Cy3-PEG2-endo-BCN, a Cyanine 3 (Cy3) dye derivative with two polyethylene glycol (PEG) units, incorporates the hydrophobic bidentate macrocyclic ligand endo-BCN, which facilitates the synthesis of macrocyclic complexes. In click chemistry, endo-BCN undergoes a catalyst-free reaction with azide-bearing molecules to yield stable triazoles.