Meso-functionalized 21-thiaporphyrins: Synthesis, DFT and phototoxicity studies in cancer cells

The synthesis of meso-functionalized 21-thiaporphyrins with N<inf>3</inf>S core was carried out by one pot reaction of thiophene diol, pyrrole and aromatic aldehyde. The active pharmacophoric groups occupied the 5,10-positions of 21-thiaporphyrins, whereas the other two meso-positions were substituted by p-tolyl or p-bromophenyl moieties. The meso-pharmacophoric groups substantially altered the optical properties of 21-thiaporphyrins, with 20–36 nm red shifts in their absorption and emission maxima as compared to the standard compound. The singlet oxygen quantum yields were 68-71% in DMSO for these 21-thiaporphyrins. The in-vitro cellular uptake and cytotoxicity studies of 21-thiaporphyrins were performed on HeLa cells. Both the 21-thiaporphyrins were found to be significantly phototoxic to cervical cancer cells with 1.9 to 2.9 µM IC<inf>50</inf> values, suggesting their potential application in photodynamic therapy.