Study On Synthesis Of Cyanine Fluorescent Probes And Their Specific Recognition Of Ions And PH

Fluorescent probes have high sensitivity and high selectivity,and are currently one of the simplest and most convenient detection methods,so they have received extensive attention and research from researchers.The cyanine group is a new type of chromophore,which has the ability to bind well to ions.By changing its structure and further modifying the substituents on the indole,it can be combined with different ions.The fluorescence changes to achieve the purpose of specific detection of specific ions.Therefore,designing and synthesizing cyanine derivatives with different structures and exploring their optical properties are of great value to the development of cyanine compounds in the field of fluorescent probes.Therefore,based on the structure of cyanine compounds,this paper designs and synthesizes A series,B series,and C series cyanine fluorescent probes,and conducts a series of optical performance tests on some of the cyanine probes.Firstly,a compound with a hemicyanine structure was designed and synthesized,using phenylhydrazine,p-sulfophenylhydrazine,and naphthol as raw materials to react with2-methylbutanone to synthesize indole derivatives;then,methyl iodide and bromoethanol were introduced.It reacts with indole derivatives to synthesize bromoethanol indole salt,methyl iodide indole salt,benzoindole salt,sulfonic acid indole salt and other compounds 1–7;respectively react with terephthalaldehyde and isobenzene A series of compounds A1–A6were synthesized by the reaction of dialdehyde and so on.In addition,compound 1 is reacted with coumarin salicylaldehyde to synthesize compound A7;compound 1 and compound 7 are reacted to form compound A8.Then,a compound with asymmetric cyanine structure was designed and optically tested.In the first step,the rhodanine monomer is synthesized,and in the second step,it is reacted with the synthesized hemicyanine A1–A5 in the next step to obtain asymmetric cyanine probes B1–B5.In order to explore its optical performance,select B1 and B3 for a series of optical tests.Among them,B1 has a certain response to Hg²⁺,Ag⁺and HSO₃^–in pure ethanol.The probe B1 is sensitive to Ag⁺,and the response time is 19 min,The detection line reaches 1.79×10^–6M.Probe B3 has a specific recognition effect on Hg²⁺in the solvent of H₂O:DMSO=3:7,the fluorescence intensity is increased by 8 times,the detection line reaches 1.54×10^–7 M,and the Stokes shift is 145 nm;In different pH solutions,the colors are clearly divided into three color bands:orange,yellow and colorless,and the maximum absorption wavelength and fluorescence intensity in the ultraviolet absorption spectrum and the fluorescence emission spectrum have also changed significantly.Finally,cyanine compounds of symmetrical structures were designed and synthesized.Their optical properties were tested.Compound 1 and compound 4 synthesized to increase their conjugated structure react with terephthalaldehyde and isophthalaldehyde to generate symmetric cyanines C1–C4.The probes C1 and C3 were selected for optical performance test.The probe C1 can selectively recognize Hg²⁺and HSO₃^–in the solvent of H₂O:CH₃CH₂OH=4:6.Among them,the recognition of mercury ions is sensitive,and the response time is 23 min.Probe C3 can selectively recognize HSO₃^–in the solvent of H₂O:CH₃CH₂OH=6:4,the maximum absorption wavelength in the ultraviolet absorption spectrum blue shifts,and the fluorescence is quenched in the fluorescence spectrum;in addition,it also has a clear response to pH.Within the range of 1.0–14.0,the solution color is clearly divided into three color bands:red,orange,and colorless,and the maximum absorption wavelength in the ultraviolet absorption spectrum and the fluorescence intensity in the fluorescence emission spectrum are also obviously show the corresponding features.