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. (C) 2017 Elsevier B.V. All rights reserved.