Synthesis And Properties Of The Fluorescent Complexes Of Rare Earth With Aromatic Compounds And Butanedioic Acid

Rare earth elements possess particular electron structure, and have some uncomparable spectroscopic properties, so their complexes can present excellent luminescent, electric and magnetic properties. The application of rare earth material is involved in such fields as biology, agriculture, medicine and military. In order to design and synthesize a series of new fluorescence complexes of rare earth that have excellent luminescent properties, we preceded the following works:1. Brief introduction to the photoluminescent mechanism of the organic complexes of rare earth, and their application are also summarized.2. A series of new red and green fluorescence complexes of rare earth(europium and teribium) with the first ligands of the aromatic compounds(1,10-phenanthroline, benzoic acid, p-methylbenzoic acid, m-chlorobenzoic acid, p-chlorobenzoic acid, p-hydroxylbenzoic acid, methoxybenzoic acid) and the second ligands of butanedioic acid have been synthesized under the best optimisation synthesis conditions.3. The molecular compositions and structures of the title complexes were characterized by means of elemental analysis, EDTA titrimetric method, FT-IR and UV spectroscopies.4. The thermal stability properties of the title complexes were studied by thermal analysis instrument. The results showed that the thermal stability properties of the complexes of rare earth with aromatic compounds and butanedioic acid have relationships with the properties of europium and teribium ions and ligands as well as the molecular structure of the title complexes. The sequence of thermal stability of the title complexes of europium is as follows: Eu₂(MCBA)₃(BDA)_0.5Cl₂·H₂O > Eu(PMBA)(BDA)·H₂O > Eu(PHBA)(BDA)·H₂O > Eu(PHEN)_1.5(BDA)_1.5·H₂O > Eu₂(PCBA)₃(BDA)Cl·H₂O > Eu₂(MBA)₂(BDA)Cl₂·2H₂O > Eu(BA)(BDA)·2H₂O. The sequence of thermal stability of the title complexes of terbium is as follows: Tb(PHEN)_1.5(BDA)_1.5·H₂O > Tb₂(MCBA)₃(BDA)_0.5Cl₂·H₂O > Tb₂(PCBA)₃(B- DA)Cl·H₂O > Tb(PMBA)(BDA)·H₂O > Tb(PHBA)(BDA)·H₂O > Tb(BA)(BDA)·2H₂O > Tb₂(MBA)₂(BDA)Cl₂·2H₂O.5. The luminescent properties of the title complexes were investigated by means of fluorescence instrument. The experimental results showed that the energy levels of the 1,10-phenanthroline and six aromatic carboxylic acids are well fitted to the excitation state energy levels of europium and teribium ions. The cross links of the second ligands of butanedioic acid caused the title complexes to form the chain and net structures, and it is helpful to energy transfer from the first ligands to center ions, and also increased the fluorescence intensity of the title complexes. The ability order of the first ligand transferring light energy to the central europium ion for the title complexes of europium was that of 1,10-phenanthroline > m-chlorobenzoic acid > benzoic acid > methoxybenzoic acid > p-methylbenzoic acid > p-hydroxylbenzoic acid > p-chlorobenzoic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the title complexes of terbium was that of methoxybenzoic acid > 1,10-phenanthroline > p-chlorobenzoic acid > m-chlorobenzoic acid > p-methylbenzoic acid > benzoic acid > p-hydroxylbenzoic acid.