Sulfo-cyanine3 azide potassium is an azide cyanine dye and fluorescent probe (Ex/Em=548/563 nm) . Sulfo-cyanine3 azide potassium can be used for synthesis of fused tricyclic heterocycles, producing immunostimulatory agents[1][2]. It contains an azide group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing alkyne groups. It can also undergo ring strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing DBCO or BCN groups.