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Combining the advantages of energetic heterocycles to achieve high-energy insensitive explosives is a significant challenge. Herein, based on high-energy tetrazole rings and highly stable 1,3,4-oxadiazole rings, a series of novel nitrogen rich energetic compounds 5–9 were successfully constructed. The related compounds were fully characterized by EA, FT-IR, NMR, DSC, and MS, and compounds 6–9 were further confirmed by X-ray single crystal diffraction. Among them, the energetic ion salts 6–8 show high thermal stability (Tdec > 250 °C) and low mechanical sensitivity (IS > 40 J, FS > 360 N), as well as good energy properties (7552–8050 m s−1, 19.4–23.3 GPa). In particular, the azo compound 9 exhibits competent comprehensive performances (Tdec = 226.2 °C, D = 8502 m s−1, P = 28.9 GPa, IS = 32 J, FS = 320 N). These results suggest that the strategy of integrating tetrazole and 1,3,4-oxadiazole and employing an azo structure as a bridging unit are effective approaches to construct high-energy insensitive materials. [ABSTRACT FROM AUTHOR]

Guided by synthetic chemistry, coordination chemistry and crystallization chemistry, a novel synthesis and crystallization strategy for laser complex energetic materials has been established in this study. In this study, a method with milder reaction conditions was adopted to design the steps and successfully synthesize urazine (H2ur). At the same time, using H2ur as the ligand, the "acid-controlled dissolution-crystallization" method was used to successfully prepare the crystalline coordination polymer Ag(H2ur)NO3 (5), and its 1D structure was confirmed by X-ray single crystal diffraction. The physicochemical property evaluation revealed that 5 has the best performance: insensitive to light, noncorrosive properties to metal shells, excellent tolerance to moisture, good thermal stability, and insensitive to mechanical stimulation. Theoretical calculations show that the compound has acceptable detonation properties (D = 7.6 km s−1, P = 31.83 GPa). In addition, hot-needle experiments show that 5 has a good DDT effect. More importantly, it has great potential for application in laser energetic materials (τ = 300 ms, E = 800 mJ). [ABSTRACT FROM AUTHOR]

A 4-amino-1,2,4-triazole (NH2-trz) based linear trinuclear Fe(ii) complex of [Fe3(NH2-trz)6(SCN)4(H2O)2](SCN)2·H2O (1) has been hydrothermally synthesized by the reaction of a NH2-trz ligand with FeSO4. A single crystal of complex 1 is able to extrude one lattice water and one coordinated water, leading to another single crystal of complex 1a with a formula [Fe3(NH2-trz)6(SCN)5(H2O)](SCN) by heating. Complex 1a can be reversed to 1 upon the reabsorption of water. Single-crystal X-ray diffraction analysis reveals that these two complexes consist of a linear trinuclear core where a central Fe1 ion is coordinated to six nitrogen atoms from six bridged NH2-trz ligands and one of the terminal Fe2 ions is coordinated to five nitrogen atoms and one oxygen atom. The terminal Fe3 ion in 1 coordinates to five nitrogen atoms and one oxygen atom; however, the terminal Fe3 ion in 1a coordinates to six nitrogen atoms. Magnetic susceptibility measurements demonstrate that they exhibited gradual spin crossover (SCO) for the central Fe(ii) ion; however, different spin transition temperatures were displayed for complexes 1 and 1a (T1/2 = 202 K for 1 and 160 K for 1a). These different spin transition temperatures arise from the different intermolecular hydrogen bonding interactions in the two complexes. [ABSTRACT FROM AUTHOR]

Three heterocyclic azo dyes of azotriazolyl-2,7-dihydroxynaphthalene (H3AD), azotetrazolyl-2-naphthol (H2ATN) and azotetrazolyl-2,7-dihydroxynaphthalene (H3ATD) have been synthesized and characterized by IR, Raman spectra, 1H, 13C NMR and X-ray single-crystal diffraction techniques and their azo–hydrazone tautomerism has been achieved by pH control and coordination-coupled proton transfer. UV-vis spectra have been used to monitor the pH-titration and metal-ion complex experiments for three solutions of H3AD, H2ATN and H3ATD and the analysis of their spectral data has provided a clear proof that the hydrazone form is the dominant tautomer in acidic and neutral solutions, while the azo form is the dominant one in alkaline solutions. Crystallographic data demonstrate that the neutral dyes exist as hydrazone tautomers but are changed to azo tautomers when they coordinate to metal ions. The time-dependent density functional theory (TD-DFT) calculations are used to demonstrate the UV-vis spectroscopic properties. [ABSTRACT FROM AUTHOR]