Magnetic modulation of exciplex fluorescence of pyrene solutions with excess of azacrown ether in the presence of ions of alkaline and alkaline-earth metals

In photoexcited polar pyrene solutions with excess of phenylaza-15-crown-5 serving as a donor an intermolecular electron transfer takes place which produces radical-ion pairs whose recombination gives rise to a fluorescent exciplex. Virtually no charge exchange between crown ether molecules and their radical-cations is observed in this process. The magnetic effect detected by changes in fluorescence reduces upon addition of diamagnetic lithium and calcium ions to the exciplex system, which is assigned to formation of paramagnetic complexes.