DACN-Based Switchable Fluorescent Click Reaction

The copper-free switchable fluorescent click reaction using 4,8-diazacyclononyne (DACN) and 3-azido-7-alkoxycoumarin was realized and applied to the conjugation of biomolecules. This new method using DACN has characteristics superior to those of the corresponding azadibenzocyclooctyne (DBCO) derivative in terms of fluorescence quantum yield and photostability under UV light irradiation.