Peculiarities of phosphorescence of complexes between aromatic molecules and beta-cyclodextrin at room temperature

Luminescence of complexes between beta-cyclodextrin and phenanthrene, fluorene, or naphthalene-d(8) in aqueous solutions was studied at room temperature. It is found that the addition of acetone, in the absence of heavy atoms, results in the phosphorescence of these complexes at 293 K due to triplet-triplet energy transfer. The conclusion is drawn that a heavy atom is necessary for population of a triplet level, because the intersystem crossing of an aromatic molecule in the cyclodextrin cavity is suppressed due to restriction of vibration-relaxation interactions with a medium. The phosphorescence multiply increases when lightscattering polycomplexes between an aromatic molecule and cyclodextrin in the presence of a heavy atom and a sensitizer are formed.