Cy5-PEG7-exo-BCN is a dye derivative of Cyanine 5 (Cy5) containing 7 PEG units. Cy5-PEG7-exo-BCN contains the lyophilic bidentate macrocyclic ligand BCN, which can further synthesize macrocyclic complexes. In click chemistry , exo-BCN can react with molecules containing azide groups to form stable triazoles in the absence of catalysts.