Small-molecule fluorescent dyes based on benzothiazole derivatives for targeting endoplasmic reticulum and tissue imaging

[Display omitted] •L1 and L3 were confirmed by single crystal X-ray diffraction analysis.•The photophysical properties of L1-L3 were systematically investigated.•These compounds were capable of effectively targeting ER in living cells.•These compounds were successfully applied to fluorescent imaging in tissue. Small-molecule fluorescent dyes with excellent biocompatibility and deep tissue permeability are playing an important part in biological development. Herein, a series of D-A typesmall-molecules L1, L2 and L3 containing different terminal groups have been designed and synthesized, of which the structures were confirmed by single crystal X-ray diffraction analysis. Interestingly, it was found that different end groups within the molecules gave an obvious effect on the fluorescent emission properties while unconspicuous influence on the absorption properties. Moreover, these compounds were successfully applied to fluorescent imaging for staining cellular endoplasmic reticulum (ER) and tissue slice from mouse exhibiting negligible cytotoxicity as well as favourable permeability. These compounds may act as probes for ER targeting and alternative bio-imaging reagents.