Abstract: Six compounds of M_2F_3·12H_2O (M=Eu, Gd, Tb, Y, Er, Lu; H_2F=Fumaric acid) have been synthesized. The structures of Eu(Ⅲ), Tb(Ⅲ), Y(Ⅲ), Er(Ⅲ) and Lu(Ⅲ) compounds have been determined by single crystal X-ray diffraction method. The complex of Eu(Ⅲ) crystallizes in triclinic space group P(1), and the coordination number of Eu~(3+) is ten. The other four complexes crystallize in monclinic space group P2_(1/c), and the coordination numbers of the metal ions are eight. Each of the complexes shows a three-dimensional net structure.

Key words: Fumaric acid, Complex, Synthesis, Crystal structure