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 [{(α-PW 11 O 39 H)Ln(H 2 O) 3 } 2 ] 6− (Ln = Nd III for 1 and Gd III for 2 ) and [{(α-PW 11 O 39 )Ln(H 2 O)(η 2,μ-1,1)-CH 3 COO} 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 [α-PW 11 O 39 ] 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 [α-PW 11 O 39 Ln(H 2 O) 3 ] 4− linked via two Ln−O−W bridges, representing the first monovacant Keggin polyoxotungstate dimers constituted by two [α-PW 11 O 39 ] 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 [(α-PW 11 O 39 )Ln(H 2 O)(η 2,μ-1,1)-CH 3 COO] 5− bridged by two (η 2,μ-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 Na 2 SO 4 as supporting electrolyte.