Preparation And Application Of Triazole-Tetrazole Mixed Poly-Heterocyclic High-Nitrogen Content Compounds

The triazole and tetrazole has become a good choice for building high-nitrogen content energetic materials.The high-nitrogen content of the tetrazole ring can increase the enthalpy of formation of the compound,which could contribute to high detonation performance,and energetic materials composed of triazole always have good safety performance.Therefore,we may get the high-nitrogen content compounds with good detonation and safety performance by combining triazole and tetrazole.There are different methods to connect these azole rings,such as connecting them directly or using nitrogen bridge.Nitrogen bridge composed compounds have goood planarity for the conjugation of the nitrogen bridge with the entire molecule.And the presence of the nitrogen bridge can increase the nitrogen content and molar formation enthalpy,so they’re the best group to be used as bridge to connect azo rings in high-nitrogen compounds,and azo bridges are the most commonly reported among the nitrogen bridges.We synthesized one novel high-nitrogen content energetic compound 1,2-bis(5-(1H-tetrazol-5-y1)-1H-1,2,4-triazol-3-yl)diazene(2-4)with triazole-tetrazole mixed poly heterocycles,using two synthesis routes from 5-amino-1H-1,2,4-triazole-3-carbonitrile(2-1).And the synthetic routes were optimized,so that the final yields reached 82.34%and 77.70%.The structure of compound 2-4,and its important novel precursor 5,5’-(diazene-1,2-diyl)bis(1H-1,2,4-triazole-3-carbonitrile)(2-2),were characterized by Fourier transform infrared(FT-IR),NMR carbon spectroscopy(13C NMR),Mass spectrometry(MS)and element analysis.Their thermal performances were measured by thermogravimetry(TG)and differential scanning calorimetry(DSC),the sensitivity properties were measured by BAM standard methods.Their heats of combustion were measured by oxygen bomb calorimeter then standard molar enthalpy of formation were calculated according to Law of Hess.At last the detonation performances were calculated with EXPLO5.The structure of novel azo linked four-heterocyclic compound,1,2-bis(5-(1H-tetrazol-5-yl)-4H-1,2,4-triazol-3-yl)diazene(H4BTTD,2-4)was conjugated planar molecules according to single crystal structure,which was beneficial to interlayer π-π interactions between tetrazoles.The abundant nitrogens in compound 2-4 were beneficial to hydrogen bonds.These two interactions could induce layered crystal stacking which drastically reduce the mechanical sensitivity.Therefore,we constructed magnesium based complex[Mg2(BTTD)(H2O)8]n(3-1)and calcium salt[Ca(H3BTTD)2(H2O)7]n(3-2)from compound 2-4.Through the single crystal X-ray diffraction experiment,the crystal structure of compounds 3-1 and 3-2 were confirmed as layered structure,meanwhile,they were all insensitivity compounds according to sensitivity experiments.Using these structural data,the causes of these layered structures were also analysed in detail in this paper to confirm the influence of such molecular structure on the macroscopic properties of energetic materials through crystal stacking.Meanwhile,the physical and chemical properties of these compounds,such as mechanical sensitivity,thermal stability and detonation performance,were also characterized systematically.Moreover,it was found that compounds 2-4 and 3-2 could be used as alternative components to prepare high purity red pyrotechnic formulation.We synthesized one novel red pyrotechnics colorant MOF[Sr2(DTDA)(H2O)6]n(4-2),from one azo-triazole intermediates,2,2’-(3,3’-azo-bis(1H-1,2,4-triazol-5-yl))diacetic acid(H2DTDA,4-1)and strontium hydroxide octahydrate under hydrothermal condition.The stucture of compound 4-2 was characterized by Fourier transform infrared(FT-IR),single crystal X-ray diffraction(XRD),powder X-ray diffraction(PXRD)and elemental analyses.Its thermal decomposition temperature was measured by thermogravimetry(TG)and differential scanning calorimetry(DSC)and the sensitivity properties were measured by BAM standard methods.A pyrotechnic formulation was designed,and the feasibility of applying compound 4-2 to a red pyrotechnic colorant was analyzed.