Two types of oxalate-bridging rare-earth-substituted Keggin-type phosphotungstates {[(α-PW11O39)RE(H2O)]2(C2O4)}(10-) and {(α-x-PW10O38)RE2(C2O4)(H2O)2}(3-).

Two types of novel oxalate-bridging rare-earth-substituted Keggin-type phosphotungstates {(α-PW(11)O(39)) RE(H(2)O)(C(2)O(4))}(10-) (RE = Y(III) for 1, Dy(III) for 2, Ho(III) for 3 and Er(III) for 4) and {(α-x-PW(10)O(38))Tm(2)(C(2)O(4))(H(2)O)(2)}(3-) for 5 have been synthesized by reaction of α-PW(11)O(39) with RE cations and oxalate ligands in aqueous solution. They have been further characterized by elemental analyses, X-ray powder diffraction (XRPD), IR spectra, thermogravimetric (TG) analysis, and single-crystal X-ray diffraction. The common features of 1-4 are that they all contain the dimeric mono-RE substituted Keggin RE(α-PW(11)O(39))(14-) subunits linked by oxalate ligands whereas 5 exhibits a one-dimensional (1D) chain architecture built by the unusual divacant α-x-PW(10)O(38) polyoxoanions and oxalate ligands. Notably, 1-5 represent the first oxalate-bridging dimers constructed by lacunary Keggin phosphotungstate-supported RE derivatives, and the unusual divacant α-x-PW(10)O(38) fragment is found for the first time. Furthermore, the room-temperature solid-state photoluminescence of 2 has been investigated. Variable-temperature magnetic susceptibility measurements indicate that 2 and 4 demonstrate weak ferromagnetic couplings within the two adjacent RE cations bridged through oxalate ligands, whereas dominant antiferromagnetic interactions are observed in 3 and 5, respectively.