Free base porphyrin–cyanine dye conjugate: synthesis and optical properties

The covalent combination of a cyanine dye (IR-783) with a tetraphenyl porphyrin unit through an ether linkage results in a photoactive system capable of producing singlet oxygen. The synthesis, characterization and photophysical properties of the resulting novel free base porphyrin–cyanine conjugate named TPPO-IR-783 (TOI) is reported. Excited state properties were studied in various solvents with differing polarity. The fluorescence is strongly solvent dependent, however this is not the case for singlet oxygen phosphorescence, which is only observed in tetrahydrofuran (THF), when comparing 8 different polar, non-polar and medium-polarity solvents. This novel type of porphyrin–cyanine photosensitizer has the ability to produce singlet oxygen and absorbs light at NIR wavelengths.