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

Abstract

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.

Preparation of Primary Explosive by Self-assembly of Combustible and Oxidizing Agents under Acid

“…6−10 Klapoẗke has made outstanding contributions in this field. Specifically, they used tetrazole derivatives as ligands to prepare a series of ECCs, such as [Cu(1-VTZ) 6 ](ClO 4 ) 2 , 11 [Cu(1-NMT) 6 ](ClO 4 ) 2 , 12 and [Cu(1-NET) 6 ](ClO 4 ) 2 13 (1-VTZ: 1-vinyl-5H-tetrazole, 1-NMT: 1N-(nitromethyl)-5H-tetrazole, 1-NET: 1-nitratoethyl-5H-tetrazole). Not surprisingly, these ECCs have the potential to be used as primary explosives.…”

“…In nitrogen-rich materials, energetic coordination compounds (ECCs) with unique coordination structures have attracted the attention of scientists due to their simple preparation, high product purity, and excellent explosive performance. − Klapötke has made outstanding contributions in this field. Specifically, they used tetrazole derivatives as ligands to prepare a series of ECCs, such as [Cu­(1-VTZ) 6 ]­(ClO 4 ) 2 , [Cu­(1-NMT) 6 ]­(ClO 4 ) 2 , and [Cu­(1-NET) 6 ]­(ClO 4 ) 2 (1-VTZ: 1-vinyl-5 H -tetrazole, 1-NMT: 1N-(nitromethyl)-5 H -tetrazole, 1-NET: 1-nitratoethyl-5 H -tetrazole). Not surprisingly, these ECCs have the potential to be used as primary explosives.…”

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

“…With the deepening of research, multidisciplinary development, and new requirements, more and more new materials have been used in primary explosives. , Among them, energetic coordination compounds (ECCs) have entered the perspective of researchers due to their unique structure and performance advantages . Because of its simple preparation, good performance, easy amplification, and high purity, it is favored by researchers, and Klapötke has made outstanding contributions in this regard. − …”

Regulation of stability and detonation performance: preparation of coordination compounds by using isomeric ligands

“…In the field of ECCs, Klapötke have made significant contributions, with their research focusing on ECCs using tetrazole derivatives as ligands. [11][12][13] However, since the [N] in the tetrazole ring is connected, it contains a lot of chemical potential energy, and the derived groups are often high-energy explosive groups, such as 1-(nitromethyl)-5H-tetrazole, 14 1-(azidomethyl)-5H-tetrazole, 15 and 1-vinyl-5H-tetrazole, 16 meaning that the ligand itself shows relatively high explosive performance. Therefore, although these [ClO 4 − ]-based complexes have high energy, they are very sensitive to mechanical stimuli, and we have found that complexes prepared using stereoisomers have different structures and properties.…”