Novel Fluorescent Probes Based On Heptamethine Cyanine Derivatives:Design And Synthesis And Their Application For CN~- Detection

Cyanide compounds are widely used in industrial activities such as mineral extraction,electroplating,polymer and fiber production.However,cyanide anion(CN~-)is one of the most toxic anions,which can be taken into body through lungs,skin,contaminated food and water.Therefore,it is important to recognize CN~-highly efficient in environmental and biological systems.In this dissertation,three novel near-infrared heptamethine cyanine derivatives were designed and synthesized,and their application in CN– detection were investigated.(1)Fluorescent probes P1 and P2 based on heptamethine cyanine derivatives were synthesized for CN– detection.Probe P1 and P2 were synthesized through the condensation reaction between 2-chloro-1-formyl-3-hydroxymethylene cyclohexene and indolium salts,the structures of P1 and P2 were characterized by 1H NMR,13 C NMR and MALDI-TOF mass spectrum.The CN– sensing performance of the probes was investigated through UV-Vis and fluorescence emission spectroscopy.Upon the addition of CN~-,the absorption peak of P1 at 776 nm and P2 at795 nm decreased gradually and accompanied by the appearance of a new absorption band at short wavelength,respectively.The apparent color change from green to brilliant yellow that could be easily observed by the naked eye.Meanwhile,the fluorescent intensity of P1 at 802 nm and P2 at 817 nm decreased gradually and the common anions did not affect the spectroscopic profiles.There were good linear relationships between the fluorescence intensity of the probes and CN~-concentrations,and the detection limits for P1 and P2 were estimated to be 0.017 μM and 0.2 μM,respectively.The sensing mechanism of the nucleophilic addition was confirmed by 1H NMR,MALDI-TOF mass spectrum and Job’s analysis.In addition,the detection of CN~-in living cells L929 with P2 was successfully realized.(2)Fluorescent probe P3 based on heptamethine cyanine derivative containing a meso-triphenylamine moiety was synthesized for CN– detection.Probe P3 was synthesized between P1 and an electron-donating moiety of triphenylamine through a modified Suzuki Miyaura method,the structure of P3 was characterized by 1H NMR,13 C NMR and MALDI-TOF mass spectrum.The CN– sensing performance of P3 was investigated through UV-Vis and fluorescence emission spectroscopy.Upon the addition of CN~-,the absorption peak of P3 at 750 nm decreased gradually and accompanied by the appearance of a new absorption band at 416 nm,which resulted in apparent color change from emerald to brilliant yellow that can be easily observed by the naked eye.Meanwhile,the fluorescent intensity of P3 at 780 nm decreased gradually and the common anions did not affect the spectroscopic properties.There was good linear relationship between the fluorescence intensity of P3 with CNconcentrations in the range of 0-5 μM in acetonitrile,and the detection limit for P3 was estimated to be 0.014 μM.The nucleophilic addition sensing mechanismwas confirmed by 1H NMR,MALDI-TOF mass spectrum and Job’s analysis.In addition,it was found that the test strips could be more easily to detect CN~-and the detection of CN~-in living cells of L929 with P3 was successfully realized.