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Abstract:Because of the high calorific value, boron-based energetic compounds will become the research focus in the field of energetic materials. At present, the research on boron-based energetic compounds has not been widely carried out in China. In this paper, according to the research status abroad, the reported boron-based energetic compounds were preliminarily classified into five categories, i.e. nitrogen-rich boron esters, poly(azole)borates, nitroboranes, nitrogen-rich borazines and azide boron compounds. The structural characteristics、synthesis routes and basic properties of these five energetic borides were introduced respectively. Finally, the development trend of boron-based energetic compounds and their application prospect in propellants were analyzed and prospected: Due to the high tension bond energy, borozines or boron nitrogen heterocyclic compounds are expected to become the new research hotspot in the field of energetic materials. The synthesis method of poly(azole)borates is relatively convenient and the performance is easy to control, so it can be considered as a new way to improve the combustion performance of fuel-rich propellants by replacing boron particles. As the boron ester energetic compounds have high oxygen content, the heats of formation and oxygen balance can be further improved by introducing polynirto rich nitrogen groups, thus the possibility of replacement of ammonium perchlorate with them can be explored.

Abstract:The characteristics of high nitrogen content, compact structure, low sensitivity, and good thermal stability make the bipyrazole structures ideal energetic backbones for the synthesis of high energy density materials. Based on different linkers, such as C─C, C─N and N─N, between monopyrazole moieties, recent progress of the five dipyrazole based energetic compounds, including 2H,2′H-3,3′-bipyrazole(Ⅰ), 1H,1′H-4,4′-bipyrazole(Ⅱ), 1′H-1,4′- bipyrazole(Ⅲ), 2"H-1,3"-bipyrazole(Ⅳ) and 1"H,2H-3,4"- bipyrazole(Ⅴ), is reviewed from the aspect of synthetic strategy, explosophore introduction and property evaluation. The development and research trends on the synthesis of bipyrazole energetic compounds are analyzed. The key development directions of bipyrazole energetic compounds in the future are as follows: screen reported bipyrazole energetic compounds with excellent performance for synthetic and application research; design and synthesize more bipyrazole compounds with excellent and comprehensive properties by explosophore and nitrogen-rich cation introduction; strengthen the studies on synthesis and properties of several bipyrazole units (such as 2"H-1,3"-bipyrazole(Ⅳ) and 1"H,2H-3,4"-bipyrazole(Ⅴ) and 1,1"-bipyrazole(Ⅵ)) and improve the research of bipyrazole energetic compounds.

Abstract:In order to study the thermal decomposition behavior of 2,4,6-trinitro-3,5-difluorophenol, the non-isothermal decomposition reaction kinetics of 2,4,6-trinitro-3,5-difluorophenol was studied by thermogravimetric-differential thermal analysis (TG-DTA). TG-DTA experiments were carried out under dynamic nitrogen atmosphere of 30 mL·min^-1 with heating rates of 5, 10, 15 K·min^-1 and 20 K·min^-1, respectively. The thermal decomposition parameters of 2,4,6-trinitro-3,5-difluorophenol, such as activation energy (E) and pre-exponential factor (A), were calculated by F-W-O, Doyle, Kissinger and Satava- Sestak methods, respectively. Results show that the compound converts into molten state first and then decompose along with rapidly exothermic. The average apparent activation energy of thermal decomposition was calculated to be 122.65 kJ·mol^-1 with a pre-exponential factor of 1.37×10¹³ min^-1, and the integral form of reaction mechanism function is g(α)=α^1/2. The calculated activation enthalpy () in the thermal decomposition process according to its activation energy and pre-exponential factor is 123.06 kJ·mol^-1, the activation entropy () is 121.46 J·mol^-1·K^-1, and the Gibbs free energy of activation () is 62.98 kJ·mol^-1.

Abstract:Starting from (1-tert-butyl-3-nitroazetidin-3-yl)methanol, a melt-cast explosive of 3-azido-1,3-dinitroazetidine (AzDNAZ) with novel gem-azidonitro energetic group was obtained through an improved azidation-salinization-nitration strategy with a total yield of 58.8%. Structures of the intermediates and AzDNAZ were characterized by ¹H NMR, ¹³C NMR, IR and element analysis. One of the intermediates, 1-t-butyl-3-azido-3-nitro-azetidinium nitrate (compound 2), was obtained for the first time with the single crystal determined by X-ray single crystal diffraction, which reveals that it crystallizes in monoclinic, space group P2(1)/n with a=0.8281(314) nm, b=0.8607(2) nm,c=1.7195(2) nm, α=90°, β=94.983(2)°,γ=90°,V=1.2210(6) nm³,Z=4, M_r=262, D_c=1.427 g·cm^-3, μ=0.174 mm^-1, F(000)=552, R=0.0418 and ωR=0.1168. Meanwhile, thermal behaviors of AzDNAZ were studied by subsequently differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TG) methods. Based on the measured values of density and heat of formation, the detonation parameters were calculated by Gaussian 09 program and Kamlet-Jacobs equations. Results show that the melting point, decomposition point, density, heat of formation, detonation velocity and detonation pressure are 78.2 ℃, 180.7 ℃, 1.75 g·cm^-3,331.73 kJ·mol^-1, 8460 m·s^-1 and 31.83 GPa, respectively, indicating AzDNAZ can be applied as a promising melt-cast explosive or an energetic plasticizer with satisfactory performances.

Abstract:In order to obtain insensitive 1,3,4-oxadiazole energetic compounds, 1,2-bis(5,5′-dinitramino-1,3,4-oxadiazol-2-)ethane(BNOE) was synthesized via hydrazinolysis, cyclization and nitration using dimethyl succinate and cyanogen bromide as raw materials with a total yield of 49.93%. Its structure was characterized by elemental analysis, FT-IR and NMR. The thermal decomposition process was studied by TG-DSC, and the mechanical sensitivities were tested according to the GJB5891-2006 method. The density was measured using the density bottle method. The solid-state heat of formation (HOF) was calculated with Gaussian 09 software. The detonation parameters were calculated with EXPLO 5 v6.02 software. Results show that the onset decomposition temperature of BNOE is 202.2 ℃ and thermal decomposition peak temperature is 208.6 ℃. The sensitivity towards impact, friction, and electrostatic of BNOE is 8.6 J, 88%, and 108.1 mJ, respectively. The measured density is 1.714 g·cm^-3, the solid heat of formation is 48.25 kJ·mol^-1. The calculated detonation velocity and pressure is 7663 m·s^-1 and 22.6 GPa, respectively. The study on cyclization mechanism of 5-methyl-2-amino-1,3,4-oxadiazole (NAOz) by Gaussian 09 show that the reaction proceeds in two stages: hydrazinolysis and ring formation.

Abstract:To explore the hydrolysis behavior and internal rule of oxadiazole nitramide compounds, the natural bond orbit(NBO) charge distribution and lowest unoccupied molecular orbital (LUMO) orbital distribution of unstable oxadiazole nitramide compounds were analyzed by theoretical calculation. LUMO orbital coverage was found in the carbon center connected with the nitramide group, which was the possible reaction site and the NBO charge at this site was the highest in the molecule (usually around 0.7 a.u), which was the main factor leading to the occurrence of hydrolysis reaction. Based on this consequence, the hydrolysis reactions of N,N′-([3,3′-bi(1,2,4-oxadiazole)]-5,5′-diyl)dinitramide and N,N′-([2,2′-bi(1,3,4-oxadiazole)]-5,5′-diyl)dinitramide (ICM-101) compounds were successfully predicted. The hydrolysis products [3,3′-bi(1,2,4-oxadiazole)]-5,5′(4H,4′H)-dione and [2,2′-bi(1,3,4-oxadiazole)]-5,5′(4H,4′H)-dione were obtained by hydrolysis experiments in boiling water. Then the corresponding structures were characterized, the site of hydrolysis reaction was identified, and the mechanism of hydrolysis reaction was elucidated. Using the method of structural equivalence, the order of the hydrolysis activity of azole nitramide compounds was put forward as follows: furazan < 3-substituted-1,2, 4-oxadiazole <1,2, 4-triazole <1,3, 4-oxadiazole < 5-substituted-1,2, 4-oxadiazole.

Abstract:A novel N-amino compound—4-amino-1,2,3-triazolo[4,5-e]furazano[3,4-b]pyrazine 6-oxide (ATFPO) was designed and synthesized by the reactions of substitution, nitrification-cyclization, neutralization and N-amination using self-synthetic 3,6-dichlorinefurazano[3,4-b]pyrazine as starting material. The structures of intermediates and target compound were characterized by means of IR spectra, ¹H NMR, ¹³C NMR and elemental analysis. The single crystal of key intermediate—tetraethyl ammonium 1,2,3-triazolo[4,5-e]furazano[3,4-b]pyrazine 6-oxide (TTFPO) was obtained, and the crystal structure was analyzed. The crystal of TTFPO belongs to monoclinic system，space group P2(1)/c, cell parameters: a=9.237(2) Å, b=22.162(5) Å, c =7.3506(17) Å, α=90°, β=98.378(4)°, γ=90°, V=1488.6(6) ų, Z=4, μ=0.100 mm^-1, F(000)=656. The study on thermal stability of ATFPO by using differential scanning calorimetry (DSC) method show that its melting point is at 208.77 ℃, the thermal decomposition peak temperatures of ATFPO are 247.13 ℃, 293.68 ℃ and 378.29 ℃, respectively. Based on the calculated (CBS-4M) heat of formation and the experimental density, the detonation parameters of ATFPO were computed using Gaussian 09 program and Kamlet-Jacobs equations. The heat of formation is 705.4 kJ·mol^-1, the detonation velocity is 8743 m·s^-1, the detonation pressure is 34.6 GPa and the detonation heat is 5970 kJ·kg^-1. The mechanical sensitivity was determined according to BAM Fall hammer method, and the impact sensitivity is 35 J. Results show that ATFPO is a novel high energy density material with good thermal stability, insensitivity and preferable detonation properties.

Abstract:In order to explore the effect of trifluoromethyl group on the performance of energetic materials, 2,6-dinitrate- 3,3,7,7-tetra-trifluoromethyl-2,4,6,8-tetraazabicyclo [3.3.0] octane (4), 2,4,6-trinitro-3,3,7,7-tetra-trifluoromethyl-2,4,6,8-tetraazabicyclo [3.3.0] octane (5) and 2,4,6,8-tetranitrate-3,3,7,7-tetra-trifluoromethyl-2,4,6,8-tetraazabicyclo [3.3.0] octane (6) were synthesized from the aza-fused ring precursor (3,3,7,7-tetra-trifluoromethyl-2,4,6,8-tetraazabicyclo [3.3.0] octane) through improved multi-step nitration in fuming nitric acid. The precursor was obtained from condensation of diaminohexafluoropropane and glyoxal. The structure of all nitration products were characterized by ¹H, ¹³C and ¹⁵N NMR. The density of compound 6 is the highest (up to 2.08 g·cm^-3) by testing with exhaust gas method. For all three compounds, the impact sensitivity measured by the dropping hammer lift is greater than 30 J, and the friction sensitivity based on BAM method is greater than 360 N. The TG-DTG analysis shows that the mass loss of all three products is more than 90% and their thermal stability decrease with the increase of nitro group. The detonation properties were estimated by Monte-Carlo statistical methods and theoretical models using Gaussian 09 calculation package. The detonation velocity and detonation pressure of compound 6 are 11937 m·s^-1 and 74.3 GPa, respectively. Due to the high density and greater electronegativity, the introduction of CF₃ group reduces the sensitivity while maintaining higher density and good detonation performance compared with that of tetranitroglycoluril (TNGU). It also opens up new ideas for the research of energetic materials.

Abstract:By using 3-bromo-2,2-bis(bromomethyl)propan-1-ol (TAOH) as starting material, a novel multi-azido energetic plasticizer bis(3-azido-2,2-bis(azidomethyl)propyl) malonate (BAAMPM) was synthesized via consecutive azidonation reaction and esterification reaction. All structures were characterized by NMR and IR spectrum. The influencing factors of azidonation reaction and esterification reaction were studied, and the optimal reaction conditions were determined as follows: for azidonation reaction, n(TBrOH)∶n(NaN₃)=1∶3.3, the reaction temperature is 90-95℃, and the reaction time is 12 h; for esterification reaction, n(TAOH)∶n(MalAc)∶n(TsOH)=2∶1∶0.13, refluxing in toluene for 15 h, and the yield and purity of BAAMPM are 89.5% and 98.5%, respectively. For BAAMPM, the glass transition temperature (T_g) and thermal decomposition peak temperature were determined by differential scanning calorimetry (DSC) as -58.3 ℃ and 231.0 ℃, respectively. According to the GJB772A-1997 method, the impact sensitivity of BAAMPM was measured as H₅₀=40.9 cm, the friction sensitivity was 28%, which indicate that BAAMPM has good low temperature performance, good thermal stability as well as relatively low mechanical sensitivities.In addition, as the viscosity and glass transition temperature tests shown, BAAMPM could notably reduce the viscosity and glass transition temperature of glycidyl azide polymer (GAP). With the increase of the proportion of BAAMPM, the more obvious improvement for the viscosity of GAP, and the larger extent of lowering glass transition temperature of GAP are achieved. For example, the viscosity of BAAMPM/GAP (4/10) at 30 ℃ is reduced by 52.65% compared with that of GAP, while its T_g is -53.2 ℃, 4.1 ℃ lower than that of GAP. Therefore, BAAMPM demonstrates good plasticizing effect on GAP.

Abstract:To satisfy the growing demand for military and civilian applications, a new energetic compound, 2-azido-6-methyl-5-nitropyrimidin-4(3H)-one(AMNP), was prepared from 5-aminotetrazole and ethyl acetoacetate through a two-step synthesis of cyclization and nitration with a total yield of 60%. Its structure was characterized by element analysis (EA), infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). The single crystal of AMNP was cultured from isopropanol. Its molecular structure and crystal structure were determined by X-ray single crystal diffraction analyzer. The crystal belongs to orthorhombic crystal system, space group Pna2₁,with M_r=196.14,a=19.800(4) Å,b=5.6660(10) Å,c=14.300(3) Å,V=1604.3(5) ų, Z=8, D_c=1.624 g·cm^-3. The thermal behavior of AMNP was studied by using the differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TG/DTG) method. Its first decomposition peak is 227.39 ℃ and the second one is 298.75 ℃, which indicate that it has a good thermal stability. According to standard BAM method, the impact sensitivity is 10 J, and the friction sensitivity is above 360 N.

Abstract:With 1.3-diaminoguanidine hydrochloride and oxalic acid as starting materials, an insensitive energetic salt of 5,5′-diamino-4,4′-dinitroamino-3,3′-bi-1,2,4-triazole triaminoguanidinium salt (TAGAT) was synthesized by cyclization, nitration and salt formation reactions. The single crystal sample of TAGAT was obtained from water by cooling method and the detailed crystal structure was characterized by X-ray diffraction analysis. Results showed that TAGAT crystallizes in the monoclinic space group P2₁/c with cell parameters of a=11.4979(5) Å, b=6.3468(2) Å, c=14.0945(5) Å, β=101.7910(10)°, V=1006.84(6) ų, Z=2, µ=0.136 mm^-1, F(000)=516.0 and its crystal density was 1.631 g·cm^-3 at 170 K. Thermal behaviors of TAGAT were investigated through TG-DSC method, indicating an onset decomposition temperature of 211 ℃. Constant-volume combustion experiment showed that the maximum gas-generating pressure of TAGAT was 6.38 MPa and the average pressure-up rates of TAGAT was 0.275 GPa·ms^-1. Based on Born-Harber Energy Cycle, the Gaussian 09 program was applied to calculate the standard generation enthalpy of TAGAT as 1218.5 kJ·mol^-1. The detonation parameters of TAGAT were calculated with the EXPLO5(V6.02) program, leading to a calculated detonation velocity of 8795 m·s^-1, a calculated detonation pressure of 28.4 GPa and a calculated gas volume of 924.9 L·kg^-1. Sensitivities toward impact and friction were determined through BAM sensitivity testers, exhibiting that the impact sensitivity of TAGAT was 32 J and the friction sensitivity of TAGAT was greater than 360 N.

Abstract:A new energetic compound 3,3"-bis(2-nitroamino-1,3,4-oxadiazol-4-yl)-5,5"-linked-1,2,4-oxadiazole (BNOBO) was synthesized starting from glyoxime through a five-step reaction. Based on the acidity of BNOBO, three energetic salts (5-7) were obtained through the reactions between BNOBO and aqueous ammonia, hydrazine and hydroxylamine, respectively. The structures of as-synthesized compounds were characterized by single-crystal X-ray diffraction, IR, NMR and element analysis. The crystal of BNOBO ammonium salt was obtained through solvent evaporation method ,the obtained results show that it belongs to a monoclinic system and C2/c space group with a=12.7490(8) nm, b=9.5957(7) nm, c=18.5965(12) nm, V=2272.1(3) nm³ and Z=4. Their thermal stability, density, detonation properties and sensitivity were evaluated by TG/DSC analysis, densitometer, EXPLO5 v6.02 software and BAM sensitivity tester, respectively. Among these new energetic compounds, BNOBO possesses the highest measured density of 1.90 g·cm^-3 and the highest onset decomposition temperature of 215 ℃. The calculated detonation velocity and pressure of BNOBO are as high as 8789 m·s^-1 and 32.7 GPa, respectively. These new energetic compounds also exhibit relatively low mechanical sensitivities, in which energetic salt 5 display the low impact sensitivity of more than 20 J and friction sensitivity of 220 N.

Abstract:The synthesis of novel high energy low sensitivity materials is important for improving of energy level and safety performance of weapons. 5,6-Diaminofurazano[3,4-b]pyrazine-4,7-dioxide (DAFPO) was firstly synthesized by oxidation reaction using 5,6-diaminofurazano[3,4-b]pyrazine as raw material. Its structure was characterized by nuclear magnetic resonance (¹H, ¹³C and ¹⁴N spectrum), infrared spectroscopy and element analysis. The single crystal of DAFPO·2H₂O was cultivated from ethyl acetate. Its crystal structure was determined by X-ray single-crystal diffraction, and the intermolecular interactions were investigated by Hirshfeld surface analysis. DAFPO·2H₂O belongs to orthorhombic system, space group Pna2₁, the crystal density is 1.806 g·cm^-3 at 296 K. The crystal is stabilized by strong O…H and N…H hydrogen bonds interactions existed in different molecules. The thermal behavior of DAFPO was studied by DSC and TG/DTG method, giving decomposition temperature at 131.8 ℃. Based on atomization reaction and Gaussian 09 software, the calculated solid heats of formation of DAFPO is 753.5 kJ·mol^-1. Its density is 1.86 g·cm^-3 by gas expansion replacement method. The calculated detonation velocity and detonation pressure predicted by EXPLO5 code are 8836 m·s^-1 and 36.0 GPa, respectively. According to standard BAM method, the impact sensitivity is above 40 J, and the friction sensitivity is above 360 N. It is found that DAFPO is a novel low sensitivity energetic material with high energy level and good safety performance.

Abstract:A novel red pyrotechnics colorant MOF [Sr₂(DTDA)(H₂O)₆]_n (1) was synthesized from one high-nitrogen content ligand with carboxylic acid, 2,2"-(3,3"-azo-bis(1H-1,2,4-triazol-5-yl)) diacetic acid (H₂DTDA) and strontium hydroxide octahydrate under hydrothermal condition. The structure of compound 1 was characterized by Fourier transform infrared (FT-IR), single crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD) and elemental analysis. Its thermal decomposition temperatures were measured by thermogravimetry (TG) and differential scanning calorimetry (DSC), and the sensitivities were tested by BAM standard methods. A pyrotechnic formulation was designed, and the feasibility of applying compound 1 to a red pyrotechnic colorant was analyzed. It is showed that the structure of compound 1 is two-dimensional (2D) structure and there are hydrogen bonds between layers. Compound 1 can also be obtained by a large-scale hydrothermal experiment. The low impact sensitivity (IS = 80 J) and friction sensitivity (FS > 360 N) indicate that compound 1 is an insensitive energetic material and can be used as a red colorant in pyrotechnic formulation.

Abstract:In order to study the performance of energetic metal-organic framework (E-MOFs) with dual ligands, MOF(Zn)-1, an E-MOFs containing dual ligands were prepared by hydrothermalmethodusing 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole and zinc formate as raw materials. The growth mechanism of MOF(Zn)-2 with 3-amino-1,2,4-triazole as ligand and MOF(Zn)-3 with 3,5-diamino-1,2,4-triazole as ligand were studied. The crystal structures of MOF(Zn)-1, MOF(Zn)-2 and MOF(Zn)-3 were analyzed by X-ray single crystal diffractometer. Results show that MOF(Zn)-2 and MOF(Zn)-3 both belong to orthorhombic system while MOF(Zn)-1 belongs to triclinic system. The study of differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TG) shows that there is only one intense exothermic process for all three materials. The decomposition temperatures of MOF(Zn)-1, MOF(Zn)-2 and MOF(Zn)-3 are 317.5, 301.5 ℃ and 308.2 ℃ at a heating rate of 5 ℃·min^-1, respectively. The sensitivity test shows that the above three materials are insensitive energetic materials (IS > 40 J, FS > 360 N, and ESI > 24.75 J). Because of the relatively high density (MOF(Zn)-1: 2.069 g·cm^-3; MOF(Zn)-2: 2.177 g·cm^-3; MOF(Zn)-3: 2.222 g·cm^-3), the predicted detonation performances are relatively good (MOF(Zn)-1: D = 5.9 km·s^-1,p = 17.88 GPa; MOF(Zn)-2: D = 6.0 km·s^-1, p =19.38 GPa; MOF(Zn)-3: D = 6.5 km·s^-1, p = 22.17 GPa).

Abstract:Polynitroadamantanes are a class of stable and prospective cage-like energetic compounds. 4-Azido-2,2,6,6-tetranitroadamantane was synthesized from diethyl malonate and paraformaldehyde via cyclization, decarboxylation, formylation, Aldol condensation, O-sulfonylation, azidation, oximation and gem-dinitration reactions with a total yield of 9.8%. The thermal stability of 4-azido-2,2,6,6-tetranitroadamantane was investigated through differential scanning calorimetry (DSC) and thermogravimetry (TG) methods. The onset decomposition temperature and the decomposition peak temperature were located at 219 ℃ and 251 ℃, respectively, indicating a good thermal stability. Compared with 2,2,6,6-tetranitroadamantane and 2,2,4,4,6,6-hexanitroadamantane, the replacement of hydrogen in C-4 by azido group resulted in decreased thermal stability, in contrast, the thermal stability was improved by replacing the gem-dinitro group in C-4 by azido group. By using desity functional theory, 4-azido-2,2,6,6-tetranitroadamantane showed a density of 1.79 g·cm^-3, a detonation velocity of 7770 m·s^-1, and a detonation pressure of 26.68 GPa. Results indicate that 4-azido-2,2,6,6-tetranitroadamantane is a high-energy compound.

Abstract:To investigate the effect of the ion source structure on the formation of doped nitrogen clusters with high nitrogen content, the conventional laser ablation ion source was improved by adding liquid nitrogen cooling and reducing the distance between nozzle of pulse valve and laser ablation spot, and nitrogen clusters doped by alkali metals and first transition metals were studied. LiN_n⁺ (n=6,8,10,12,14,16,18), Li₂N_n⁺ (n=8,10,12), NaN_n⁺ (n=2~27), VN_n⁺ (n=6,8,9,10,11,13,15), V₂N_n⁺ (n=17,19,21), CrN_n⁺ (n=2,4,6,8,9,11) and Cr₂N_n⁺ (n=9,10,11) were observed by time of flight mass spectrometer (TOF-MS). Results indicate that the improved ion source can significantly increase the number of generated doped nitrogen clusters and their nitrogen content. In addition, the type of doped metals has a great influence on the composition of generated clusters. In each type of metal-doped nitrogen clusters, the most abundant clusters are LiN₈⁺, NaN₁₂⁺, VN₁₁⁺ and CrN₈⁺, respectively.

Abstract:In order to study the formation rule of hydrogen bonds in pentazole non-metal salts and its influence on stability, the Reduced Density Gradient (RDG) theoretical analysis method was used. The hydrogen bonding interactions of a single N₅^- anion and its surrounding cations in the structure were investigated. The hydrogen bond length was read from the single crystal structure of each compound, and the strength was obtained from the RDG analysis. Results show that N₅^- anion can form two types of hydrogen bonds, N—H…N and O—H…N, with N—H and O—H proton donors with electro positivity. O—H…N hydrogen bonds are stronger, while N—H…N hydrogen bonds are weaker. There are two factors influencing the stability of N₅^- anion, one is the structure symmetry of N₅^- anion, and the other is the graphene-like structure that forms a crystal plane layer. Under the interaction of hydrogen bonding, N₅^- anion maintain good structural symmetry (biguanidinium pentazolate salt, 10) and graphene-like structure (3,6,7-triamino-7H-[1,2,4]triazolo[4,3-b] [1,2,4]triazol-2-ium pentazolate salt, 12), which can significantly improve the stability and bring the decomposition temperature up to 124.8 and 120.9 ℃. On the contrary, if the hydrogen bonding causes serious deformation of N₅^- anion structure, which leads to the loss of symmetry and fails to provide planar stacking (oxalohydrazinium pentazolate salt, 3 and 4,4’,5,5′-tetraamino-3,3′-bi-1,2,4-triazol-2-ium pentazolate salt, 4), the stability of the N₅^- anion will decrease significantly, and the decomposition temperature is only 95 ^oC.

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