Nitroimidazole And Pyridine Ketones Energetic Materials Synthesis, Structure And Thermal Decomposition Behavior

Many researchers are attracted by the heterocyclic energetic compounds with rich nitrogen for its specialty. The research of imidazole and pyridine with nitro groups becomes a focus in this field because many of them have rich nitrogen and high formation enthalpy; furthermore, these heterocyclic nitro-aromatic ring systems can form largeπbonds which are similar to the structure of benzene, and play an important role in improving the energetic density and stability of energetic materials. Of which a few metal salts could be used as burning rate catalysts and the organic nitrogen-rich energetic salts could be as next generation of green energetic materials.The main contents and results were as follows:Four kinds of ligands were firstly synthesized: 2,4-dinitroimidozale (3), 3,5-dinitro-2-hydroxy pyridine (19), 3,5-dinitro-4-hydroxy pyridine (20) and 3,5-dinitro-4-hydroxy N-hydroxide pyridine (21). Furthermore, 15 kinds of complexes derived from the ligand 3 were prepared, covering most of the alkali metals, alkali-earth metals and a several transition metals. Single crystals of the ligand 3 and six compounds were successfully grown. In addition, 12 kinds of nitrogen-rich organic energetic salts derived from 19, 20 and 21 were synthesized, covering ammonium, diethyl amine, hydrazine hydrate, guanidine carbonate and 3-amino-l,2,4-triazole. We also have grown single crystals of two compounds. All of these newly complexes were characterized and confirmed by melting point determination, element analysis, IR, XRD, ~1HNMR etc.Single crystals of the nine kinds of compounds were characterized by X-ray single crystal diffraction analysis and their molecular structures are compared and discussed. The results showed that the transmetal compounds are monomer and the alkali metals (alkaline earth) compounds are polymer containing the chelating ligands withη3,η2 and/orη1 coordination modes. The static electronic interaction between cation and anion contributes to the formation of the stabile organic nitrogen-rich energetic salt molecules.The thermal decomposition behaviors of ten complexes have been performed by TG and DSC analyses in order to study their thermal decomposition behavior and stabilities. The rule of some complexes were discovered. The analyses reveal that most compounds loss water molecules about 100℃with an endothermic process. An intensive exothermic process was found for each compound in the range of 200～400℃, generally breaking up nitro groups in the first stage, followed by collapse of the imidazole ring framework with the formation of metal oxides and carbon as residue finally.