Axial substitution of a precursor resulted in two high-energy copper(ii) complexes with superior detonation performances

Abstract

The design and synthesis of explosives with high performance, good thermal stability, and low sensitivity is an important subject for the development of energetic materials. Energetic complexes have recently emerged as a promising energetic material form. As one of the representatives, [Cu(Htztr)₂(H₂O)₂]_n (H₂tztr = 3-(1H-tetrazol-5-yl)-1H-triazole) was previously reported with good energetic performance, outstanding thermostability (T_dec = 345 °C) and low sensitivity to impact and friction stimuli. However, due to the existence of water molecules, its effective energy density is remarkably decreased, resulting in a diminished detonation performance. In order to further improve the detonation performance, using [Cu(Htztr)₂(H₂O)₂]_n as a precursor, {[Cu(Htztr)(H₂O)]NO₃}_n (1) and [Cu(H₂tztr)₂(HCOO)₂]_n (2) were synthesized by the axial substitution reaction with NO₃⁻ and HCOO⁻. The structures of 1 and 2 were characterized by single crystal X-ray diffraction. Both of them exhibit high thermal stabilities and insensitivities to impact and friction. Moreover, the same DFT calculation methodology shows that the heat of detonation of 2 (3.5663 kcal g⁻¹) is significantly higher than that of the precursor [Cu(Htztr)₂(H₂O)₂]_n (2.1281 kcal g⁻¹). Meanwhile, the empirical Kamlet–Jacobs equations were used to theoretically predict the detonation properties of the title complexes, and the results show that 1 and 2 have excellent detonation velocity (D) and detonation pressure (P).