The Synthesis, Characterization And Luminescence Mechanism Of A Yellow-Emitting Terbium Complex

This paper deals with terbium complexes.Two terbium complexes, Tb(BAC)₃Phen(BAC:Benzoylacetone;Phen:1,10- phenanthroline),and Tb(AcAc)₃Phen(AcAc:Acetylacetone)were synthesized,with the emphasis on Tb(BAC)₃Phen for its detailed characterization and luminescence mechanism.First of all,through screening experiments,optimum synthesis technique was found:reaction temperature 78℃,reaction time 2 hours, pH between 7.0 and 7.5.The complex's structure was confirmed as Tb(BAC)₃Phen through elemental analysis and infrared absorption analysis.UV-vis absorption analysis indicated that the major absorption was from the ligand's absorption,and the optical gap of the complex was 3.48eV.According to the results of the cyclic voltammetry and UV-vis absorption spectra,the LUMO and HOMO energy levels of the complex were calculated as -2.05eV and -5.53eV,respectively.The analysis of excitation and emission spectra and photoluminescence spectra showed that the best excitation wavelength of the complex was 381nm,the color purity was 0.8988,the full width at half-maximum was 10.5nm,and the CIE coordinates were X=0.4898,Y=0.4679.The maximum lightemitting wavelength were 615nm,meaning that the complex is a yellow-white emitting material,different from ordinary terbium complex. Meanwhile,TG and film property measurement results showed that the complex has a good thermal stability and a good film property.Besides, the device of the complex also showed a good diode's property.All of these results showed that the complex could be used as a good rare earth electroluminescent material.Secondly,under the same reaction environment,another terbium complex was synthesized.Through elemental analysis and infrared absorption analysis,its molecular formula was obtained as Tb(AcAc)₃Phen. Similarly,from the results of the cyclic voltammetry,the LUMO and HOMO energy level of the complex were calculated as -3.01eV and -5.58eV,respectively.The analysis of excitation and emission spectra and photoluminescence spectra showed that the best excitation wavelength of the complex was 335nm,the color purity was 0.8739,the full width at half-maximum was 10.9nm,and the CIE coordinates were X=0.3585,Y =0.5917.The maximum light-emitting wavelength was 550nm.It can be concluded that the complex is a green emitting material with a good thermal stability. At last,the luminescence mechanism of Tb(BAC)₃Phen was discussed briefly,and the intermolecular energy transfer mode was suggested.It can be concluded that the ligand Phen transferr the energy from BAC and the energy absorbed itself to the terbium ions,followed by light-emitting from terbium ions.The theory that ligand disturbs rare earth ions in emitting was proposed to explain Tb(BAC)₃Phen's emitting.