The Design,Synthesis And Applications Of ESIPT-based Fluorescent Probes

Fluorescent probes are well known for their advantages of high sensitivity,remarkable specificity,rapid response,convenient manipulation and wide range of detection.Combined with cell imaging technology,fuorescent probes make it possible for us to "see into cells" with a temporal resolution of cell signaling process without invasiveness.Therefore,the design,synthesis and application of fluorescent probes have gained more and more attentions in the field of chemistry,biology,material science and medical science.In this dissertation,we first review the history of organic fluorescent molecules,discuss the physical principles of fluorescence and have a brief browse of classification of fluorephores.Then,we review recent progess in fluorescent probes for fluoride anion and hydrogen peroxide,respectively.Finally,we discuss our attempts to create novel kinds of probes for F-and H2O2 based on ESIPT and PET process.Firstly,we designed and synthesized two fluorescent chemosensors(SiOPI and SiOPIC)based on the principles of ESIPT and the cleavage of Si-O bond.SiOPI exhibits excellent selectivity and sensitivity towards fluoride anion,and quick response as well.It was also remarkable that SiOPI could apparently differentiate fluoride anion from hydroxide anion,which was critical in.the fluoride detection.By tracking the sensing processusing 1H NMR,29Si NMR,and ESI-MS,a stepwise sensing mecha-nism was presented that was in a good accordance with what we observed and concluded from photophysical measurements.The stepwise sensing process included a cleavage of Si-O bond,the formation of t-BuPh2SiF2-,and a subsequent deprotonation in the presence of excess fluoride anions.As soon as the Si-O bond was broken due to the introduction of fluoride anion,a masked ESIPT was activated.A fluorescent turn-shift was observed and could be practically applied in the fluoride detection.Then we developed two fluorescent probes(P1 and P2)for rapid detection of H2O2 in alkaline environment based on the principles of ESIPT and PET.HPNO,the core fluorephore of PI,was.dramatically effected by solvent properties,which was one of ESIPT fluorephore characteristics.The deprotonation of HPNO and B-HBO showed significant shift in the emission.The color change of B-HBO's deprotonation could even be observed by naked eye,implying its potential in pH indicator.In the H2O2 measurement,we found P1 responds to H2O2 under basic conditions with a fluorescence signal shift,while the fluorescence of P2 was turned-off.Both probes offered excellent sensitivity and selectivity towards H2O2.Moreover the apparently accelerated reaction rate might provide a new solution for real-time sensing of H2O2.Comparied with P1,P2 showed a much better sensitivity.What's more,to the best of our knowledge,P2 was the first example of BODIPY derivative applied for H2O2 detection.In conclusion,several fluorescent chemosensers have been designed,synthesized and fully characterized.These fluorescent probes perform special applications in detection for fluoride anion and hydrogen peroxide,and provide new strategies and solutions for chemosensors.