Computational investigations into the substituent effects of -N?, -NF?, -NO?, and -NH? on the structure, sensitivity and detonation properties of N, N'-azobis(1,2,4-triazole).
A series of derivatives of N, N'-azobis(1,2,4-triazole) substituted by -N?, -NF?, -NO?, and -NH? groups was studied using the density functional theory method. To reveal the orbital interactions clearly and interpret the stability of the title compounds, natural bonding orbital (NBO) analysis was carried out. Strong p-? and ?-? conjugation interactions exist in molecules. Substituent effects on the geometrical and electronic structures, aromaticity of the triazole ring, electronic sensitivity, impact sensitivity, thermal stability, density, solid state heat of formation [?H(f)(s)], detonation velocity (D), detonation pressure (P), and specific impulse (I(s)) were investigated. Substituent groups have significant and differing effects on performance. -N?, -NF?, and -NO? groups are very helpful for enhancing D and P, but the case is different for the -NH? group. The order of the contribution of various groups to P and D is -NF?>?-NO??>?-N??>?-NH?. -NF? brings the highest D and P, but the lowest I(s). -NO? results in the secondary highest D and P and the best electronic stability.-N? gives relatively low D, P and stability, but the highest ?H(f)(s) and I(s). -NH? leads to the lowest D and P, while giving the best impact and thermal stabilities. Therefore, it is necessary to consider various aspects comprehensively according to the practical requirements for each compound designed. Taking both detonation performance and sensitivity into consideration, introducing -NH? and -N? into N, N'-azobis(1, 2, 4-triazole) may be a good choice for designing high-energy density materials.