Iminocoumarin based fluorophores: Indispensable scaffolds for rapid, selective and sensitive detection of thiophenol

摘要

Off-on fluorescence probes for the detection of thiophenol were designed based on the reaction mechanism to ensure rapid sensing process. 2,4-DinitrophenylsuIfonyl based probes with iminocoumarin fluorophores were validated by theoretical calculations for their off-fluorescence states. Reaction of these probes with thiophenol released strong fluorescent iminocoumarin species with good response times. These results, upon comparing with reported probes, confirmed that higher pK_(aH) values of the imino nitrogen of iminocoumarins are important for rapid sensing process. Reactivity of these probes was limited to only thiophenol and no reaction was observed with aliphatic thiols. The benzothiazole substituted probe displayed up to 260-fold fluorescence enhancement upon reaction with thiophenol. Sensing of the analyte by the probe was characterized by change in color from red to yellow and with appearance of the green fluorescence. A detection limit up to 6.9 x 10~(-9) M was also determined for this probe.