Preparation And Fluorescence Emission Characteristics Of Bidentate Schiff Base Type Polymer-rare Earth Complexes

Bonding type polymer-rare earth complexes luminescence material not only hasexcellent photoluminescence, but also has easy processing characteristics of polymersand good mechanical properties, which is a high performance luminescence material. Inphotoluminescence, electroluminescence, optical communications, lasers, solar energyconversion system and other fields, the light-emitting materials have potential and veryimportant application prospect. In this paper, bidentate Schiff base ligand whichconcurrently has dual function of sensibilization and coordination was bonded to the sidechains of polysulfone (PSF) via a polymer nucleophilic substitution reaction (oraldehyde reaction) and a Schiff base reaction,then coordinate with rare earth ions, twokinds of Schiff base (SB) type polymer-rare earth complexes luminescence materialswere prepared successfully. And their fluorescence emission properties andluminescence mechanism were deeply investigated. The research for the development ofhigh performance bonding type polymer-rare earth complexes luminescence materialshas significant scientific significance and potential application prospects.In this study, firstly，based on1,4-dichloro methoxy butane which was used aschloromethylation reagent, chloromethylation polysulfone (CMPSF) throughFriedel-Crafts alkylation reaction was gotten. Then use CMPSF as the starting material,p-hydroxy benzaldehyde (HBA) as nucleophilic reagent, the functionalization ofchloromethylation polysulfone (CMPSF) through the nucleophilic substitution reactionwhich brought about bonding p-hydroxy benzaldehyde (HBA) ligands modifiedpolysulfone PSF-BA was improved. Next, the schiff base reaction was begun betweenthe PSF-BA and3-aminopyridine (AP), the side chain bonding benzaldehyde/aminopyridine type bidentate schiff base (SB) ligands functionalization ofpolysulfone (PSF-SB) was prepared. The chemical structure of PSF-SB wascharacterized by FT-IR spectrum and1H-NMR spectrum. The effects of main factors onthe nucleophilic substitution reaction were examined, and the reaction conditions wereoptimized. The experimental results show that the rate of the nucleophilic substitutionreaction is independent of the concentration of the nucleophilic HBA, indicating that thisis a typical unimolecular nucleophilic substitution reaction i.e. SN1. The optimal reactionconditions are as follows: N, N-dimethylacetylamide (DMAC) as solvent, temperature of90℃, time of10h. In these conditions, the BA bonding quantity of modifiedpolysulfone is1.67mmol/g. With DMF as solvent, temperature of60℃, the schiff basereaction was begun between the PSF-BA and3-aminopyridine (AP) for4h. Then thefunctionalized polysulfone PSF-SB was prepared, and the SB bonding quantity is1.54mmol/g.By using Kornblum oxidation method, the chloromethyl groups ofchloromethylation polysulfone (CMPSF) was oxidized with dimethyl sulfoxide (DMSO)as oxidant, and transformed to aldehyde (AL) groups, resulting in modified polysulfonePSF-AL. Next, the schiff base reaction was begun between the PSF-AL and3-aminopyridine (AP), another kind of bidentate schiff base ligands functionalization ofpolysulfone i.e. the main chain modified aldehyde/aminopyridine type bidentate schiffbase ligands functionalization of polysulfone PSF-MSB was prepared successfully. Thechemical structure of the second kind of functional polysulfone PSF-MSB was alsocharacterized by FT-IR spectrum and1H-NMR spectrum. The effects of main factorssuch as reaction temperature, the amount of catalyst and acid-binding agent NaHCO3onthe modification reaction were investigated emphatically. This reaction needs to beadded KI and NaHCO3to promote, under the temperature of80℃for10h, thenmodified polysulfone PSF-AL was obtained whose bonding quantity is1.58mmol/g. Theschiff base reaction between PSF-AL and3-aminopyridine (AP) under the conditions ofDMF as solvent, temperature of60℃for5h, then bidentate schiff base ligands functionalization of polysulfone PSF-MSB was prepared, and bonding quantity of MSBis1.42mmol/g.Next, the coordination reactions between PSF-SB and Eu3+and Tb+3ion wereallowed to carry out, preparing the binary polymer-rare earth complexsPSF-(SB)3-Eu(Ⅲ) and PSF-(SB)3-Tb(III). The ternary complexesPSF-(SB)3-Eu(Ⅲ)-(Phen)1was also prepared by using small molecular1,10-phenanthroline (Phen) as the second ligand. The chemical structures of thecomplexes were characterized by Fourier Transform Infrared spectroscopy (FTIR) andUV absorption spectra. In this work, the fluorescence emission properties of the solutionand the film for the complexes were mainly investigated, and especially, theirflorescence emission properties and luminous mechanism were investigated in depth.The experimental results show that the macromolecular ligand PSF-SB can effectivelysensitize the fluorescence emission of Eu(Ⅲ) ion, suggesting that it produces significantAntenna effect. Due to the conjugated big π system of SB, functional polysulfonePSF-SB itself can produce strong fluorescence, but after forming the binary complexPSF-(SB)3-Eu(Ⅲ), its fluorescence emission is weaken greatly. But the SB ligandbonded on the side chains of PSF-SB has no sensibilization for the fluorescenceemission of Tb(Ⅲ) ion, in contrast, a energy back transfer from the excited state5D3ofTb(Ⅲ) ion to the triplet state T1of the SB ligand will occur. The fluorescence emissionintensity of the ternary complex PSF-(SB)3-Eu(Ⅲ)-(Phen)1is stronger than that of thebinary complex PSF-(SB)3-Eu(Ⅲ). The thin films of the binary complex and ternarycomplex were also prepared, which can emit strong characteristic fluorescence of Eu(Ⅲ)ion. And the fluorescence emission intensity of ternary complex film is better than thatof binary complex, and the thermal stability is better, too.Finally, using the similar study method, the coordination reactions between PSF-SBand rare earth ions were allowed to carry out, preparing the binary polymer-rare earthcomplexs PSF-(MSB)3-Eu(Ⅲ) and PSF-(MSB)3-Tb(III). The ternary complexPSF-(MSB)3-Eu(Ⅲ)-(Phen)1was also prepared by using small molecular 1,10-phenanthroline (Phen) as the second ligand. The fluorescence emission propertiesof the complexes were studied. The experimental results show that the macromolecularligand PSF-MSB also can effectively sensitize the fluorescence emission of Eu(Ⅲ) ion,but it has no sensibilization for the fluorescence emission of Tb(Ⅲ) ion. Thefluorescence emission intensity of the solution and film of PSF-(MSB)3-Eu(Ⅲ)-(Phen)1are stronger than that of the binary complex PSF-(MSB)3-Eu(Ⅲ), and the thermalstability is better, too.