The properties of catenated nitrogen molecules, molecules containing internal chains of bonded nitrogen atoms, is of fundamental scientific interest in chemical structure and bonding, as nitrogen is ...uniquely situated in the periodic table to form kinetically stable compounds often with chemically stable N–N bonds but which are thermodynamically unstable in that the formation of stable multiply bonded N2 is usually thermodynamically preferable. This unique placement in the periodic table makes catenated nitrogen compounds of interest for development of high-energy-density materials, including explosives for defense and construction purposes, as well as propellants for missile propulsion and for space exploration. This review, designed for a chemical audience, describes foundational subjects, methods, and metrics relevant to the energetic materials community and provides an overview of important classes of catenated nitrogen compounds ranging from theoretical investigation of hypothetical molecules to the practical application of real-world energetic materials. The review is intended to provide detailed chemical insight into the synthesis and decomposition of such materials as well as foundational knowledge of energetic science new to most chemists.
The domino Michael/Mannich (DMM) annulation reaction between an N-sulfinyl lithiodienamine and an electrophilic alkene is developed for the synthesis of chiral 2-amino cyclohexenes, a key building ...block in asymmetric synthesis. The DMM reaction proceeds at low temperature while maintaining the stereochemical fidelity. The product functionalized amino cyclohexenes, here obtained in 55–82% yield with diastereomeric ratios as high as >19:1.
Preparation of a redox-frustrated high-energy-density energetic material is achieved by gentle protolysis of MnN(SiMe3)22 with the perchlorate salt of the tetrazolamide H2N t BuMeTzClO4 (Tz = ...tetrazole), yielding the Mn6N6 hexagonal prismatic cluster, Mn6(μ3-NTz t BuMe)6(ClO4)6. Quantum mechanics-based molecular dynamics simulations of the decomposition of this molecule predict that magnetic ordering of the d 5 Mn2+ ions influences the pathway and rates of decomposition, suggesting that the initiation of decomposition of the bulk material might be significantly retarded by an applied magnetic field. We report here experimental tests of the prediction showing that the presence of a 0.5 T magnetic field modulates the ignition onset temperature by +10.4 ± 3.9 °C (from 414 ± 4 °C), demonstrating the first example of a magnetically modulated explosive.
Reaction of 1,3-diazidopropane with an electron-rich Mn(II) precursor results in oxidation of the metal center to a Mn complex with concomitant assembly of the macrocyclic ligand into the ...1,2,3,4,8,9,10,11-octaazacyclotetradeca-2,9-diene-1,4,8,11-tetraido (OIM) ligand. Although describable as a Werner Mn(V) complex, analysis by X-ray diffraction, magnetic measurements, X-ray photoelectron spectroscopy, cyclic voltammetry, and density functional theory calculations suggest an electronic structure consisting of a Mn(III) metal center with a noninnocent OIM diradical ligand. The resulting complex, (OIM)Mn(NH t Bu), reacts via proton-coupled electron transfer (PCET) with phenols to form phenoxyl radicals, with dihydroanthracene to form anthracene, and with (2,4-ditert-butyltetrazolium-5-yl)amide to extrude a tetrazyl radical. PCET from the latter generates the isolable corresponding one-electron reduced compound with a neutral, zwitterionic axial 2,4-ditert-butyltetrazolium-5-yl)amido ligand. Electron paramagnetic resonance and density functional theoretical analyses suggest an electronic structure wherein the manganese atom remains Mn(III) and the OIM ligand has been reduced by one electron to a monoradical noninnocent ligand. The result indicates PCET processes whereby the proton is transferred to the axial ligand to extrude t BuNH2, the electron is transferred to the equatorial ligand, and the central metal remains relatively unperturbed.
New regimes of energy density in energetic materials may be achieved by replacement of oxidizing nitro groups with stronger oxidants such as oxychlorine species. We report the energetic material ...1,3‐di‐tert‐butyltetrazolium‐5‐imidoperchloratomanganese(II) 2, which crystallizes as an oligomeric cubane cluster. Bomb calorimetry on the amorphous, solvent‐free phase gives an energy density of at least 40±3 MJ L−, higher than hydrocarbon combustion in air, more than twice that of traditional energetic nitramines, and ≈70 % higher than that of the unmetalated tetrazolium perchlorate salt without metal linkage. The effects of solid‐state structure, charge, and lattice energy on the energy of 2 are discussed.
Energy to burn: Energy density of a tetrazole‐based, perchlorate‐containing energetic material is increased by covalent attachment of the strongly oxidizing perchlorate anions into the structure.
The refractive index study of copoly(arylene-siloxane)s constructed with amide, ester, or ether linkage units was conducted to synthesize a step-growth polymer for application in flexible displays. ...The copoly(arylene-siloxane) based materials have potential use in optical applications due to their durability, flexibility, and possession of good optical clarity properties when compared to conventional silica-filled polydimethylsiloxane-based materials. Measurement of refractive index (RI) was used as the main mode of analysis due to its direct correlation to optical clarity and material flexibility. Synthesis and characterization, including RI compiled data, was performed for six series of step-growth polymers. Effects of different linkage units, namely amides, esters, and ethers, adjacent to at least one six-membered cyclic unit (aromatic or aliphatic) were evaluated. It was observed that the refractive index of these polymers was directly proportional to the aryl content; however, the influence on RI was not equal across all types of linkage units. The highest RI copolymer, poly(4,4-methylenediphenyl diisocyanate-co-carbinol-terminated polydimethylsiloxane) (MDI-SD1.0k), yielded refractive index 1.470 and molecular weight (M
n
) 16,100 g/mol; however, the copolymer poly(toluene-2,4-diisocyanate-co-carbinol-terminated polydimethylsiloxane) (TDI-SD) had the highest RI (1.462) per phenyl content. The 4,4-methylenediphenyl diisocyanate (MDI), toluene-2,4-diisocyanate (TDI), and hydrogenated methylenediphenyl-4,4-diisocyanate (HMDI) amide containing linkages best improved the refractive indices of the materials studied.
The main goal of this work is to synthesize novel high-energy density materials (HEDMs) that possess a balance of high heats of decomposition with kinetic stability. In contrast to the standard ...approach in the field of energetics research, we are looking into the inclusion of non-CHNO atoms (in particular, transition metals) into energetic materials. In general, the inclusion of metals into energetic materials is seen as “diluting” the energy density since most of the energy is derived from the formation of hot, lightweight gaseous molecules such as N2, CO2, and H2O whereas metals typically form solid metal oxides upon combustion. However, we propose the replacement of high energy ionic bonds with covalent-like bonds, through protolysis of acidic, amine containing fuels with metal bis(amides), will result in the decrease in lattice energy of the material and thus increase the energy output.To this end, a heterocubane cluster of 1,3-di-tert-butyltetrazolium-5-imidoperchlorato-manganese (II) was synthesized through protolysis of 5-amino-1,3-di-tert-butyltetrazolium perchlorate with Mn(N(SiMe3)2)2. Combustion analysis of the amorphous, solvent-free phase gives an energy density of at least 40 ± 3 MJ/L, higher than hydrocarbon combustion in air, more than twice that of the current state-of-the-art high-energy materials, and 86% higher than that of the tetrazolium perchlorate salt without metal linkage.Similarly, the reaction of 1-tert-butyl-3-methyltetrazolium perchlorate with Mn(N(SiMe3)2)2 results in a hexagonal prismatic M6N6 cluster of bridging tetrazolimido ligands and terminal perchlorates. The replacement of the 1-position tert-butyl group with a methyl group results in a detonatable material when heated rapidly using an incandescent wire. Combustion analysis of the amorphous solid again shows an increase in energy-density in comparison with the tetrazolium perchlorate salt. Further analysis of the decomposition event was performed through temperature jump time-of-flight mass spectrometry (T-jump TOF-MS) with varying heating rates to determine the activation energy for decomposition.In an effort to replace perchlorate due to its cytoxicity, periodate salts of the aforementioned ligands were synthesized. Periodate and perchlorate anions possess similar oxidative potentials however, periodate is more environmentally benign and therefore, could result in “greener” energetics. However, due to the lability of the iodine-oxygen bond, only undesirable, redox reaction byproducts have been isolated.Lastly, a series of multinuclear clusters were prepared using neutral 5-amino-tetrazole precursors rather than perchlorate or periodate salts. Reactions of Mn(N(SiMe3)2)2 with 1,3-di-tert-butyltetrazolium-5-aminide result in dimers Mn2(μ-NtBu2Tz)2(NR2)2L2 or Mn2(μ-NtBu2Tz)2(NR2)2 depending on the solvent used. Reaction of Mn(N(SiMe3)2)2 with 5-amino-2-tert-butyltetrazole results in a hexamanganese cluster Mn6(μ3-NtBuTz)2(μ2-NHtBuTz)4(NR2)4.
PDF
