Electronic spectra and excited-state dynamics of van der Waals clusters of anthracene with aliphatic and aromatic ethers: dependence of exciplex formation on donor (ether) ionization potential

Abstract

We have carried out a systematic study of exciplex formation from photoexcited van der Waals complexes of anthracene with a variety of ethers, under collision-free conditions of a supersonic jet. Unlike some of the previously reported results, we have observed only narrow bands in the fluorescence excitation spectra. The exciplex fluorescence was observed only from the complex containing donor moiety with the lowest ionization potential (viz., 1,4-dimethoxybenzene), thus providing clear evidence for the dependence of exciplex formation on the ionization potential of the donor (ether) moiety. These results indicate that the energy of the charge transfer state relative to that of the initially prepared locally excited state determines the efficiency of the exciplex formation. In contrast to the previous report of exciplex formation in anthracene/diethyl ether and anthracene/anisole systems, we have observed only van der Waals type emissions from the locally excited states.