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Time‐Resolved Study of the Sensitized Formation and Decay of 1O 2 ( 1δ g ) in the Presence of Cyclodextrins*
Author(s) -
Sanramé Carlos N.,
Rossi Rita H. de,
Argüello Gustavo A.
Publication year - 1998
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.1751-1097.1998.tb02502.x
Subject(s) - chemistry , singlet oxygen , photochemistry , aqueous solution , cyclodextrin , excited state , equilibrium constant , singlet state , absorption (acoustics) , absorption spectroscopy , oxygen , ketone , organic chemistry , physics , quantum mechanics , nuclear physics , acoustics
The effect of β‐cyclodextrin and β‐hydroxypropyl‐cyclodextrin on some properties of the aromatic ketone 1‐H‐phenalen‐1‐one and its sulfonate derivative 1‐H‐phen‐alen‐1‐one‐2‐sulfonic acid was measured in aqueous solution. From the changes in the UV‐visible range of the absorption spectra, the association equilibrium constants for the formation of inclusion complexes were determined. Because these ketones are very efficient sensitizers for the generation of singlet oxygen, time‐resolved infrared luminescence was used to measure the lifetime of singlet oxygen in D 2 O. Cyclodextrins are weak deactivating agents of singlet oxygen; the upper limits for the bimolecular deactivation constants are 2 times 10 5 M −1 s −1 and 1 times 10 5 M −1 s −1 for β‐cyclodextrin and β‐hydroxypropyl‐cyclodextrin, respectively. Besides, they do not affect noticeably the extent of formation of singlet oxygen; this result is explained in terms of relocation of the sensitizer (exit from the cyclodextrin cavity) in the triplet excited state.