Trinitromethyl-Substituted 1H-1,2,4-Triazole Bridging Nitropyrazole: A Strategy of Utterly Manipulable Nitration Achieving High-Energy Density Material.

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.

Synthesis and detonation characters of 3,4,5-1H-trinitropyrazole and its nitrogen-rich energetic salts.

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.

N-Site Regulation of Pyridyltriazole in Cp*Ir(N̂N)(H2O) Complexes Achieving Catalytic FA Dehydrogenation.

A series of novel Cp*Ir complexes with nitrogen-rich N̂N bidentate ligands were developed for the catalytic dehydrogenation of formic acid in water under base-free conditions. These complexes were synthesized by using pyridyl 1,2,4-triazole, methylated species, or pyridyl 1,2,3-triazole as a N-site regulation ligand and were fully characterized. Complex 1-H2O bearing 1,2,4-triazole achieved a high turnover frequency of 14192 h-1 at 90 °C in 4 M FA aqueous solution. The terminal and bridged Ir-H intermediates of 1-H2O were successfully detected by 1H NMR and mass spectrometry measurements. Kinetic isotope effect experiments and density functional theory (DFT) calculations were performed; then a plausible mechanism was proposed involving the ß-hydride elimination and formation of H2. Water-assisted H2 release was proven to be the rate-determining step of the reaction. The distribution of Mulliken charges on N atoms of triazole ligand internally revealed that the ortho site N2 of 1-H2O with a higher electron density was conducive to efficient proton transfer. Additionally, the advantage of water-assisted short-range bridge of 1,2,4-triazole moieties led to a higher catalytic activity of 1-H2O. This study demonstrated the effectiveness of nitrogen-rich ligands on FA dehydrogenation and revealed a good strategy for N site regulation in the development of new homogeneous catalysts.

Precisely Controlling Ancillary Ligands to Improve Catalysis of Cp*Ir Complexes for CO2 Hydrogenation.

The regulation of ancillary ligands is critical to improve catalysis of Cp*Ir complexes for CO2 hydrogenation. Herein, a series of Cp*Ir complexes with N^N or N^O ancillary ligands were designed and synthesized. These N^N and N^O donors were derived from the pyridylpyrrole ligand. The solid-state structures of Cp*Ir complexes featured a pendant pyridyl group in 1-Cl and 1-SO4 and a pyridyloxy group in 2-Cl, 3-Cl, 2-SO4, and 3-SO4. These complexes were employed as catalysts for CO2 hydrogenation to formate in the presence of alkali under a pressure range of 0.1-8 MPa and temperature range of 25-120 °C. The catalytic activity of 2-SO4 with a pyridyloxy pendant group dramatically outperformed that of 1-SO4 and 3-SO4. The TOF of conversion of CO2 into formate reached 263 h-1 at 25 °C under a total pressure of 8 MPa (CO2/H2 = 1:1). The experiments and density functional theory calculations revealed that a pendant base in metal complexes plays a key role in the rate-determining heterolytic H2 splitting and enhancing the proton transfer by forming a hydrogen bonding bridge thereby improving the catalytic activity.

Three-Dimensional Metal-Organic Frameworks as Super Heat-Resistant Explosives: Potassium 4,4'-Oxybis[3,3'-(5-tetrazol)]furazan and Potassium (1,2,4-Triazol-3-yl)tetrazole.

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.

Ambient Cross-linking System Based on the Knoevenagel Condensation Reaction between Acetoacetylated Sucrose and Aromatic Dicarboxaldehydes.

An ambient cross-linking system based on the Knoevenagel condensation reaction between acetoacetylated sucrose and aromatic dicarboxaldehydes was demonstrated. In this study, we use a rheological instrument to measure the gel time to predict and elucidate the likely reaction mechanism of the system, and we prepare films based on the mechanistic results. Acetoacetylated sucrose and 4,4'-biphenyldicarboxaldehyde were used as raw materials, piperidine was used as the catalyst, and nonvolatile dimethyl sulfoxide (DMSO) was used as the solvent. After mixing 4,4'-biphenyldicarboxaldehyde and piperidine for 30 min, the acetoacetylated sucrose was added, thus producing the shortest gel time. Then, the gel was characterized by Fourier transform infrared spectroscopy. In addition, three films were prepared by this approach with different aromatic dicarboxaldehydes, and the properties of the coatings were characterized by differential scanning calorimeter, dynamic mechanical analysis thermogravimetric analysis, and swelling ratio. It was found that these films have high Young's modulus, high glass transition temperatures, high pencil hardnesses, and low swelling ratios.

Extraordinarily large kinetic isotope effect on alkene hydrogenation over Rh-based intermetallic compounds.

A series of Rh-based intermetallic compounds supported on silica was prepared and tested in alkene hydrogenation at room temperature. H2 and D2 were used as the hydrogen sources and the kinetic isotope effect (KIE) in hydrogenation was studied. In styrene hydrogenation, the KIE values differed strongly depending on the intermetallic phase, and some intermetallic compounds with Sb and Pb exhibited remarkably high KIE values (>28). An extraordinarily high KIE value of 91, which has never been reported in catalytic reactions at room temperature, was observed particularly for RhPb2/SiO2. RhPb2/SiO2 also showed high KIE values in the hydrogenation of other unsaturated hydrocarbons such as phenylacetylene and cyclohexene. The density functional theory calculation focused on the surface diffusion of hydrogen suggested no contribution of the quantum tunneling effect to the high KIE values observed. A kinetic study revealed that the dissociative adsorption of H2 (D2) was the rate-determining step in the styrene hydrogenation over RhPb2/SiO2. We propose that the large KIE originates from the quantum tunneling occurring at the hydrogen adsorption process with the aid of the specific surface structure of the intermetallic compound and adsorbate alkene.