A novel mixed-valence coordination polymer [Cu(en)2H2O]2• 8H2O was synthesiszed under a hydrothermal condition and characterized by elemental analysis, IR, UV, TG-DSC and single-crystal X-ray diffraction. The title compound crystllized in a monoclinic crystal system, with space group P21/c, a＝1.88678(12) nm, b＝2.30383(14) nm, c＝2.61234(16) nm, α＝90°, β＝95.844(1)°, γ＝90°, V＝11.2964(12) nm3, Z＝4, Dc＝3.954 g/cm3, R1＝0.0975, and wR2＝0.2041. The structural refinement indicates that the title compound forms a one-dimensional chain from the polyanions ( )6－ through O bridge. The result of TG-DSC shows that the title compound is thermally more stable than α-H3PW12O40•H2O.

Key words: hydrothermal synthesis, crystal structure, polyoxometallate, mixed-valence, Keggin structure