Synthesis And Application Of Novel Fluorescence Probe For Cyanide Anion

Among anions cyanide is one of the most lethal poisons known.It can be absorbed through the lungs,gastrointestinal tract,and skin,leading to vomiting,convulsions,loss of consciousness,and eventual death.Nevertheless,cyanide is widely used in electroplating,gold mining,mineral extraction,polymer production and other industrial activities.For fluorescent cyanide sensing,methods have been developed based on versatile mechanisms,including specific chemical reaction,hydrogen-bonding interaction,metal complex ensemble displacement,excited-state intramolecular proton transfer and supramolecular self-assembly.However,many of the reported CN sensors suffer from several limitations such as long responding time,poor application in the"naked-eye" detecting,severely interference from F-and AcO-,working only in organic media.Thus,undoubtedly development of an effective and selective cyanide-sensing system in aqueous environment is highly desirable.In this regard,two novel optical chemosensors based on the nucleophilic addition of cyanide ions were designed and synthesized.Significantly colorimetric and fluorescent responses of the probe toward cyanide were realized in aqueous medium with high selectivity.The main contents and results are outlined as follows:1.A new coumarin based chromo-fluorogenic probe 7-（diethyl-amino）-3-[（E）-2-（4-nitrophenyl）-ethenyl]-2H-1-benzopyran-2-one（2d）based on intramolecular charge transfer（ICT）was designed and synthesized.The sensing property and mechanism of probe 2d for CN^-were studied through UV-vis and fluorescence spectroscopy.Probe 2d shows highly sensitive and selective for detection of CN^-in HEPES buffer（CH3CN:H2O=1:1,v/v,pH=7.4）.The cyanide addition on the electron-deficient alkene bridge interrupts theπ-conjugation in probe 2d,which obstructs the ICT process and results in a color change from yellow to colorless and a significant fluorescence enhancement at 410 nm.Job’s plot analysis revealed a 1:1 stoichiometry for the interaction between the probe 2d and cyanide anion with detection limit of 0.14μM.The probe was also used for fabrication of test strips that could be used in practical.2.A new carbazole derivative 2-[（1E）-2-[6-（benzothiazolyl）-9-ethyl-9H-（carbazol-3-yl）]-ethenyl]-3-methyl-benzothiazolium iodide（3d）based on intramolecular charge transfer（ICT）was synthesized and its anion sensing property was studied.Probe 3d acts as an efficient colorimetric and ratiometric fluorescent probe for detection of cyanide ions in HEPES buffer（DMSO:H₂O=1:9,v/v,pH=7.4）.The cyanide addition to the benzothiazolium group induces an obstruction in an intramolecular charge transfer（ICT）and produces a dramatic hypsochromic shift in the absorption（152 nm）and emission（165 nm）profiles of probe 3d.The change in color of the solution was prominent and could be easily seen by the naked eye.Probe 3d forms a 1:1 adduct with CN^-with detection limit of 0.09μM.The probe 3d was successfully applied for the detection of CN^-in live cells.