Anion-Engineered Energetic Cu(II)-Based Complexes to Balance High Energy and Low Sensitivity

Laser-sensitive primary explosives (LSPEs) face a fundamental challenge in balancing energy release efficiency and mechanical safety for practical applications. Herein, we propose an innovative anion synergistic regulation strategy to address this bottleneck. Leveraging the unique protonation-driven coordination behavior of protonated pyridine-4-carbohydrazide ([HPDCA]⁺, featuring protonated pyridinic nitrogen and chelating carbohydrazide groups), three novel copper(II)-based energetic complexes with dual-structure (coordinated anions and free anions) were successfully synthesized, Cu(HPDCA)₂(H₂O)(NO₃)₄ (ECC-1), Cu(HPDCA)₂(ClO₄)₄ (ECC-2), and Cu(HPDCA)₂(NO₃)₂(ClO₄)₂ (ECC-3). Through comprehensive characterization (FT-IR, single-crystal XRD, PXRD, SEM/EDS) and quantum chemical calculations, we systematically elucidated the anion-mediated synergy (NO₃^- vs ClO₄^-) in regulating molecular architecture, thermal stability, mechanical sensitivity, and laser ignition performance. Thus, a quantitative structure-property relationship was established, linking "anion configuration─coordination bond strength─hydrogen-bond density─decomposition kinetics─sensitivity thresholds." The results demonstrate that the dual-anion system ECC-3 achieves a balance between high energy output (detonation velocity: 7330 m s^-1, laser ignition threshold: 78 mJ) and low mechanical sensitivity (friction sensitivity: 18 N) through functional segregation: the planar NO₃^- anions enhance lattice stability and desensitization, while the tetrahedral ClO₄^- anions optimize energy release efficiency and laser responsiveness. This work provides an innovative molecular design strategy for developing next-generation LSPEs that simultaneously possess both high energy performance and intrinsic safety characteristics.