Tuning the Structures and Photophysical Properties of D1-A-π-D2 Fluorophores by Terminal Donors (D2).

In order to investigate the influence of terminal donors on the structures and photophysical properties of D-A prototype fluorophores, three D1-A-π-D2 fluorophores with different terminal donors (D2) have been synthesized and characterized in this study. Assisted by density functional theory calculations, this study has found that terminal donors (D2) affect the molecular packing modes by modifying the intermolecular interactions. Localized orbital locator function analysis (LOL-π) indicated that increasing the numbers of aromatic rings of terminal donors (D2) would give rise to wider π-electrons delocalization, leading to the red-shifted absorption and emission properties of such compounds. Time-dependent density functional theory calculations indicated that the long absorption peaks of such compounds mainly come from the electron transfers between π-D2 and A (π-D2 → A) moieties. Meanwhile, terminal donors (D2) affect the type and charge amount of excitation process.