Theoretical studies on vicinal-tetrazine compounds: furoxano-1,2,3,4-tetrazine-1,3,5-trioxide (FTTO-α) and furoxano-1,2,3,4-tetrazine-1,3,7-trioxide (FTTO-β)

Di- and trioxides of triazolotetrazine: Computational prediction of crystal structures and estimation of physicochemical characteristics

Simulation of crystal structures of series 1(2)-R-1(2)H-[1,2,3]triazolo[4,5-e][1,2,3,4]tetrazine 5,7-dioxides, 1,5,7-trioxides, 4,6-dioxides and 3,4,6-trioxides was carried out using an original technique based on the method of atom-atom potentials and quantum chemistry. The effect of the position of the substituent in the triazole ring on the change in the crystal structures of these compounds and their thermochemical characteristics was studied for the first time. For some of synthesized compounds, thermochemical characteristics were investigated and differential scanning calorimetry curves were obtained. Detonation parameters were calculated, on the basis of which the prospects for the use of the considered compounds were assessed.

The unusual combination of beauty and power of furoxano-1,2,3,4-tetrazine 1,3-dioxides: a theoretical study of crystal structures

The thermodynamic stability of the furoxan ring annullated with 1,2,3,4-tetrazine 1,3-dioxide cycle was studied. Crystal structure prediction based on global energy minimization in the framework of the atom-atom potential functions method was performed for isomeric furoxano-tetrazinedioxides (FuxTDOs): [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 1,5,7-trioxide (1) and [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 1,4,6-trioxide (2). The Coulomb energy was calculated with advanced point charge models fitted with high accuracy to the molecular electrostatic potentials of these molecules. The pressure and velocity of detonation of compounds 1 and 2 were estimated using the calculated enthalpy of formation and predicted molecular crystal density, which allows us to consider these compounds as high energetic materials.

Synthesis and theoretical studies on nitrogen-rich salts of bis[4-nitraminofurazanyl-3-azoxy]azofurazan (ADNAAF)

Multi-furazan compounds bis[4-nitramino- furazanyl-3-azoxy]azofurazan (ADNAAF) and its derivatives were first synthesized by our research group, and their structures were characterized by IR, ¹H-NMR, ¹³C-NMR spectrums, and element analysis. ADNAAF was synthesized by nitration reaction of bis[4-aminofurazanyl-3-azoxy]azofurazan (ADAAF), and then reacted with ammonium hydroxide, hydrazine hydrate, and guanidine nitrate to obtain three salts marked as salt 1, 2, and 3, respectively. The thermal stabilities of the three salts were supported by the results of DSC analysis, which shows the decomposition temperatures are all above 190 °C. Their densities, enthalpies of formation, and detonation properties were studied by density functional theory (DFT) method. Salt 1 has the best detonation pressure (P), 37.42 GPa, and detonation velocity (D), 8.88 km/s, while salt 2 has the best nitrogen content and heat of detonation (Q), 1.27 kcal mol^-1. The detonation properties of salt 1 is similar to that of 1,3,5-trinitro-1,3,5-triazineane (RDX). It means that the ammonium cation can provide the better D and P than the cation of hydrazine and guanidine. The three cations offer the enthalpies of formations in the order of hydrazinium > guanidinium > ammonium. Graphical Abstract Nitrogen-rich salts of bis[4-nitraminofurazanyl-3-azoxy]azofurazan(ADNAAF).

Theoretical studies of the structure, stability, and detonation properties of vicinal-tetrazine 1,3-dioxide annulated with a five-membered heterocycle. 2. Annulation with a pyrazole ring

1,2,3,4-Tetrazine (vicinal-tetrazine) high-energy-density compounds (HEDCs) are receiving increasing attention due to their promise as explosives. We have performed a series of studies of vicinal-tetrazine 1,3-dioxides annulated with a range of five-membered heterocycles, considering their potential as high-energy, low-sensitivity explosives. In the present work, 12 pyrazolo-1,2,3,4-tetrazine 1,3-dioxides (pyrazolo-TDOs), P1-P12, were studied theoretically. Their geometrical structures in the gas phase were studied at the B3LYP/6-311++G(d,p) level of density functional theory (DFT). Their gas-phase enthalpies of formation were calculated by the homodesmotic reaction method. Their enthalpies of sublimation and solid phase enthalpies of formation were also predicted. Their detonation properties were estimated with the Kamlet-Jacobs equations, based on their predicted densities and enthalpies of formation in the solid state. Their bond dissociation activation energies (BDAEs) and the available free space in the lattice of each compound were calculated to evaluate their stabilities. P1, P4, and P11 were found to achieve the energy level of RDX and have acceptable stabilities, and are therefore considered to be the three most promising pyrazolo-TDOs for use as high-energy, low-sensitivity explosives. We believe that further studies, both experimental and theoretical, of these three targets would be worthwhile.

Theoretical studies of the structure, stability, and detonation properties of vicinal-tetrazine 1,3-dioxide annulated with a five-membered heterocycle. 1. Annulation with a triazole ring

1,2,3,4-Tetrazine (vicinal-tetrazine) high-energy-density compounds (HEDCs) are receiving increasing attention due to their promise as explosives. We have performed a series of studies of vicinal-tetrazine 1,3-dioxides annulated with a range of five-membered heterocycles, considering their potential as high-energy, low-sensitivity explosives. In the present work, twelve 1,2,3-triazol-1,2,3,4-tetrazine 1,3-dioxides (TTDOs; T1-T12) were studied theoretically. Their geometric structures in the gas phase were studied at the B3LYP/6-311++G(d,p) level of density functional theory (DFT). Their gas-phase enthalpies of formation were calculated by the homodesmotic reaction method. Their enthalpies of sublimation and solid-phase enthalpies of formation were also predicted. Their detonation properties were estimated with the Kamlet-Jacobs equations, based on their predicted densities and enthalpies of formation in the solid state. Their bond dissociation activation energies (BDAEs) and the available free space in the lattice of each compound were calculated to evaluate their stabilities. T2, T5, and T11 were found to have higher energies than RDX and acceptable stabilities, and are therefore considered to be the three most promising TTDOs for use as high-energy, low-sensitivity explosives. We believe that further studies, both experimental and theoretical, of these three targets would be worthwhile.