Modern high-energy density materials (HEDM), where energetic nitrogen rich salts are among the most recent and exciting developments, continue to attract considerable interest. [4] The use of nitrogen-containing anions and cations contributes to high heats of formation and high densities arising from the large number of inherently energetic N-N and C-N bonds. Salt-based energetic materials often possess advantages over non-ionic molecules since these salts tend to exhibit lower vapor pressures and higher densities than their atomically similar non-ionic analogues.
The decomposition of these compounds results predominantly in the generation of dinitrogen which makes them very promising candidates for applications requiring environmentally friendly highly energetic materials. Syntheses of these energetic salts involve the combination of unique cations and anions containing energetic functionalities. Most of the cations are based on bulky organic species with high nitrogen-containing heterocycles predominating, such as triazole, tetrazole, triazine, and tetrazine. Most frequently the anion is inorganic, such as nitrate, perchlorate, and dinitramide. [7] Since some organic anions have considerable nitrogen content and are expected to have attractive stabilities toward friction, impact, and heat, they are also good candidates for energetic salt design, e.g., 5,5′-azotetrazolate, [8] 3,5-dinitro-1,2,4-triazolate, [9] 4,5-dinitroimidazolate, [9] 3-nitro-triazolate, 5-nitro-tetrazolate, iminobis(5-tetrazolate), [8c] 5′-bis(tetrazolate), [8c] bisdinitroimidazolate, 3-nitro-1,2,4-triazol-5-one, [13] picrate, 3-amino-6-nitroamino-tetrazine anion, and trinitroimidazole. Recently, copper complexes of N,N-bis-( (2)H-tetrazol-5yl)amine (H 2 Bta) (1) were reported. The acidic protons of H 2 Bta enable the formation of the corresponding salts by reactions with nitrogen-rich bases. Although there are several reports of Bta salts, most of them appear in patents or unpublished documents. [18] Previously we reported bis(4-amino-1,2,4-triazolium) Bta which when subjected to microwave heating gave rise to a nano powder. [8c] This result catalyzed us to continue our study of Bta salts which have a high nitrogen content (Scheme 1). Thus, compounds 2, 3, and 4 were synthesized by taking advantage of the acidity of H 2 Bta and its reactions with bases. With the exception of the synthesis of bis(5-amino-1,2,3,4-tetrazolium) Bta, 4, in which methanol was used as the solvent, it is possible to carry out all of the other reactions including H 2 Bta with ammonia, hydrazine, guanidine carbonate and aminoguanidine bicarbonate in water to form 2, 3, 5, and 6. Reacting the barium salt of Bta [18b] with the corresponding sulfates in water gave 7, 8, and 9.
Density is one of the most important physical properties of any energetic material. As can be seen in Table , the densities of most of the new salts range between ∼ 1.5 to ∼ 1.7 g cm -3 . Calculated values are in close agreement. It is noteworthy