Syntheses And Luminescence Of β-diketones With Aryl And Their Europium Complexes

In this paper, ten new β-diketone ligands containing rigid structure of aromatic ring group were synthesized through the acylation reaction between dibenzofuran or dibenzothiophene and acetyl chloride and then followed by the Claisen keto-ester condensation reaction. The ten β-diketone are as follows : 2-（3-p-chlorophenyl-1, 3-oxopranoyl）-dibenzofuran（HL¹）, 2-（3-p-chlorophenyl-1, 3-oxopranoyl）-dibenzothio phene（HL²）, 2-（3-p-methylphenyl-1,3-oxopranoyl）-dibenzofuran（HL³）, 2-（3-pmethylphenyl-1, 3-oxopranoyl）-dibenzothiophene（HL⁴）, 2-（3-phenyl-1,3-oxopranoyl）-dibenzofuran（HL⁵）, 2-（3-phenyl-1, 3-oxopranoyl）-dibenzothiophene（HL⁶）, 2-[3-（2-quinolyl）-1, 3-oxopranoyl)-dibenzofuran（HL⁷）, 2-[3-（2-quinolyl）-1, 3-oxopranoyl)-dibenzothiophene（HL⁸）, 2-[3-（2-naphthyl）-1, 3-oxopranoyl)- dibenzofuran（HL⁹）,2-[3-（2-naphthyl）-1, 3-oxopranoyl)- dibenzothiophene（HL¹0）. The structures and properties of all the ligands were analyzed and characterized by NMR, MS, IR spectra and UV-visible absorption spectra. The results showed that ketone and enol tautomer structures of all the ligands can coexist in the solid state or in solution, but the enol tautomer predominantes.In this paper, the binary complexes of the as-aboved ligands Ln L₃ⁿ·2H₂O（Ln =Eu, Sm, Tb, Dy, n = 1-10） were synthesized, and the ternary complexes of europium（Ⅲ） were synthesized with 2, 2’- bipyridine（bipy） and 1, 10- phenanthroline（phen）as the second ligands. The composition and structure of all europium（Ⅲ） complexes were speculated through IR spectra, TG-DTA analysis, and UV-visible spectra. The photoluminescence spectra of these complexes showed that all of europium（Ⅲ）complexes can emit characteristics flurescence of Eu³⁺ ion, with the predominant5D0→7F2 transition, namely electric dipole transition, which leads to the red light emission at wavelength of 613 nm. At the same time, we found that the characteristic fluorescence of Sm³⁺(Tb³⁺ or Dy³⁺) ion did not appear in binary complexes of samarium（Ⅲ）（terbium（Ⅲ） or dysprosium（Ⅲ）） ion with the ligands, which suggested that the lowest excited level of Sm（Ⅲ）（Tb（Ⅲ） or Dy（Ⅲ）） ion does not match with triplet energy of the ligands, so the ligands can not effectively transfer the energy they absorb to rare earth ions and make it glow, namely the ligands can not sensitize the rare earth ions.The complexes of Eu（L2）3·phen doped with rare earth ions Sm（Ⅲ）, Tb（Ⅲ）were synthesized. The structures of doped complexes were characterized through IR spectra and TG-DTA analysis. The photoluminescence spectra of these complexes showed that the doping of the rare earth ions did not change the structure of the complexes and only affected the luminescence intensity, and the different rare earth ions had different effection on the luminescence performance of the complexes.Moreover, the matching degree between the lowest excited level of the doped rare earth ions and triplet energy of the ligand played an important role in the luminescence of the rare earth complexes.