, i.e., an orthorhombic unit cell (Pbca). A fit of the isothermal compression data to the Birch-Murnaghan equation of state reveals the high compressibility of BTA. An analysis of the volume change with pressure yields a bulk modulus and its derivative similar to that of high-nitrogen content molecular crystals. Upon laser heating to approximately 1100 K, the sample decomposed while pressurized at 2.1 GPa, resulting in a graphitic compound. Finally, numerical simulations demonstrate that the minimum energy conformation is not experimentally observed since a higher energy conformation allows for a more stable dense packing of the BTA molecules.

Structure, Thermal Behaviour, and Energetic Properties of 4-Amino-1,2,4-triazole Dinitroguanidine Salt

A novel nitrogen-rich energetic compound 4-amino-1,2,4-triazole dinitroguanidine salt (4-ATDNG) was synthesized and fully characterized. Its crystal, thermal behaviour, and detonation properties were investigated by X-ray diffraction, thermogravimetry-derivative thermogravimetry-differential scanning calorimetry (TG-DTG-DSC) coupling system, and the Kamlet–Jacobs equation. In view of the obtained values such as the critical temperature of thermal explosion (Tb, 186.36°C), entropy of activation (ΔS≠, 60.22 J mol–1 k–1), enthalpy of activation (ΔH≠, 143.24 kJ mol–1), free energy of activation (ΔG≠, 116.34 kJ mol–1), detonation pressure (P, 29.78 GPa), detonation velocity (V, 8.28 km s–1), and impact sensitivity (h50 = 135 cm), it is proposed that 4-ATDNG possesses excellent thermal stability and has the potential to be a useful energetic material in the future.

Structure and properties of 1-amino-2-nitroguanidinium nitrate

A nitrogen-rich energetic material 1-amino-2-nitroguanidinium nitrate was fully investigated.

Synthesis and characterization of a new family of energetic salts based on guanidinium cation containing furoxanyl functionality

A new family of energetic salts based on a guanidinium cation containing furoxanyl functionality was synthesized and well characterized.

Synthesis and characterization of new energetic derivatives containing a high nitrogen content moiety and picryl group: a new strategy for incorporating the picryl functionality

The synthesis of new picryl derivatives containing a high nitrogen content moiety from new starting materials are reported.

Nitrogen-rich energetic monoanionic salts of 3,4-bis(1H-5-tetrazolyl)furoxan

3,4-Bis(1H-5-tetrazolyl)furoxan (H(2)BTF, 2) and its monoanionic salts that contain nitrogen-rich cations were readily synthesized and fully characterized by multinuclear NMR ((1)H, (13)C) and IR spectroscopy, differential scanning calorimetry (DSC), and elemental analyses. Hydrazinium (3) and 4-amino-1,2,4-triazolium (7) salts crystallized in the monoclinic space group P2(1)/n and have calculated densities of 1.820 and 1.764 g cm(-3), respectively. The densities of the energetic salts range between 1.63 and 1.79 g cm(-3), as measured by a gas pycnometer. Detonation pressures and detonation velocities were calculated to be 23.1-32.5 GPa and 7740-8790 m s(-1), respectively.