New conjugated organic dyes with various electron donors: One- and two-photon excited fluorescence, and bioimaging

Abstract

Six new fluorescent donor-π bridge-acceptor (D-π-A) structural molecules with various electron donors were synthesized and fully characterized. Influence of electron-donating strength on optical properties was investigated by the systematic alteration of the electron donors. The optical properties of the dyes were successfully tuned by choosing different electron donors. All the dyes in solution show strong one-photon excited fluorescence (OPEF) and high quantum yield. With increasing electron-donating strength of donors, dye 5 with diphenylamine and dye 6 with (4,4′-diethoxyphenyl)amino substituents, exhibit strong two-photon excited fluorescence (TPEF), and the large two-photon absorption (TPA) cross-section values are 1378 GM for 5 and 1654 GM for 6. The structure–property relationships were detailed through quantum chemical calculations and X-ray crystallography. The results of living cell imaging experiments show the values of them in one- or two-photon fluorescence microscopy bioimaging applications.