Vibrational and Electronic Spectroscopy of the Fluorene Cation

The fluorene cations, C13H10+ and C13D10+, have been formed by both electron impact ionization and vacuum ultraviolet photoionization, deposited in an argon matrix at 12K and studied via Fourier transform infrared and ultraviolet/visible absorption spectroscopy. Harmonic vibrational frequencies have been calculated using density functional theory (B3LYP/6-31G(d,p)) and vibrational band assignments made. Good agreement is found. Dramatic differences have been observed in the infrared band intensities of the cations compared to their neutral parents. Two excited electronic band systems have been observed and compared with previous photoelectron spectroscopic results. New calculations of the fluorene cation excited states have been performed using configuration interaction singles (CIS), CIS with a doubles correlation correction (CIS(D)), time-dependent Hartree?Fock (TDHF), and time-dependent density functional theory (TDDFT) with SVWN, BLYP, and B3LYP functionals. Theoretically, 12 low-lying excited states were found, six of which match closely with PES and optical band energies. Certain additional visible and IR bands, which appear only with higher electron impact ionization energies, are ascribed to the singly dehydrogenated neutral C13H9 (C13D9) fragment. TDDFT calculations on the excited states and B3LYP calculations of the infrared and Raman-active vibrations of the C13H9 (C13D9) product are consistent with this attribution. Evidence is presented for matrix-trapped cationic fragments, probably dehydrogenated species. The fluorene cations, C13H10+ and C13D10+, have been formed by both electron impact ionization and vacuum ultraviolet photoionization, deposited in an argon matrix at 12K and studied via Fourier transform infrared and ultraviolet/visible absorption spectroscopy. Harmonic vibrational frequencies have been calculated using density functional theory (B3LYP/6-31G(d,p)) and vibrational band assignments made. Good agreement is found. Dramatic differences have been observed in the infrared band intensities of the cations compared to their neutral parents. Two excited electronic band systems have been observed and compared with previous photoelectron spectroscopic results. New calculations of the fluorene cation excited states have been performed using configuration interaction singles (CIS), CIS with a doubles correlation correction (CIS(D)), time-dependent Hartree?Fock (TDHF), and time-dependent density functional theory (TDDFT) with SVWN, BLYP, and B3LYP functionals. Theoretically, 12 low-lying excited states were found, six of which match closely with PES and optical band energies. Certain additional visible and IR bands, which appear only with higher electron impact ionization energies, are ascribed to the singly dehydrogenated neutral C13H9 (C13D9) fragment. TDDFT calculations on the excited states and B3LYP calculations of the infrared and Raman-active vibrations of the C13H9 (C13D9) product are consistent with this attribution. Evidence is presented for matrix-trapped cationic fragments, probably dehydrogenated species