Exciplexes in Perfluorohydrocarbon. Charge-Transfer Interaction between Exciplexes and Perfluorohexane

Abstract

Abstract The rate constants for photochemical processes of pyrene in perfluorohexane (PFH) and hexane containing N,N-dimethylaniline (DMA) have been determined by analyzing the rise and decay curves of the pyrene–DMA exciplex to study the interaction between electronically polar exciplex and an extremely nonpolar solvent, PFH. In PFH, the dissociation of the exciplex to the original pyrene in the excited singlet state and DMA was decelerated and the radiationless deactivation of the exciplex to the ground states was accelerated. In the case of the naphthalene–triethylamine exciplex system, the radiationless deactivation of the exciplex was also much faster in PFH than in hexane. These results suggest charge-transfer interactions between the polar exciplexes and PFH. The negative charges of the exciplexes may transfer to the strongly electronegative fluorine atom(s) of PFH. The deceleration of the back reaction and the acceleration of the radiationless deactivation seem to lead the efficient fluorescence quenching of pyrene and naphthalene by amines in PFH.