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POLYMER BOUND PYRROLE COMPOUNDS–VI. PHOTOPHYSICAL PROPERTIES OF MONOMERIC MODELS FOR POLYSTYRENE‐BOUND PORPHYRINS
Author(s) -
LL SANTIAGO,
SESÉ MARÍA L.,
MÁRTIRE DANIEL O.,
BRASLAVSKY SILVIA E.,
TRULL FRANCESC R.
Publication year - 1991
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1991.tb03922.x
Subject(s) - photochemistry , porphyrin , flash photolysis , chemistry , quantum yield , quenching (fluorescence) , polystyrene , phosphorescence , intramolecular force , nitro , singlet state , singlet oxygen , monomer , pyrrole , excited state , triplet state , fluorescence , polymer , molecule , reaction rate constant , kinetics , oxygen , organic chemistry , physics , alkyl , quantum mechanics , nuclear physics
— 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, O 2 ( 1 Δ g ), 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 φ f , φ T and φ δ (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 O 2 ( 1 Δ g ) 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 O 2 ( 1 Δ g ) production by the sensitizer. The consequences of these results for the use of polystyrene‐bound porphyrins in sensitized photooxidation processes are discussed.