Theoretical study of effects of introducing varying linkages into bis-triazoles on energetic performance

A series of novel bis-triazole compounds was designed by combining high-energy functionalities (nitro and nitramino groups) as substituents with each triazole and incorporating of varying linkages into the bis-triazoles. Then, their heats of formation (HOFs), energetic properties, HOMO-LUMO, electrostatic potential, and impact sensitivity were studied theoretically to facilitate further developments. In general, all the designed compounds possess much higher HOFs than RDX, -CH₂-CH₂-, -N=N-, or -NH-NH- linkages contribute to increase the HOFs, while incorporation of the bridge group -O-CH₂-CH₂-O- shows negative effect on HOFs. Detonation properties of most of the designed compounds can be comparable with or even better than ones of RDX, suggesting that designing the bridged bis-triazoles-based derivatives with energy-rich substituents is an efficient method to obtain potential energetic compounds. Considering the detonation performance and impact sensitivity, -NH-(I), -N=N- (V), and -NH-NH- (VI) are favorable bridged groups between energetic moieties for designing efficient energetic materials (EMs).

Density Functional Theory (DFT) Study on the Structures and Energetic Properties of Isomers of Tetranitro-bis-1,2,4-triazoles

A series of isomers of tetranitro-bis-1,2,4-triazoles were designed, and their electronic structures, heats of formation, densities, detonation performances, thermal stabilities, and impact sensitivities were investigated by density functional theory (DFT). The structure and energetic properties of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were also calculated at the same level. On comparing with the detonation velocity and pressure and bond dissociation energy (BDE) of HMX, it was found that four isomers (BT2, BT5, BT6, BT7) have higher detonation performances than HMX and three isomers (BT5, BT6, BT7) have better thermal stabilities than HMX. The calculated results of impact sensitivities indicated that all of the designed isomers have more sensitivity than HMX. The calculated results of energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) indicated that all of the designed isomers were more easily excited than HMX in the chemical reaction process. In particular, 3,3',5,5'-tetranitro-1,1'-bis-1,2,4-triazoles (BT5) exhibited excellent detonation performances (9464 m s^-1, 39.44 GPa) and good thermal stability (BDE 256.81 kJ mol^-1). The results indicated that the isomerization of tetranitro-bis-1,2,4-triazoles could improve their detonation performance or thermal stability and might lead to a promising isomer possessing both good performance and high thermal stability.

Theoretical design of bis-azole derivatives for energetic compounds

Bis-azole derivatives are a new class of energetic materials with features that include high nitrogen content, high heat of formation (HOF), high detonation performance and insensitivity to external stimuli. In this paper, 599 new bis-azole compounds were designed in a high-throughput fashion using bis-azole molecules of high density and high thermal decomposition temperature as the basic structure, and high energy groups such as nitro (–NO₂) and amino groups (–NH₂) as substituents. The molecular geometry optimization and vibration frequency analysis were performed using the DFT-B3LYP/6-311++G(d,p) method. The calculation results show that none of bis-azole derivatives exhibit a virtual frequency. Additionally, the density, heat of formation and characteristic height (h₅₀) of the above compounds were obtained. Detonation performances were predicted by the Kamlet–Jacobs equations, and their structures and performances were studied. Furthermore, correlations between the performance parameters and the parent structure of the molecule, the number of substituting group and configuration were summarized, revealing promising potential candidates for high-energy density materials (HEDMs).

Bis-azole derivatives are a new class of energetic materials with features that include high nitrogen content, high heat of formation (HOF), high detonation performance and insensitivity to external stimuli.