Comparative study of two copper perchlorate hydrazide complexes: impact of coordination chemistry on laser sensitivity and energetic properties

Abstract

As the energy output carrier of the laser initiation sequence in the current safe and effective laser ignition technology, laser-sensitive primary explosives have attracted great attention. The development of energetic coordination compounds (ECCs) is a major research direction for novel laser-sensitive primary explosives. This paper presents the synthesis, structural characterization, and performance analysis of two copper(II) perchlorate-based ECCs, [Cu(BH)₂(ClO₄)₂] (ECCs-1) and [Cu(BH)₃](ClO₄)₂ (ECCs-2). By modulating the coordination chemistry through varying reaction conditions, the two compounds exhibit different structures, thermal stabilities, mechanical sensitivities, and laser ignition performances. Single-crystal X-ray diffraction reveals that ECCs-1 adopts an octahedral coordination environment, while ECCs-2 forms a distorted octahedral structure with three hydrazide groups coordinating to copper(II). The energetic properties of ECCs-1 and ECCs-2 were evaluated using differential scanning calorimetry (DSC), hot needle tests, and mechanical sensitivity measurements. ECCs-1 exhibits superior laser sensitivity, with a lower ignition energy threshold compared to ECCs-2. Furthermore, time-dependent density functional theory (TD-DFT) simulations elucidate the differences in charge transfer and excitation processes between the two compounds, highlighting the influence of coordination chemistry on their laser ignition behaviors. This work provides insights into the design and performance tuning of laser-sensitive ECCs via coordination chemistry, offering new avenues for the development of safer and more efficient energetic materials.