Synthesis,Structures And Performance On Energetic Oxadiazoles And Tetrazoles

The extensive use of energetic materials in the military field has promoted their continuous development and innovation.The preparation of new energetic compounds with higher detonation performance,lower sensitivity,better chemical and thermal stability is a hot topic in the field of energetic materials.The transformation of energetic materials from traditional CHON-type energetic compounds to high-nitrogen energetic compounds has caused nitrogen heterocycles(such as oxadiazole,triazole,tetrazole,etc.)to receive widespread attention.The design of modern energetic materials not only considers the composition of the molecule,but also pays attention to the influence of the crystal structures and the weak interaction on the performance of energetic compounds.In this thesis,oxadiazole with high density and high oxygen content and tetrazole with high nitrogen content and high enthalpy of formation are taken as the research objects.The two energetic units are functionalized with different energetic groups and different structural assemblies.As results,a series of new oxadiazole and tetrazole energetic compounds were designed and synthesized.The effects of molecular and crystal structures on the physicochemical and energetic properties of energetic compounds were analyzed and discussed.This thesis includes energetic organic compounds and energetic metal complexes,and is mainly divided into the following five parts:1.Energetic tetracyclic oxadiazolesUsing[-NH-NH-],[-N=N-]and[-N=N(O)-]groups as energetic bridges,fourteen compounds with four oxadiazole rings were synthesized.Their structures were determined by various characterization methods and single crystal X-ray diffraction.The large amount of hydrogen bonding between the compounds makes the compounds show excellent thermal stability(T_d:204-322?).The detonation performance and mechanical sensitivity of these compounds were studied.The hydrazinium salt shows excellent overall performance.Its detonation velocity(D)is 9043 m s^-1and the detonation pressure(P)is 35.0 GPa.This compound was insensitive,with an impact sensitivity(IS)greater than 40 J and a friction sensitivity(FS)more than 360 N.Four oxadiazole rings were assembled by ring-to-ring direct connection,and thirteen new nitramine-functionalized tetra-oxadiazoles were synthesized.Their structures were determined by various characterization methods and single crystal X-ray diffraction.The formation of ionic salts planarizes the molecular structure and greatly improves the thermal stability of the neutral compound from 84 to 187-303?.Such a phenomenon was analyzed from the perspective of the bond length and bond dissociation energy of N-NO₂,the formation of hydrogen bonds,the electrostatic potential of the molecular surface and weak interactions.Among them,the hydroxylaminium salt shows excellent detonation performance(D:9030 m s^-1;P:36.0 GPa)and mechanical sensitivity(IS:12 J;FS:180 N).2.5-Azidotetrazolate hydroxylaminium salt and its hydroxylamine adductThe hydroxylaminium salt and its hydroxylamine adduct were obtained by reacting azidotetrazole with different equivalents of hydroxylamine.The structures of the two energetic compounds were confirmed by single crystal X-ray diffraction.The introduction of the hydroxylamine molecule realizes the transition from the 2D hydrogen bond framework of the ionic salt to the 3D hydrogen bond framework of the adduct,improving thermal stability and reducing sensitivity.The weak interactions between compounds and the role played by hydroxylamine molecules in the structure were studied.The hydroxylamine adduct shows the best detonation performance(D:9307 m s^-1;P:32.5 GPa)and mechanical sensitivity(IS:10 J;FS:140 N)among all azidotetrazole energetic compounds.3.Energetic dinitramine methylene-bridged furazan-tetrazolesUsing[-N(NO₂)-CH₂-N(NO₂)-]group as the energetic bridge,three new furazan energetic compounds were synthesized,and their structures were determined by single crystal X-ray diffraction.Dinitramine methylene-bridged furazan-tetrazole has a unique U-shaped molecular structure and 3D layered crystal arrangement,which makes it show good mechanical sensitivity.Comparing with compounds with similar structures,this compound has the best detonation performance(D:9043 m s^-1;P:35.6 GPa).4.Alkali metals-based furazan complexes as green primary explosivesAlkali metal(sodium,potassium,rubidium,cesium)ions were coordinated with the DBMF^2-ligand to obtain four metal complexes,which underwent single crystal X-rays diffraction to confirm their structures.DBMF^2-exhibits different U and N shapes with different metals,and its energy and the influence of electron cloud density on the coordination environment under different configurations were analyzed by quantum calculation.The detonation velocities of the sodium and potassium complexes were 8212m s^-1and 8227 m s^-1,respectively,and their impact sensitivities are 4 J and 2 J,respectively,which are better than those of lead azide,respectively.At the same time,the environmental impact of these two complexes is much less than that of lead azide,which indicates they can be used as green primary explosives.5.Silver-based tetrazole coordination polymers as primary explosives with positive oxygen balanceFive metal complexes were obtained by the coordination of silver ions,monocyclic tetrazole ligands and oxygen-rich anions,and the structures were confirmed by single crystal X-ray diffraction.The unit cell stacking of these complexes was analyzed from the perspective of the effect of different tetrazole ligands.These metal complexes have high densities(d:3.12-3.60 g cm^-3)and excellent thermal stability(T_d:251-348?).Mechanical sensitivity test results(IS:1-5 J;FS:2-50 N)show that these complexes are initiating agents.Explosive(initiating)experiments are used to compare the differences in the initiating performance of these complexes.Three oxygen balance methods(theoretical calculations,explosion equations,and combustion experiments)were used to confirm that the two complexes coordinated by silver ions,5-nitrotetrazole ligands,and nitrate/perchlorate showed positive oxygen balance.