Structure and properties of pentazole ionic salts

Context

Based on the periodic density functional theory, we systematically studied 13 kinds of anhydrous pentazole non-metallic ionic salts synthesized by other scientists (PA-1 ~ PA-13)[Chem-An Asian J, 13(8):924-928 6, J Am Chem Soc 140(48):16488-16494 7, J Mater Chem A 7(20):12468-12479 8, Chem-An Asian J 14(16):2877-2882 9]. The results show the following: first, the heat of formation of PA-1 ~ PA-13 exceeds that of TNT and RDX. The heat of formation of PA-9 reaches 1357.56 kJ/mol, and it has excellent detonation performance (D = 9.41 km/s, P = 34.79 GPa, Q = 7.78 kJ/g), demonstrating the potential of high-energy ionic salts. Second, in cations, the introduction of -NH₂ or -OH substituents is beneficial to improving the heat of formation and detonation performance, while the introduction of -COOH substituents is unfavorable for the improvement of the heat of formation and detonation performance. Third, replacing -NH₂ with -OH can improve the chemical reactivity of pentazole ionic salts, while increasing the number of -NH₂ or introducing carbonyl groups will reduce the reactivity. Forth, the introduction of -NH₂ can enhance the hydrogen bonding and increase the electron density of pentazole ionic salts, and the introduction of -COOH can enhance the van der Waals interaction and the steric hindrance effect. Fifth, with other conditions remaining unchanged, the larger the volume of the cation, the greater the impact sensitivity and friction sensitivity of the ionic salt as actually measured, and the more stable the ionic salt is.

Method

All calculations in this paper are performed using Gaussian 16 based on density functional theory. Firstly, the structures of the derivatives were optimized at the level of B3LYP-D3/6-311G**, and then single-site energy calculations were carried out at the level of M06-2X-D3/def2-TZVPP, in order to explore the influence of different cation structures on various properties of pentazole ionic salts.