Photophysical Characteristics of Polarity-Sensitive and Lipid Droplet-Specific Phenylbenzothiadiazoles

In this study, we present a series of solvatochromic phenylbenzothiadiazoles that display dual emission from the locally excited (LE) and intramolecular charge transfer (ICT) excited states. The donor-acceptor derivatives are highly sensitive to polarity changes, which can be monitored by differences in emission efficiency, spectroscopic shifts and variations of the LE/ICT ratio. One of the compounds in the series, containing a thiomethyl substituent, emerged as an excellent blue emitting stain for intracellular lipid droplets, a biomarker for various types of cancer. In addition, a non-emissive nitro derivative becomes fluorescent upon bioreduction in hypoxic cancer cells and accumulates in lipid droplets with a high signal-to-background ratio.

Automated summary

A series of solvatochromic phenylbenzothiadiazoles with dual emission properties were studied, showing sensitivity to polarity changes and potential applications in staining intracellular lipid droplets as well as fluorescence in hypoxic cancer cells. The compounds demonstrate differences in emission efficiency, spectral shifts, and ratios of locally excited and intramolecular charge transfer states.