Synthesis Of Novel Fluorescent Probes Towards Metal Ions And Studies On Their Properties And Applications

The development of industry and technology contributes the increasing environmental contamination issues in recent years.Among them,adverse influences of heavy metal ions on human health are well known.Recent researches have indicated that fluorescent probes exhibit many characters such as efficient and low-cost as well as high selectivity and sensitivity to toxic heavy metals,therefore they could be used to monitor and detect them in situ for both aquatic and biotic lives.In this paper,we synthesized four novel fluorescent probes L,Q,Y and W based on rhodamine,quinaldine and 1,8-naphthalic anhydride.The structures of intermediates and target molecules have been characterized by ¹HNMR,¹³CNMR,IR,MS and elemental analysis.?1?Probe L binds to Cr³⁺with high selectivity and reversibility in EtOH/H₂O?4:1?by UV-vis and fluorescence spectroscopy analysis.The binding stoichiometry between L and Cr³⁺is 1:1,the binding constant K_a is 1.1244×10⁴,the detection limit of L is 6.8077×10^-77 M.The probe L exhibits excellent fluorescence sensing ability to Cr³⁺over a wide range of pH?6¹0?.Cell imaging experiments showed that L is cell-permeable thus it could be applied for studies in live cells.?2?Probe Q has unique selectivity to Al³⁺with“off-on”fluorescent feature,and the interaction between Q and Al³⁺can not be affected by other metal ions.The changing of solution color could be observed by naked eye that before and after Q combining with Al³⁺.The association constant?K_a?is calculated to be 9.9125×10³,the detection limit of L is 2.5733×10^-77 M,which is lower than that of drinking water?0.2 mg/L?.The probe was applied to confocal imaging experiments of MCF-7 cells successfully.?3?The probe Y showed recognition towards Pb²⁺over other metal ions in ethanol,the reversibility and recognition of Y to Pb²⁺have been identified.The binding stoichiometry between Y and Pb²⁺is 1:1,association constant K_a is 1.0431×10⁴,the detection limit is 6.3198×10^-77 M.The probe could be applied to detect Pb²⁺in the range of p H 6.5⁹.0.The cell imaging experiments showed that green fluorescence in HL-7702 cells has been formed by complex between Y and Pb²⁺.?4?Probe W was responds to divalent metal ions based on ICT and PET mechanism,and then accompanied fluorescence quenching.The binding stoichiometry between W and M²⁺is 1:1.The fluorescent sensing behavior was not affected by other metal ions and exhibited good reversibility.