Synthesis And Metal Ion Recognition Properties Of Coumarin-based Fluorescent Probes

Metal ions exist widely in the natural environment and play an important role in life activities.For example,Cu²⁺and Co²⁺participate in a variety of life activities of the human body,but excessive intake can affect important organs which can cause diseases.Therefore,it is necessary to find a method that can test metal ions quickly and accurately.Compared with other traditional spectral analysis,fluorescent probe has been the most popular method that has low maintenance price,high-sensitivity and so many advantages that those traditional methods do not have.So using this kind of method to detective metal ions has already drawn attention from many researchers from different fields such as analytical chemistry,biochemistry and medicine.Coumarin used as fluorophore in fluorescent probe because of a series of excellent properties such easy modification,good light stability,large Stokes Shift,and high fluorescence quantum yield.In this paper,several coumarin fluorescent probes are designed and synthesized.We used ultraviolet-visible spectrum and fluorescence spectrum to research the recongnition effect between probes and metal ions.The main research contents are divided into the following three parts:In the first part,fluorescent probes L1 and L2 have been designed and synthesized.Both probes L1 and L2 identify of metal ions by fluorescence quenching.The structures of the probes L1 and L2 were determined by ¹H NMR and MS.The recognition performance of probes L1 and L2 for metal ions was studied by UV and FL.Using the coordination ratio measured by Job's plot,it is determined that the coordination ratio of probe L1 to Co²⁺or Ni²⁺is 1:2,and the probe L2 to Cu²⁺or Ni²⁺is 1:1,these probes showed notable fluorescence quenching response.In addition,the detection limit of probe L1 for Co²⁺and Ni²⁺can reach10^-77 M,10^-66 M,and the binding constant reach 10⁶ M^-1,10⁵ M^-1.The detection limit of probe L2 for Cu²⁺,Ni²⁺can be reach 10^-1010 M,10^-99 M,and the binding constant reach 10⁷ M^-1,10⁶M-1.In the second part,fluorescent probes L3 and L4 were designed and synthesized based on 1,3-diaminoguanidine hydrochloride and aminoguanidine hydrochloride.The structures of the probes L3 and L4 were determined by 1H NMR and MS.The recognition performance of the probes L3 and L4 for metal ions was studied by UV and FL.And the coordination ratio of probe L3 to Co2+is 1:2,and the probe L4 to Fe3+is 3:1.It can be effective,sensitive,and specificitive to detect these metal ions.These probes showed notable fluorescence enhancement response.Moreover,the detection limit of probe L3 for Co2+can reach 10-6 M and the binding constant reach 10⁵ M^-1.The detection limit of probe L4 for Fe³⁺can reach 10^-7M and the binding constant reach 106 M-1.In the third part,fluorescent probes L5 and L6 were designed and synthesized based on benzophenone hydrazine and 5-butoxy-m-phenylenedihydrazide.The methods of representation and exploration are the same as above.The coordination ratio of probes L5 to Cu²⁺is 2:1.The coordination ratio of probes L6 to Cu²⁺is 1:1.When probe L5 and L6 detects Cu²⁺,probes L5 showed fluorescence enhancement response,while probe L6 showed fluorescence quenching.The detection limit of probe L5 for Cu²⁺can reach 10^-55 M and the binding constant reach 105 M-1.The detection limit of probe L6 for Cu2+can reach 10-6 M and the binding constant reach 10⁵ M^-1.