A dicyanoisophorone-based highly sensitive and selective near-infrared fluorescent probe for sensing thiophenol in water samples and living cells.

Thiophenol (PhSH) is an important sulfhydryl compound in organic synthesis, but it is also a volatile environmental pollutant with high toxicity to organisms. Herein, we reported a novel near-infrared (NIR) probe (1) for turn-on fluorescence detection of PhSH. The probe was prepared by coupling 2,4-dinitrophenyl (DNP) to a dicyanoisophorone-based fluorophore (2). PhSH can specifically perform a nucleophilic aromatic substitution on probe 1 and result in the release of fluorophore 2, thus achieving a turn-on fluorescence response (λ = 693 nm). A dramatic color change from red (λ = 525 nm) to blue (λ = 668 nm) was also observed. This fluorescent assay displayed a large Stokes shift (∼133 nm) and a high sensitivity for PhSH, as well as a low detection limit (34 nM). Moreover, probe 1 was successfully applied to monitor PhSH in real water samples and image PhSH in living cells.