Synthesis Of Novel Schiff-base Optical Chemosenors For Anions

Chapter 1: The concept and design principles of fluorescence sensor for anions are introduced.Chapter 2: A new and simple receptor HL derived from quinoline-2-carbaldehyde and 2,4-dinitrophenylhydrazine was synthesized and explored as a colorimetric sensor for cyanide ion in DMSO/H2O(7:3,v/v)medium.Addition of cyanide ion to HL resulted in a color change from yellow to wine red with a significant bathochromic shift(~125 nm)in the absorption maxima,which makes naked eye detection possible.The experimental results reveal that the formation of anionic species from deprotonation of the hydrazone N=H moiety by CN-is responsible for the spectral changes.The sensor exhibits high selectivity and sensitivity for CN-ion and the detection limit were found to be 0.37 × 10-6M.Moreover,the HL–CN-complex was reversibly bound and HL could be recovered by treatment with Ag+ or Cu2+and reused without loss of sensing ability.Finally,the use of a test strip of probe HL to detect cyanide was reported.Chapter 3: A new fluorescent probe 4’-hydroxy-3’-((8-quinolineimino)methyl)-4-biphenylcarbonitrile(L)has been synthesized for the sequential detection of Zn2+ and PPi in aqueous ethanolic(3/2,v/v)HEPES buffer(p H7.1).Addition of Zn2+ to the solution of L resulted in a red shift(Δλ = 18 nm)with a pronounced enhancement in the fluorescence intensity,while there was no enhancement in presence of other metal ions.The subsequent addition of PPi anion can switch off the fluorescence signal by bringing the Zn2+ ion out of the coordination cavity of the chemosensor L.No interference was observed from other anions,making the L–Zn2+ ensemble a highly sensitive and selective PPi probe.The detection limit is 5.31×10-8M and 9.41×10-8M for Zn2+ and PPi,respectively.The sensing process is reversible and the probe may be recycled for further use.Cell imaging studies demonstrate that this sensor is capable of sensing Zn2+ and PPi in living cells.Chapter 4: A new colorimetric and flurescence chemosensor L based on1-naphthylamine and 4-trifluoromethylbenzaldehyde was prepared and its sensing behavior toward various anions was explored.L exhibited selective fluorescent response toward HSO4-with fluorescence intensity enhancement in CH3CN-H2O(3:2,v/v)solution.In addition,L shows a highly selective colorimetric response to HSO4-ions by changing its color from yellow to colorless immediately.The sensor displayed high sensitivity to hydrogen sulfate and the detection limit was calculated to be 1.44×10-7M.The sensing mechanism has been suggested to proceed via a hydrolysis process of the Schiff base group.The hydrolysis product has been isolated and further identified by 1H NMR and MS.Moreover,the probe could be used as a practical,visible colorimetric test kit for HSO4-.