Einfluß des Silberkations auf das Fluoreszenzverhalten polyzyklischer aromatischer Kohlenwasserstoffe

Abstract

Abstract Combining the results of fluorescence and triplet-triplet absorption measurements, the influence of silver perchlorate on the excited states of pyrene, phenanthrene, 9-cyanophenanthrene, 9,10-diphenylanthracene and 9,10-dicyanoanthracene in fluid solutions has been investigated. In corre­ spondence with a small energy gap between the lowest excited singlet state and the nearest lower triplet state an external heavy atom effect has been found to be responsible for the fluorescence quenching in the case of pyrene, phenanthrene and 9-cyanophenanthrene. In the case of 9,10-diphenylanthracene and 9,10-dicyanoanthracene, where this energy gap is large, an exciplex emission is observed with no significant increase of triplet state formation. Furthermore, 9-cyanophenanthrene and 9,10-dicyanoanthracene under similar experimental conditions form ground state complexes with AgCIO4 with a red-shifted fluorescence. From time-resolved fluorescence measurements a dynamic equilibrium of association in the excited state is deduced.