Abstract：Three rare-earth complexes [CeL4](OTf)3·2H2O(L=tetraisopropylmethylene -diphosphonate; OTf=trifluoromethanesulfate), [Dy(OTf)2L2(H2O)2](OTf)(CH3CN) and [DyL4](OTf)3·L·2H2O were prepared by the reaction of Ln(OTf)3(Ln=Ce，Dy) and (iPrO)2P(O)CH2P(O)(iPrO)2 in CH3CN. Their compositions were confirmed and their properties were characterized by elemental analysis, infrared spectra, 1H and 31P NMR spectroscopy, fluorescence spectra and DTA-TGA. The data of elemental analysis of these complexes are in good agreement with the formula given above. In the infrared spectra of all these complexes, there are obvious shifts of some important absorption bands, such as the PO or S—O bands, illustrating that the ligands L or OTf ions were coordinated to the lanthanide ions. The signals in 1H NMR spectrum at approximately 1.2, 2.4 and 4.5 have been assigned to the resonance of H atoms in the ligand L, and these signals in the spectrum of complexes are highfield shifted compared to that of free ligand due to the electron cloud of Ln—O band moving towards to P—O band. The sharp single peaks were found in the 31P NMR spectrum, and the chemical shifts are at 18.705 6 for free ligand L, 18.543 5 for complex Ⅰ, 18.273 1 for complex Ⅱ, and 18.489 4 for complex Ⅲ. The excitation and emission signals of Ce(Ⅲ) ion were in view of electric dipole transition from 4f15d1 to 4f7. The fluorescence spectroscopy shows that the excitation peak of [CeL4](OTf)3·2H2O is at 249 and 300 nm, and a strong emission peak is at 641 nm. The existence of two coordination water molecules in [Dy(OTf)2L2(H2O)2](OTf)(CH3CN) makes both the excitation and emission peaks weaker than that of [DyL4](OTf)3·L·2H2O. The coordination model of rare-earth with diphosphonic ligand was also discussed. All of these complexes are eight-coordinated. The complexes [CeL4](OTf)3·2H2O and [DyL4](OTf)3·L·2H2O are highly-symmetrical, in which four bidentate ligands L are coordinated to Ce and Dy atoms respectively while the OTf ions and the water molecules are not coordinated. In the complex [Dy(OTf)2L2(H2O)2](OTf)(CH3CN), two L molecules, two water molecules and two OTf ions are coordinated to Dy atom while one OTf ion and one solvent molecule CH3CN are not coordinated.
Key words：Rare-earth complex;Spectra characterization;Coordination model
