π–π* Emission from a tetrazine derivative complexed with zinc ion in aqueous solution: a unique water-soluble fluorophore

Abstract
A 3,6-bis(5-amino-2-pyridyl)-1,2,4,5-tetrazine exhibits strong π–π* fluoresce in the presence of zinc ion (Zn2+) in aqueous solution, whereas it is not fluorescent in the absence of Zn2+ as well as in the presence of competing metal ions.