Novel PAMAM dendrimers with porphyrin core as potential photosensitizers for PDT applications

The photophysical properties of meso-substituted tetraphenyl porphyrins with PAMAM branches, and one peripherally-modified derivative with thiazole groups were studied in DMF solution. The singlet states of the compounds were characterized by means of absorption and fluorescence spectroscopies. The triplet state decay kinetics and the triplet–triplet absorption spectra were determined by laser flash photolysis. Triplet state spectra showed intense absorbance with a maximum at around 450 nm and other bands in the regions of 300–400 and 500–800 nm, for all compounds. The triplet quantum yields (Φ_T) and the singlet oxygen quantum yields (Φ_Δ) were estimated to be ca. 0.50 and 0.45, respectively. From the present results, it is inferred that the triplet states of these molecules allow an efficient energy transfer to molecular oxygen, which makes them potentially suitable for photodynamic therapy.