Derivatization of a rigid meso-substituted heptamethine cyanine dye

A novel electroneutral rigid meso-sulfophenyloxy substituted heptamethine dye was synthesized in six steps. Selective derivatization of one sulfonamide group with octanedioic acid introduced the carboxy end group attached through the hexamethylene linker, which provided the dye solubility in water. Absorbance of the dye in the near infrared region makes it promising for covalent labeling of biomolecules.