Energetic Coordination Compounds Research Articles

1- and 2-Tetrazolylacetonitrile as Versatile Ligands for Laser Ignitable Energetic Coordination Compounds.

1- and 2-Tetrazolylacetonitrile (1- and 2-TAN) have been synthesized by the reaction of chloroacetonitrile with 1H-tetrazole under basic conditions. They further were reacted with sodium azide in the presence of zinc(II) chloride to form 5-((1H-tetrazol-1-yl)methyl)-1H-tetrazole (1-HTMT) and 5-((2H-tetrazol-2-yl)methyl)-1H-tetrazole (2-HTMT). The nitrogen-rich compounds have been applied as ligands for Energetic Coordination Compounds (ECCs) and show interesting coordinative behavior due to different bridging modes. The structural variability of the compounds has been proved by low-temperature X-ray analysis. The ECCs were analyzed for their sensitivities to provide information about the safety of handling and their capability to serve as primary explosives in detonator setups to replace the commonly used lead styphnate and azide. All colored ECCs were evaluated for their ignitability by laser initiation in translucent polycarbonate primer caps. In addition, the spin-crossover characteristics of [Fe(1-TAN)6](ClO4)2 were highlighted by the measurement of the temperature-dependent susceptibility curve.

N‐Azidoethyl azoles through N‐alkylation under highly harmonized reaction conditions: Synthesis, characterization, and complexation as energetic coordination compounds

AbstractOrganic azides are universally important in many areas of chemistry, particularly in organic synthesis. The availability of these azides often depends on specific transfer reagents and reaction conditions, or only work with certain substrates. Customizable transfer reagents offer a safe and direct pathway to desired compounds, thereby increasing the availability of N‐alkyl‐azides. In an effort to streamline the synthesis and broaden the scope of N‐azidoethyl‐containing molecules, three different versatile azidoethyl transfer reagents were synthesized and a uniform reaction protocol with azoles as substrates, including imidazole, pyrazole, 1,2,3‐triazole, 1,2,4‐triazole, and tetrazole was established. The resulting azidoethyl‐azoles were further used as ligands for energetic coordination compounds in an effort to create new lead‐free primary explosives. A comprehensive characterization of the transfer reagents, the azidoethyl‐containing products, and energetic coordination compounds was conducted using multinuclear nuclear magnetic resonance (NMR), elemental analysis, mass spectrometry, and infrared spectroscopy (IR). Furthermore, their thermal stability and sensitivity toward friction and impact were determined as well as the detonation properties were calculated by using the EXPLO5 code.

Assembly of 1D Helical Energetic Coordination Polymers Using a Flexible Bridged Furazan-triazole Cation.

Two new energetic coordination compounds with 1D helical chain structures have been synthesized. First, the polyamine precursor 4,5-diamino-2-((4-amino-1,2,5-oxadiazole-3-yl)methyl)-2,4-dihydro-3H-1,2,4-triazole-3-imino chloride salt (TATAF-Cl) is obtained by incorporating 4-(chloromethyl)-1,2,5-oxadiazol-3-amine with 4H-1,2,4-triazole-3,4,5-triamine. Using a simple hydrothermal method, two energetic complexes, Ag(TATAF)(ClO4)2 (ECP-1) and Ag(TATAF)(NO3)2·H2O (ECP-2), with a helical 1D MOF structure of furazan and triazole were synthesized. Compounds ECP-1 and ECP-2 have relatively high nitrogen and oxygen content (N + O%: 52.04%, 61.04%), excellent crystal density (2.229 g cm-3, 2.116 g cm-3 at 298 K) and high heat of detonation (1.18 kcal g-1, 1.06 kcal g-1), good detonation performance (P: 35.34 GPa, 29.52 GPa; Dv: 8412 m s-1, 7794 m s-1), and moderate sensitivity (IS: 8 J, 13 J; FS: 72 N, 64 N). Structurally, the Ag+ of the two ECPs is coordinated with two energetic cations, two perchlorates, or one nitrate via tetragonal coordination to form a single helical structure that is interspersed up and down in two directions.

Elevating the energetic capabilities of metal coordination compound by incorporating nitrate anions

In the realm of energetic materials research, there has been notable interest in energetic coordination compounds (ECCs) owing to their remarkable thermal stability and resistance to mechanical stimuli. This study...

Synthesizing new Bi-structure energetic coordination compounds using ternary components

[Ag(1-APZ-5-HCA)(ClO4)2]n (ECPs-1) has a dual structure of ionic salt and coordination compounds. It also has the advantages of high ClO4− content and oxygen balance, acceptable mechanical stimulation and excellent explosion performance.

Synthesis of energetic coordination compounds based on pyrazole and 4-chloropyrazole via co-melting crystallization method

Using pyrazole, 4-chloropyrazole, Cu(NO3)2, and Cu(ClO4)2 as raw materials, the target crystals of ECCs can be directly obtained by co-melting and heating, offering a more efficient alternative to traditional solvent-based preparation methods.

Preparation of Highly Energetic Coordination Compounds with Rich Oxidants and Lower Sensitivity Based on Methyl Groups.

Revamping the structure of energy storage is an efficient strategy for striking a balance between the performance and sensitivity of energetic materials to achieve high energy and reduced sensitivity. In continuation of prior research, this study utilized the ligand 3,5-dimethyl-1H-pyrazole-4-carbonhydrazide (DMPZCA) and innovatively designed and synthesized the compound ECCs [Cu(HDMPZCA)2(ClO4)2](ClO4)2·2H2O (ECCs-1·2H2O). Compared with the former research, solvent-free compound ECCs-1 refers to an innovative material characterized by a dual structure involving ionic salts and coordination compounds. Due to these unique structures, ECCs-1 exhibits an increased [ClO4-] content, a higher oxygen balance constant (OB = -7.9%), and improved mechanical sensitivity (IS = 8 J, FS = 32 N). Theoretical calculations support the superior detonation performance of ECCs-1. Additionally, experimental results confirm its ignition capability through lower-threshold lasers and highlight the outstanding initiation potential and explosive power, making it a suitable candidate for primary explosives.

Regulating the Coordination Environment by Using Isomeric Ligands: Enhancing the Energy and Sensitivity of Energetic Coordination Compounds.

Transforming the energy storage structure is an effective approach to achieve a balance between the detonation performance and the sensitivity of energetic compounds, with a goal of high energy and low sensitivity. Building upon previous work, this study employed an isomeric compound 1H-pyrazole-3-carbohydrazide (3-PZCA) as a ligand and creatively designed the energetic coordination compound (ECC) Ag(3-HPZCA)2(ClO4)3 (ECC-1). It is a novel material with a dual structure of ionic salts and coordination compounds, which represents the first report of such a structure in Ag(I)-based ECCs. With its unique structures, ECC-1 exhibits a larger [ClO4-] content, a higher oxygen balance constant (OB = 0%), and superior mechanical sensitivity (IS = 13 J and FS = 40 N). Theoretical calculations indicate that ECC-1 has a higher detonation performance compared to previous work. Furthermore, the explosive experiment testing results demonstrate that it can be ignited by lower-threshold lasers and possesses excellent initiation capability and explosive power, making it suitable not only as a primary explosive but also as a secondary explosive.

Study on Primary Explosive: Cu(ClO4)2-Based Energetic Coordination Compounds as a Template

Study on Primary Explosive: Cu(ClO₄)₂-Based Energetic Coordination Compounds as a Template

Application of 1- and 2-propargyl-tetrazole in laser-ignitable energetic coordination compounds

1- and 2-Propargyl-tetrazole (1- and 2-PryTz) were synthesized by reaction of propargyl bromide with sodium tetrazolate and used as ligands in energetic coordination compounds (ECCs) and evaluated concerning their thermal and mechanical sensitivities. Furthermore, the two nitrogen-rich compounds 1-((1H-1,2,3-triazol-4-yl)methyl)-1H-tetrazole (TriMT, 3) and 1-((1-(2-(1H-tetrazol-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)-1H-tetrazole (TriMTET, 4) were prepared. Both were characterized by IR spectroscopy, NMR measurements, and low-temperature X-Ray diffraction analysis. Due to the highly endothermic enthalpy of formation of the propargyl-tetrazole ligands, powerful, yet relatively safe to handle, laser-ignitable ECCs were obtained.

The Adjustability of Physicochemical Properties: Comparison of 1-Vinyl-5H-tetrazole and 1-Allyl-5H-tetrazole as Ligands in 3d Metal Energetic Coordination Compounds

Energetic coordination compounds (ECCs) show promising properties to be used as potential substitutes for highly toxic lead-containing primary explosives. The concept is to combine the three building blocks: (i) ligand, (ii) transition metal, and (iii) anion, acting as (i) fuel, (ii) matrix, and (iii) oxidizer (e.g., ClO4-, NO3-, ClO3-) or energetic component (e.g., DN-, N3-, picrate, styphnate, trinitrophloroglucinate). By variation of the ligands, the complexes' properties can be adjusted toward their desired performance and sensitivities. In the present study, 1-vinyl-5H-tetrazole (1-VTZ, 1) and 1-allyl-5H-tetrazole (1-ATZ, 2) were used as nitrogen-rich endothermic ligands to form 3d metal (Mn2+, Fe2+, Cu2+, Zn2+, Co2+, Ni2+)-based ECCs. The influence of the introduction of an unsaturated C-C bond (1-ETZ vs 1-VTZ and 1-PTZ vs 1-ATZ) on the performance and sensitivity of the complexes is discussed, as is the lengthening of the alkenyl chain (1-VTZ vs 1-ATZ). For further insights, the novel complexes were compared to literature-known complexes based on N1-substituted C2- and C3-derived tetrazole ligands, respectively. The ligand 1-VTZ (1) was prepared by elimination of hydrogen chloride from 1-(2-chloroethyl)-5H-tetrazole in methanolic KOH solution. 1-ATZ (2) was obtained by a heterocyclization reaction of allylamine with triethyl orthoformate and sodium azide in an acetic acid medium. All compounds were intensively characterized with analytical methods such as XRD, IR, EA, DTA, TGA, and sensitivity measurements (IS and FS). The energetic performances were visibly evaluated in fast heating experiments. Furthermore, PETN initiation and laser ignition experiments were carried out for promising ECCs.

Energetic coordination compounds: self-assembled from the nitrogen-rich energetic C-C bonded pyrazoles and triazoles.

In energetic materials research, energetic coordination compounds (ECCs) have received much attention due to their high thermal stability and insensitivity to mechanical stimuli. The energetic characteristics of ECCs can be modified by combining various metal cations, potent anions, and ligands. In this study, we have synthesized two energetic ligands, 5-(4-nitro-1H-pyrazol-3-yl)-1H-1,2,4-triazol-3-amine (NPTA) and (Z)-N-(5-(4-nitro-1H-pyrazol-3-yl)-2,4-dihydro-3H-1,2,4-triazol-3-ylidene)nitramide (NPTN), from a commercially viable starting material and reacted them with nitrate salts of various 3d metals (e.g., Ni, Co, Zn) to obtain six new ECCs, [Ni(NPTA)(H2O)3]2·2NO3 (1), [Co(NPTA)(H2O)3]2·2NO3 (2), [Zn(NPTA)(H2O)3]2·2NO3 (3), [Ni(NPTN)(H2O)3]2 (4), [Co(NPTN)(H2O)3]2 (5), and [Zn(NPTN)(H2O)3]2 (6) under ambient conditions. All the newly prepared ECCs were characterised through PXRD, IR, SEM, and TGA-DSC analysis. Furthermore, single crystal analysis proved that 1-6 are dimeric complexes. Moreover, 1-6 show excellent density ranges from 1.94 to 2.06 g cm-3 and remarkable thermal stability (216-352 °C), and are highly insensitive towards impact (>40 J) and friction (>360 N), describing their potential as high performing energetic materials. All the ECCs revealed good enthalpy of combustion (-6.3 to -9.94 kJ g-1). Additionally, the Hirshfeld surface and 2D fingerprint analysis were used to understand the close contact of atoms within the molecules. High crystal densities, thermal stabilities and low sensitivities make the synthesized ECCs interesting for further studies and potential applications as safe high-energy dense materials.

The combined effect of pyrazole and amino groups: preparation of novel energetic coordination compounds with high ClO4− content

Cu(H2DAPZCA)2(ClO4)4 (EIsCCs-1) has a multi-functional structure composed of an ionic salt and a coordination compound. It also has the advantages of high ClO4− content and oxygen balance, acceptable mechanical stimulation and excellent explosion performance.

A three-dimensional energetic coordination compound (BLG-1) with excellent initiating ability for lead-free primary explosives.

Exploration of advanced lead-free primary explosives is a challenging issue in the field of energetic materials. Herein, we designed and synthesized a novel N-rich copper bromate energetic coordination compound (ECC) [Cu(ATRZ)(BrO3)2]n (BLG-1, ATRZ: 4,4'-azo-1,2,4-triazole) by a simple one-step reaction. BLG-1 is the first reported three-dimensional (3D) N-rich copper bromate ECC. Its interesting 3D reticular architecture contributed to its highest thermal decomposition temperature (Td: 226 °C) and crystal density (ρ: 2.69 g cm-3) among N-rich copper bromate ECCs. More importantly, a primary charge of BLG-1 as little as 3 mg could reliably detonate compressed RDX, and 1 mg could detonate CL-20. These incredible values indicated that BLG-1 had an ultra-powerful initiating ability far superior to that of previously reported primary explosives. BLG-1 had improved mechanical sensitivities (IS: 13 J; FS: 1 N) and electrostatic sensitivity (EDS: 240 mJ) compared with those of the typical lead-based primary explosive, lead azide (IS: 4J; FS: 0.75N; EDS: 5 mJ). In particular, BLG-1 had a low laser-initiation threshold of 13 mJ at 808 nm, suggesting that it could serve as a laser-ignitable primary explosive. This work suggests that BLG-1 is a promising candidate with engreat practical application prospects for lead-free primary explosives.

Cupric coordination compounds with multiple anions: a promising strategy for the regulation of energetic materials.

To seek new high energetic materials, N-methylene-C-bridged nitrogen-rich heterocycle 1-((4,5-diamino-4H-1,2,4-triazol-3-yl)methyl)-1H-1,2,4-triazol-3,5-diamine (DATMTDA) (2) was first synthesized, and two copper coordination compounds ([Cu12(OH)4(ClO4)4(H2O)4(DATMTDA)12](ClO4)16·12H2O (3) and [Cu3(OH)(ClO4)(DATMTDA)3](ClO4)3(NO3) (4)) based on 2 were formed by introducing different anions. These compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. The crystal structures of compounds 3 and 4 are similar and crystallize in monoclinic systems with the P21/c space group, while the central copper atoms show different coordination behaviors. However, the structure of compounds 3 and 4 is analogous to a three dimensional structure owing to the O atom of OH-, forming coordinate bonds with three copper cations. The NBO charge of 2 was calculated using density functional theory to understand its coordination modes. The Hirshfeld surface calculation reveals that 3 and 4 have strong intermolecular interactions. The thermal decomposition processes, non-isothermal kinetics, and enthalpies of formation and sensitivities of these compounds were investigated. By introducing one NO3- of compound 4 to replace one ClO4- in compound 3, compound 4 shows lower density and lower decomposition peak temperature but lower sensitivity and a higher formation enthalpy than compound 3. The complex 4 possesses an outstanding catalytic effect for the decomposition of AP than that of complex 3. The results illustrate the possibility of introducing various anions into energetic coordination compounds for the regulation of energetic materials.

1-(Nitratomethyl)-5H-tetrazole: A Highly Sensitive Ligand with Improved Oxygen Balance for Laser-Ignitable Coordination Compounds.

For the first time, the highly sensitive 1-(nitratomethyl)-5H-tetrazole (1-NAMT) was synthesized, representing the shortest possible 1-(nitratoalkyl)-5H-tetrazole with a combined nitrogen and oxygen content of 81.4%. Compared to its related ethyl derivative, 1-(nitratoethyl)-5H-tetrazole, it exhibits improved oxygen balance, resulting in higher detonation parameters. 1-NAMT was thoroughly analyzed by single-crystal diffraction experiments accompanied by elemental analysis, IR spectroscopy, and multinuclear (1H, 13C, and 14N) NMR measurements. The thermal behavior of 1-NAMT was analyzed by differential thermal analysis supported by thermogravimetric analysis. Furthermore, energetic coordination compounds (ECCs) of Cu with different inorganic (e.g., nitrate, chlorate, and perchlorate) and nitroaromatic anions (e.g., picrate and styphnate) were synthesized and thoroughly analyzed. It is shown that the formation of ECCs with nitroaromatic anions (Tdec ∼ 180 °C) is a suitable strategy to improve the rather low thermal stability of 1-NAMT (125 °C).

Energetic coordination compounds of late 3d metals with 1N-(Nitromethyl)-5H-tetrazole, a ligand with astonishing properties from the rare class of N-nitromethyl azoles

The hardly accessible N-nitromethyl moiety is introduced onto the 1,5H-tetrazole scaffold, representing the fourth and fifth ever synthesized N-nitromethyl azoles. Both compounds 1-(Nitromethyl)-5H-tetrazole (2a) and 2-(Nitromethyl)-5H-tetrazole (2b) are thoroughly analyzed by low-temperature single-crystal X-ray diffraction experiments, complemented by elemental analysis, multinuclear (1H, 13C, 14N, 15N) NMR as well as IR spectroscopy. Sensitivity measurements towards external stimuli revealed two highly insensitive compounds. Additionally, 2a was applied as ligand for energetic coordination compounds of 3d transition metals (e.g. Cu, Fe, Ni, and Zn) in combination with oxidizing nitrate, chlorate and perchlorate anions. The synthesized ECCs were analyzed by low-temperature single-crystal X-ray diffraction experiments, elemental analysis and IR spectroscopy. The thermal behavior of all compounds was investigated by differential thermal analysis and the sensitivities towards impact and friction was measured. Due to the lack of information about the properties of N-nitromethyl azoles, the complete insensitivity towards external stimuli of 2a and 2b supports first hints of a sensitivity decreasing influence of the N-nitromethyl moiety, which is highly desired when designing new high explosives. Additionally, the functional group is able to introduce meltability into molecular scaffolds.

Trinitro‐orcinolate and Trinitro‐resorcinate – Sensitivity Trends in Nitroaromatic Energetic Materials**

Abstract5‐Methyl‐2,4,6‐trinitrobenzene‐1,3‐diol (trinitro‐orcinol, H2TNO) as a close structural relative to the well‐known energetic materials trinitroresorcinol (styphnic acid) and trinitrotoluene (TNT) is prepared in high purity and analyzed concerning its vapor pressure using the transpiration method. Several energetic coordination compounds (ECCs) of its respective anion were produced and compared with structurally close styphnate complexes to give an insight into physiochemical trends of the ECC. The synthesized compounds were further analyzed by elemental analysis, IR spectroscopy, differential thermal analysis and low temperature X‐ray diffraction analysis. To classify the reported compounds among the energetic materials, they were tested for their sensitivities towards mechanical stimuli such as impact, friction and electrostatic discharge as well as their behavior towards flame.

1,5-Dimethyltetrazole as a ligand in energetic 3d5 to 3d10-metal coordination compounds

During the last decade, energetic coordination compounds gained considerable attention due to the simple adjustments in their physicochemical properties. By combining different metal cations, energetic anions, and ligands, those compounds can be adapted for their intended use. This study used 1,5-dimethyltetrazole (3) as a highly endothermic, easily accessible, and insensitive ligand. It is a structural isomer to 1-ethyl-5H-tetrazole (1-ETZ), which was recently described as a suitable ligand. 1,5-Dimethyltetrazole was synthesized using two different methods: (1) reaction of acetone with azido (trimethyl) silane and (2) reaction of acetoxime benzenesulfonate with sodium azide. Subsequently, 1,5-dimethyltetrazole was reacted with the perchlorate salts of different 3d metals (e.g., Mn, Fe, Co, Ni, Cu, Zn) to obtain new energetic coordination compounds (ECCs). In addition, copper (II) complexes with 2,4,6-trinitro-phenolate anions were synthesized. The resultant complexes were investigated through low-temperature, single crystal diffraction experiments complemented by elemental analysis, infrared spectroscopy, and differential thermal analysis. Moreover, sensitivities towards impact and friction were investigated. In this study, all ECCs exhibited impact sensitivities between 2 and 10 ​J, friction sensitivities between 128 and 360 ​N, and thermal stabilities of up to 360 ​°C.

1-(Azidomethyl)-5H-Tetrazole: A Powerful New Ligand for Highly Energetic Coordination Compounds.

Highly energetic 1‐(azidomethyl)‐5H‐tetrazole (AzMT, 3) has been synthesized and characterized. This completes the series of 1‐(azidoalkyl)‐5H‐tetrazoles represented by 1‐(azidoethyl)‐5H‐tetrazole (AET) and 1‐(azidopropyl)‐5H‐tetrazole (APT). AzMT was thoroughly analyzed by single‐crystal X‐ray diffraction experiments, elemental analysis, IR spectroscopy and multinuclear (1H, 13C, 14N, 15N) NMR measurements. Several energetic coordination compounds (ECCs) of 3d metals (Mn, Fe, Cu, Zn) and silver in combination with anions such as (per)chlorate, mono‐ and dihydroxy‐trinitrophenolate were prepared, giving insight into the coordination behavior of AzMT as a ligand. The synthesized ECCs were also analyzed by X‐ray diffraction experiments, elemental analysis, and IR spectroscopy. Differential thermal analysis for all compounds was conducted, and the sensitivity towards external stimuli (impact, friction, and ESD) was measured. Due to the high enthalpy of formation of AzMT (+654.5 kJ mol−1), some of the resulting coordination compounds are extremely sensitive, yet are able to undergo deflagration‐to‐detonation transition (DDT) and initiate pentaerythritol tetranitrate (PETN). Therefore, they are to be ranked as primary explosives.