2,2'-Azobis(1,5'-bitetrazole) with a N10 Chain and 1,5'-Bitetrazolate-2N-oxides: Construction of Highly Energetic Nitrogen-Rich Materials Based on C-N-Linked Tetrazoles

Taming of Triazole, Tetrazole, and Azido Groups: Nitrogen-Rich Energetic Materials with High Thermal Stabilities

Nitrogen-rich energetic materials are of interest due to their potential use as high-energy-density materials in various applications. However, most compounds with a high nitrogen content show poor thermal stabilities, which may limit their use in certain applications. In pursuit of nitrogen-rich energetic materials, this study presents the synthesis and characterization of two nitrogen rich energetic compounds, namely 3-azido-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-amine (3, C3H3N11, N%: 79.78) and (E)-1,2-bis(3-azido-1-(1H-tetrazol-5-yl)-1H-1,2,4-triazol-5-yl) diazene (7, C6H2N22, N%: 80.62). Compounds 3 and 7 have high thermal stabilities of 216 and 221 °C, respectively, making them the most thermally stable among metal-free primary explosives. Additionally, they show good energetic performance (vD: 8345 m s-1; P: 25.17 GPa; vD: 8275 m s-1; P: 25.57 GPa), making them potential candidates for metal-free high energy primary explosive. The energetic salts of 3 and 7 were also investigated. Among them, hydrazinium salt 11 displays better energetic performance (vD: 9089 m s-1; P: 30.55 GPa), which was on par with those of cyclotetramethylene tetranitramine (HMX). This research contributes to the exploration of nitrogen-rich energetic materials with potential applications in various fields.

Bifunctional Nitrogen-Rich Heterocyclic Compounds: Synthesis, Photoluminescence and Energetic Properties

Nitrogen-rich heterocyclic frameworks have attracted enormous interest in organic chemistry and materials science. However, their potential for developing photoluminescent materials remains underexplored due to their relatively low molecular stabilities. In this work, two tricyclic fused nitrogen-rich fluorescent heterocycles were synthesized and characterized. The photophysical properties of the synthesized 4 and 5 were investigated through theoretical and experimental studies. In addition, their physicochemical and energetic properties and the performance as an additive to the perovskite absorption layer of the perovskite solar cell were also studied.

Catalytic Tetrazole Synthesis via [3+2] Cycloaddition of NaN3 to Organonitriles Promoted by Co(II)-complex: Isolation and Characterization of a Co(II)-diazido Intermediate

The [3+2] cycloaddition of sodium azide to nitriles to give 5-substituted 1H-tetrazoles is efficiently catalyzed by a Cobalt(II) complex (1) with a tetradentate ligand N,N-bis(pyridin-2-ylmethyl)quinolin-8-amine. Detailed mechanistic investigation shows the intermediacy of the cobalt(II) diazido complex (2), which has been isolated and structurally characterized. Complex 2 also shows good catalytic activity for the synthesis of 5-substituted 1H-tetrazoles. These are the first examples of cobalt complexes used for the [3+2] cycloaddition reaction for the synthesis of 1H-tetrazoles under homogeneous conditions.

Highly Dense N-N-Bridged Dinitramino Bistriazole-Based 3D Metal-Organic Frameworks with Balanced Outstanding Energetic Performance

Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal-organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N'-([4,4'-bi(1,2,4-triazole)]-3,3'-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n (K-MOF) and sodium [Na2BDNBT]n (Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm-3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557-9724 m/s, detonation pressure (DP) of 30.41-36.97 GPa, positive heat of formation of 122.52-242.25 kJ mol-1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30-40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2- and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20.

Pushing the Limit of Oxygen Balance on a Benzofuroxan Framework: K2DNDP as an Extremely Dense and Thermally Stable Material as a Substitute for Lead Azide

Because of environmental and health impacts, there is an ongoing necessity to develop sustainable primary explosives to replace existing lead-based analogues. Now we describe a potential primary explosive, dipotassium 4,6-dinitro-5,7-dioxidobenzo[c][1,2,5]oxadiazole 1-oxide (K2DNDP), which exhibits an excellent thermal stability (Tdec = 281 °C), positive oxygen balance (+4.79%), and a calculated crystal density of ρ = 2.274 g cm-3 at 100 K. Its physicochemical properties concomitantly with its straightforward synthesis make it a potential replacement for lead-based initiators.

Enhancing Conjugation Effect to Develop Nitrogen-Rich Energetic Materials with Higher Energy and Stability

This work reports a strategy by enhancing conjugation effect and synthesizes a symmetrical and planar compound, 1,2-bis (4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazol-2-yl)diazene (NL24). The incorporation of azo and 1,2,3-triazole moieties manifests a synergistic effect, amplifying the conjugation effect of the azo bridge and thereby elevating the stability of NL24 (Td: 263 °C, IS: 7 J). Notably, NL24, possessing a structural configuration comprising four tetrazoles harboring a total of 24 nitrogen atoms, exhibits excellent detonation performances (ΔHf: 6.06 kJ g-1, VD: 9002 m s-1). This strategy achieves the balance of energy and stability of polycyclic tetrazoles and provides a direction for high-performance energetic materials.

Synthesis of Bridged Tetrazoles with Promising Properties and Potential Applications by a One-Step Finkelstein Reaction

Numerous nitramine bridged compounds which show promising combinations of properties have already been identified in the area of energetic materials. In this work, four new nitrazapropane bridged tetrazoles, as well as four new trinitrazaheptane tetrazoles and three oxapropane bridged tetrazoles were synthesized and fully characterized. These new compounds can all be synthesized by a simple, one-step synthesis using Finkelstein conditions. All of these new energetic materials were characterized using NMR spectroscopy, single crystal X-ray diffraction, vibrational analysis and elemental analysis. The thermal behaviour of these compounds was studied by differential thermal analysis (DTA) and partly by thermogravimetric analysis (TGA). The BAM standard method was used to determine the sensitivities towards impact (IS) and friction (FS). The enthalpies of formation were calculated at the CBS-4M level, and the energetic performances were calculated using the EXPLO5 (V6.06.01) computer code. The properties of the new compounds were compared to each other as well as to the known energetic material RDX. Moreover, the iron(II) and copper(II) perchlorate complexes with 1,3-bis-1,1-tetrazolylnitrazapropane as ligand were prepared and investigated.