Synthesis,Structures And Luminescence Sensing Properties Of Europium(?) And Terbium(?) Metal-organic Coordination Polymers

Metal-organic coordination polymers?CPs?are self-assembled from bridging organic ligands and metal ions or clusters through coordinate bonds or supramolecular interactions.Luminescent CPs have attracted much attention because of their potential applications in fluorescent materials,electroluminescent devices and chemical sensors.Compared with transition-metal coordination polymers,luminescent lanthanide-metal coordination polymers?Ln-CPs?possess a lot of interesting characteristics,such as high color purity,narrow emission peaks and relatively long luminescence lifetimes.However,selective and sensitive detection of trace amounts of metal ions and nitroaromatic compounds in the presence of other interfering analogues based on Ln-CPs is still a challenge due to their strong electron affinities and absorption capacities which lead to false responses and poor selectivity for analytes.Adding to this,visualizing luminescent Ln-CPs for sensing purpose is still at infant stage.In this dissertation,a series of one-dimentional?ID?,two-dimentional?2D?and three-dimentional?3D?Eu?III?and Tb?III?-based CPs were synthesized and used as sensors for selectively detecting different metal ions and nitroaromatic compounds.The single crystal structures and photoluminescence properties of these compounds were characterized.The sensing mechanism towards metal ions and nitroaromatic compounds was also explored.Furthermore,luminescent test papers made from Eu?III?-/Tb?III?-CPs can be as excellent sensory materials for practical application.The main points and topics in this dissertation are summarized as follows:?1?Red luminescent sensors based on anionic Eu?III?-CPs for sensitively and selectively detecting 4-nitrophenol?4-NP?and Fe3+ ions.Two kinds of Eu?III?-based coordination polymers have been synthesized under hydrothermal/solvothermal condition by treating Eu?III?ions with 1,2,4,5-benzenetetracarboxylic acid?H2BTEC?and biphenyl-4,4'-dicarboxylate?H2BPDC?in the aqueous solution and mixed H2O-DMF,respectively.[Eu?H2O?5?BTEC?2][H?C5H6N2?]·3H2O?1?possesses an anionic zig-zag chain constructed from the BTEC ligands and[EuO4?H2O?5]nodes,while[Eu?BPDC?2]?CH3?2NH2?2?bears a 3D anion framework with protonated[(CH3]2?NH2?]+ molecules as guest.The luminescent properties of both compound 1 and 2 in solid and suspension state were investigated,and they exhibit the characteristic sharp emission bands of Eu3+ at 593-691 nm.The strong emission of compound 1 and 2 could be quenched significantly by trace amounts of Fe3+ ion or 4-NP even in the presence of other competing interference analytes.In contrast,other metal ions and aromatic compounds do not cause emission quenching.The possible fluorescence quenching mechanism was also discussed.?2?Green luminescent sensors based on Tb?III?-CPs for selectively detecting 4-NP and Fe3+ ions.Two Tb???-based coordination polymers Tb?BTEC?0.5?HCOO??H2O?2?3?and[Tb?H2O?5?BTEC?]·[H?C5H6N2?]·3H2O?4?have been synthesized by using benzene-1,2,4,5-tetracarboxylate?BTEC?as bridging ligand and 4-aminopyridine as auxiliary ligand under hydrothermal condition.Compound 3 possesses dimeric[Tb2?BTEC?4?HCOO?2?H2O?4]building blocks which are linked by BTEC linkers to generate a two-dimentional honeycomb layer.Compound 4 possesses one-dimensional zig-zag chains decorated with carboxylate functional sites and contains protonated 4-aminopyridine guests in its interlayer channel.Luminescent measurements indicated that both compound 3 and 4 exhibit four sharp emission bands at 489-620 nm,which are assigned to characteristic 5D4?7Fj?J = 6,5,4,3?transitions of the Tb3+ ions,respectively.The green emissions of both compound 3 and 4 have been used for qualitative and quantitative identification of 4-NP and Fe3+ through luminescence quenching mechanism without affected by other competing analogs.The possible detection mechanisms have been analyzed by UV-Vis absorption spectra,powder X-ray diffraction?PXRD?and emission lifetime measurements.?3?Green dual-channel luminescence sensor for UO₂²⁺ ion based on an anionic Tb???-based CP.A 3-D Tb???-based coordriantion framework,[Tb?BPDC?2]·?CH3?2NH2?5?was synthesized by solvothermal reaction of biphenyl-4,4'-dicarboxylic acid?H2BPDC?with Tb?NO3?3·6H2O in the mixture H2O-DMF.It is the first efficient dual-channel luminescence sensor for aqueous UO₂²⁺ ion.Compound 5 possesses an anionic three-dimensional framework and protonated dimethylamine molecules embedded within the channels.Intense green emission of compound 5 could be highly selectively and sensitively quenched by UO₂²⁺ions even in the coexistence of other competing metal ions.The possible sensing mechanism was proposed as well based on both suppression of luminescence resonance energy transfer and enhancement of intermolecular electronic transfer.?4?Visual red and green luminescence test papers based on compounds 1 and 3-5 for practical detection application.The red luminescence paper based on compound 1 and green luminescence papers based on compound 3 and 4 were utilized to selectively sense Fe3+ion and 4-NP among analogues.For sensing 4-NP,after seven cycles soaking-washing,the test paper can still return to the strong red emission with a little reduction from the original fluorescence intensity.However,no restoring emission was observed for sensing Fe3+ ion suggesting that formation of Fe3+@1,Fe3+@3,Fe3+@4 composites in test paper occurred.In addition to this,the green test paper prepared based on compound 5 was used to selectively discriminate UO₂²⁺ ion among various metal ions.