Mechanistic analysis of the fluorescence quenching of dodecyloxo(methoxo)tetraphenylporphyrinatoantimony by 9,10-dimethylanthracene in an artificial membrane constructed by a phospholipid liposome

As a model for photodynamic therapy, photosensitization with dodecyloxo(methoxo)tetraphenylporphyrinatoantimony bromide was investigated in a phospholipid liposome (LP) constructed with 1,2-diparmitoyl-sn-glycerol 3-phosphocholine. The adsorption isotherms of the sensitizer into the LP showed Langmuir-type adsorption with binding constants in the order of 106 M−1. The sensitizer was bound to the LP by hydrophobic interactions with the dodecyloxo ligand and the core of the LP membrane. The photosensitized oxygenation reaction of 9,10-dimethylanthracene (DMA) with the sensitizer in the LP occurred efficiently at 0.73 of the limiting quantum yield. Fluorescence quenching and kinetic analysis suggested that the reaction proceeded through photoinduced electron transfer from DMA to the excited singlet state of the sensitizer.