Symmetric, Asymmetric Charge Transfer Process of Substituted Stilbene or Its Analogues and the One-Photon-/Two-Photons-Excited Emission

Abstract

Abstract The luminescence behaviors of a series of symmetrically and asymmetrically substituted stilbene or its analogues on one-photon excitation (OPE) and two-photons excitation (TPE) have been investigated and compared. To understand the influence of intramolecular charge transfer upon the fluorescence properties, steady-state and time-resolved fluorescence spectra on one-photon-/two-photons-excitation, the solvent effect and the linear absorption spectra as well as the relative fluorescence quantum yields were examined. Based on the quantum chemical calculations of the charge density and the twisted intramolecular charge transfer (TICT) model, the luminescence properties have been interpreted. The results obtained have shown that the OPE and the TPE fluorescence behaviors are both strongly influenced by the intramolecular charge transfer process and by the planarity of effective fluorophore under the excited state. On the other hand, for a given dye, its luminescence behaviors on one-photon- and two-photons-excitation are very much alike, which means that the knowledge of two-photon fluorescence properties can be obtained by understanding the one-photon fluorescence behaviors.