PHOTOCHEMISTRY IN CYCLODEXTRINS

The photochemistry of two ketones with contrasting excited state reactivity (benzophenone and 4-phenylbenzophenone) incorporated into β-cyclodextrin (β-CD) was investigated. The formation of a 1:1 benzophenone-β-CD complex was demonstrated by UV spectroscopy and the association constant K was determined to be 670 ± 60 mol-1 dm3. However, the reactive ketone triplet state was quenched by the carbohydrate, preventing the observation of room temperature phosphorescence (RTP). The possibility that the 3n,π* state was self-quenched in a 2:1 complex was ruled out on the basis of the observed photochemistry and the temperature dependence of the quenching. In contrast, the RTP of the related compound, 4-phenylbenzophenone, in β-CD solution was demonstrated for the first time. © 1990.