Cai-Xia Xu

3,4-Diamino-1,2,4-triazole based energetic salts: synthesis, characterization, and energetic properties

The protonation or metathesis synthesis and energetic properties of a new class of energetic materials, energetic salts of 3,4-diamino-triazole (DATr), are described. They were characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), differential scanning calorimetry (DSC), and X-ray single-crystal diffraction. The DSC results showed that these salts had acceptable thermal stabilities; the decomposition temperatures of these salts, except compound 4, were over 200 °C. The density of the series of salts ranged from 1.704 g cm−3 (2 and 6) to 1.82 g cm−3 (7), placing them in a class of relatively dense compounds, and the heats of formation were calculated with the Gaussian 03 suite of programs. All the salts except 5 exhibited promising detonation performances (detonation pressure: 21.5–32.8 GPa, detonation velocity: 7017–8620 m s−1), which were much higher than both those of TNT, and salt 4 was even comparable to RDX. Impact sensitivities were also determined by hammer tests and the results ranged from 8 J (sensitive) to >40 J (insensitive).

Structural Diversity and Properties of M(II) Coordination Compounds Constructed by 3-Hydrazino-4-amino-1,2,4-triazole Dihydrochloride as Starting Material

Twelve metal coordination compounds with two triazole derivatives, namely, {[Mn(HATr)2](ClO4)2}n (1), [Mn(HATr)3]Cl(ClO4) (2), [Co3(ATr)6(H2O)6](ClO4)6·4.5H2O (3), [Co(HATr)3]Cl(ClO4) (4), [Co2Cl2(HATr)2(H2O)2(CH3OH)2]Cl2·2H2O (5), [Ni3(ATr)6(H2O)6](ClO4)6·4.5H2O (6), [Ni(HATr)3]Cl(ClO4) (7), [Ni2Cl2(HATr)2(H2O)4](ClO4)2·4H2O (8), [Ni2(HATr)2(H2O)6](ClO4)4·2H2O (9), {[Zn(HATr)2](ClO4)2}n (10), [Zn(HATr)3]Cl(ClO4) (11), and {[Cd4(HATr)8](CdCl4)Cl2(ClO4)4}n (12), when HATr = 3-hydrazino-4-amino-1,2,4-triazole and ATr = 4-amino-1,2,4-triazole, were prepared under diverse conditions and structurally characterized. Compounds 1, 10 and 12 exhibit one-dimensional zigzag chain structures; 2, 4, 7, and 11 possess mononuclear structures; 3 and 6 display trinuclear structures, while 5, 8, and 9 feature binuclear structures. Hydrogen bonds link these compounds into three-dimensional structures. The thermal stability and energetic properties also were determined.

Two coordination polymers with 3-hydrazino-4-amino-1,2,4-triazole as ligand: synthesis, crystal structures, and non-isothermal kinetic analysis

Two coordination polymers, [Mn2(HATr)4(NO3)4·2H2O]n (1) and [Cd2(HATr)4(NO3)4·H2O]n (2), were obtained from the corresponding metal nitrate with 3-hydrazino-4-amino-1,2,4-triazole (HATr) and characterized through elemental analysis and IR spectroscopy. The structures were determined by single-crystal X-ray diffraction. The results show that both complexes crystallize in the triclinic P-1 space group and have six-coordinate distorted octahedral structures, which are made up of infinite 1-D chains running along the a axis of metals linked by bridging-chelating HATr ligands. The coordination sites are in agreement with the computational results. Additionally, the decomposition temperatures were determined by differential scanning calorimetry and the kinetic parameters were calculated using Kissinger’s and Ozawa–Doyle’s methods; the energies of combustion for 1 and 2 were −7186.25 and −6922.53 kJ M−1 and the enthalpies of formation were obtained as −1002.35 and −457.27 kJ M−1, respectively. Graphical Abstract

Nitrogen-rich salts of 1-aminotetrazol-5-one: oxygen-containing insensitive energetic materials with high thermal stability

1-Aminotetrazol-5-one (ATO) is a new insensitive nitrogen-rich energetic compound with quite attractive detonation properties (D = 8.88 km s−1, P = 35.0 GPa), but its formation always requires harsh conditions to facilitate the process. In this contribution we presented an improved synthesis route of ATO in excellent yields and high purity. A large variety of nitrogen-rich salts of ATO were synthesized by means of Bronsted acid–base or metathesis reactions, and confirmed by single-crystal X-ray diffraction for the first time. These compounds were fully characterized by FT-IR and multinuclear NMR spectroscopy, elemental analysis (EA) and differential scanning calorimetry (DSC). All the salts except 7a decompose at temperatures over 220 °C; in particular, the aminoguanidinium salt and 3,4-diamino-1,2,4-triazolium salt are fairly stable with a decomposition temperature of 259 °C and 261.5 °C, respectively. Based on heats of formation calculated with Gaussian 09 and combined with experimentally determined densities, detonation properties of the energetic salts were obtained. They exhibit good thermal stability, excellent impact sensitivities (>40 J), reasonable detonation pressures (23.6–31.0 GPa) and velocities (7.53–8.72 km s−1) and might be potentially insensitive energetic materials.

Eco-friendly energetic complexes based on transition metal nitrates and 3,4-diamino-1,2,4-triazole (DATr)

Four eco-friendly energetic metal complexes of 3,4-diamino-1,2,4-triazole (DATr), including manganese (1), cobalt (2), nickel (3), and zinc (4), were synthesized by reacting DATr·HCl with the corresponding metal (Mn(II), Co(II), Ni(II), and Zn(II)) nitrate in aqueous solution and characterized by using Fourier transform-infrared spectroscopy and elemental analyses. The single crystals of 2, 3, and 4 were obtained and determined by X-ray single-crystal diffraction analysis. All three complexes crystallize in the monoclinic crystal system and belong to P2(1)/n space group. The thermal decomposition processes were investigated by differential scanning calorimeter (DSC) and thermogravimetry–derivative thermogravimetry analyses. The results show that the decomposition temperatures of 1–4 are above 260 °C, depending upon their onset DSC peaks. It can be predicted that these complexes based on 3,4-diamino-1,2,4-triazole have good thermal stability. The nonisothermal kinetic parameters of decomposition were calculated by using Kissinger and Ozawa–Doyle’s methods. Furthermore, the sensitivities of these complexes to impact, friction, and flame were determined. Sensitivity tests revealed that 2 was more sensitive to external stimuli compared to the other three complexes. Graphical Abstract Four nitrate-containing metal complexes based on 3,4-diamino-1,2,4-triazole are described as eco-friendly energetic coordination compounds. Their synthesis, characterization, and some energetic properties are studied. The figure reveals the crystal structure of zinc (II) complex and also suggests the coordination mode of metal complexes.

Synthesis, crystal structure and properties of a new 1D polymeric nitrogen-rich energetic complex {TAG[Li(BTO)(H2O)]}n based on 1H,1′H-5,5′-bitetrazole-1,1′-diolate

A novel energetic coordination polymer, or a new anionic metal–organic framework (MOF), of {TAG[Li(BTO)(H2O)]}n based on 1H,1′H-5,5′-bitetrazole-1,1′-diolate (BTO), was developed based on the reaction of BTO with triaminoguanidinium chloride (TAG·HCl) and lithium hydroxide (LiOH), and characterized by elemental analysis and IR spectroscopy. The crystal structure was determined by single-crystal X-ray diffraction measurements. Results show that the polymer belongs to the monoclinic space group C/2c with a density of 1.678 g cm−3, and the cell parameters were as follows: a = 15.6560(5) A, b = 6.3323(19) A, c = 23.8140(7) A, β = 91.342(3)°, V = 2360.20(12) A3, Z = 8, F(000) = 1232. The central lithium cation was coordinated by two N atoms, two O atoms from BTO ligands, and the O atom from one coordination water molecule. The infinite 1D-zigzag-chains were made up of the central lithium cations linked by bridging-chelating BTO ligands. The thermal decomposition of {TAG[Li(BTO)(H2O)]}n was studied based on technologies of differential scanning calorimetry (DSC) and thermogravimetry-differential thermogravimetry (TG-DTG). The non-isothermal kinetics parameters were calculated through the Kissinger and the Ozawa–Doyle methods, and the apparent activation energy was 236.6 kJ mol−1 and 233.1 kJ mol−1, while the critical temperature of thermal explosion was 231.6 °C. The enthalpy of formation for the polymer was also determined through the combustion heat data, measured by using oxygen bomb calorimetry, as 29.5 kJ mol−1. Additionally, the sensitivities towards impact and friction were assessed with relevant standard methods, the results show that the polymer can act as an insensitive explosive with its high nitrogen-content.

A 1D cadmium complex with 3,4-diamino-1,2,4-triazole as ligand: synthesis, molecular structure, characterization, and theoretical studies

An energetic complex, [Cd2(μ-Cl)4Cl2(DATr)2]n (1) (DATr = 3,4-diamino-1,2,4-triazole), was synthesized from DATr·HCl and cadmium(II) chloride. The product was characterized by Fourier transform infrared spectroscopy analysis, elemental analysis, X-ray diffraction analysis, and differential scanning calorimeter (DSC) analysis. The central cadmium(II) ions in 1 are six-coordinate twisted octahedral structures, which are made up of 1D chains linked by bridging chlorides. The results of the DSC analysis suggest the temperature of decomposition to be above 503.15 K. Furthermore, the kinetic properties of decomposition are studied by Kissinger’s and Ozawa–Doyle’s methods, and the calculated average activation is 166.5 kJ M−1, which means the complex is stable under normal conditions. In addition, the energy of combustion was measured by oxygen bomb calorimetry. The critical temperature of thermal explosion and parameters of thermodynamics of 1 were calculated. The periodic structure of 1 has been calculated based on the density functional theory. The theoretical results explain the electronic structure and thermal dynamic properties. Graphical abstract A new 1D Cd complex based on 3,4-diamino-1,2,4-triazole was synthesized and structurally characterized. Its thermal stability, non-isothermal kinetics analysis, and theoretical calculation were studied, and energy of combustion was also measured.

Synthesis, crystal structures and thermal stabilities of zinc coordination polymers containing the 3-hydrazino-4-amino-1,2,4-triazole ligand

Abstract Two zinc coordination polymers, {[Zn(HATr)2](NO3)2}n (1) and {[Zn2(HATr)4](ZnCl4)(NO3)2·H2O}n (2), were synthesized from reactions of 3-hydrazino-4-amino-1,2,4-triazole dihydrochloride (HATr·2HCl) with Zn(NO3)2. The polymers were characterized by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), elemental analysis, and differential scanning calorimetry. The crystal structures revealed that 1 and 2 have 1-D-chain structures, which were further assembled to form 3-D-frameworks by hydrogen bonds. Thermal analyses showed that these two compounds have thermal stability up to 280 °C. The energies of combustion, enthalpies of formation, critical temperatures of thermal explosion, entropies of activation (ΔS≠), enthalpies of activation (ΔH≠), and free energies of activation (ΔG≠) were also measured and calculated. Furthermore, the sensitivities of 1 and 2 toward impact, friction, and static were determined, which revealed that 1 and 2 were less sensitive than Ni(N2H4)3(NO3)2.