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PHOTOINDUCED TRANSIENT PHENOMENA IN CYCLODEXTRIN SOLID COMPLEXES: PHOTOCHEMISTRY OF AROMATIC KETONES
Author(s) -
Barra Mónica,
Scaiano J. C.
Publication year - 1995
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.1751-1097.1995.tb05239.x
Subject(s) - benzophenone , photochemistry , phosphorescence , flash photolysis , chemistry , hydrogen atom abstraction , ketone , triplet state , reactivity (psychology) , fluorescence , xanthone , radical , kinetics , stereochemistry , molecule , organic chemistry , medicine , physics , alternative medicine , pathology , quantum mechanics , reaction rate constant
— The photochemistry of benzophenone (BP) in cyclodextrin (α‐, ß‐ and γ‐CD) solid complexes has been examined by time‐resolved diffuse reflectance laser‐flash photolysis techniques. Benzophenone is photoreduced as a consequence of hydrogen abstraction from the CD cavity. Both BP phosphorescence and diphenylketyl radical fluorescence spectra in CD solid complexes were recorded at room temperature. Lifetime distribution analysis is used in order to describe the dynamics of triplet decay. The most probable BP triplet lifetime is found to decrease as the size of the CD cavity decreases (α‐CD = 0.3 (µs, ß‐CD = 0.5 µs and γ‐CD = 1.2 (µs). This observation contrasts with that for xanthone, a more rigid, yet structurally related ketone (α‐CD = 8 µs, ß‐CD = 3 µ.s and γ‐CD = 0.6 (µs) studied previously. The differences are interpreted in terms of changes in triplet reactivity and of restrictions on molecular mobility.