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

• Six new dyes with various electron donors were synthesized in high yield through simple reactions.
• The optical properties of the dyes were successfully tuned by the different electron donors.
• All dyes in solution show strong one-photon excited fluorescence and high quantum yield.
• Dyes 5 and 6 exhibit strong TPEF with large TPA cross-section.
• OPFM and TPFM imaging of them in HepG2 cell line was demonstrated.

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.

One- and two-photon fluorescence of six dyes, being promising in bioimaging applications, were successfully tuned through varying electron donors.Figure optionsDownload as PowerPoint slide