Renaissance of dinitroazetidine: novel hybrid energetic boosters and oxidizers

Schindler C., Rykaczewski K., Becker M., Anantpur M., Sausa R., Johnson E., Orlicki J., Bukowski E., Sabatini J.

Despite their favorable properties, azetidines are often overlooked as lead compounds across multiple industries. This is often attributed to the challenging synthesis of densely functionalized azetidines in an efficient manner. In this work, we report the scalable synthesis and characterization of seven azetidines with varying regio- and stereochemistry, and their application as novel azetidine-based energetic materials, enabled by the visible light-mediated aza Paternò-Büchi reaction. The performance and stark differences in physical properties of these new compounds make them excellent potential candidates as novel solid melt-castable explosive materials, as well as potential liquid propellant plasticizers. The nitroazetidine materials synthesized exhibit reasonable sensitivities, higher densities, better oxygen balances, increased detonation pressures and velocities, as well as improved specific impulses, compared to the state-of-the-art materials. This work highlights the scalability and utility of the visible-light aza Paternò-Büchi reaction and demonstrates the impact of stereochemical considerations on the physical properties of azetidine-based energetics. Considering the versatility and efficiency of the presented synthetic strategies, we expect that this work will guide the development of new azetidine-based materials in the energetics space as well as other industries, including pharmaceuticals and agrochemicals.

Muravyev N.V., Wozniak D.R., Piercey D.G.

During the development of novel energetic materials first analysis of synthesized compound includes both physico-chemical characterization and energetic potential evaluation. Evaluation of energetic performance includes determination of the detonation parameters,...

Zlotin S.G., Churakov A.M., Egorov M.P., Fershtat L.L., Klenov M.S., Kuchurov I.V., Makhova N.N., Smirnov G.A., Tomilov Y.V., Tartakovsky V.A.

Novel efficient synthetic strategies, including green methodologies, to basic and perspective high-energy density compounds, bearing active oxygen sources ( C -, N - and O -nitro groups and N -oxide fragments) and high-enthalpy polynitrogen heterocycles, are briefly overviewed. Recently developed synthetic approaches to nitro group-free hypergolic ionic liquids (HILs) and strained 1,5-diaza- bicyclo[3.1.0]hexane derivatives capable of ultrafast ignition upon mixing with an oxidizer, and to high-energy liquid hydrocarbons with strained cyclopropane fragments are also considered. Physicochemical properties, energetic performances and potential applications of energetic compounds and composites as key components of explosives, powders and solid or liquid rocket propellants are critically discussed with a focus on original reports published in the period 2016–2021.

Muravyev N.V., Meerov D.B., Monogarov K.A., Melnikov I.N., Kosareva E.K., Fershtat L.L., Sheremetev A.B., Dalinger I.L., Fomenkov I.V., Pivkina A.N.

• Impact, friction, and thermal sensitivity data for 150 CHNOFCl species is reported. • Impact testing of high-melting and low-sensitive compounds is most challenging. • Mechanical sensitivity generally increases with the energy content of compound. • Increasing of detonation performance without compromising sensitivity is possible. Mechanical and thermal hazards are critical for chemical compounds. Foremost, the design of novel energetic materials that are stable, insensitive, but have a detonation performance superior to in-service materials is of great interest. However, a single source of safety data for hazardous materials with explosophoric functionalities is still missing. Herein, an experimental database on thermal stability, impact, and friction sensitivity for 150 CHNOFCl compounds is presented. Mechanical sensitivity is discussed in detail: particle size and shape effects, instrument design, and experimental protocol are considered. The entire dataset was analyzed using the simple descriptors of molecular structure. Mechanical sensitivity was found to be linearly correlated with the maximal heat of explosion for certain classes of compounds (nitrobenzenes, furazans, pyrazoles, etc.). Consideration of all species shows that previously proposed sensitivity increase with an energy content rise is relevant, although it is not strict line, as was assumed, but rather a widened “strip”. A new parameter, safety factor, is proposed to combine two types of sensitivity data. With this factor, the limiting values of mechanical sensitivity at a given energy content are provided that represent the state-of-art development of energetic materials and may be used for screening and design of novel compounds.

Larin A.A., Shaferov A.V., Kulikov A.S., Pivkina A.N., Monogarov K.A., Dmitrienko A.O., Ananyev I.V., Khakimov D.V., Fershtat L.L., Makhova N.N.

AbstractA series of novel energetic materials comprising of azo‐bridged furoxanylazoles enriched with energetic functionalities was designed and synthesized. These high‐energy materials were thoroughly characterized by IR and multinuclear NMR (1H, 13C, 14N) spectroscopy, high‐resolution mass spectrometry, elemental analysis, and differential scanning calorimetry (DSC). The molecular structures of representative amino and azo oxadiazole assemblies were additionally confirmed by single‐crystal X‐ray diffraction and X‐ray powder diffraction. A comparison of contributions of explosophoric moieties into the density of energetic materials revealed that furoxan and 1,2,4‐oxadiazole rings are the densest motifs while the substitution of the azide and amino fragments on the nitro and azo ones leads to an increase of the density. Azo bridged energetic materials have high nitrogen‐oxygen contents (68.8–76.9 %) and high thermal stability. The synthesized compounds exhibit good experimental densities (1.62–1.88 g cm−3), very high enthalpies of formation (846–1720 kJ mol−1), and, as a result, excellent detonation performance (detonation velocities 7.66–9.09 km s−1 and detonation pressures 25.0–37.7 GPa). From the application perspective, the detonation parameters of azo oxadiazole assemblies exceed those of the benchmark explosive RDX, while a combination of high detonation performance and acceptable friction sensitivity of azo(1,2,4‐triazolylfuroxan) make it a promising potential alternative to PETN.

Chaplygin D.A., Larin A.A., Muravyev N.V., Meerov D.B., Kosareva E.K., Kiselev V.G., Pivkina A.N., Ananyev I.V., Fershtat L.L.

Promising high-nitrogen and eco-friendly energetic salts with excellent detonation performance based on a 5-(trinitromethyl)tetrazolate core were prepared.

Anisimov A.A., Ananyev I.V.

An interrelation between the density and lattice energy of molecular crystals is analyzed based on the results of quantum chemical calculations of model supramolecular associates. Using the Interacting Quantum Atoms approach and calculations of molecular volume changes upon the onset of intermolecular interactions, it was found that the deformation energy (a contribution to the lattice energy) depends on the “densification” of a molecule. The significance of these dependences under variation of the electron density isosurface used for molecular volume calculations is studied. An important role is demonstrated of the choice of the isosurface for consistent description of intermolecular interactions using the geometric approach based on the volume and density and the energy treatment based on the lattice energy.

Yang Z., Wu Y., He P., Cao W., Manzoor S., Zhang J.

The development of green energetic materials is based on environmental friendliness, safety and performance improvement. It is of great significance to design and synthesize new nitrogen rich salts for a new generation of green energetic materials. In the present work, a series of 3-amino-5-hydrazinopyrazole energetic salts comprising energetic anions were synthesized and were characterized using elemental analysis, IR spectroscopy and differential scanning calorimetry (DSC). Compounds 1-5 were further confirmed by single crystal X-ray diffraction and the sensitivities were measured by the standard BAM methods. Additionally, the structure-property relationship was elucidated from the experimental results and theoretical calculations. Energetic salts of 2 and 5 exhibited high heat of formation (5, 1160.06 kJ mol-1), high decomposition temperature (2, 172 °C; 5, 186 °C), excellent detonation performance (2, Dv, 9076 m s-1, P 34.1 GPa; 5, Dv, 8974 m s-1, P 31.9 GPa), moderate sensitivity towards outer stimuli and high nitrogen contents (2, 41.03%; 5, 63.84%). This work increases future prospects for the design of insensitive and novel high-energy green energetic material.

Spackman P.R., Turner M.J., McKinnon J.J., Wolff S.K., Grimwood D.J., Jayatilaka D., Spackman M.A.

CrystalExplorer is a native cross-platform program supported on Windows, MacOS and Linux with the primary function of visualization and investigation of molecular crystal structures, especially through the decorated Hirshfeld surface and its corresponding two-dimensional fingerprint, and through the visualization of void spaces in the crystal via isosurfaces of the promolecule electron density. Over the past decade, significant changes and enhancements have been incorporated into the program, such as the capacity to accurately and quickly calculate and visualize quantitative intermolecular interactions and, perhaps most importantly, the ability to interface with the Gaussian and NWChem programs to calculate quantum-mechanical properties of molecules. The current version, CrystalExplorer21, incorporates these and other changes, and the software can be downloaded and used free of charge for academic research.

Suponitsky K.Y., Anisimov A.A., Ananyev I.V., Lashakov A.A., Osintseva S.V., Zalomlenkov V.A., Gidaspov A.A.

It is well known that the densest molecular crystals formed by molecules consisting of C, H, N, O, and F atoms are those of polynitro compounds that do not and cannot participate in strong intermolecular interactions. At the same time, many “typical” organic crystals are also stabilized by weak intermolecular contacts, such as C–H···O(N), O(N)···π, H···H, and so forth. However, the density of such crystals is significantly lower. In this work, we report the synthesis and properties of 1,3,5-triazine derivatives containing both trinitromethyl and/or trinitroethoxy, as well as isopropoxy groups. It was shown by X-ray structural analysis and quantum chemistry calculations that the crystal structures of the obtained 1,3,5-triazine derivatives were stabilized by weak interactions only, such as NO2···NO2, O···π, C–H···O, C–H···N, and H···H contacts. The effects from various types of weak intermolecular contacts on crystal density were evaluated. No strong correlation was found between the energy of interactions, decrease of system volume caused by such interactions, and an increase in crystal density. It was demonstrated that crystal packing can be studied effectively by a recently proposed method via the analysis of ΔOED criterion describing the density increase of molecule and its fragments upon crystal formation from isolated molecules.

Suponitsky K.Y., Smol'yakov A.F., Ananyev I.V., Khakhalev A.V., Gidaspov A.A., Sheremetev A.B.

AbstractBeing a liquid at room temperature, the crystalline form of 3,4‐dinitrofurazan (DNF) has long been the subject of theoretical predictions. Its detonation performance in the solid state was calculated based on very high crystal density (1.89–2.02 g/cm3) predicted by different theoretical schemes. Using zone melting technique, we were able to grow a DNF single crystal of suitable quality for X‐ray diffraction study. The experimental density was found to be 1.917 g/cm3 at 100 K, which corresponds to 1.85 g/cm3 at room temperature, that is lower than erlier predictions. We found that the ortho‐nitro groups of DNF are not equivalent and behave differently upon the crystal structure formation, which was not taken into account in the theoretical estimates carried out earlier. It has now been shown that using the ΔOED‐based densification approach, this “ortho‐effect” can be clarified and quantified. The observed effect is probably characteristic of all polynitro compounds, where nitro groups are brought together, and should be kept in mind when constructing high density materials.

Wurzenberger M.H., Gruhne M.S., Lommel M., Braun V., Szimhardt N., Stierstorfer J.

The almost ancient and very sensitive silver fulminate (SF), which was involved in the establishment of fundamental chemical concepts, was desensitized for the first time with different nitrogen-rich triazoles and tetrazoles, yielding SF complexes [Agx(CNO)x(N-Ligand)y] (x = 1-4; y = 1-3). These were accurately characterized (X-ray diffraction, scanning electron microscopy, IR, elemental analysis, differential thermal analysis, and thermogravimetric analysis) and investigated concerning their energetic character. The highly energetic coordination compounds suddenly show, in contrast to SF, sensitivities in a manageable range and are therefore safer to handle. In particular, compounds [Ag4(CNO)4(BTRI)] [3; BTRI = 4,4'-bis(1,2,4-triazole)] and [Ag4(CNO)4(2,2-dtp)] [8; 2,2-dtp = 1,3-di(tetrazol-1-yl)propane] show values in the range of desired lead styphnate alternatives with similar energetic performances. The crystal structure experiments reveal silver cluster formation in all complexes with distinct argentophilic interactions close to 2.77 A. Furthermore, it was possible to synthesize 8 in a one-pot reaction, avoiding the isolation of highly sensitive SF.

Wozniak D.R., Salfer B., Zeller M., Byrd E.F., Piercey D.G.

The azo-coupling of 1- and 2-amino-4-nitro-1,2,3-triazole yielded two new energetic compounds whose detonation properties compete with that of HMX. Though the calculated performances are impressive, the regioisomers have differing sensitivities and detonation behavior. One has sensitivities similar to a very sensitive primary explosive, while the other has sensitivities more comparable to a sensitive secondary explosive. This serves as an example of the ability to tailor the sensitivities and end use of energetic compounds via regioisomerization.

Gettings M.L., Thoenen M.T., Byrd E.F., Sabatini J.J., Zeller M., Piercey D.G.

This work reports the first compound containing both a tetrazole and an azasydnone ring, a unique energetic material. Several energetic salts of the tetrazole azasydnone were synthesized and characterized, leading to the creation of new secondary and primary explosives. Molecular structures are confirmed by 1 H and 13 C NMR, IR spectroscopy, and X-ray crystallographic analysis. The high heats of formation, fast detonation velocities, and straight-forward synthesis of energetic azasydnones should capture the attention of future energetics research.

Yount J.R., Zeller M., Byrd E.F., Piercey D.G.

Electrochemical azo coupling of guanazine yields novel thermally insensitive high-explosive. DFT and EXPLO6.05 calculations reveal energetic properties that rival RDX making this a potentially cheap, and green alternative to traditional energetics.

Vinogradov D.B., Fershtat L.L.

Deltsov I.D., Vinogradov D.B., Monogarov K.A., Fershtat L.L.

Shaferov A., Ananyev I., Monogarov K., Fomenkov I., Pivkina A., Fershtat L.

AbstractDesign and synthesis of new energetic materials retains its urgency in chemistry and materials science. Herein, rational construction and regioselective synthesis of a series of energetic compounds comprising of a methylene‐bridged combination of 1,2,5‐oxadiazole and nitrogen‐rich azoles (1,2,4‐triazole and tetrazole) enriched with additional explosophoric functionalities (nitro and azo moieties) is presented. All target materials were thoroughly characterized using IR and multinuclear NMR (1H, 13C, 14N, 15N) NMR spectroscopy, high‐resolution mass spectrometry, X‐ray diffraction, and differential scanning calorimetry. All synthesized energetic substances showed good thermal stability (up to 239 °C) and low mechanical sensitivity, while their performance reached or exceeded the level of TNT.

Egorov M.P., Ananikov V.P., Baskir E.G., Boganov S.E., Bogdan V.I., Vereshchagin A.N., Vil’ V.A., Dalinger I.L., Dilman A.D., Eliseev O.L., Zlotin S.G., Knyazeva E.A., Kogan V.M., Kononov L.O., Krayushkin M.M., et. al.

A key goal of organic chemistry is to develop new principles for the control of reactions, which can be used to create promising materials demanded in all fields of scientific research and industry. This review is an overview of the scientific advances, which have been made by the N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences in the past decade within the framework of current trends in organic chemistry. The review covers the results, which are significant for fundamental research and hold great promise for the application in different areas, from the production of materials, petrochemistry, and chemical ecology to medicine, agriculture, and food industry.

Charushin Valery N., Verbitskiy Egor V., Chupakhin Oleg N., Vorobyeva Daria V., Gribanov Pavel S., Osipov Sergey N., Ivanov Andrey V., Martynovskaya Svetlana V., Sagitova Elena F., Dyachenko Vladimir D., Dyachenko Ivan V., Krivokolysko Sergey G., Dotsenko Viktor V., Aksenov Aleksandr V., Aksenov Dmitrii A., et. al.

The chemistry of heterocyclic compounds has traditionally been and remains a bright area of chemical science in Russia. This is due to the fact that many heterocycles find the widest application. These compounds are the key structural fragments of most drugs, plant protection agents. Many natural compounds are also derivatives of heterocycles. At present, more than half of the hundreds of millions of known chemical compounds are heterocycles. This collective review is devoted to the achievements of Russian chemists in this field over the last 15–20 years. The review presents the achievements of leading heterocyclists representing both RAS institutes and university science. It is worth noting the wide scope of the review, both in terms of the geography of author teams, covering the whole of our large country, and in terms of the diversity of research areas. Practically all major types of heterocycles are represented in the review. The special attention is focused on the practical applications of heterocycles in the design of new drugs and biologically active compounds, high-energy molecules, materials for organic electronics and photovoltaics, new ligands for coordination chemistry, and many other rapidly developing areas. These practical advances would not be possible without the development of new fundamental transformations in heterocyclic chemistry.The bibliography includes 2237 references.

Zhang C., Wang Y., Zhang M., Zeng Y., Huang Q., Lin Z., Zhu C.

Sausa R.C., Batyrev I.G.

Ananyev I.V., Fershtat L.L.

The possibility to estimate the electron population of Bader’s interatomic surfaces using the electron density function values at the (3, −1) critical points is discussed taking the results of quantum chemical calculations of three model sets of isolated atomic aggregates as examples. A relevant method based on the approximation of normal distribution of the electron density over the interatomic surface is proposed and verified. The range of applicability of this approximation is considered using the results of calculations for a new model set.

Vinogradova E.E., Larin A.A., Gazieva G.A.

A simple synthesis of novel hybrid molecules containing methylidenehexahydroimidazo[4,5-d]imidazol-2(1H)-one and 1,2,5-oxadiazole moieties is based on the Eschenmoser sulfide contraction involving alkylative precoupling of thioglycolurils with 3(4)-bromoacetyl-1,2,5-oxadiazoles. The proposed method does not require using toxic PPh3 for sulfur extrusion. The synthesized compounds may serve as platforms for constructing both new bioactive and new high- energy compounds.

Deltsov I.D., Ananyev I.V., Meerov D.B., Fershtat L.L.

Liu Y., Guo Q., Yuan X., Feng S., Zhu S., Chen Y., Gou R., Zhang S., Xu Y., Lu M.

The combination of high energetic performance and high stability is an ongoing pursuit in exploring new energetic materials. However, the traditional methods for incorporating fuel and oxidant constituents into a molecule usually give rise to a contradiction between high energy and insensitivity. Now a significant self-assembly strategy was employed to prepare two energetic materials via supramolecular assembly of nitrogen-rich furazan-triazole compound and oxidants. Their supramolecular structures were determined and investigated by single-crystal X-ray diffraction. The effective self-assembly of 3-amino-4-(4,5-diamino-1,2,4-triazole-3-yl)-furazan (TATF) with oxidants leads to a good balance between energetic performances and stabilities. It is worth noting that the crystal densities and detonation performances of compounds 1 and 2 are higher than those of their precursor TATF. Especially, these materials possess good detonation performances (D: 8725-8817 m·s−1; P: 31.9-32.2 GPa). Meanwhile, these supramolecular assembly energetic materials exhibit higher thermal stabilities and lower mechanical sensitivities than RDX. The high energy and low sensitivity of compounds 1 and 2 indicate that the self-assembly is an effective and facile strategy to construction of advanced energetic materials.

Larin A.A., Degtyarev D.D., Ananyev I.V., Pivkina A.N., Fershtat L.L.

Energetic materials science is undergoing a global renaissance aiming to reach an ideal combination between reliable synthetic strategies, high performance and acceptable molecular stabilities. In this work, design and synthesis of novel energetic non-hydrogen furoxan assemblies has been successfully realized. Fine tunability of molecular composition in a series of furoxan-based materials was achieved by the variation of a number of heterocyclic rings and employing N-oxide regioisomerism strategy. Using this approach, advanced energetic regioisomeric azo-bridged bifuroxan assemblies 6 and 7 as well as 3,4′-dinitro-3′,4-bifuroxan 8 with the excellent overall performance were synthesized. Calculations of Hirshfeld surfaces and molecular electrostatic potentials were conducted to better understand the relationship between the molecular structure and mechanical sensitivity in the synthesized series of energetic materials. It was found, that the supramolecular aggregation of 3,4′-dinitro-3′,4-bifuroxan 8 molecules in crystal is more anisotropic that is commonly believed to be more favorable pattern for the low sensitive substances. All target materials have high densities (1.88–1.95 g cm−3), acceptable thermal stabilities (up to 165 °C), high enthalpies of formation (1.6–2.4 kJ g−1) and positive oxygen balance to CO (up to + 25%). As a result, these compounds exhibit high detonation velocities (9.1–9.5 km s−1), excellent heats of explosion (6.6–7.2 kJ g−1) and combustion performance (Isp = 269–281 s). Therefore, these furoxan-based advanced energetic materials unveil new opportunities in search of next-generation functional organic materials for various applications.

Shaferov A.V., Arakelov S.T., Teslenko F.E., Pivkina A.N., Muravyev N.V., Fershtat L.

AbstractThe development of liquid energetic fuels with improved properties is an important topic in space propulsion technologies. In this manuscript, a series of energetic ionic liquids incorporating a 1,2,5‐oxadiazole ring and nitrate, dicyanamide or dinitramide anion was synthesized and their physicochemical properties were evaluated. The synthesized compounds were fully characterized and were found to have good thermal stabilities (up to 219 °C) and experimental densities (1.21–1.47 g cm−3). Advantageously, 1,2,5‐oxadiazole‐based ionic liquids have high combined nitrogen‐oxygen contents (up to 64.4 %), while their detonation velocities are on the level of known explosive TNT, and combustion performance exceeds those of benchmark 2‐hydroxyethylhydrazinium nitrate. Considering the established hypergolicity with H2O2 in the presence of a catalyst, and insensitivity to impact, synthesized ionic liquids have strong application potential as energetic fuels for space technologies.

Epishina M., Kulikov A., Ananyev I.V., Anisimov A.A., Monogarov K.A., Fershtat L.

The preparation of multipurpose high-energy materials for space technologies remains a challenging task and such materials usually require special precautions and fine tunability of their functional properties. To unveil new opportunities en route to high-performance energetic materials, novel potential melt-castable explosives and energetic plasticizers incorporating a (1,2,3-triazolyl)furazan scaffold enriched with nitro and nitratomethyl explosophoric functionalities were synthesized. The successful implementation of the regiodivergent approach enabled the preparation of regioisomeric (nitratomethyltriazolyl)furazans that possessed significantly different physicochemical properties classifying the target materials as melt-castable substances or energetic plasticizers. Hirshfeld surface calculations supported by energy framework plots were also performed to better understand the relationship between the molecular structure and sensitivity. All the prepared (1,2,3-triazolyl)furazans show high nitrogen–oxygen contents (76–77%), good experimental densities (up to 1.72 g cm−3) and high positive enthalpies of formation (180–318 kJ mol−1) resulting in good detonation performances (D = 7.1–8.0 km s−1; P = 21–29 GPa). Overall, this work unveils novel strategies for the construction of balanced energetic melt-castable substances or plasticizers for various applications.

Chaplygin D.A., Larin A.A., Meerov D.B., Monogarov K.A., Pronkin D.K., Pivkina A.N., Fershtat L.L.

AbstractA regioselective approach toward the synthesis of a set of new (2‐vinyltetrazolyl)furoxans as potential energetic monomers has been realized. All target energetic materials were thoroughly characterized by spectral and analytical methods. Moreover, crystal structures of two representative heterocyclic systems were studied by single‐crystal X‐ray diffraction. Prepared high‐energy substances have high combined nitrogen‐oxygen content (63‐71 %), high enthalpies of formation and good detonation parameters (D: 6.7–7.8 km s−1; P: 18–28 GPa). Mechanical sensitivities of the synthesized vinyltetrazoles range these explosives from highly sensitive to completely insensitive. Using calculations of molecular electrostatic potentials (ESP), structural factors influencing the impact sensitivity were revealed. Overall, newly synthesized (2‐vinyltetrazolyl)furoxans are of interest as promising energetic monomers due to the presence of the vinyl moiety and explosophoric heterocyclic combination, while their performance exceeds that of benchmark explosive TNT.