Band-Shape Analysis of teh Charge-Transfer Fluorescence in Barrelene-Based Electron Donor-Acceptor Compounds

Article abstract of DOI:10.1021/j100061a006

In this paper we analyze the band shapes of the stationary fluorescence spectra for the radiative charge transfer recombination D⁺-A^- -> D-A + hν in a series of barrelene-based organic bridged donor (D)-acceptor (A) molecules D-A, exploring solvent polarity and temperature effects on the band shape.Free energy changes for charge recombination, medium reorganization energies, and intramolecular reorganization energies (for high- and medium-frequency vibrational modes) were evaluated from the band maximum energies and the full widths at half-maximum and from the fits of standard Franck-Condon factors to the entire fluorescence band shape.Utilization of a single high-frequency intramolecular model (<*>hω_i = 1300 cm^-1) in conjunction with solvent modes provided a satisfactory fit of the band shape; however, such an analysis results in unphysically large medium reorganization energies for nonpolar solvents (0.30 - 0.45 eV) and their large temperature dependence.The inclusion of medium-frequency (<*>hω = 500 cm^-1) intramolecular modes in the band-shape analysis is important for the proper distinction between solvent and intramolecular reorganization.