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Solvent Isotope Effect on the Rate Constants of Singlet‐Oxygen Quenching by edta and Its Metal Complexes
Author(s) -
Hessler Diane P.,
Frimmel Fritz H.,
Oliveros Esther,
Braun André M.
Publication year - 1994
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19940770325
Subject(s) - chemistry , singlet oxygen , quenching (fluorescence) , kinetic isotope effect , reactivity (psychology) , metal , reaction rate constant , oxygen , photochemistry , solvent , acceptor , singlet state , deuterium , inorganic chemistry , metal ions in aqueous solution , excited state , kinetics , organic chemistry , fluorescence , medicine , alternative medicine , pathology , condensed matter physics , physics , quantum mechanics , nuclear physics
Abstract The reactivity of singlet oxygen (O 2 ( 1 Δ g )) with edta and its metal complexes with Al 3+ , Cu 2+ , Fe 3+ , and Mn 2+ was investigated. The emission of singlet oxygen at 1270 nm in D 2 O was measured in order to determine the quenching efficiency of edta and edta‐metal complexes for different metal/edta ratios. The sum of the rate constant ( k r + k q ) of the chemical reaction between singlet oxygen and the acceptor ( k r ) and of the physical quenching of singlet oxygen by the acceptor ( k q ) was obtained by a Stern‐Volmer analysis. Measurements of the oxygen consumption in H 2 O were used to determine quantum yields of the sensitized photooxidation, and the combined results of these experiments allowed the determination of k r and k q separately. A strong isotope effect was observed between the deuterated and the hydrogenated solvents. This effect was shown to be independent of the analytical procedure used. The isotope effect, as well as the reactivity of edta and its metal complexes, depend markedly on the complexed metal ion.