Synthesis, Characterization And Properties Of Lanthanide Luminescent Complexes Containing Phenyl Linked Bi- And Tri-Terpyridine Derivatives Ligands

As a result of their excellent luminescent properties, the rare earth luminescent complexes containing the terpyridine ligand have aroused widelyattention. In order to diversify the species of the lanthanide luminescent complexes and to construct rare earth coordination complexes with unique photophysical properties, two known compounds ofl,3-di([2,2’:6’,2"-terpyridin]-4’-yl)benzene (Li) and 1,4-di([2,2’:6’,2"-terpyridin]-4’-yl)benzene(L2) and tribromide 1,3,5-tris{[4’-(2,2’:6’2"-terpyridine-yl)-1-pyridinium-yl] methylene} benzene(L3) were synthesized. Further,14binuclear and 7 three nuclear new lanthanide luminescent complexes were obtained by reactions of the three ligands (L1, L2, L3) with the rare earth nitrate salts, respectively. All of them were characterized by IR,1HNMR, MS, thermal gravimetric analysis and elemental analysis. The luminescent properties of these complexes were also investigated by UV-vis, fluorescence spectroscopyand phosphorescence spectrum. In addition, a new fournuclear metal compound based onL2 were accidentally obtained by reaction of L2 withTb(NO3)3 and Zn(NO3)2using hydrothermal method, and its crystal structure was determined by single-crystal X-ray diffraction analysis.First of all,14binuclear lanthanide complexes [Ln2(L1)(NO3)6·xH2O] (Ln=Eu 1a, Tb 1b, Sm 1c, Dy 1d, Nd 1e, Yb 1f, Er 1g), [Ln2(L2)(NO3)6·xH2O] (Ln=Eu 2a, Tb 2b, Sm 2c, Dy 2d, Nd 2e, Yb 2f, Er 2g)were obtained by reactions of L1,L2 with Ln(NO3)3·xH2O under the ratio of 1:2. The fluorescence spectroscopies of these complexes reveal that L1 and L2 can sensitize the luminescence of Eu3+,Tb3+,Sm3+ Dy3+ inthe visible regionand Nd3+ and Yb3+ inthe NIR region.Furthermore, the reactions of tridentate L3 with Ln(NO3)3·xH2O at a ratio of 1:3, afforded 7three nuclear complexes[Ln3(L3)(NOs)9·xH2O] (Ln=Eu 3a, Tb 3b, Sm 3c, Dy 3d, Nd 3e, Yb 3f, Er 3g). The fluorescence spectroscopies of the complexes demonstrate that L3 can sensitize the luminescence of Sm3+,Eu3+,Tb3+,Dy3+ inthe visible regionand Nd3+ and Yb3+ inthe NIR region.Finally, The phosphorescence spectrum of Gd2-L1,Gd2-L2,Gd3-L3 complexes provide the theoretical basis on the energy transfer of the ligand L1,L2,L3.The discussion on the luminescent intensity, fluorescent lifetime and quantum yields of the three different series compounds were carried out from the viewpoint of structure characteristics of L1-L3 and their energy transfer efficiency. It is worth mentioning that the compounds Eu2-L2 and Tb3-L3 show long fluorescent lifetime about 1.104 milliseconds and 1.019 milliseconds,and the quantum yields of the compound Eu2-L2 reaches 26.97%, which have potential application value on the photo-luminescent materials.