Synthesis, Structures And Luminescence Properties Of Rare Earth Polymers With TPTZ And H₂BDC

In this work, seven new metal-organic frame works were prepared through mixing rare earth ions with TPTZ and H2BDC ligands on the solvothermal condition. In addition, four rare earth clusters with TPTZ, TTA and mNBA as ligands also have been synthesized. The study on their structures showed that there have many factors that affect the structures of the metal-organic frame works, such as:the species of central rare earth ion, the ratio of reactants and the solvent. By changing these conditions, we have synthesized11kinds of rare earth crystal complexes. The formulas are as follows:1:{[Eu3(TPTZ)2(BDC)3(NO3)3]·2H2O}n2:{[Eu(TPTZ)(BDC)(NO3)]·2.5H2O}n3:{[Eu(TPTZ)(BDC)1.5]·2.5H2O}n4:{[Eu(DMF)(BDC)1.5(H2O)]}n5:{[Dy(TPTZ)(BDC)1.5]·H2O}n 6:{[Sm(TPTZ)(BDC)(H2O)2]·Cl·H2O}n7:{[Yb(TPTZ)(BDC)1.5]·H2O}n8:[Eu2(TPTZ)2(mNBA)6(H2O)2]·CH3OH9:[Eu(TPTZ)(CF3COO)(H2O)5]·Cl210:[Er(TPTZ)(TTA)Cl2]11:[Yb(TPTZ)Cl(H2O)4]·Cl2Moreover, the fluorescence properties of the crystals have been studied as follows:we have analyzed the fluorescence excitation and emission spectrum of complexes1,2,3,4,5,6,8and9in the visible region, the results showed that:the fluorescence intensity of the europium complexes1-4were all strong, in which the complex{[Eu(TPTZ)(BDC)1.5]·2.5H2O}n (3) was the strongest, and the order is:(3)>(1)>(4)>(2). We found that the emission intensity is related to both the ability of energy transfer of ligands and the crystal structures of the four europium complexes. The emission intensity of polymers5and6were all significantly weaker than that of europium complexes.We have measured the fluorescence decay curve of complexes1,2,3,4,5,6,8and9, and then analyzed their fluorescence lifetime, respectively. Wherein the fluorescence lifetime of europium complexes were the longest, reached to507.4～1020μs; and the fluorescence lifetime of dysprosium complexes was56.4μs; of samarium was98.3μs. For those europium crystal complexes, we found that there are not necessarily link between the fluorescence intensity and fluorescence lifetime. Finally, we tested the fluorescence quantum yield of the six europium complexes. Among the four europium polymers1-4, the fluorescence quantum yield of compound1is45.69%, which also has the longest fluorescence lifetime. The quantum yield of the remaining three europium complexes were31.00%,37.03%and17.41%, respectively, that is (1)>(3)>(2)>(4), which is consistent with the sequence of their lifetimes but not consistent with the order of their fluorescence intensity, all those showed that there is no necessary link between the fluorescence intensity and the fluorescence quantum yield. As for the two crystal europium clusters8and9, the quantum yield were26.96%and19.03%, respectively, which also related to their crystal structures.