Assembly Chemistry between Lanthanide Cations and Monovacant Keggin Polyoxotungstates: Two Types of Lanthanide Substituted Phosphotungstates [{(α-PW11O39H)Ln(H2O)3}2]6- and [{(α-PW11O39)Ln(H2O)(η2,μ-1,1)-CH3COO}2]10-

Two 2:2 types of monolanthanide substituted polyoxometalates [{(alpha-PW11O39H)Ln(H2O)(3)}(2)](6-) (Ln=Nd-III for 1 and Gd-III for 2) and [{(alpha-PW11O39)Ln(H2O)(eta(2),mu-1,1)-CH3COO}(2)](10-) (Ln=Sm-III for 3, Eu-III for 4, Gd-III for 5, Tb-III for 6, Ho-III for 7 and Er-III for 8) have been synthesized in aqueous solution and characterized by elemental analyses, IR spectra, UV-vis-NIR spectra, thermogravimatric analyses and single-crystal X-ray diffraction. The common structural features are that they are constructed from monovacant Keggin-type polyoxoanions [alpha-PW11O39](7-) and trivalent lanthanide cations. Both 1 and 2 are essentially isomorphous, and the molecular structure is built by two symmetrically related monolanthanide substituted Keggin units [alpha-PW(11)O(39)Ln(H2O)(3)](4-) linked via two Ln-O-W bridges, representing the first monovacant Keggin polyoxotungstate dimers constituted by two [alpha-PW11O39](7-) polyoxoanions and two lanthanide cations in polyoxometalate chemistry. 3-8 are also isostructural and display another dimeric structure constructed from two monolanthanide substituted units [(alpha-PW11O39)Ln(H2O)(eta(2),mu-1,1)-CH3COO](5-) bridged by two (eta(2),mu-1,1)-acetato ligands. The photoluminescence properties of 4 and 6 were investigated at room temperature. Magnetic susceptibility measurements of 1, 3, 4, 7 and 8 between 2 and 300 K exhibit that their magnetic behaviors mainly result from the spin-orbital coupling interactions as well as weak antiferromagnetic exchange interactions within magnetic centers. The electrochemical properties of 1, 3, 4, 5, 7 and 8 were studied by means of cyclic voltammetry in aqueous solution with 0.5 M Na2SO4 as supporting electrolyte.