Synthesis And Properties Of New Fluorescent Probes Based On Rhodamine

In recent years, due to the heavy metal pollution has attracted more and more attention, using the fluorescent probe to realize the qualitative and quantitative analysis of metal ions has become one of the hottest research fields. The fluorescent probe based on rhodamine is one of the most important classes due to the ring-opening of spirocyclic system has more excellent spectroscopic properties such as large molar extinction coefficient, high fluorescence quantum yield, long excitation and emission wavelengths extending to the visible region. In this paper, by modifying of recognition group, rhodamine B was used as precursor to synthesis a variety of fluorescent probes which can test different metal ions selectively, and we also studied the mechanism of recognition deeply. The details are as follows:(1) Two fluorescent probes L1 and L2 based on rhodamine for detecting Fe3+ were designed and synthesized. Meanwhile, the fluorescent properties of probes were also investigated in DMF-H2O (1/1, V/V). The result showed that L1 and L2 were highly selective recognition of Fe3+ and other metal ions basically didn’t interfere with the probes’recognition. When the concentration of Fe3+ was in the range of 60-120μM and 40-300 μM, there was a good linearity between the fluorescence intensity of probes and the concentration of Fe3+, respectively.(2) Two fluorescent probes L3 and L4 based on rhodamine B for detecting Hg2+ was designed and the fluorescent properties were studied by fluorescence spectroscopy. AS expected, the results showed that L3 and L4 were highly selective recognition of Hg2+ and other metal ions basically didn’t interfere with the probes’recognition in CH3OH-H2O(7/3, V/V,20mM HEPES, pH 7.2). A good linear relationship was shown between the relative fluorescence intensity of probes and the concentration of Hg2+ in the range of 4-80 μM and 0-11 μM. According to the reversibility experiments, the recognition of L4 for Hg2+ is reversible, while the recognition of L3 is irreversible. Therefore, we use the HPLC, MS and X-ray crystallography to discuss this mechanism.(3) Two dual fluorescent probes L5 and L6 based on rhodamine B for detecting Fe3+ and Cu2+ was designed and the fluorescent properties were analyzed by spectroscopic. The results showed that two probes were highly selective and sensitive for Fe3+ in fluorescence spectra and Cu2+ in UV-vis absorption spectra in CH3OH-H2O(1/1, V/V). When the concentration of Fe3+ and Cu2+ were in the micromole level, there was a good linearity between the fluorescence intensity and UV-vis absorption, respectively. We emphasized the mechanism of L5’s recognition, founding this recognition for Fe3+ and Cu2+ is reversible, and the complex-ratio is 1:1.