Novel Colorimetric And Fluorescent Schiff-base Probes Based On Julolidine For The Detection Of Ions

Chapter 1: The concept and principles of Schiff-base fluorescence sensor design are introduced.And the latest research progress in recent years on the development of Schiff-base fiuorescence sensors for ion recognition is reviewed.Chapter 2: A reversible fluorescent-colorimetric Schiff-base receptor（L）derived from julolidine and aminourea was developed for the selective sensing of Al³⁺ ions in buffered aqueous medium.Sensor L demonstrated the presence of Al³⁺ ions by both fluorescence enhancement and an instantaneous color change of solution from colorless to yellow.L forms complex with Al³⁺in 1:1 ratio as supported by Job’s plot analysis and mass spectroscopic measurement.The sensitivity of the fluorescent based assay（4.67 n M）for Al³⁺ is far below the WHO acceptable limit（7.41μM）in drinking water.Furthermore,L was employed for imaging the Al³⁺ ion in living biological cells.Chapter 3:A new and simple julolidine based molecular receptor system L linked to 4-phenylsemicarbazide through an imine moiety has been synthesized and characterized.In HEPES-buffered Me OH–H2O（4 : 1,v/v,p H=7.4）solution,L selectively binds Cu²⁺ to form a 1:1 ligand/metal complex,leading to a color change from green to yellow and significant fluorescence quenching at 540 nm.The in situ formed L–Cu²⁺ complex is further utilized to sense cyanide ions with high selectivity and fluorescence enhancement performance via metal displacement assay.The detection limit is 2.28×10-7 M and 1.33×10-8 M for Cu²⁺ and CN-,respectively.The sensor has been successfully applied to detect cyanide in water samples.The fluorescence imaging experiments in living cells were also demonstrated,which concludes that the sensor is capable of sensing Cu²⁺ and CN-in living cells.Chapter 4:An efficient julolidine based probe for the dual sensing of Al³⁺and Cu²⁺ was synthesized.The addition of Al³⁺ to the solution of L in Me OH generates an obvious color change from yellow to orange and a noticeable fluorescence enhancement accompanied with red shift from 540 nm to 570 nm.In addition,this sensor can detect Cu²⁺ in HEPES-buffered Me CN-H2O（1:1,v/v,p H=7.4）solution with obvious fluorescence quenching and colour change from yellow to brown.The binding modes were confirmed by fluorescence,absorption,IR,ESI-MS and 1H NMR titrations.The detection limits were calculated to be 6.38×10-8M and 6.7×10-8M for Al³⁺ and Cu²⁺,respectively.This probe has also been applied successfully for the detection of Cu²⁺ in water samples.