TIME-RESOLVED STUDY OF THE SENSITIZED FORMATION AND DECAY OF O-1(2)((1)DELTA(G)) IN THE PRESENCE OF CYCLODEXTRINS

The effect of beta-cyclodextrin and beta-hydroxypropyl-cyclodextrin on some properties of the aromatic ketone 1-H-phenalen-1-one and its sul fonate derivative 1-H-phenalen-1-one-2-sulfonic acid was measured in a queous solution, From the changes in the UV-visible range of the absor ption spectra, the association equilibrium constants for the formation of inclusion complexes were determined. Because these ketones are ver y efficient sensitizers for the generation of singlet oxygen, time-res olved infrared luminescence was used to measure the lifetime of single t oxygen in D2O. Cyclodextrins are weak deactivating agents of singlet oxygen; the upper limits for the bimolecular deactivation constants a re 2 x 10(5)M(-1)s(-1) and 1 x 10(5)M(-1)s(-1) for beta-cyclodextrin a nd beta-hydroxypropyl-cyclodextrin, respectively. Besides, they do not affect noticeably the extent of formation of singlet oxygen; this res ult is explained in terms of relocation of the sensitizer (exit from t he cyclodextrin cavity) in the triplet excited state.