Cy3-PEG3-endo-BCN is a derivative of the dye Cyanine 3 (Cy3) containing three PEG units. It includes a lipophilic bidentate macrocyclic ligand (BCN), which can be utilized for synthesizing macrocyclic complexes. In click chemistry, endo-BCN can form stable triazoles with azide-containing molecules under catalyst-free conditions.