Synthesis And Ion Recognition Of Fluorescence Probes Based On Nitrogen-Containing Heterocyclic Compounds

Molecular recognition,as an important research areain supramolecular chemistry,plays vital roles in chemical,environmental and life sciences.Some nitrogen-containing heterocyclic compounds including imidazopyridine,benzimidazole and 8-aminoquinoline have been widely used in molecular recognition due to their good fluorescence properties.In this thesis,five fluorescent probes based on these nitrogen-containing heterocyclic compounds have been designed and synthesized.The spectral properties and ion recognition behaviors were investigated,and the results are as follows:1.A new probe L1 based on imidazopyridine structure has been designed and synthesized.It shows fluorescence responses to Zn2+ in acetonitrile/Tris 1:1?v/v??9:1,v/v,Tris-Hcl 10 mM,pH = 7.4?,the emission variations terminated when 15 equiv of Zn2+ was used,L1 and Zn2+forms a complex through 1:1 binding stoichiometry,and the detection limit is 2.7 ?M.So L1 exhibits excellent selectivity to Zn2+ with fluorescence response to Zn2+.2.A new benzimidazole-based fluorescent probe L2 has been designed and synthesized.It exhibits fluorescence responses to Hcy and Cys in HEPES/ethanol?9:1,v/v,pH = 7.4?solution.The emission variations terminated when 100 Hcy/Cys was added,L2 exhibits excellent selectivity to Hcy.The detection limit of L2 for Hcy and Cys are 9.0×10-6 M and 9.1×10-6 M,respectively.The probe can be used within pH 6-8.The density functional theory calculation results show that the L2-Cys adduct displays ESIPT process,adduct of L2-Hys does not have ESIPT property.So L2 exhibits excellent selectivity to Hcy and Cys through regulating ESIPT.3.Two new probes L3 and L4 based on 8-aminoquinoline derivatives have been designed and synthesized.The probes show fluorescence responses to Zn2+ in DMSO/HEPES?1:1,v/v,pH =7.4?.The emission variations terminated when 15 equiv of Zn2+ was added,both L3 and L4 can bind Zn2+through a 1:1 binding stoichiometry,thethe detection limits of the probes for Zn2+are9.7×10-5 M and 1.6×10-5 M,respectively.Thus L3 and L4 exhibit excellent selectivity to Zn2+with fluorescence response to Zn2+.4.A new benzimidazole-based probe L5 has been designed and synthesized,which shows fluorescence responses to Zn2+ in HEPES?pH = 7.4?,The emission variations terminated when10 equivalent of Ag⁺ is added,L5 and Ag⁺ interacts with a 1:1 binding stoichiometry,and the detection limit is 5.0 ?M.So L5 exhibits excellent selectivity to Ag⁺.