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

Strongly fluorescent electrodeficient tetrazines substituted with cationic heterocycles have been prepared. These compounds can be reversibly reduced at a high potential and consequently they are strong oxidants in the excited state. 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 via a dynamic quenching mechanism. Beyond their photooxidizing properties, these new molecules have 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.