The synthesis, characterization, and energetic properties of diazido heteroaromatic high-nitrogen C-N compound, 3,6-diazido-1,2,4,5-tetrazine (DiAT), are reported. Its normalized heat of formation (NDeltaHf), experimentally determined using an additive method, is shown to be the highest positive NDeltaHf compared to all other organic molecules. The unexpected azido-tetrazolo tautomerizations and irreversible tetrazolo transformation of DiAT are remarkable compared to all other polyazido heteroaromatic high-nitrogen C-N compounds, for example, 2,4,6-triazido-1,3,5-triazine; 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine; 4,4',6,6'-tetra(azido)azo-1,3,5-triazine; and 2,5,8-tri(azido)-1,3,4,6,7,9,9b-heptaazaphenalene (heptazine).

The synthesis of compounds known as high-nitrogen energetic materials has been the focus of our group for the past decade. High-nitrogen compounds form a unique class of energetic materials deriving most of their energy from their very high positive heats of formation rather than from oxidation of the carbon backbone, as with traditional energetic materials.[1] The high nitrogen content typically leads to high densities, and the low amount of hydrogen and carbon also allows for a good oxygen balance to be achieved more easily; oxygen balance is a measure of the oxygen/fuel ratio in a compound. We have demonstrated that high-nitrogen materials can show remarkable insensitivity to electrostatic discharge, friction, and impact.One high-nitrogen system extensively studied by our group is the 1,2,4,5-tetrazine ring. We have synthesized several energetic 1,2,4,5-tetrazines having applications as propellants, explosives, and pyrotechnic ingredients.[2] In the pursuit of new high-nitrogen materials with novel properties, we have recently been studying azo-1,2,4,5-tetrazines.We became interested in the synthesis of azo-1,2,4,5-tetrazines from our previous studies on azo-1,2,5-oxadiazoles. We found that 327 kJ mol À1 of energy is gained in the transformation of 4,4'-hydrazobis-(1,2,5-oxadiazol-3-amine) to 4,4'-azobis(1,2,5-oxadiazol-3-amine) (Scheme 1). The latter material is a thermally stable, insensitive explosive.[3] Extrapolating from these data, 3,3'-azobis(6-amino-1,2,4,5-tetrazine)

The performance of a high explosive is measured by its detonation velocity (v D (km sec À1 )) and detonation pressure (P CJ (kbar)). These parameters are determined by the oxygen balance (OB CO ), [1a] density (1), and heat of formation (DH f ), [1b] the higher the oxygen balance, density, and heat of formation, the better the performance. The energy of traditional polynitro compounds (Scheme 1) is primarily derived from the combustion of the carbon backbone using the oxygen carried by the nitro group. [2] For modern polynitro compounds (Scheme 2), the performance is enhanced not only by an excellent oxygen balance but also by a ring/cage strain which improves both the heat of formation and density. [4] Recently, a new class of energetic compounds containing a large fraction of nitrogen has been investigated. [5][6][7][8] These "high-nitrogen" compounds form a unique class of energetic materials [5a, 9] whose energy is derived from their very high positive heat of formation rather than from the combustion of the carbon backbone or the ring/cage strain (Scheme 3). The high heat of formation is directly attributable to the large number of inherently energetic NÀN and CÀN bonds.High-nitrogen compounds containing polyazides possess even higher heats of formation because their energy content rapidly increases with the number of energetic azido groups in the molecule. However, they are notorious for their extreme sensitivity [10a] to spark, friction, and impact (H 50 ) [10b] as well as poor thermal stability, [10a, 11, 12] so their applications are very limited. Examples include 3,6-diazido-1,2,4,5-tetrazine [13] and cyanuric azide (2,4,6-triazido-1,3,5-triazine; [14] Scheme 4).

Primary explosives are used in small quantities to generate a detonation wave when subjected to a flame, heat, impact, electric spark, or friction. Detonation of the primary explosive initiates the secondary booster or main-charge explosive or propellant. Longterm use of lead azide and lead styphnate as primary explosives has resulted in lead contamination at artillery and firing ranges and become a major health hazard and environmental problem for both military and civilian personnel. Devices using lead primary explosives are manufactured by the tens of millions every year in the United States from primers for bullets to detonators for mining. Although substantial synthetic efforts have long been focused on the search for greener primary explosives, this unresolved problem has become a ''holy grail'' of energetic materials research. Existing candidates suffer from instability or excessive sensitivity, or they possess toxic metals or perchlorate. We report here four previously undescribed green primary explosives based on complex metal dian- ions and environmentally benign cations, (cat) 2[M II (NT)4(H2O)2] (where cat is NH 4؉ or Na ؉ , M is Fe 2؉ or Cu 2؉ , and NT ؊ is 5-nitrotetrazolato-N 2 ). They are safer to prepare, handle, and transport than lead compounds, have comparable initiation efficiencies to lead azide, and offer rapid reliable detonation comparable with lead styphnate. Remarkably, they possess all current requirements for green primary explosives and are suitable to replace lead primary explosives in detonators. More importantly, they can be synthesized more safely, do not pose health risks to personnel, and cause much less pollution to the environment.copper ͉ green ͉ iron ͉ primary explosives ͉ tetrazole

No abstract

The synthesis of low-density, nanoporous materials has been an active area of study in chemistry and materials science dating back to the initial synthesis of aerogels. These materials, however, are most often limited to metal oxides, e.g., silica and alumina, and organic aerogels, e.g., resorcinol/formaldehyde, or carbon aerogels, produced from the pyrolysis of organic aerogels. The ability to form monolithic metallic nanocellular porous materials is difficult and sometimes elusive using conventional methodology. Here we report a relatively simple method to access unprecedented ultralow-density, nanostructured, monolithic, transition-metal foams, utilizing self-propagating combustion synthesis of novel transition-metal complexes containing high nitrogen energetic ligands. During the investigation of the decomposition behavior of the high-nitrogen transition metal complexes, it was discovered that nanostructured metal monolithic foams were formed in a post flame-front dynamic assembly having remarkably low densities down to 0.011 g cm(-3) and extremely high surface areas as high as 270 m(2) g(-1). We have produced monolithic nanoporous metal foams via this method of iron, cobalt, copper, and silver metals. We expect to be able to apply this to many other metals and to be able to tailor the resulting structure significantly.

We present data for batch-to-batch variation of silver nanoparticles (AgNPs) synthesized with orange peel extract. These samples were prepared in the CEM microwave for 15 min. The relative standard deviation (as a measure of precision) is provided and is, in most cases, less than 20%.

The synthesis and properties of various 1,2,4,5‐tetrazine explosives and energetic materials are described. These are the nitrate and perchlorate salts of 3,6‐diguanidino‐1,2,4,5‐tetrazine, the nitrate and perchlorate salts of 3,6‐diguanidino‐1,2,4,5‐tetrazine‐1,4‐di‐N‐oxide, 3,6‐bis(1H‐1,2,3,4‐tetrazol‐5‐ylamino)‐1,2,4,5‐tetrazine and its 1,4‐di‐N‐oxide derivative, 3,3′‐azobis(6‐amino‐1,2,4,5‐tetrazine) and its oxidation products.