title: Physico-chemical modeling of the role of free radicals in photodynamic therapy. III. Interactions of stable free radicals with excited photosensitizers studied by kinetic ESR spectroscopy.
abstract: The loss of paramagnetism of the stable free radical 4,4'-di-tert.-butyl- diphenyl-1-nitroxy during illumination of the photosensitizer meso-tetrahydroxyphenyl chlorine by light above 620 nm in the absence of oxygen has been followed by kinetic ESR spectroscopy. Addition of the spin trap alpha-(4-pyridyl-1-oxide)- N-tert.-butyl-nitrone reduces the initial rate of the disappearance of the free radical enabling to separate triplet-doublet interactions from processes between radicals stemming from the triplet sensitizer and the stable free radical. Kinetic treatment of the mechanism suggested yielded the rate constant of the triplet-doublet interaction proceeding via electron transfer being about 6% of the rate constant of the overall interaction including both energy transfer and electron transfer.
authors.affiliation: Central Research Institute for Chemistry of the Hungarian Academy of Sciences, Budapest.
authors.forename: T
authors.initials: T
authors.lastname: Kriska
authors.forename: L
authors.initials: L
authors.lastname: Korecz
authors.forename: I
authors.initials: I
authors.lastname: Nemes
authors.forename: D
authors.initials: D
authors.lastname: Gál
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D007700:Kinetics; D008956:Models, Chemical; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000737:chemistry*
chemical_list: C096005:4,4'-di-(tert-butyl)diphenyl-1-nitroxy; D001713:Biphenyl Compounds; D005609:Free Radicals; D017319:Photosensitizing Agents