Abstract— Several porphyrin esters used as models for polystyrene‐bound porphyrins have been prepared and their excited states have been studied by laser flash photolysis, IR phosphorescence of singlet molecular oxygen, O2(1Δg), and steady‐state fluorescence. The photophysical properties of the porphyrin esters in solution are affected by the presence of nitro group(s) in the chain. In this case, an important decrease in φf, φT and φδ (to ca 0.7–0.4 of the value for the parent dimethyl ester) is observed. This is mainly due to intramolecular electron‐transfer quenching [by the nitro group(s)] of the first excited singlet state of the porphyrin. The thermodynamic feasibility of this deactivation pathway has been confirmed polarographically. Quenching of the porphyrin triplet state and of O2(1Δg) by the nitro groups is negligible. The present conclusions explain also the results obtained previously for the photooxidation of bilirubin sensitized by the parent insoluble polystyrene‐bound porphyrins. In that case the photooxidation rates were correlated directly with the quantum yield of O2(1Δg) production by the sensitizer. The consequences of these results for the use of polystyrene‐bound porphyrins in sensitized photooxidation processes are discussed.
|Nombre de pàgines||9|
|Revista||Photochemistry and Photobiology|
|Estat de la publicació||Publicada - de febr. 1991|