Syntheses And Luminescence Of Heterofluorene Bridged Bis(β-diketones) And Their Europium Complexes

In this paper, a series of novel bis（β-diketone） ligands were synthesized through Friedle-Crafts acylation reaction and Claisen condensation reaction with dibenzothiophene anddibenzofuran as the raw materials. Eight bis（β-diketones） are as follows:2,6-bis（1,3-dioxo-butyl）-dibenzothiophene（L¹ï¼‰,2,8-bis（1,3-dioxobutyl）-dibenzothiophene（L²ï¼‰,2,8-bis（1,3-dio-xobutyl）-dibenzofuran（L³ï¼‰,2,8-bis（3-phenyl-1,3-oxopranoyl）-dibenzothiophene（L⁴）,2,8-bis（3-phenyl-1,3-oxopranoyl）-dibenzofuran（L⁵）,2,6-bis（1,3-dioxopentyl）-dibenzothiophene（L⁶）,2,8-bis（1,3-dioxopentyl）-dibenzothiophene（L⁷）,2,8-bis（1,3-dioxopentyl）-dibenzofuran（L⁸）. With IR spectra, UV-vis spectra,1H NMR/13C NMR and HRMS, all of these ligandswere characterized and determined. The IR and1H NMR spectra indicated that all compoundsshowed their prevailing enol isomers in solid state and in CDCl3solvent.With L1-L8as ligands, we synthesized eight binary complexes of europium, and eightternary complexes with1,10-phenanthroline as the synergic ligand. All complexes werecharacterized through IR spectra, UV-vis spectra, TG-DTA analysis, elementary analysis andfluorescence spectra. The photoluminescence spectra of these complexes showed the strongcharacteristic Eu³⁺ion emission peaking at611nm, which indicated that ligands L1-L8caneffectively sensitize Eu³⁺ions to enhance5D0→7F2transition. The fluorescence intensities ofthe ternary complexes are remarkably stronger than those of the binary complexes. At thesame time, complexes of Tb³⁺ion and Sm³⁺ion with the ligands were also synthesized, andno characteristic emission due to these two ions was observed, which indicated that the ionscan not be sensitized by the ligands in the complexes.In order to study the ’’columinescence effect’’ in complexes, we selected ligand L1tosynthesize the binary and ternary europium complexes doped with nonluminescent rare earthions (La³⁺, Gd³⁺, Y³⁺). The complexes showed the thermal stablities and IR spectra similar tothose of corresponding undoped europium complexes. There is no linear relationship betweenthe fluorescence intensity and the amount of the nonluminescent rare earth ions, but at asuitable ratio of Eu to La （Gd, Y）, we found the fluorescence enhancement effect resulted bythe addition of nonluminescent rare earth ios.