Preparation, crystal structures, thermal decompositions and explosive properties of two new high-nitrogen azide ethylenediamine energetic compounds

Abstract

Two new multi-ligand coordination compounds of copper(II) ethylenediamine (en) azide and cobalt(III) ethylenediamine azide, [Cu₂(en)₂(N₃)₄]_n (1) and Co(en)₂(N₃)₂(NO₃) (2), were synthesized and characterized by elemental analysis and FT-IR spectroscopy. The crystal structures were determined by X-ray single crystal diffraction. The obtained results show that the crystals of 1 and 2 belong to the monoclinic, C2/c space group. The metal cations are six-coordinated with the azido ligands and ethylenediamine molecules through nitrogen atoms. The coordination modes of the azido-groups were μ-1, μ-1,1 and μ-1,1,3 modes for 1, and μ-1 mode for 2. Under a nitrogen atmosphere, with a heating rate of 5 K min⁻¹, the thermal decompositions contain two main exothermic stages in the DSC curves corresponding to the TG-DTG curves. The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa's method, respectively. The energies of combustion, enthalpies of formation, critical temperature of thermal explosion, entropies of activation (ΔS^≠), enthalpies of activation (ΔH^≠), and free energies of activation (ΔG^≠) were measured and calculated. The sensitivity properties were also determined with standard methods and the results showed that 1 had a much higher flame sensitivity and lower impact sensitivity.