Synthesis And Application Of Novel Europium Complex-based Luminescent Probes For Singlet Oxygen

Time-gated?or time-resolved?luminescence bioassay technique using lanthanide complexes as luminescent probes allows effective elimination of effects of background fluorescence and scattered lights,which enables the technique to be widely useful in bioscience and medical testing.Singlet oxygen?¹O₂?,one of highly reactive molecule in reactive oxygen species,plays important roles in both biological and environmental systems,and also is the key oxidant in photodynamic therapy?PDT?of neoplastic diseases.Therefore,the detection of ¹O₂ in bio-samples in situ is of great significance.In this thesis,a novel luminescent probe for ¹O₂ based on a visible light-excited europium complex,[Eu?pfdap?₃?DPBT?],has been designed and synthesized by conjugating a¹O₂-responsive group,9,10-dimethyl anthracene,with a visible light-excited europium luminophore,for luminescence detection of ¹O₂.Due to the luminescence quenching effect of9,10-dimethyl anthracene moiety to europium luminophore,the luminescence of[Eu?pfdap?₃?DPBT?]is very weak.After reaction with ¹O₂,9,10-dimethyl anthracene moiety is oxidized to its endoperoxide derivative,which enables the long-lived luminescence of the europium complex to be restored.The probe showed advantages of high selectivity,sensitivity,and suitable to be used for detecting ¹O₂ in complicated biological systems.Based on time-gated luminescence imaging technique,the generation of ¹O₂ during photodynamic process of tumor cells was successfully visualized using[Eu?pfdap?₃?DPBT?]as a probe.On the basis of above results,two novel bis??-diketonyl?-substituted anthracene ligands,1,8-H₂dapfp and 1,5-H₂dapfp,as well as their Eu³⁺complexes,[Eu?1,8-dapfp?₂]^-and[Eu2?1,5-dapfp?3?tpy?2],were further designed and synthesized.The intermediates and final products were characterized by mass spectrometry,NMR and elemental analysis.The characterization results of fluorescence properties of two complexes and their reaction products with ¹O₂ revealed that the fluorescence properties of two complexes were unchanged before and after reaction with ¹O₂,indicating that two complexes cannot be used for the detection of ¹O₂.Based on the experimental results,the reason of no-response of two complexes to ¹O₂ was assumed.