Synthesis And Properties Of Pyrazolate Coupled Triazolium-based Energetic Salts

The development of new energetic materials with high energy,high thermal stability and low sensitivity is the permanent goal of the field of explosive research.However,the requirements of high energy and low sensitivity of the energetic materials are quite often contradictory to each other,most energetic materials with high performance characteristics concomitantly tend toward greater sensitivity.The design of the energetic salts based on nitrogen-rich azole compounds with high heat resistance is one of the effective strategies to solve the problem.Azole compounds contain large number of N-N and C-N bonds,which result in high heat of formation,high density and high thermal stability.Moreover,their energetic salts have good adjustability,and both of anion and cation can be modified independently.Through careful design of the anionic and cationic components,energetic materials with excellent detonation performance,high heat resistance and low sensitivity are expected to be produced.In this thesis,a new C-N linked heterocoupled energetic compound potassium4-(5-amino-3-nitro-1H-1,2,4-triazol-1-yl)-3,5-dinitropyrazole(KCPT)was designed and synthesized successfully along with its neutral compound HCPT and thirteen energetic salts,which were then fully characterized using ¹H NMR,¹³C NMR,IR and elemental analysis.KCPT,HCPT,triaminoguanidinium salt,3,4,5-triamino-1,2,4-triazolium salt and copper(II)complex were further determined by single-crystal X-ray diffraction.And topological analysis confirmed that KCPT was a novel 3D MOF.All the compounds exhibit excellent thermal stabilities with decomposition temperatures over the range 215 ^oC-340 ^oC.Among these,guanidinium salt exhibits the highest thermal stability(T_d=340?).KCPT has a decomposition temperature as high as 325?,which is comparable to that of TATB(T_d=330?).The thermostability of KCPT was further investigated by thermogravimetric analysis(TGA)and isothermal long-term experiment.The measured densities of HCPT and its enegetic salts ranged between 1.65-1.98 g cm^-3,and KCPT has the highest density(d=1.98 g cm^-3).The sensitivities of the compounds were measured,and some salts can be classed as insensitive energetic materials(IS>40 J,FS>360 N).Meanwhile,suitable impact and friction sensitivities of KCPT were determined,equal to 7.5 J and 240 N,respectively.Formation of the nitrogen-rich salts results in a marked decrease in the impact sensitivity values.The heats of formation of HCPT and its energetic salts were calculated to range from 529.4 k J mol^-1 to 1211.7 k J·mol^-1by Gaussian software based on the designed isodesmic reactions.The detonation pressures and velocities of these energetic salts were calculated by EXPLO5 program(version 6.01)to be between 26.5-37.8 GPa and8236-9167 m s^-1,respectively.The neutral compound HCPT exhibits the best detonation performance(v _D=9167 m s^-1,P=37.8 GPa)among these compounds,superior to that of HMX(v _D=9059 m s^-1,P=39.2 GPa).The detonation pressure and velocity of KCPT were calculated using the EXPLO5 program and the improved method on the basis of the empirical Kamlet formula and the calculated values using the two methods are similar.KCPT(v _D=8457 m s^-1,P=32.5 GPa)exhibits the best calculated detonation performance among the reported super heat-resistant explosives,being superior to most of the energetic potassium salts.Based on the overall performance,KCPT,HCPT and guanidinium salt are promising heat-resistant explosives.A novel azo energetic compound linked by -N=N-(E)-1,2-bis(1-(3,5-dinitro-1H-pyrazol-4-yl)-3-nitro-1H-1,2,4-triazol-5-yl)diazene(HDCPT)and the known azo compound 3,3'-dinitro-5,5'-azo-1H-1,2,4-trizole(HDNAT)were designed and synthesized along with their seven new energetic salts.And the azo groups were reduced by hydrazine salt,furnishing two novel energetic compounds linked by-NH-NH-.Their structures were confirmed by IR spectroscopy,¹H and ¹³C NMR spectroscopy,and elemental analysis.The crystal structures of HDCPT,its bis(ammonium)salt,bis(guanidinium)salt,HDNAT and the corresponding hydrazine compound were determined by single-crystal X-ray diffraction.The thermal stabilities of these compounds were measured.Most of the compounds exhibit excellent thermal stabilities with decomposition temperatures in the range of 254-355 ^oC.HDCPT(T_d=301?)exhibits better thermal stability than HMX(T_d=287?).The measured density of the eleven compounds are ranged in 1.70-1.94 g cm^-3,in which HDCPT possesses the highest density(d=1.94 g cm^-3).Suitable impact sensitivity of HDCPT was determined to be 19 J,which is lower than that of HMX(IS=7.4 J)and RDX(IS=7 J).Formation of nitrogen-rich salts remarkably decrease the impact sensitivities,and some salts can be placed in the class of insensitive energetic materials(IS>40 J,FS>360 N).The positive heats of formation of all the salt were calculated between 123.9-1038.5 k J mol^-1.HDCPT possesses the highest heat of formation(?H_f=1095.7 k J mol^-1).The heats of formation of the azo compounds are higher than those of their corresponding hydrazine compounds.The detonation velocity and pressure of the neutral compounds and their nitrogen-rich salts were calculated using EXPLO5 to be 8072-9292 m s^-1 and 23.5-38.4 GPa.The neutral azo compound HDCPT has the best detonation performance(v _D=9292 m s^-1,P=38.4 GPa),superior to that of HMX.The bis(ammonium)salt of HDNAT possesses relatively high calculated detonation parameters(v _D=9071 m s^-1,P=32.9 GPa)and insensitivity.Therefore,HDCPT and bis(ammonium)salt of HDNAT are potential alternatives to HMX in explosive applications based on their detonation properties and stabilities.A unique and facile approach has been developed to synthesize3,4,5-triamino-1,2,4-triazole,which is combined with 3,5-dinitropyrazolate anion as the cationic component,furnishing a unique inner salt 3,5-dinitro-4-(3,4,5-triamino-4H-1,2,4-triazol-1-ium-1-yl)-4H-pyrazol-4-ide(CPTY)and the corresponding intra-molecular salt 3,4,5-triamino-4H-1,2,4-triazol-1-ium3,5-dinitropyrazol-1-ide.And the oxidative product of the inner salt(HCPT)was also prepared.Their structures were fully characterized using by IR spectroscopy,¹H and ¹³C NMR spectroscopy,elemental analysis and single-crystal X-ray diffraction.CPTY exhibits superior thermal stability,with a decomposition temperature as high as 359?(5? min^-1),which is superior to that of the corresponding intra-molecular salt,TATB and LLM-105.And the thermostability of CPTY was further investigated by TGA and isothermal long-term experiment.CPTY possesses a relatively high density(1.82 g cm^-3)to the level of new high-energy-density materials(1.8-2.0 g cm^-3).The sensitivities of the salts with respect to impact and friction were investigated.And CPTY exhibits insensitivities to impact and friction(IS>40 J,FS>360 N)which is nearly comparable to those of TATB.The heats of formation of CPTY and the corresponding intra-molecular salt were calculated to be 555.8 k J mol^-1 and 355.1 k J mol^-1,respectively.The detonation pressures and velocities of the new salts were determined using the EXPLO5 program(v6.01).CPTY exhibits a relatively high detonation performance(v _D=8750 m s^-1,P=31.5 GPa),which is superior to those of TATB,LLM-105 and the corresponding intra-molecular salt.Thus,the highly attractive physicochemical and detonation properties of CPTY make it promising for use as a new heat-resistant explosive.Natural bond orbital(NBO)analysis was performed to provide a better understanding of the structure of CPTY,indicating that it is a novel inner salt with two oppositely charged heterocycles.