Long-Lived Room-Temperature Phosphorescence of Arene–Beta-Cyclodextrin–Hydrocarbon Complexes in the Presence of Oxygen.

Room-temperature phosphorescence (RTP) of arenes, naphthalene-d8 and phenanthrene, in complexes with β-cyclodextrin (βCD) in the presence of a third component, tert-butylbenzene or p-tert-butyltoluene, providing the appearance of long-lived arene RTP, has been studied. The RTP lifetimes τph of naphthalene-d8 in the naphthalene-d8–βCD–tert-butylbenzene and naphthalene-d8–βCD–p-tert-butyltoluene complexes in the presence of oxygen are 14 and 4.8 s, respectively, and increase up to 16.4 and 6.6 s after oxygen removal. The rate constants of the phosphorescence quenching in these complexes are 34.4 and 76 L mol−1 s−1, respectively, indicating a high degree of naphthalene-d8 isolation from oxygen in the supramolecular system based on βCD. The highest value of τph for phenanthrene in the phenanthrene–βCD–tert-butylbenzene complex in the presence of oxygen is 2.4 s. The RTP decay in the presence of oxygen is always the superposition of two exponents, which is the general property of such three-component complexes, and indicates the presence of two types of phosphorescing complexes. The proposed structures of the complexes have been calculated by the quantum-chemistry method. The mechanism of the arene RTP quenching by oxygen is discussed with the use of the calculated structures of the complexes. [ABSTRACT FROM AUTHOR]