Polymer Bound Pyrrole Compounds .6. Photophysical Properties of Monomeric Models for Polystyrene-bound Porphyrins

SANTIAGO NONELL, MARÍA L. SESÉ, DANIEL O. MÁRTIRE, SILVIA E. BRASLAVSKY, FRANCESC R. TRULL

Research output: Indexed journal article Articlepeer-review

10 Citations (Web of Science)

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.

Original languageEnglish
Pages (from-to)185-193
Number of pages9
JournalPhotochemistry and Photobiology
Volume53
Issue number2
DOIs
Publication statusPublished - Feb 1991

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