New highly electrodeficient cationic fluorescent tetrazines: a step toward the strongest purely organic photooxidants

Fluorescent strongly electrodeficient tetrazines substituted with cationic heterocycles have been prepared. These compounds can be reversibly reduced at a high potential and consequently their excited state is a strong oxidant. As a result of their very strong photooxidant character, their fluorescence is quenched in the presence of toluene, m-xylene styrene and sometimes even benzene, through a photoinduced electron transfer reaction with a dynamic quenching mechanism. Beyond their photooxidizing properties, these new molecules have a potential towards the realization of new fluorescence sensors. As an example, tetrazine 3 has been dispersed on silica particles and we have demonstrated that its fluorescence is quenched upon exposure to benzene vapors.