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2,3-bis(2-pyridyl)-5,6-dihydropyrazine and a protonated phenanthroline (Phen) have been synthesized and the structure of protonated Phen is established by X-ray diffraction single crystal structure analysis. The coordination reactions of Phen, 2,2'- bipyridine and 2,3-bis(2-pyridyl)-5,6-dihydropyrazine with rare earth ions in low pH have been studied. The results show that 2,3-bis(2-pyridyl)-5,6-dihydropyrazine is hydrolyzed to be 2,2’-pyridil and protonated ethylenediamine. Meanwhile, Phen combines with proton, which results that nitrogen atoms can not coordinate with rare earth ions. The molecular formula of protonated Phen is C12H8N2HCl·H2O. It crystallizes in the triclinic space group P -1 (2), with a = 7.1212(14) Å, b = 7.2786(15) Å, c = 20.817(4) Å, α = 90.00º, β = 96.69(3) º, γ = 90.00 º, V = 1071.65(379) Å3, Z = 4.

A series of novel ternary rare earth complexes showing attractive luminescence properties were prepared with both neutral and anion ligands. Three azatriphenylene neutral ligands, 1,10-phenanthroline (phen), dipyrido [3,2-a: 2′,3′-c] quinoxaline (dpq) and dipyrido [3,2-a: 2′,3′-c] phenazine (dppz) were investigated systematically as sensitizers in the ternary rare earth complexes. Benzoate ions (BA − ) and phenoxyacetate ions (POA − ) were chosen as anion ligands. The compositions of these complexes were characterized by elemental analysis, rare earth coordination titration, molar conductivity measurement, IR spectroscopy, UV–vis absorption spectroscopy, 1 H NMR spectroscopy and TGA–DTA. The luminescence spectra, luminescence decay time and quantum efficiency of the complexes were also studied. The very strong luminescence intensities and rather long luminescence lifetimes (typically > 1.0 ms) were achieved for both Eu 3+ and Tb 3+ ternary complexes with phen and dpq as neutral ligands. Moreover, high quantum efficiencies (40–60%) were also obtained for Eu 3+ ternary complexes with phen and dpq as neutral ligands.

Two terbium complexes were synthesized, with dibenzoylmethane (HDBM) as the first ligand and 1,10-phenanthroline (phen), dipyrido[3,2-a:2',3'-c] quinoxaline as the second ligand. The studies of elemental analysis, rare earth complexometric titration, molar conduction, IR spectra, UV spectra, fluorescence excitation and emission spectra indicate that the complexes have the compositions of Tb (DBM)3 phen and Tb (DBM)3dpq. The results show that the rare earth ion (Tb3+) was bonded with the carbonyl oxygen atom of DBM and nitrogen atoms of phen and dpq. For the terbium complexes prepared by precipitation, the peak positions of the transitions were similar with the ones of the common complexes. The peaks at 490, 545, 586 and 621 nm were assigned to the D4 --7F6, 5D4 --7F6, D4 --7F6, 5D4 --7F6 transitions. For the fluorescence intensities of their 5D4 --7F6, 5D4 --7F5 and 5D4 --7F4 transitions were lower than that of the 5D4 --7F3 transition, the terbium complexes did not exhibit the characteristic fluorescence (green), but strong red fluorescence. The reason why terbium complexes exhibit the red fluorescence was investigated in the paper by studying the triplet state of ligands, the energy level transitions of complexes and the aggregation state of particles.

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.