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.