A phenothiazine coumarin-based red emitting fluorescent probe for nanomolar detection of thiophenol with a large Stokes shift

By introducing phenothiazine framework as an electron donating component, we have developed a unique deep-red functional fluorescent dye 5b, bearing excellent photophysical properties. Using dye 5b as a platform, we further constructed a novel red emitting fluorescent probe (1) for thiophenol on the basis of a unique thiophenol-mediated substitution-cyclization-hydrolysis reaction cascade. Probe 1 exhibits highly selective and sensitive response to thiophenol over aliphatic thiols, with a detection limit of 2.9 nM (S/N = 3). Moreover, this probe features a remarkable large Stokes shift (141 nm) in PB buffer (pH = 7.4, containing 1 mM CTAB). Importantly, it was successfully applied for detection of thiophenol both in real water samples and in living HeLa cells, indicating that this probe has great potential for practical applications.