On the Mechanism of Quenching by Amines: A New Method for Investigation of Interactions with Triplet States
作者:
Robert H. Young,
D. Brewer,
R. Kayser,
R. Martin,
D. Feriozi,
Richard A. Keller,
期刊:
Canadian Journal of Chemistry
(NRC Available online 1974)
卷期:
Volume 52,
issue 16
页码: 2889-2893
ISSN:0008-4042
年代: 1974
DOI:10.1139/v74-420
出版商: NRC Research Press
数据来源: NRC
摘要:
Rate constants for the quenching of singlet oxygen by a series of substitutedN,N-dimethylanilines were obtained by a direct method employing a dye-laser. The Hammett ρ value obtained from the data (−1.71) suggests that a (partial) charge-transfer complex may be responsible for the quenching action. This rate data was combined with that obtained for the total quenching action on the sensitized photooxidation of 1,3-diphenylfuran. The quenching action on the photooxidation reaction is due to both the quenching of singlet oxygen and the quenching of the triplet state of the sensitizer (rose bengal or methylene blue). The combination of the data from each series of experiments resulted in rate constants of quenching of the triplet states of the sensitizers. A number of theN,N-dimethylanilines quenched the triplet states at the diffusion limit. Hammett ρ values (−1.86 for rose bengal and −4.19 for methylene blue) indicate that charge-transfer intermediates are probably responsible for the quenching action. This was confirmed by the observation of a transient intermediate assigned to the charge-transfer radical of methylene blue. The technique used here represents a novel approach to the investigation of triplet states.
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