Synthesis and Characterization of Bis(triaminoguanidinium) 5,5′‐Dinitrimino‐3,3′‐azo‐1H‐1,2,4‐triazolate – A Novel Insensitive Energetic Material

The synthesis of 5,5′‐diamino‐3,3′‐azo‐1H‐1,2,4‐triazole ( 3 ) by reaction of 5‐acetylamino‐3‐amino‐1H‐1,2,4‐triazole ( 2 ) with potassium permanganate is described. The application of the very straightforward and efficient acetyl protection of 3,5‐diamino‐1H‐1,2,4‐triazole allows selective reactions of the remaining free amino group to form the azo‐functionality. Compound 3 is used as starting material for the synthesis of 5,5′‐dinitrimino‐3,3′‐azo‐1H‐1,2,4‐triazole ( 4 ), which subsequently reacted with organic bases (ammonia, hydrazine, guanidine, aminoguanidine, triaminoguanidine) to form the corresponding nitrogen‐rich triazolate salts ( 5 – 9 ). All substances were fully characterized by IR and Raman as well as multinuclear NMR spectroscopy, mass spectrometry, and differential scanning calorimetry. Selected compounds were additionally characterized by low temperature single‐crystal X‐ray diffraction measurements. The heats of formation of 4 – 9 were calculated by the CBS‐4M method to be 647.7 ( 4 ), 401.2 ( 5 ), 700.4 ( 6 ), 398.4 ( 7 ), 676.5 ( 8 ), and 1089.2 ( 9 ) kJ · mol^–1. With these values as well as the experimentally determined densities several detonation parameters were calculated using both computer codes EXPLO5.03 and EXPLO5.04. In addition, the sensitivities of 5 – 9 were determined by the BAM drophammer and friction tester as well as a small scale electrical discharge device.     

Synthesis and Characterization of 3,3′‐Bis(Dinitromethyl)‐5,5′‐Azo‐1H‐1,2,4‐Triazole

The synthesis of 3,3′‐bis(dinitromethyl)‐5,5′‐azo‐1H‐1,2,4‐triazole ( 5 ) using the readily available starting material 2‐(5‐amino‐1H‐1,2,4‐triazol‐3‐yl)acetic acid ( 1 ) is described. All compounds were characterized by means of NMR, IR, and Raman spectroscopy. The energetic compound 5 was additionally characterized by single‐crystal X‐ray diffraction and DSC measurements. The sensitivities towards impact, friction and electrical discharge were determined. In addition, detonation parameters (e.g. heat of explosion, detonation velocity) of the target compound were computed using the EXPLO5 code based on the calculated (CBS‐4M) heat of formation and X‐ray density.     

A Study of 5‐(1,2,4‐Triazol‐C‐yl)tetrazol‐1‐ols: Combining the Benefits of Different Heterocycles for the Design of Energetic Materials

The synthesis and full structural and spectroscopic characterization of three 5‐(1,2,4‐triazol‐C‐yl)tetrazol‐1‐ol compounds with selected energetic moieties including nitrimino ( 5 ), nitro ( 6 ) and azido ( 7 ) groups are reported. The influence of those energetic moieties as well as the C? C connection of a tetrazol‐1‐ol and a 1,2,4‐triazole on structural and energetic properties has been investigated. All compounds were well characterized by various means, including IR and multinuclear NMR spectroscopy, mass spectrometry, and DSC. The molecular structures of 5 – 8 were determined in the solid state by single‐crystal X‐ray diffraction. The standard heats of formation were calculated on the CBS‐4M level of theory utilizing the atomization energy method, revealing highly positive values for all compounds. The detonation parameters were calculated with the EXPLO5 program and compared to the common secondary explosive RDX. Additionally, sensitivities towards impact, friction and electrostatic discharge were determined.     

Synthesis of a Novel Double Salt: Ammonium 3,4‐Diamino‐1,2,4‐triazolium Styphnate

Nitrogen‐rich double salt ammonium 3,4‐diamino‐1,2,4‐triazoliumstyphnate (NH₄ · DATr · TNR) ( 2 ) with good thermal stability was successfully synthesized by reacting 3,4‐diamino‐1,2,4‐triazolium chloride aqueous solution with styphnic acid methanol solution under the reaction medium of aqueous ammonia. The title double salt was characterized by elemental analysis (EA), Fourier transformation infrared spectrum (FT‐IR), and X‐ray single‐crystal diffraction. It crystallizes in the monoclinic crystal system with space group P2₁/n. Its density is 1.780 g · cm^–3. Compound 2 is thermal stable below 200 °C by the differential scanning calorimetry (DSC) test. The non‐isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa‐Doyle's method, respectively. In addition, compound 2 showed low friction and impact sensitivities.     

Energetic Materials Based on 5,5′‐Diamino‐4,4′‐dinitramino‐3,3′‐bi‐1,2,4‐triazole

A simple and straightforward synthesis of 5,5′‐diamino‐4,4′‐dinitramino‐3,3′‐bi‐1,2,4‐triazole by the selective nitration of 4,4′,5,5′‐tetraamino‐3,3′‐bi‐1,2,4‐triazole is presented. The interaction of the amino and nitramino groups improves the energetic properties of this functionalized bitriazole. For a deeper investigation of these properties, various nitrogen‐rich derivatives were synthesized. The new compounds were investigated and characterized by spectroscopy (¹H and ¹³C NMR, IR, Raman), elemental analysis, mass spectrometry, differential thermal analysis (DTA), X‐ray analysis, and impact and friction sensitivities (IS, FS). X‐ray analyses were performed and deliver insight into structural characteristics with which the stability of the compounds can be explained. The standard enthalpies of formation were calculated for all compounds at the CBS‐4M level of theory, revealing highly positive heats of formation. The energetic performance of the new molecules was predicted with the EXPLO5 V6.02 computer. A small‐scale shock reactivity test (SSRT) and a toxicity test gave a first impression of the performance and toxicity of selective compounds.     

Hydroxylammonium 5‐Nitriminotetrazolates

The hydroxylammonium salts of monodeprotonated 5‐nitriminotetrazole ( 4 ), double deprotonated 5‐nitriminotetrazole ( 5 ), 1‐methyl‐5‐nitriminotetrazole ( 6 ), and 2‐methyl‐5‐nitraminotetrazole ( 7 ) have been prepared in high yield from the corresponding 5‐nitriminotetrazoles as free acids and an aqueous solution of hydroxylamine or the metathesis reactions of hydroxylammonium hydrochloride with the silver salt of the corresponding nitriminotetrazole, respectively. The energetic salts 4 – 7 were fully characterized by single‐crystal X‐ray diffraction ( 4 – 6 ), NMR spectroscopy, IR‐ and Raman spectroscopy as well as DSC measurements. The sensitivities towards impact, friction and electrical discharge were determined. In addition, several detonation parameters (e.g. heat of explosion, detonation velocity) were computed by the EXPLO5.04 computer code based on calculated (CBS‐4M) heats of formation and X‐ray densities.     

Synthesis and Characterization of 3,4,5‐Triamino‐1,2,4‐triazolium and 1‐Methyl‐3,4,5‐triamino‐1,2,4‐triazolium Iodides

3,4,5‐Triamino‐1,2,4‐triazolium iodide ( 1 ) was obtained in good yield and purity and characterized using vibrational (IR, Raman) and multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁵N), EA, MS, DSC, and X‐ray crystallography. The compound was synthesized by two different methods rendering two different polymorphs (α and β) as proved by X‐ray measurements, vibrational spectroscopy and DSC. 1‐Methyl‐3,4,5‐triamino‐1,2,4‐triazolium iodide ( 2 ) was synthesized by reaction of guanazine with methyliodide and fully characterized by the same techniques mentioned above. Both compounds showed to be suitable starting materials for the synthesis of guanazinium salts of energetic interest.     

Synthesis and Characterization of the New Heterocycle 5‐(4‐Amino‐1,2,4‐triazol‐3‐on‐5′‐yl)‐1H‐tetrazole and Some Ionic Nitrogen‐Rich Derivatives

A new heterocycle consisting of a tetrazole ring attached to an amino‐triazolone ring, namely 5‐(4‐amino‐1,2,4‐triazol‐3‐on‐5′‐yl)‐1H‐tetrazole ( 3 ) as well as its ammonium ( 2 ), hydroxylammonium ( 3 ), and sodium salt ( 4 ), is introduced. Its ammonium salt ( 2 ) is formed starting from tetrazole‐5‐carboxamide oxime ( 1 ), which is reacted with diaminourea (carbonyldihydrazide) in aqueous media. All compounds 2 , 3 , 4 , 5 were structurally characterized by single crystal X‐ray diffraction. The thermal behavior was investigated using differential scanning calorimetry, and the sensitivities towards impact, friction, and electrostatic discharge were determined. Furthermore, several detonation parameters were calculated with the program EXPLO5 to determine the potential use of these compounds as highly energetic materials.     

3,3′‐Bi(1,2,4‐oxadiazoles) Featuring the Fluorodinitromethyl and Trinitromethyl Groups

Here we report on the preparation of two hydrogen atom free 3,3′‐bi(1,2,4‐oxadiazole) derivatives. 5,5′‐Bis(fluorodinitromethyl)‐3,3′‐bi(1,2,4‐oxadiazole) was synthesised by fluorination of diammonium 5,5′‐bis(dinitromethanide)‐3,3′‐bi(1,2,4‐oxadiazole). For our previously reported analogue 5,5′‐bis(trinitromethyl)‐3,3′‐bi(1,2,4‐oxadiazole), a new synthetic route starting from new 3,3′‐bi(1,2,4‐oxadiazolyl)‐5,5′‐diacetic acid was developed. In this course also hitherto unknown 5,5′‐dimethyl‐3,3′‐bi(1,2,4‐oxadiazole) was isolated. The compounds were characterised by multinuclear NMR spectroscopy, IR and Raman spectroscopy, elemental analysis as well as mass spectrometry. X‐ray diffraction studies were performed and the crystal structures for the 5,5'‐dimethyl and 5,5'‐(fluorodinitromethyl) derivatives are reported. The energetic 5,5'‐(fluorodinitromethyl) and 5,5'‐(trinitromethyl) compounds do not contain any hydrogen atoms and show remarkable high densities. Furthermore, the thermal stabilities and sensitivities were determined by differential scanning calorimetry (DSC) and standardised impact and friction tests. The heats of formation were calculated by the atomisation method based on CBS‐4M enthalpies. With these values and the room‐temperature X‐ray densities, several detonation and propulsion parameters, such as the detonation velocity and pressure as well as the specific impulse of mixtures with aluminium, were computed using the EXPLO5 code.     

Syntheses and Promising Properties of Dense Energetic 5,5′‐Dinitramino‐3,3′‐azo‐1,2,4‐oxadiazole and Its Salts

A planar energetic molecule with high density, 5,5′‐dinitramino‐3,3′‐azo‐1,2,4‐oxadiazole ( 4 ), was obtained by the nitration of 5,5′‐diamino‐3,3′‐azo‐1,2,4‐oxadiazole using 100 % nitric acid. In addition, selected nitrogen‐rich salts were prepared. Of them, the neutral compound 4 and its hydroxylammonium salt, 6 , were further confirmed by single‐crystal X‐ray diffraction. Physicochemical and energetic properties including density, thermal stability, and sensitivity were investigated. The energetic performance from the calculated heats of formation and experimental densities indicates that many of them have potential applications as energetic materials.     

Synthesis and Characterization of 5‐(1,2,4‐Triazol‐3‐yl)tetrazoles with Various Energetic Functionalities

In this contribution the synthesis and full structural as well as spectroscopic characterization of three 5‐(1,2,4‐triazol‐3‐yl)tetrazoles along with selected energetic moieties like nitro, nitrimino, and azido groups are presented. The main goal is a comparative study on the influence of those variable energetic moieties on structural and energetic properties. A complete characterization including IR and Raman as well as multinuclear NMR spectroscopy of all compounds is presented. Additionally, X‐ray crystallographic measurements were performed and reveal insights into structural characteristics as well as inter‐ and intramolecular interactions. The standard enthalpies of formation were calculated for all compounds at the CBS‐4M level of theory and reveal high positive heats of formation for all compounds. The calculated detonation parameters (using the EXPLO5.05 program) are in the range of 8000 m s^?1 (8097 m s^?1 ( 5 ), 8020 m s^?1 ( 6 ), 7874 m s^?1 ( 7 )). As expected, the measured impact and friction sensitivities as well as decomposition temperatures strongly depend on the energetic moiety at the triazole ring. The C? C connection of a triazole ring with its opportunity to introduce a large variety of energetic moieties and a tetrazole ring, implying a large energy content, leads to the selective synthesis of primary and secondary explosives.     

Nitrogen‐Rich 5,5′‐Bistetrazolates and their Potential Use in Propellant Systems: A Comprehensive Study

A large variety of twice‐deprotonated nitrogen‐rich 5,5′‐bistetrazolates, that is, the ammonium ( 1 ), hydrazinium ( 2 ), hydroxylammonium ( 3 ), guanidinium ( 4 ), aminoguanidinium ( 5 ), diaminoguanidinium ( 6 ), triaminoguanidinium ( 7 ), and diaminouronium ( 8 ) salts, have been synthesized. Energetic compounds 1 – 8 were fully characterized by single‐crystal X‐ray diffraction (except 8 ), NMR spectroscopy, IR and Raman spectroscopy, and differential scanning calorimetry (DSC) measurements. With respect to their potential use in propellant applications, the sensitivity towards impact, friction, and electrical discharge were determined. Several propulsion and detonation parameters (e.g., heat of explosion, detonation velocity) were computed by using the EXPLO5 computer code based on calculated (CBS‐4M) heats of formation and X‐ray densities. Additionally, the performance of 1 – 8 in various formulations was investigated by calculating the specific energy and specific impulse of the compounds under isochoric conditions.     

Synthesis and Investigation of 2,6‐Bis(picrylamino)‐3,5‐dinitro‐pyridine (PYX) and Its Salts

2,6‐Bis(picrylamino)pyridine ( 1 ; pre‐PYX) and 2,6‐bis(picrylamino)‐3,5‐dinitropyridine ( 2 ; PYX) were synthesized using an improved literature method. Compounds 1 and 2 were reinvestigated in detail and the X‐ray structures ( 1 : ρ=1.698 g cm^?3 at 173 K; 2 : ρ=1.757 g cm^?3 at 298 K) are given. The reactions of 2 with different bases, such as alkali metal hydroxides (sodium, potassium, rubidium, cesium), and N‐bases (ammonia, hydrazine, hydroxylamine, guanidinium carbonate, aminoguanidine bicarbonate) are reported, as well as metathesis reactions producing energetic salts. Several energetic compounds were synthesized and characterized for the first time using vibrational (IR, Raman) and multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, and DSC. The crystal structures of four energetic salts were determined using low temperature single‐crystal X‐ray diffraction. Heats of formation for the metal‐free species were calculated using the Gaussian 09 software. Detonation parameters were estimated using the EXPLO5 program. The sensitivities towards impact, friction, and electrostatic discharge were also determined.     

On triazoles XLV [1]. synthesis of 5,7‐diamino‐1,2,4‐triazolo[1,5‐a] [1,3,5]triazines

Dedicated to Professor András Messmer on the occasion of his 80^th birthday The reaction of differently substituted 5‐amino‐1,2,4‐triazoles ( 5 ) with isothiourea derivatives ( 3 ) to yield isomeric 5,7‐diamino‐1,2,4‐triazolo[1,5‐a][1,3,5]triazines ( 6 and 7 ), previously described as not proceeding in melt, was performed in different solvents as well as in the melt at 150‐160°. It was proved that the above reaction had rather general validity. The structure of isomers 6 and 7 were proved spectroscopically. The structure of 6/5 (Q = ethylamino) was corroborated with single crystal X‐ray diffraction determination, as well.     

Nitroxy/Azido‐Functionalized Triazoles as Potential Energetic Plasticizers

The synthesis of a series of nitroxy‐ and azido‐functionalized compounds, based on 4‐amino‐3,5‐di(hydroxymethyl)‐1,2,4‐triazole, for possible use as an energetic plasticizers is described. All compounds were fully characterized. Two of them were further confirmed by X‐ray single crystal diffraction. Energetic performance was calculated by using EXPLO5 v6.01 based on calculated heats of formation (Gaussian 03) and experimentally determined densities at 25 °C. The results show that the nitration product 1‐nitro‐3,5‐di(nitroxymethyl)‐1,2,4‐triazole, containing a nitro group and two nitroxy groups, exhibits good detonation properties (D=8574 m s^?1, P=32.7 GPa). In addition, its low melting point makes it very attractive as an energetic plasticizer in solid propellants.     

Maximum Compaction of Ionic Organic Explosives: Bis(hydroxylammonium) 5,5′‐Dinitromethyl‐3,3′‐bis(1,2,4‐oxadiazolate) and its Derivatives

Within this contribution on bis(oxadiazoles) we report on bis‐hydroxylammonium 5,5′‐dinitro‐methyl‐3,3′‐bis(1,2,4‐oxadiazolate), which (to the best of our knowledge) shows the highest density (2.00 g cm^?3 at 92 K, 1.95 g cm^?3 at RT) ever reported for an ionic CHNO explosive. Also the corresponding bis(ammonium) salt shows an outstanding density of 1.95 g cm^?3 (173 K). The reaction of the 3,3′‐bis(1,2,4‐oxadiazolyl)‐5,5′‐bis(2,2′‐dinitro)‐diacetic acid diethyl ester with different nitrogen‐rich bases, such as ammonia, hydrazine, hydroxylamine, and triaminoguanidine causes decarboxylation followed by the formation of the corresponding salts (cation/anion stoichiometry 2:1). The reactions are performed at ambient temperature in H₂O/MeOH mixtures and furnish qualitatively pure products showing characteristics of typical secondary explosives. The obtained compounds were characterized by multinuclear NMR spectroscopy, IR and Raman spectroscopy, as well as mass spectrometry. Single‐crystal X‐ray diffraction studies were performed and the structures of all compounds were determined at low temperatures. The thermal stability was measured by differential scanning calorimetry (DSC). The sensitivities were explored by using the BAM drophammer and friction test. The heats of formation were calculated by the atomization method based on CBS‐4M enthalpies. With these values and the X‐ray densities, several detonation parameters such as the detonation pressure, velocity, energy, and temperature were computed using the EXPLO5 code.     

Synthesis and Characterization of Various Photosensitive Copper(II) Complexes with 5‐(1‐Methylhydrazinyl)‐1H‐tetrazole as Ligand and Perchlorate,Nitrate, Dinitramide,and Chloride as Anions

The preparation of 5‐(1‐methylhydrazinyl)‐1H‐tetrazole monohydrate ( 1 ?H₂O) and various copper(II) complexes with perchlorate ( 2 and 3 ), nitrate ( 4 , 5 , and 6 ), dinitramide ( 7 ), and chloride ( 8 ) is described. The coordination compounds (monomers, dimers, and polymers) were characterized through infrared spectroscopy and elemental analysis. Further, the structures of 2 and 4 – 8 were determined by single‐crystal X‐ray diffraction. Compound 1 can act as a bidentate ligand in its neutral form (HMHT) and as a μ₂‐ or μ₃‐bridging ligand in its deprotonated form (MHT). The energetic properties of the synthesized complexes, such as their sensitivities toward impact and friction, were determined, and laser ignition tests were performed. New information about the laser initiation process and the role of the anion in the initiation criterion was obtained. The perchlorate complexes 2 (T_decomp=217 °C) and 3 (T_decomp=206 °C) are potential primary explosives.     

The Chemistry of 5‐(Tetrazol‐1‐yl)‐2H‐tetrazole: An Extensive Study of Structural and Energetic Properties

5‐(Tetrazol‐1‐yl)‐2H‐tetrazole ( 1 ), or 1,5′‐bistetrazole, was synthesized by the cyclization of 5‐amino‐1H‐tetrazole, sodium azide and triethyl orthoformate in glacial acetic acid. A derivative of 1 , 2‐methyl‐5‐(tetrazol‐1‐yl)tetrazole ( 2 ) can be obtained by this method starting from 5‐amino‐2‐methyl‐tetrazole. Furthermore, selected salts of 1 with nitrogen‐rich and metal (alkali and transition metal) cations, including hydroxylammonium ( 4 ), triaminoguanidinium ( 5 ), copper(I) ( 8 ) and silver ( 9 ), as well as copper(II) complexes of both 1 and 2 were prepared. An intensive characterization of the compounds is given, including vibrational (IR, Raman) and multinuclear NMR spectroscopy, mass spectrometry, DSC and single‐crystal X‐ray diffraction. Their sensitivities towards physical stimuli (impact, friction, electrostatic) were determined according to Bundesamt für Materialforschung (BAM) standard methods. Energetic performance (detonation velocity, pressure, etc.) parameters were calculated with the EXPLO5 program, based on predicted heats of formation derived from enthalpies computed at the CBS‐4M level of theory and utilizing the atomization energy method. From the analytical and calculated data, their potential as energetic materials in different applications was evaluated and discussed.     

Preparation of N‐(4′,6′‐difluoro‐2′‐hydroxybenzyl)‐monoaza‐15‐crown‐5 and x‐ray crystal structure of potassium thiocyanate complex: A molecular partition wall

Armed monoaza‐15‐crown‐5 having a 4′,6′‐difluoro‐2′‐hydroxybenzyl group as an additional binding site ( 2 ) has been prepared by the Mannich reaction of N‐methoxymethylmonoaza‐15‐crown‐5 with 3,5‐difluorophenol. The reactive site on 3,5‐difluorophenol for the Mannich reaction was predicted by an electrostatic potential calculation (density functional calculation, SVWN/DN* method). Ligand 2 is interesting, because it has two possible binding sites (phenolic OH group and fluorine atom) in the side arm. An X‐ray crystal structure of the potassium thiocyanate complex of ligand 2 revealed that the oxygen atom of the phenolic OH group binds to the potassium cation incorporated in the crown ether ring, and two water molecules are enclosed by two armed crown ethers with the crown ethers forming partition walls.     

Energetic Salts Based on an Oxygen‐Containing Cation: 2,4‐Diamino‐1,3,5‐triazine‐6‐one

A family of energetic salts with high thermal stability and low impact sensitivity based on an oxygen‐containing cation, 2,4‐diamino‐1,3,5‐triazine‐6‐one, were synthesized and fully characterized by IR and multinuclear (¹H, ¹³C) NMR spectroscopy, elemental analysis, and differential scanning calorimetry. Insights into their sensitivities towards impact, friction, and electrostatics were gained by submitting the materials to standard tests. The structures of 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate, 2,4‐diamino‐1,3,5‐triazine‐6‐one sulfate, 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, 2,4‐diamino‐1,3,5‐triazine‐6‐one 5‐nitrotetrazolate were determined by single‐crystal X‐ray diffraction; their densities are 1.691, 1.776, 1.854, and 1.636 g cm^?3, respectively. Most of the salts decompose at temperatures over 180 °C; in particular, the salts 2,4‐diamino‐1,3,5‐triazine‐6‐one nitrate and 2,4‐diamino‐1,3,5‐triazine‐6‐one perchlorate, which decompose at 303.3 and 336.4 °C, respectively, are fairly stable. Furthermore, most of the salts exhibit excellent impact sensitivities (>40 J), friction sensitivities (>360 N), and are insensitive to electrostatics. The measured densities of these energetic salts range from 1.64 to 2.01 g cm^?3. The detonation pressure values calculated for these salts range from 14.6 to 29.2 GPa, and the detonation velocities range from 6536 to 8275 m s^?1; these values make the salts potential candidates for thermally stable and insensitive energetic materials.