title: Analysis of fluorescence quenching of coumarin derivatives by 4-hydroxy-TEMPO in aqueous solution.
abstract: The fluorescence quenching of different coumarin derivatives (7-hydroxy-4-methylcoumarin, 5,7-dimethoxycoumarin, 7-amino-4-methyl-3-coumarinylacetic acid, 7-ethoxy-4-methylcoumarin, 7-methoxycoumarin, 7-hydroxycoumarin, 7-hydroxy-4-methyl-3-coumarinylacetic acid and 7-amino-4-methylcoumarin) by 4-hydroxy-TEMPO in aqueous solutions at the room temperature was studied with the use of UV-Vis absorption spectroscopy as well as a steady-state and time-resolved fluorescence spectroscopy. In order to understand the mechanism of quenching the absorption and fluorescence emission spectra of all coumarins along with fluorescence decays were recorded under the action of 4-hydroxy-TEMPO. The Stern-Volmer plots (both from time-averaged and time-resolved measurements) displayed no positive (upward) deviation from a linearity. The fluorescence quenching mechanism was found to be entirely dynamic, what was additionally confirmed by the registration of Stern-Volmer plots at different temperatures. The Stern-Volmer quenching constants and bimolecular quenching rate constants were obtained for all coumarins studied at the room temperature. The findings demonstrate the possibility of developing an analytical method for the quantitative determination of the free radicals' scavenger, 4-hydroxy-TEMPO.
authors: Faculty of Chemistry, University of Gdansk, Wita Stwosza 63, 80-952, Gdansk, Poland, kzam@chem.univ.gda.pl.
authors: Krzysztof
authors: K
authors: Żamojć
authors: Wiesław
authors: W
authors: Wiczk
authors: Bartłomiej
authors: B
authors: Zaborowski
authors: Dagmara
authors: D
authors: Jacewicz
authors: Lech
authors: L
authors: Chmurzyński
mesh_terms: D003374:Coumarins / Q000032:analysis* / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D005453:Fluorescence; D016166:Free Radical Scavengers / Q000737:chemistry*; D019811:Hydroxylamine / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry*
chemical_list: D003374:Coumarins; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D014867:Water; D019811:Hydroxylamine; C505333:TEMPOL-H