Synthesis and phototoxicity of polyethylene glycol (PEG) substituted metal-free and metallo-porphyrins: effect of PEG chain length, coordinated metal, and axial ligand.

Treatment of 5,10,15,20-tetra(pentafluorophenyl) porphyrins with polyethylene glycol (PEG) halides and sodium sulfide is a mild and efficient route to water-soluble PEG substituted porphyrins. The method has been used to access a series of free-base and metallated PEG porphyrins, which have been investigated for photodynamic activity against Human Caucasian colon adenocarcinoma (Caco2) cells. Toxicity, in the presence and absence of light, is shown to be affected by the length of the PEG chain, nature of coordinated metal and axial ligand.