新型多硝基吡啶酮类含能化合物的合成、结构表征及热分解行为的研究

　　新型多硝基吡啶酮类含能化合物的合成、结构表征及热分解行为的研究
　　Burning rate catalyst can improve and adjust the combustion performance of propellants and it is an indispensable component in the prescription of propellant.It focuses on the improvement of combustion performance of propellant to unify the high energy with low sensitivity of burning catalysts. Many researchers are attracted by the heterocyclic energetic compounds with rich nitrogen for its specialty.Among them,the research of pyridine with nitro groups becomes a branch 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.They are quite insensitive with heat,friction,spark and strike to external action.Therefore,it is Block neodymium magnet potential to be good energetic catalysts in the future research.Due to the presence of hydroxyl groups on the pyridine ring of hydroxylpyridines(its tautomer is pyridone),it is easier to synthesize their corresponding metal salt.We therefore selected polynitropyridone as starting materials of our energy containing compounds and a series of metal salts derived from polynitropyridones were designed and prepared.Their structures and thermal stabilities were characterized to provide evidence for the study of catalytic mechanism from microscopic aspect and theoretic support in the application as a potential combustion catalyst.
　　The main content and results were as follows:(1) Three kinds of dinitropyridone compounds were synthesized:3,5-dinitro-2-hydroxy pyridone, 3,5-dinitro-4-hydroxy pyridone and 3,5-dinitro-4-hydroxy N-hydroxide pyridone.The compounds 1 and 2 were obtained by one-step synthesis,while the compound 3 were synthesized by 4 steps and its yield was improved in some extent.Furthermore,46 kinds of complexes were synthesized with these three 3,5-dinitropyridone ligands,covering most of the alkali metals,alkali-earth metals,transition metals and rare earth metals.The complexes were characterized and confirmed by melting point determination,element analysis,IR,etc.(2) Single crystals of ten compounds(including the ligand 2) suitable for X-ray single crystal diffraction analysis were successfully grown and characterized.On the basis of the achievements of the past work of our group,the molecular structures of these compounds are discussed and compared.The enol form of ligand 2 is different from the keto form of ligand 1 and ligand 3.
　　The complexes of barium with ligands 1 and 2 are different,to some extent,from each other in structure:both compounds are binuclear bridged by carbonyl groups.The complex of ligand 3 is,however,a polymer without coordination with carbonyl group.The coordination mode of transition metals with the ligands is basically identical.All complexes exhibit distorted octahedral coordination,equatorially by four waters and axially by two nitrogen atoms or oxygen atoms from two ligands,with an inversion center located on the metal atom.Each pyridone is monodentate.There exist a number of intra-and inter-molecular hydrogen bonds in the pyridone between carboxyl http://www.chinamagnets.biz and nitro groups of ligand and water molecules as well as between water molecules.Within the structures of complexes with 2 or 3,each molecule connects two othermolecules through its four coordinated water molecules to form tri-centered hydrogen bonds,which link the molecules into an infinite one-dimensional chain.The tri-centered hydrogen bonds are one donor with two proton acceptors.The single crystals of neodymium with 2 and 3 are obtained.To our interest,during coordination the ligand 3 was probably decomposed to oxalic acid.The neodymium center is coordinated with two monodentate ligands,two chelate oxalates to form a one-dimensional chain and linked by hydrogen bonds to form three-dimensional network.(3) The thermal decomposition behaviors of complexes have been performed by TG/DTG and DSC analyses in order to study their thermal stabilities.As is shown in the results,the complexes are inclined to dehydration at first stage and the temperatures of decomposition of all compounds at second stage are all above 200℃.Of the studied complexes,the complex of nickel with 3,5-dinitro-2-hydroxypyridine shows the initial thermal decomposition temperature of 358℃and one exothermic peak at 368℃,with the heat release of 3409 J/g.Both the decomposition temperature and the heat release value are higher than those of the corresponding lead(Ⅱ) salts and indicated that the nickel(Ⅱ) compound could be a promising energetic catalyst in RDX-CMDB propellants.