Synthesis and fluorescence properties of ten lanthanide benzene-1,3,5-tricarboxylate complexes.

Ten new lanthanide benzene-1,3,5-tricarboxylate complexes Tb(btc).6H(2)O (1), nano-scale Tb(btc).6H(2)O (2), Tb(2)(btc)(2)(phen)(3).4H(2)O (3), TbLn(Hbtc)(2)(phen)(2) Cl(2).H(2)O [Ln=Y(4), and Gd (5), btc=benzene-1,3,5-tricarboxy-late], TbLa(btc)(2)(phen)(3).6H(2)O (6) and TbM(btc)(C(2)H(5)OH)(2)Cl(2).2H(2)O [M=Zn (7), Cd (8), Mn (9) and Ni (10)] have been synthesized and characterized. The fluorescence intensity of nano-scale complex (2) is stronger than that of the complex (1), indicating that there are new and special fluorescence properties in nano-scale complex due to the nano-scale effect and quenching by the proximity of surface defects. The fluorescence intensity of the ternary complex (3) is stronger than that of the binary complex (1). The studies of the fluorescence spectra and lifetimes of the other seven complexes show obviously different results. The luminescent intensity of the complexes (4), (5), (6), (7) and (8), which contain the metal ions Y(3+), La(3+),Gd(3+), Zn(2+) and Cd(2+), increased remarkably. Complexes (9) and (10), containing Mn(2+) and Ni(2+), respectively, exhibit fluorescence quenching, which is caused by the unsaturated d-layer electrons consuming the energy in the form of radiative transition.

Fluorescent property of the Gd3+-doped terbium complexes and crystal structure of [Tb(TPTZ)(H2O)6]Cl3.3H2O.

The complex of Tb(TPTZ)Cl(3).3H(2)O was synthesized by adding the ethyl alcohol solution of TbCl(3) (1 mmol) to the solution of 2,4,6-tris-(2-pyridyl)-s-triazine(TPTZ, 1 mmol) with constant stirring. The solution which had been filtered was kept at the room temperature for 4 weeks, and then a kind of transparent crystal was formed. Besides, nine kinds of solid complexes in the different molar proportion of terbium to gadolinium had been synthesized by adopting the similar method mentioned above. It was inferred from the elemental analysis and rare earth complexometry that the composition of these complexes is (Tb(x)Gd(y))(TPTZ)Cl(3).3H(2)O (x : y = 0.9 : 0.1, 0.8 : 0.2, 0.7 : 0.3, 0.6 : 0.4, 0.5 : 0.5, 0.4 : 0.6, 0.3 : 0.7, 0.2 : 0.8, 0.1 : 0.9). The absorption spectra and photoluminescence of the complexes were determined in dimethylsulfoxide (DMF), which showed that the excitation of the complexes is mostly ligand based. The triplet state energy level of TPTZ was measured, indicating that the lowest excitation state energy level of Tb(III) and the triplet state energy level of TPTZ match well each other. The fluorescent data indicated that the fluorescent emission intensity of Tb(3+) ions would be enhanced in the complexes after terbium was doped with Gd(3+) ion. When x : y was 0.5 : 0.5, the fluorescent emission intensity was the largest. The result obtained by testing the X-ray diffraction of the monocrystal revealed that the molecular formula of the mono-crystal complex is [Tb(TPTZ)(H(2)O)(6)]Cl(3).3H(2)O. The number of metal ion coordinates is nine, and the tridentate TPTZ and six water molecules are bonded with terbium respectively. Besides, it also revealed that the monocrystal belongs to the monoclinic system, and space group Cc with the following unit cell parameters is a = 1.4785 (3) nm, b = 1.0547 (2) nm, c = 1.7385 (4) nm, beta = 94.42 (3) degrees, V = 2.7028 (9) nm(3) and Z = 4.