Synthesis and Electrochemical Behavior of Electron‐Rich s‐Tetrazine and Triazolo‐tetrazine Nitrate Esters

Abstract

We have prepared energetic nitrate ester derivatives of 1,2,4,5-tetrazine and 1,2,4-triazolo[4,3-b]-[1,2,4,5]-tetrazine ring systems as model compounds to study the electrochemical behavior of tetrazines in the presence of explosive groups. The model compounds showed lower thermal stabilities relative to PETN (pentaerythritol tetranitrate), but slightly improved mechanical sensitivities. The presence of electron-rich amine donors leads to a cathodic shift of the tetrazine redox potentials relative to those of previously reported tetrazine explosives. At these potentials, electron-rich tetrazines with either covalently bound or co-dissolved nitrate ester groups are irreversibly reduced. Effectively, changes in the electronic structure of tetrazines affect their electrochemical response to the presence of nitrate ester groups. Thus, it may be possible to develop tetrazine-based electrochemical sensors for the detection of specific explosives and electrocatalysts for their disposal.

Fused heterocycle-based energetic materials (2012–2019)

“…For 15, the addition of the second N-oxide group makes its impact sensitivity slightly higher than that of 14. . 26 Intermolecular hydrogen bonding with the N-H group in 16 leads to a relatively high density (1.79 g cm À3 ). However, low thermal, impact and friction stabilities were observed because of the trinitrate group in the molecule (Table 9), which limits its practical application as an HEDM.…”

“…However, low thermal, impact and friction stabilities were observed because of the trinitrate group in the molecule (Table 9), which limits its practical application as an HEDM. 26 Azide and nitramino groups were used to modify the fused tetrazine ring as well. 3-Amine-6-azido-1,2,4-triazolo [4,3- 28) was synthesized with an azo-bridge (Scheme 12).…”

“…The notable combination of high calculated performance and low sensitivity makes 30 a promising explosive candidate (Table 10). 29 Following the synthesis of 30, 4-amino-3,7-dinitrotriazolo-[5,1-c][1,2,4]triazine (31) was obtained by reacting nitroacetonitrile with 5-amino-3-nitro-1H-1,2,4-triazole, 23,26 and further study by the oxidation of 31 with hypouorous acid led to its oxidation product, 4-amine-3,7-dinitro-[1,2,4]triazolo[5,1c][1,2,4]triazine-1-oxide (32) (Scheme 13). Compounds 31 and 32 display similar or better performance than RDX, and also show excellent insensitivity toward mechanical stimuli (Table 10).…”

Novel helix-shape bis[1,2,4]triazolo[4,3-b:3′,4′-f][1,2,4,5]tetrazines: synthesis, optical and charge-transfer properties

“…On the one hand, they are inert to electrooxidation, which is consistent with literary data, on the other hand, they undergo quasi-reversible electroreduction at a potential of BÀ0.92 AE 0.01 V (vs. Fc/Fc + in MeCN), while the literature Tz derivatives exhibit reversible one-electron reduction to relatively stable radical anions. 7,21,30,31 After reduction at more positive potentials, a new anodic peak of irreversible oxidation appears (at a scan rate of 100 mV s À1 ). We assume that in the case of the studied compounds, reduction occurs as a two-electron process and leads to the formation of dianions (rather than radical anions), which undergo a rapid chemical reaction, probably protonation to the corresponding mono-anion.…”

“…Thus, there are only few publications describing the optical and electrochemical properties of TTzs. 21,22 Even more challenging is the synthesis and study of the properties of tricyclic bis [1,2,4]triazolo [4,3-b:3,4-f][1,2,4,5]tetrazines (bisTTzs). For a long time it was not possible to obtain a bisTTz framework, since an attempt to condense 3,6-dihydrazinyl-Tz with diethoxymethyl acetate ended in the annulation of only one triazole ring, resulting in a TTz derivative.…”