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

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. Electron‐rich tetrazine explosives: New electron‐rich s‐tetrazine and triazolo‐tetrazine explosives have been synthesized (see figure). The electrochemistry of these materials is irreversible, unlike that of previously reported tetrazine compounds. This irreversibility is attributed to interaction between nitrate ester groups and the electron‐rich tetrazine radical anions.