2,2′-Bipyridine derivatives containing aza-crown ether: Structure, two-photon absorption and bioimaging

• Two simple dyes based on aza-crown ether were synthesized.
• The crystal structure of dye 2 was studied.
• Linear and nonlinear optical properties of dyes 1–2 were investigated.
• The results revealed that the dyes 1–2 have much large δ2PA.
• TPFM imagings of two dyes in HepG2 cell line were demonstrated.

Two novel 6-phenyl-2,2′-bipyridine derivatives based on aza-crown ether groups were synthesized and characterized, one of which was characterized by single crystal X-ray diffraction determination. Their linear photophysical properties were systematically investigated in various solvents. The nonlinear photophysical properties were investigated by two-photon induced fluorescence method. Both dyes exhibited large two-photon absorption cross-section (δ2PA). The cytotoxicity of the dyes was evaluated in HepG2 cell line to assess the potential application for biomedical imaging. Two-photon fluorescence microscopy (TPFM) imaging of two dyes in HepG2 cell line was demonstrated, which indicated that introduction of the hydrophilic aza-crown ether facilitates biological compatibility of dyes.