Abstract

The time-resolved Raman spectra of the first triplet state–in resonance with the Tn←T1 absorption at 370 nm–and of the radical cation transient–in resonance with the R+⋅∗←R+⋅ absorptions at 370 nm and in the 560-600 nm range-are reported for fluorene. The triplet state Raman spectra of dibenzofuran and dibenzothiophen are also given. The vibrational assignments, resonance Raman activity and intensity enhancement effects are studied. On this basis, the structures and electronic configurations of the triplet state and radical cation transients and the nature of the resonant Tn←T1 and R+⋅∗←R+⋅ transitions are discussed. It turns out from this investigation that the title molecules present close analogies with biphenyl. The insertion of a methylene group or a heteroatom does not disturb markedly the electronic properties of the ground state, the first triplet state and the radical cation transient of biphenyl.