Fluorinated diphenylpolyenes: Ground- and excited-state geometry studied by absorption and fluorescence spectroscopy

Abstract Low-temperature absorption and fluorescence spectra of all-trans-1,4-diphenyl-1,2,3,4-tetrafluoro-1,3-butadiene (FDPB) and 1,6-diphenyl-1,2,3,4,5,6-hexafluoro-1,3,5-hexatriene (FDPH) were measured in hydrocarbon and 2-methyltetrahydrofuran solvents. The hypsochromic shift of the absorption bands, as compared with their hydrocarbon analogues, indicates a strong non-planarity in the S 0 ground state. Large Stokes shifts (about 6900 cm −1 for FDPB and about 11000 cm −1 for FDPH) depending very slightly on the solvent polarity can be explained by changes in the nuclear geometry when passing from the S 0 to the S 1 state.