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−

Abstract

Two types of novel oxalate-bridging rare-earth-substituted Keggin-type phosphotungstates {[(α-PW₁₁O₃₉) RE(H₂O)]₂(C₂O₄)}¹⁰⁻ (RE = Y^III for 1, Dy^III for 2, Ho^III for 3 and Er^III for 4) and {(α-x-PW₁₀O₃₈)Tm₂(C₂O₄)(H₂O)₂}³⁻ for 5 have been synthesized by reaction of [α-PW₁₁O₃₉]⁷⁻ 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-PW₁₁O₃₉)]₂¹⁴⁻ subunits linked by oxalate ligands whereas 5 exhibits a one-dimensional (1D) chain architecture built by the unusual divacant [α-x-PW₁₀O₃₈]¹¹⁻ 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-PW₁₀O₃₈]¹¹⁻ 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.