1, 3, 5-Triazine-cored derivatives dyes containing triphenylamine based two-photon absorption: Synthesis, optical characterization and bioimaging

A series of new one, two and three-branched two-photon absorption triazine dyes containing triphenylamine with a π-bond and a σ-electron pair as a bridge, and different electron-donating groups, have been synthesized and their photophysical properties have been systematically investigated. These dyes showed obvious solvatochromic effects, i.e., significant bathochromic shifting of the emission spectra and larger Stokes shifts were observed in more polar solvents mainly due to intramolecular charge-transfer (ICT). The two-photon absorption (2PA) cross section values were determined by two-photon excited fluorescence (TPEF) measurements in DMF. This result further proved that a σ-electron pair as a bridge is an efficient way to transfer charge as well as a π bridge to provide a large 2PA cross section, and that their 2PA cross section values (δ) increase with increasing electron-donating strength of the end group and branch number. In addition, two-photon fluorescence cell imaging of dye 7a in HeLa and MCF-7 cancer cells was demonstrated.

► We designed and synthesized six two-photon absorption triazine dyes.
► Six dyes contain triphenylamine with a π-bond and a σ-electron pair as bridge.
► Linear and nonlinear optical properties of six dyes were investigated.
► Two-photon fluorescence cell imaging of dye 7a were demonstrated.
► The results revealed that σ-electron pair as bridge can also induce the large δ.