Towards groundbreaking green energetic materials

1/8/2016There is an increasingly pressing need for new, high-performance, environmentally benign energetic materials. Indeed, the state-of-the-art explosives and propellants are causing growing concern over their detrimental impact on the environment and human health. It is extremely challenging to find alternatives to the compounds currently in use, which are high performing, relatively insensitive and inexpensive to synthesize. This challenge requires the synthesis of new types of compounds. This dissertation summarizes my contribution to this effort. The approach of the Christe-Haiges research group to the synthesis of new energetic materials involves the targeting of groundbreaking, novel, highly challenging species, the development of efficient synthetic pathways and the characterization of these species. ❧ Chapters 2-3 deal with derivatives of 3,5-dinitro-1,2,4-triazole, an energetic building block with suitable properties for potential applications. In CHAPTER 2 the improved synthesis of 3,5-dinitro-1H-1,2,4-triazole (HDNT) and the first structural characterizations of that compound, which had been used in situ for decades, are described. This chapter also discusses the identifcation and structural characterization of common impurities formed when literature synthetic methods are followed. Some of these impurities were found to be dangerously more sensitive than the targetted HDNT. CHAPTER 3 describes the synthesis and structural characterization of over twenty 3,5-dinitro-1,2,4-triazolate (DNT) salts and polymorphs thereof, most of which are highly thermally stable and insensitive. ❧ CHAPTER 4-CHAPTER 7 describe the syntheses of hydro‐borane and ‐borate compounds with energetic ligands. Halogen‐free boron‐based energetic materials are promising compounds because of their environmentally benign combustion products and because of the high heat of formation of boron oxide. CHAPTER 4 describes the synthesis of salts of nitroazolate‐trihydroborate complex anions using, among several nitroazolates, some of the precursors described in CHAPTER 2 and CHAPTER 3. CHAPTER 5 describes the synthesis and full characterization of the first room temperature‐stable solid salts of trinitromethyl‐trihydroborate. The compounds demonstrate that boron hydrides can form stable derivatives even with highly oxidizing moieties. CHAPTER 6 describes the synthesis of the dinitramide‐substituted ammonia‐borane NH₃.BH₂[N(NO₂)₂], another example of a surprisingly stable energetic boron compound and the first structurally characterized Group 13‐dinitramide compound. CHAPTER 7 describes the observation of several dinitramide‐hydroborates, which demonstrates the potential use of dinitramide as a weakly coordinating anion. ❧ CHAPTER 8 describes the synthesis and characterization of nitryl cyanide, a small molecule which had long eluded synthesis. This species is another spectacular example of the combination of a strong oxidizer and a reducing group. The energy density of this molecule is extremely high and the compound could eventually serve as a replacement for hydrazine as a monopropellant. ❧ CHAPTER 9 describes the synthesis of fluorodinitramide, a particularly reactive and marginally stable compound which was characterized by low‐temperature NMR and vibrational spectroscopy. The study of the compound provided insight into the stability of the intriguing fluoronitroamine family