The radical cation of bithiophene: An experimental and theoretical study

The electronic absorption spectrum of the bithiophene radical cation prepar ed by gamma-irradiation in a glassy Freon matrix is presented, together wit h the Raman spectra excited at 550 and 425 nm, in resonance with the two ab sorption bands. The 425 nm excited Raman spectrum was also recorded in a ro om temperature acetonitrile solution, in this case the radical cation was g enerated via a photoinduced electron transfer reaction. The resonance Raman spectra were interpreted with the help of density functional theory calcul ations. The results indicate the existence of at least two rotamers of the bithiophene radical cation. The time-domain method was applied to the simul taneous fitting of the absorption and resonance Raman spectra.