Synthesis And Properties Characterization Of N-stablization Rhodamine-based Fluorescent Chemosensors

Fluorescent probe which consists of fluorophore in conjunction with suitablerecognition group gives out the easily detectable fluorescent signal when it hasinteraction with the target analytes. Fluorimetry is rapidly performed, isnondestructive, is highly sensitive, is suitable for high-throughput screeningapplications, and can afford real information on the localization and quantity of thetargets of interest. Rhodamines are highly favorable because of their excellentphotophysical properties, such as high extinction coefficients, excellent quantumyields, great photostability, and relatively long emission wavelengths.Based on the “on-off” system of rhodamine spirolactam, eleven novelN-stablization rhodamine-based fluorescent chemosensors were synthesized..Comparing with rhodamine B, N-stablization rhodamine increased in co-planar andrigidity which lead to the enlargement of fluorescence intensity when they were usedto detect metal ions. According to the experiments about the absorption andfluorescent spectra, we found that:(1) Fluorescent probe1can be used for the detection of Fe3+ions in water with abroad pH span (5–8). As expected, it exhibited high selectivity and sensitivity forFe3+over other commonly coexistent metal ions in water. The detection limit wasmeasured to be1.5μM. The significant changes in the fluorescence color could beused for naked-eye detection. Furthermore, fluorescence imaging experiments of Fe3+ions in living MGC803cells demonstrated its value of practical applications inbiological systems.(2) Fluorescent probe7displayed a high selectivity for Fe3+in aqueous solution(CH3OH: H2O=3:2, v/v). The significant changes in the fluorescence color could beused for naked-eye detection. The Job’s plot, IR and1H NMR indicated the formationof1:1complexes between7and Fe3+. The reversibility established the potential of theprobe as chemosensor for Fe3+detection. The probe showed a high selectivity inaqueous solution and could be performed in a range of pH value between5and9. (3) A simple paper test strip system for the rapid monitoring of Fe3+wasdeveloped, indicating its convenient use in environmental samples.(4) Fluorescent probes9-11exhibited good selectivity for Al3+in acetonitrile.