Alkali and transition metal (Ag, Cu) salts of bridged 5-nitrotetrazole derivatives for energetic applications

A family of energetic salts based on the novel 5-(5-nitrotetrazole-2-ylmethyl)-tetrazolate anion (NTTz(-)) with alkali metals (Li+ 6, Na+ 7, K+ 8, Rb+ 9 and Cs+ 10) were synthesized by the reaction of the free acid 5-(5-nitrotetrazole-2-ylmethyl)-tetrazole with a suitable alkali metal base (bicarbonate or carbonate) in alcohol or water. The sodium salt (7) was, in turn, used to form salts containing the NTTz(-) anion and Ag+ (11) or Cu2+ (12, 13a and 13b) cations. The new compounds were characterized by IR, Raman and NMR spectroscopy, mass spectroscopy, elemental analysis and differential scanning calorimetry (DSC). In addition, the solid-state structure of the NTTz(-) anion was determined by diffraction methods using X-ray analysis. We also assessed the energetic properties of the compounds using standardized (BAM) tests. Interestingly, the silver and copper salts are easily and safely initiated by the laser beam generated by a Raman machine and some of the compounds reported here have promising properties for applications as a new class of nitrogen-rich, more environmentally-friendly energetic materials.