A novel two-photon absorbing dye derived from a V-shaped chromophore containing triphenylamine and dipicolinate: Synthesis and application as probe for proton, water, mercury ion and cell imaging

• The molecule exhibits large two-photon absorption activity.
• The pKa value of the pH probe is in the range of 4.5–6.5.
• The molecule exhibits high sensitivity and selectivity for mercury ion.
• The fluorescence can be made to measure water content of organic solvents.
• The molecule is a promising label potentially applicable for the tracking of biomolecules.

A novel two-photon absorbing dye (TP-Py) was synthesized by introduction of a formyl group into the triphenylamine fragment of a V-shaped compound (compound 1). Compared to the corresponding compound 1, TP-Py exhibits enhanced two-photon absorption activity. When measured by Z-scan technique at 800 nm, the two-photon cross-section of TP-Py in THF was 1380 GM. Meanwhile, the introduction of a formyl group in compound 1 greatly improves the potential application of the molecule. TP-Py exhibits significant absorption and fluorescence spectral sensitivities in response to changes in pH. Especially, the pKa value of the pH probe is in the range of 4.5–6.5, which is critical for precisely assessing the cellular acidic environments. The fluorescence of TP-Py can be made to measure water content of organic solvents. The detection limit was calculated to be 0.04% for THF. The probing behaviors of TP-Py toward metal ions were investigated via absorption spectra as well as one- and two-photon fluorescence changes. The results indicated that TP-Py exhibits high sensitivity and selectivity for mercury ion. TP-Py was also chosen for two-photon cell imaging. The two-photon scanning microscopy experiment suggests that TP-Py is a promising label potentially applicable for the tracking of biomolecules.

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