New energetic materials: Synthesis and characterization of copper 5-nitriminotetrazolates

The energetic compounds 5-nitriminotetrazole (H2AtNO2, 1), 1-methyl-5-nitriminotetrazole (1MeHAtNO2, 2) and 2-methyl-5-nitraminotetrazole (2MeHAtNO2, 3), were reacted with Cu(NO3)2 · 3H2O and CuCl2 · 2H2O, respectively, in water as well as in aqueous ammonia solution. The syntheses yielded the complexes [Cu(HAtNO2)2(H2O)4] (4), [Cu(AtNO2)(NH3)3]2 (5), (NH4)2[Cu(AtNO2)2(H2O)2] (6), [Cu(1MeAtNO2)2(NH3)2] (7), [Cu(2-MeAtNO2)2(2-MeHAtNO2)2] (8), [Cu(2MeAtNO2)2]∞ (9), [Cu(2-MeAtNO2)2(NH3)2] (10), and [Cu(2MeAtNO2)2(NH3)4] · H2O (11). All complexes were characterized using low temperature single crystal X-ray diffraction, IR spectroscopy, elemental analysis, and differential scanning calorimetry. The magnetic properties of six of the complexes were investigated. Due to the energetic characters, the sensitivities towards impact and friction were investigated using the BAM drophammer and friction tester. The values range from “very sensitive”, comparable to primary explosives, to “insensitive” depending on the amount of water or ammonia coordinated. Since Cu(II) salts can be used for colorants in pyrotechnics, the combustions and flame colors were discovered to be intensively green.

Graphical abstractEight energetic copper(II) complexes were synthesized using three different 5-nitriminotetrazoles as ligands. The complexes are promising candidates as green colorants in smokeless pyrotechnical compositions. All complexes were characterized using low temperature single crystal-ray diffraction, IR spectroscopy, elemental analysis and differential scanning calorimetry. In addition the magnetic and energetic properties as well as the sensitivities were determined.Figure optionsDownload full-size imageDownload as PowerPoint slide