Nitroaminofurazans with Azo and Azoxy Linkages: A Comparative Study of Structural, Electronic, Physicochemical, and Energetic Properties

The structural, electronic, and physicochemical properties of 4,4′-bis­(nitramino)­azofurazan and 4,4′-bis­(nitramino)­azoxyfurazan as high-energy density materials were compared. In addition, a new family of nitrogen-rich energetic salts based on these two nitroaminofurazans were synthesized and fully characterized. On the basis of experimental evidence and theoretical calculations, 4,4′-bis­(nitramino)­azoxyfurazan and its ionic derivatives were found to exhibit higher detonation velocities and pressures, and higher densities than their azofurazan analogues which supports the added value of introduction of the N-oxide moiety into energetic materials. The solid state features for the two nitroaminofurazans were studied in detail by X-ray diffraction and noncovalent interaction index which identify additional hydrogen-bonding and extensive edge-to-face π–π stacking interactions arising from the presence of the azoxy N-oxide

3,3′-Dinitroamino-4,4′-azoxyfurazan and Its Derivatives: An Assembly of Diverse N–O Building Blocks for High-Performance Energetic Materials

On the basis of a design strategy that results in the assembly of diverse N–O building blocks leading to energetic materials, 3,3′-dinitroamino-4,4′-azoxyfurazan and its nitrogen-rich salts were obtained and fully characterized via spectral and elemental analyses. Oxone (potassium peroxomonosulfate) is an efficient oxidizing agent for introducing the azoxy <i>N</i>-oxide functionality into the furazan backbone, giving a straightforward and low-cost synthetic route. On the basis of heats of formation calculated with Gaussian 03 and combined with experimentally determined densities, energetic properties (detonation velocity, pressure and specific impulse) were obtained using the EXPLO v6.01 program. These new molecules exhibit high density, moderate to good thermal stability, acceptable impact and friction sensitivities, and excellent detonation properties, which suggest potential applications as energetic materials. Interestingly, 3,3′-dinitroamino-4,4′-azoxyfurazan (<b>4</b>) has the highest calculated crystal density of 2.02 g cm^–3 at 173 K (gas pycnometer measured density is 1.96 g cm^–3 at 298 K) for <i>N</i>-oxide energetic compounds yet reported. Another promising compound is the hydroxylammonium salt (<b>6</b>), which has four different kinds of N–O moieties and a detonation performance superior to those of 1,3,5,7-tetranitrotetraazacyclooctane (HMX), and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclododecane (CL-20). Furthermore, computational results, viz., NBO charges and ESP, also support the superior qualities of the newly prepared compounds and the design strategy

Balancing Excellent Performance and High Thermal Stability in a Dinitropyrazole Fused 1,2,3,4-Tetrazine

The key to successfully designing high-performance and insensitive energetic compounds for practical applications is through adjusting the molecular organization including both fuel and oxidizer. Now a superior hydrogen-free 5/6/5 fused ring energetic material, 1,2,9,10-tetranitrodipyrazolo­[1,5-d:5′,1′-f]­[1,2,3,4]­tetrazine (<b>6</b>) obtained from 4,4′,5,5′-tetranitro-2<i>H</i>,2′<i>H</i>-3,3′-bipyrazole (<b>4</b>) by N-amination and N-azo coupling reactions is described. The structures of <b>5</b> and <b>6</b> were confirmed by single crystal X-ray diffraction measurements. Compound <b>6</b> has a remarkable room temperature experimental density of 1.955 g cm^–3 and shows excellent detonation performance. In addition, it has a high decomposition temperature of 233 °C. These fascinating properties, which are comparable to those of CL-20, make it very attractive in high performance applications

Balancing Energy and Stability of Nitroamino-1,2,4-Oxadiazoles through a Planar Bridge

By integrating two approachesan ethene bridge to enhance safety and planarity to support good densitywe have achieved new high-energy-density materials 4–8. Compounds 4–8 show good detonation performance (Dv = 8037–9305 m s–1 and DP = 24.7–33.4 GPa) and large enthalpies of formation (260.1–1444.9 kJ mol–1). The detonation velocity of compound 8 (9305 ms–1) approaches that of HMX (9320 ms–1), which suggests it is a competitive high-energy-density material

Energetic Multifunctionalized Nitraminopyrazoles and Their Ionic Derivatives: Ternary Hydrogen-Bond Induced High Energy Density Materials

Diverse functionalization was introduced into the pyrazole framework giving rise to a new family of ternary hydrogen-bond induced high energy density materials. By incorporating extended cationic interactions, nitramine-based ionic derivatives exhibit good energetic performance and enhanced molecular stability. Performance parameters including heats of formation and detonation properties were calculated by using <i>Gaussian 03</i> and <i>EXPLO5</i> v6.01 programs, respectively. It is noteworthy to find that 5-nitramino-3,4-dinitropyrazole, <b>4</b>, has a remarkable measured density of 1.97 g cm^–3 at 298 K, which is consistent with its crystal density (2.032 g cm^–3, 150 K), and ranks highest among azole-based CHNO compounds. Energetic evaluation indicates that, in addition to the molecular compound <b>4</b>, some ionic derivatives, <b>9</b>, <b>11</b>, <b>12</b>, <b>17</b>, <b>19</b>, and <b>22</b>, also have high densities (1.83–1.97 g cm^–3), excellent detonation pressures and velocities (<i>P</i>, 35.6–41.6 GPa; <i>v</i>_D, 8880–9430 m s^–1), as well as acceptable impact and friction sensitivities (IS, 4–30 J; FS, 40–240 N). These attractive features highlight the application potential of nitramino hydrogen-bonded interactions in the design of advanced energetic materials

Energetic Multifunctionalized Nitraminopyrazoles and Their Ionic Derivatives: Ternary Hydrogen-Bond Induced High Energy Density Materials

Diverse functionalization was introduced into the pyrazole framework giving rise to a new family of ternary hydrogen-bond induced high energy density materials. By incorporating extended cationic interactions, nitramine-based ionic derivatives exhibit good energetic performance and enhanced molecular stability. Performance parameters including heats of formation and detonation properties were calculated by using <i>Gaussian 03</i> and <i>EXPLO5</i> v6.01 programs, respectively. It is noteworthy to find that 5-nitramino-3,4-dinitropyrazole, <b>4</b>, has a remarkable measured density of 1.97 g cm^–3 at 298 K, which is consistent with its crystal density (2.032 g cm^–3, 150 K), and ranks highest among azole-based CHNO compounds. Energetic evaluation indicates that, in addition to the molecular compound <b>4</b>, some ionic derivatives, <b>9</b>, <b>11</b>, <b>12</b>, <b>17</b>, <b>19</b>, and <b>22</b>, also have high densities (1.83–1.97 g cm^–3), excellent detonation pressures and velocities (<i>P</i>, 35.6–41.6 GPa; <i>v</i>_D, 8880–9430 m s^–1), as well as acceptable impact and friction sensitivities (IS, 4–30 J; FS, 40–240 N). These attractive features highlight the application potential of nitramino hydrogen-bonded interactions in the design of advanced energetic materials

Tetranitroacetimidic Acid: A High Oxygen Oxidizer and Potential Replacement for Ammonium Perchlorate

Considerable work has been focused on developing replacements for ammonium perchlorate (AP), a primary choice for solid rocket and missile propellants, due to environmental concerns resulting from the release of perchlorate into groundwater systems, which has been linked to thyroid cancer. Additionally, the generation of hydrochloric acid contributes to high concentrations of acid rain and to ozone layer depletion. En route to synthesizing salts that contain cationic FOX-7, a novel, high oxygen-containing oxidizer, tetranitro­acetimidic acid (TNAA), has been synthesized and fully characterized. The properties of TNAA were found to be exceptional, with a calculated specific impulse exceeding that of AP, leading to its high potential as a replacement for AP. TNAA can be synthesized easily in a one-step process by the nitration of FOX-7 in high yield (>93%). The synthesis, properties, and chemical reactivity of TNAA have been examined

1,1-Diamino-2,2-dintroethene (FOX-7) in Copper and Nickel Diamine Complexes and Copper FOX-7

1,1-Diamino-2,2-dinitroethene (FOX-7) reacts readily with copper nitrate in an aqueous solution of potassium hydroxide to form pea green Cu­(FOX)₂(H₂O)₂ (<b>5</b>). FOX-7 complexes of copper and nickel supported by a variety of diamines including Cu­(en)₂(FOX)₂(H₂O) (<b>1</b>), Cu­(pn)₂(FOX)₂ (<b>2</b>), Cu­(bipy)­(FOX)₂(H₂O)₄ (<b>3a</b>), Cu­(bipy)₂(FOX)₂(H₂O)_2.5 (<b>3b</b>), Cu­(bipy)­(FOX)₂(DMSO)₂·2DMSO (<b>3c</b>), Cu­(phen)₃(FOX)₂(H₂O)₃ (<b>4</b>), (Ni)₂(phen)₆(FOX)₄(NO₃)₃(H₂O)₂ (<b>6</b>), and Ni­(bipy)₃(FOX)₂(H₂O)₄ (<b>7a</b>) were obtained via metathesis reactions with potassium-FOX (K-FOX). Surprisingly FOX-7, in the presence of Ni­(II) and bipyridyl in a mixed solvent of methanol and dimethyl sulfoxide, gave a chelated FOX carbamate anion resulting in the compound Ni­(bipy)₂(FOX–CO₂)·(DMSO) (<b>7b</b>). All metal salts were characterized by infrared, elemental analysis, and differential scanning calorimetry (DSC). Single-crystal X-ray diffraction structures were obtained for compounds <b>1</b>,<b> 2</b>,<b> 3c</b>,<b> 6</b>, and <b>7b</b>

Nitrogen-Rich 5-(1-Methylhydrazinyl)tetrazole and its Copper and Silver Complexes

Nitrogen-rich 5-(1-methylhydrazinyl)­tetrazole (<b>1</b>, MHT) was synthesized by using a straightforward method. White plate crystals of <b>1</b> were isolated in acetonitrile and crystallized in the monoclinic system <i>P</i>2₁/<i>c</i> (# 14) (<i>a</i> = 3.8713(18) Å, <i>b</i> = 12.770(6) Å, <i>c</i> = 9.974(5) Å, α = 90°, β = 93.397(6)°, γ = 90°, <i>V</i> = 492.3(4) ų, <i>Z</i> = 4). The reactions of Cu­(II) and Ag­(I) ions in aqueous solution with <b>1</b> were investigated and found to form two complexes under mild conditions. The crystal structures of <b>2</b> and <b>3</b> are discussed with respect to the coordination mode of the MHT anion. Thermal stabilities were determined from differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests. Impact sensitivity was determined by BAM standards showing that these MHT salts are insensitive to impact (>40 J) confirmed by UN standards. The energies of combustion of <b>1</b>–<b>3</b> were determined using oxygen bomb calorimetry values and were used to obtain the corresponding enthalpies of formation. Combined with these data above, the neutral MHT is an attractive nitrogen-rich ligand for metallic energetic materials. Its copper and silver coordinated complexes are of interest as potential “green” metal energetic materials with high thermal stability as well as low sensitivity to impact and a high molar enthalpy of formation

Nitrogen-Rich 5-(1-Methylhydrazinyl)tetrazole and its Copper and Silver Complexes

Nitrogen-rich 5-(1-methylhydrazinyl)­tetrazole (<b>1</b>, MHT) was synthesized by using a straightforward method. White plate crystals of <b>1</b> were isolated in acetonitrile and crystallized in the monoclinic system <i>P</i>2₁/<i>c</i> (# 14) (<i>a</i> = 3.8713(18) Å, <i>b</i> = 12.770(6) Å, <i>c</i> = 9.974(5) Å, α = 90°, β = 93.397(6)°, γ = 90°, <i>V</i> = 492.3(4) ų, <i>Z</i> = 4). The reactions of Cu­(II) and Ag­(I) ions in aqueous solution with <b>1</b> were investigated and found to form two complexes under mild conditions. The crystal structures of <b>2</b> and <b>3</b> are discussed with respect to the coordination mode of the MHT anion. Thermal stabilities were determined from differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TGA) tests. Impact sensitivity was determined by BAM standards showing that these MHT salts are insensitive to impact (>40 J) confirmed by UN standards. The energies of combustion of <b>1</b>–<b>3</b> were determined using oxygen bomb calorimetry values and were used to obtain the corresponding enthalpies of formation. Combined with these data above, the neutral MHT is an attractive nitrogen-rich ligand for metallic energetic materials. Its copper and silver coordinated complexes are of interest as potential “green” metal energetic materials with high thermal stability as well as low sensitivity to impact and a high molar enthalpy of formation