The design and synthesis of a high-energy-density material (HEDM) that simultaneously possesses high energy and low sensitivity is a challenging task. This study reports an effective strategy for constructing polynitro-substituted bicyclic fused ring frameworks. A series of polynitro [1,2,4] triazolo [4,3-b] pyridazine fused rings with nitrogen-rich NH2/NHNH2/NHOH groups were first synthesized by straightforward routes, and were characterized by chemical (NMR, MS, IR spectroscopy, and single-crystal X-ray diffraction) as well as experimental analysis (sensitivity towards friction, impact, and DSC-TGA test). Their detonation properties (detonation velocity, detonation pressure, etc.) were predicted by the EXPLO5 program. These new polynitro fused ring compounds were found to exhibit high density, high decomposition temperature, and acceptable impact and sensitivity, making them promising high-energy-density materials (HEDM). It is worth noting that the excellent energetic properties (density: 1.932 g cm-3, Vdet: 9585 m s-1; PCJ: 41.8 GPa), superior to those of HMX (1,3,5,7-tetranitrotetraazacyclooctane), highlight compound 5 as the highest-performing bicyclic fused ring energetic compound reported to date. Computational considerations of 5 and 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) suggest that its structural character provides a good balance between energy and safety (sensitivity: 36 J, 324 N). This work demonstrates the effectiveness of introducing polynitro groups into the multi-ring planar skeleton and provides a generalizable design synthesis strategy for developing new HEDMs.

A series of novel cobalt complexes with a methyl substituted pyridine-2-thiol ligand were developed for the catalytic electroreduction of CO2. Kinetic isotope effect (KIE) and density functional theory (DFT) calculations were performed. The synergism of para-N of mercaptopyridine in proton transfer resulted in a higher catalytic activity for 1. This study demonstrated the effect of introducing an electron-donating group on CO2 electroreduction.

The polynitroazole plays an important role in the design of high‐energy density materials. A series of nitrogen‐rich salts based on trinitromethyl‐substituted 1 H ‐1,2,4‐triazole bridging nitropyrazole was prepared. These newly synthesized salts were fully characterized by chemical analysis (infrared, NMR, and mass spectroscopy) as well as experimental tests (thermostability and sensitivities). Their detonation properties (detonation velocity, detonation pressure, etc.) were determined by the EXPLO5 program on the basis of density and heat of formation. These nitrogen‐rich salts show moderate thermostabilities and low sensitivities (IS ≥ 10 J, FS ≥ 252 N) due to intermolecular hydrogen bonding interactions. The most promising high‐energy insensitive compound is salt 2, which possesses a high density (1.80 g cm −3 ), relatively high thermal stability (149 °C), low sensitivity (IS = 30 J, FS = 252 N), good detonation velocity (8997 m s −1 ) and detonation pressure (36.7 GPa) which is comparable to cyclotrimethylenetrinitramine (RDX). This study supports the efficiency of utilizing nitrogen‐rich salts combined with trinitromethyl‐substituted systems in the development of new high‐energy, insensitive energetic materials.

Aminotriazole is a privileged structural motif in the design of various thermostable and insensitive energetic materials. A series of 3-nitro-1H-pyrazole-5-yl-bridged/fused 4,5-diamino-4H-1,2,4-triazoles was prepared via the cycloaddition of carboxyl pyrazole as a raw material. These newly synthesized compounds and their corresponding salts were fully characterized by chemical analysis (single-crystal X-ray diffraction, infrared, NMR, and mass spectroscopy) as well as experimental tests (thermostability and sensitivities). Their detonation properties (detonation velocity, detonation pressure, etc.) were determined with the EXPLO5 program on the basis of crystal density and calculated heat of formation with the Gaussian 09 suite. These pyrazole-triazoles show very high thermostabilities (Td > 320 °C) and low mechanical sensitivities (IS ≥ 25 J, FS ≥ 288 N) due to intermolecular hydrogen bonding interactions in polycyclic triazoles. In particular, tricyclic 3a displays an ultrahigh decomposition temperature of 371 °C, surpassing that of 2,2',4,4',6,6'-hexanitrostilbene (HNS) and can be used as a candidate for heat-resistant explosives. Dinitroamino compounds 2 (PCJ = 38.58 GPa, Vdet = 9268 m s-1) and 2d (PCJ = 36.15 GPa, Vdet = 8913 m s-1) were found to show excellent detonation performance, with 2 being comparable to 1,3,4,7-tetranitro-1,3,5,7-tetrazocane (HMX). Furthermore, compound 1 exhibits desirable detonation properties (PCJ = 34.74 GPa, Vdet = 9284 m s-1), high thermostability (333 °C), and low sensitivities (IS > 40 J, FS > 360 N), making it a promising HMX replacement. This study supports the superiority of utilizing the polycyclic pyrazole-triazole system in the development of new high-energy insensitive energetic materials.

The design and synthesis of insensitive energetic materials are a necessary and challenging work. The synthesis of novel nitrogen-rich salts based on 5-(5-Nitro-1H-1,2,4-triazol-3-yl)-1H-tetrazole (H2NTT) has been presented. Structural characterization of these two salts was accomplished by utilizing NMR, MS, IR spectroscopy, and X-ray diffraction. The standard heats of formation were calculated, and the differential scanning calorimetry (DSC) and sensitivity test were carried out. Their detonation performances were estimated by EXPLO 5 program. These newly synthesized salts showed highly positive heat of formation and low sensitivity. It is noteworthy that the diaminoguanidine salt b exhibited good detonation performance superior to traditional explosive TNT (Trinitrotoluene), making it a prospective candidate for insensitive energetic material. Two novel nitrogen-rich salts based on the 5-(5-Nitro-1H-1,2,4-triazol-3-yl)-1H-tetrazole (H2NTT) were synthesized and fully characterized. The good detonation performance and low sensitivity make them for prospective insensitive green energetic materials.image

The crystal morphology of highly explosive cyclotrimethylenetrinitramine (hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)) has been characterized by the crystal-face-indexing method in combination with single-crystal X-ray diffraction and rotation imaging techniques. As a result, the morphology importance of the facets in RDX crystals grown in acetone and dimethyl sulfoxide (DMSO) is on the order of (111) approximate to (210) > (021) approximate to (102) > (001) approximate to (010) approximate to (100) and (111) > (210) > (010) > (001) approximate to (021), respectively. Crystal sizes have also been measured along the a-, b-, and c-axes, which show a less-preferred orientation of RDX crystals than octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals. In addition, the {111} and {210} facets show good thermodynamic stability, while the appearance of the other facets is dynamically affected by solution conditions during the growth of RDX crystals from the hundred-micrometer scale to the millimeter scale. After crystal face indexing, surface models were built for the dominant {111} and {210} facets as well as the special {010} facet. On the surface of the {111} facet, the outstanding H and O atoms lead to a regular arrangement of positive and negative charges. For the {210} facet, twisted grooves are observed on the surface in the Connelly surface model. More interestingly, large hollows with dimensions of 11.6 x 11.8 & Aring;(2) are generated on the surface of the {010} facet. The high adsorption ability of the hollows to DMSO molecules plays a key role in the enhanced morphology importance of the {010} facet in DMSO, as evidenced by molecular dynamics simulations. All of these results can be applied to the morphology control of energetic crystals and will be a good reference to the interfacial interaction of the RDX crystal in both polymer-bonded explosives (PBXs) and propellants.

Nitro groups have been demonstrated to play a decisive role in the development of the most powerful known energetic materials. Two trinitromethyl-substituted 1H-1,2,4-triazole bridging nitropyrazoles were first synthesized by straightforward routes and were characterized by chemical (MS, NMR, IR spectroscopy, and single-crystal X-ray diffraction) and experimental analysis (sensitivity toward friction, impact, and differential scanning calorimetry-thermogravimetric analysis test). Their detonation properties (detonation pressure, detonation velocity, etc.) were predicted by the EXPLO5 package based on the crystal density and calculated heat of formation with Gaussian 09. These new trinitromethyl triazoles were found to show suitable sensitivities, high density, and highly positive heat of formation. The combination of exceedingly high performances superior to those of HMX (1,3,5,7-tetranitrotetraazacyclooctane), and its straightforward preparation highlights compound 8 as a promising high-energy density material (HEDM). This work supports the effectivity of utterly manipulable nitration and provides a generalizable design synthesis strategy for developing new HEDMs.

The development of energetic materials is still facing challenges due to the inherent contradiction between energy and sensitivity. Two new nitrogen-rich energetic salts of 3,4,5-1H-trinitropyrazole (HTNP) were synthesized. They are fully characterized by X-ray diffraction, NMR, MS and IR spectroscopy. The DSC and BAM tests were carried out as well. These TNP salts show high thermostability and high positive heat of formation. Their detonation performances were calculated by the EXPLO5 program. Most noteworthy is that DATr salt exhibits superior sensitivity and detonation performance comparable to secondary explosive RDX, making it promising for use as a new-generation green energetic material.

To investigate the accuracy of the currently used three auxiliary methods(atomization energy,equivalent bonding and isodesmic reaction methods)for calculating the heat of formation(HOF)values,the structure optimization and frequency calculations were performed for 160 kinds of novel energetic molecules at the B3LYP/6-311G(d,p)theoretical level.The molecules were subject to single-point energy calculations at the MP2/6-311++G(d,p)theoretical level.The HOF values were calculated using the three commonly used auxiliary reactions(atomization energy method,equivalent bonding method,and atom equivalent method)by extracting thermodynamic values and electronic energies,where the results were compared with the HOF values directly output by the G4(MP2)-6X method,and the regression coefficients were fitted for each method.The linear regression equation was established,which can be used in combination with B3LYP/6-311G(d,p)//MP2/6-311++G(d,p)theoretical level to obtain the calculation accuracy of G4(MP2)-6X method.The enthalpies of formation of 160 kinds of substances at different theoretical levels and enthalpies of formation calculation methods were calculated.The correla-tion of the three methods was found to be:atomization energy method＞equivalent bonding method＞atom equivalent method.

Surfacestructures and properties are particularly importantforvarious materials, as they can transport to the bulk properties inspecial cases and affect the applications of materials. Thermal stabilityis one of the key factors that determine the engineering applicationsof energetic cocrystals (ECCs). Here, in situ morphology and crystalstructure characterization techniques were applied to investigatethe thermal decomposition of hexanitrohexoazaisowurtzitane/1-methyl-3,4,5-trinitro-1H-pyrazole(CL-20/MTNP), an important CL-20-based energetic cocrystal, underisothermal conditions. An unexpectedly low thermal stability was observedfor the CL-20/MTNP cocrystal. The decomposition temperature can beas low as 140 & DEG;C with the evolution of surface defects startingfrom 100 & DEG;C. After decomposition, the cocrystal transformed to & gamma;-CL-20 in a porous morphology. Based on the facet indexingresult, the surface model was also constructed for the cocrystal.In combination with the surface structure and channel-like crystalstructure, a surface-induced decomposition mechanism was proposed,which provides a new perspective on the thermal stability of ECCs,and will be valuable for the estimation of thermal/chemical stabilityfor other cocrystal materials. Based on insitu morphology and crystal structure characterizationtechniques, thermal decomposition of energetic cocrystal CL-20/MTNPwas observed at a much lower temperature than previously reported.A novel surface-induced decomposition mechanism was proposed basedon the experimental observation and crystal structure analysis, whichrefreshes the understanding of the thermal stability of energeticcocrystals.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A large polymolybdate-templated {Ag49Mo16} cluster protected by six thiacalix[4]arene (TC4A) molecules was synthesized by a one-pot solvothermal reaction. Structural analysis shows that the {Ag49Mo16} is assembled by inserting a [Mo6O22](8-) cluster into a [Ag49Mo10@(TC4A)(6)] cage, representing the first polyoxometalate-templated Ag cluster protected by calixarene macrocyclic ligands. The solution stability and photoelectric properties of {Ag49Mo16} are discussed. Furthermore, this POM-templated Ag nanocluster realized electrocatalytic CO2 reduction applications, and 44.75% CO faradaic efficiency (FE) was obtained at a voltage of -0.8 V (vs. RHE).

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Parallel flow electrolysis is widely used in copper cathode production because of the high current density and good product quality that can be achieved; however, fundamentals of the technology are still not fully understood. Internal circulation theory was applied to study this process. Electrolyte and cathode copper were analyzed by inductively coupled plasma optical emission spectroscopy, STAR-CCM + simulation, and optical and scanning electron microscopy. Deportment of byproducts, such as arsenic, antimony, bismuth, and lead, from the electrolyte to the cathode was also studied.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Isothermal decomposition kinetics play an important role in the stability assessment, risk assessment, and reaction mechanism inference of energetic materials. Herein, the thermal decomposition of nitro-1,2,4-triazol-3-one (NTO) was investigated using a self-development isothermal decomposition gas manometric device at both high and low temperature ranges. The kinetic parameters were calculated by model-free method and model-fitting method. The results show that the activation energies determined by these two methods are in good agreement. At 473-493 K, the entire decomposition process of NTO showed two distinct stages. The activation energy (E-a) and pre-exponential factor (lnA) in the first stage are 260.1 +/- 11.5 kJ mol(-1) and 52.5 +/- 2.9 s(-1), respectively, while they are 166.0 +/- 24.5 kJ mol(-1) and 28.4 +/- 6.1 s(-1) in the second stage. At 383-423 K, the initial decomposition process of NTO was investigated. During this process, E-a is 99.8 +/- 3.2 kJ mol(-1) and lnA is 11.5 +/- 1.0 s(-1). According to the kinetic results, a mechanism was speculated to be the transition of a rate-limiting step from nucleation and nuclei growth to the gas diffusion. Moreover, the E-a-lnA sets were found to lie on the kinetic compensation regression line, which indicates that the kinetic data in this work are reliable. All the results will further support and complement the kinetic database of NTO.

Crystal structure evolution of high-explosive HMX from -100 to 160 degrees C was studied by in situ single-crystal X-ray diffraction. Thermal expansion properties and the changes in atomic vibration and molecular conformation were investigated. Anisotropic thermal expansion was observed with a preferred direction along the b-axis. More interplanar defects may be generated between the (011) and (020) facets due to the large increasing rate of their interplanar spacings ((3.23 +/- 0.09) x 10(-4) and (6.98 +/- 0.05) x 10(-4) & Aring;/degrees C), which may significantly influence the interfacial interaction between HMX crystals and polymer binders in plastic-bonded explosive. Atomic displacement parameter (ADP) investigation reveals that the farther away from the center ring, the stronger the atomic vibrations. Compared with the linear increase of the unit cell parameters, the increase of ADP is proportional to temperature, following an exponential growth model. Compression of the central ring along one direction and expansion along the opposite direction were also observed. The vibrations and rotations of the nitro groups related to the central ring were further identified and confirmed by Raman spectroscopy, demonstrating the flexibility of the nitro groups. Based on the observations, a mechanism was proposed for the molecular conformation transformation of HMX during the beta-delta phase transition. All the results are not only beneficial to a comprehensive understanding of the thermal properties of HMX on the atomic and molecular levels but also provide an important reference for the manufacturing, processing, and storage of HMX and other energetic materials.

Heat-resistant explosives play an irreplaceable role in specialized applications. Two energetic metal-organic frameworks (EMOFs), potassium 4,4'-oxybis[3,3'-(5-tetrazol)]furazan and potassium (1,2,4-triazol-3-yl)tetrazole, featuring a three-dimensional metal-organic framework structure, were first synthesized and characterized by chemical (1H NMR, 13C NMR, MS, IR spectroscopy, and single-crystal XRD) and physicochemical analyses (sensitivity toward friction, impact, electrostatic, and DSC-TGA test). The new 3D EMOFs were found to show high thermostability, highly positive heat of formation, and suitable sensitivities. The Hirshfeld surface was further analyzed in order to explore the effect on sensitivities. Their detonation properties (detonation velocity, detonation pressure, etc.) were calculated by the EXPLO5 program. K2NTT exhibits extremely high decomposition temperatures of up to 361 °C; meanwhile, its detonation performance is comparable to that of TATB and other energetic potassium salts, which makes it a promising heat-resistant explosive.

Energetic complexes represent a crucial research direction for the design and synthesis of novel energetic materials. In this work, 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), a significant explosive compound with exceptional comprehensive properties, was selected as the ligand for coordinating with various metal ions. Four novel energetic complexes, Ni(C4H3N6O5)2·DMF (1), Co(C4H3N6O5)2·2DMF (2), Mn(C4H3N6O5)3·3/2DMF (3), and Cu3(C4H2N6O5)3·3DMF (4) were successfully synthesized, and their crystal structures were identified by a single-crystal X-ray diffraction technique. The structural analyses illustrated that LLM-105 can form either a mononuclear metal complex after the deprotonation of one amino group or a trinuclear metal complex after the deprotonation of two amino groups. Compound 1 exhibits a planar quadrilateral geometry, while both compounds 2 and 3 display distorted octahedral configurations. Compound 4 has three metal centers and exhibits two coordination configurations of distorted tetragonal pyramid geometry and planar quadrilateral geometry. The detonation performances of compounds 1–4 were also theoretically calculated, revealing their favorable explosive properties. These findings emphasize the diverse coordination modes of LLM-105 and the structural variability and adjustability of its complexes, offering valuable insights for regulating both the structure and performance of the LLM-105 complex as well as researching its deprotonation.