Synthesis And Recognition Performance Of Probes For Metal Cations Based On Coumarin

Heavy metal ion pollution can cause long-term harm to the environment and human health.Therefore,the method of detecting common heavy metal ions quickly,simply and accurately has become a research hotspot.Fluorescence analysis methods have attracted much attention for the detection of heavy metal ions in the environment with good selectivity,strong anti-interference and rapid response.This article was based on the design principle and development trend of coumarin fluorescent probes,five kinds of fluorescent probes capable of detecting heavy metal ions were designed and synthesized,and their recognition performance was studied.The coumarin fluorescent probes A1 and A2 with single and double DPA recognition units were designed and synthesized.Probe A1 with a single DPA recognition unit has poor selectivity to common metal ions.In C₂H₅OH/H₂O?8:2,v/v?,probe A2 with double DPA recognition unit showed a highly efficient and unique recognition effect on Fe³⁺.A2 and Fe³⁺were combined in a ratio of 1:1 by a nonlinear curve fitting of the fluorescence titration.The complexation constant is 4.44×10⁴ M^-11 which indicated the strong affinity of A2 to Fe³⁺,with a detection limit of 2.80×10^-6 M.Three coumarin fluorescent probes B1,B2 and B3 containing mercaptoethanol,hexahydropyridine dithiocarboxylic acid derivatives and 2-thienylmethylthiol units were designed and synthesized.Both probes B1 and B2 have some selectivity for Hg²⁺and exhibit enhanced fluorescence.B1 can specifically recognize Hg²⁺in C₂H₅OH/H₂O?3:7,v/v?solution with a 1:1 ratio.The detection limit is 1.90×10^-6 M and the complexation constant was calculated to be 6.88×10⁴ M^-1.B2 can selectively recognize Ag⁺and Hg²⁺with the fluorescence enhancement and red shift in CH₃CN/H₂O?1:1,v/v?solution.The detection limit of B2 is 4.09×10^-7 M to Hg²⁺and the complexation constant is 1.70×10⁵ M^-1.B3displayed a high selectivity for Fe³⁺over other common cations in CH₃CN/H₂O?3:7,v/v?solution.The probe showed a 1:1 binding stoichiometry to Fe³⁺,and the detection limit and the complexation constant of B3 are 8.30×10^-7 M and 3.03×10⁴ M^-1,respectively.