Conformation-dependent intramolecular exciplex formation in jet-cooled bichromophores

Bichromophore compounds consisting of anthracene and naphthalene subunits linked by the alkyl (CH2)3 and the ethereal CH2–O–CH2 chain have been studied under supersonic jet conditions in the region of the first electronic transition of anthracene by laser-induced fluorescence. Intramolecular exciplex formation has been observed in the 1-substituted naphthalene derivative involving the CH2–O–CH2 spacer, whereas the trimethylene bridge compound as well as the 2-substituted naphthalene ethereal derivative exhibit only the resonance fluorescence characteristic of a locally excited anthracene molecule. These different behaviours reproduce the photophysical properties of these bichromophores in solution and have been discussed in terms of ground-state geometries.