An unprecedented trimer based on monovacant Dawson anion: [(α2-P2W17O61)Ln(H2O)4]321− (Ln = LaIII, CeIII and PrIII)

Abstract

Three unprecedented trimers based on monovacant Dawson-type polyoxotungstates Na₁₂[Ln(H₂O)₉]₂[(α₂-P₂W₁₇O₆₁H₄)La(H₂O)₄]₆·100H₂O (Ln = La^III (1)) and Na₂₄[Ln(H₂O)₈]₂[(α₂-P₂W₁₇O₆₁H₂)Ln(H₂O)₄]₆·56H₂O (Ln = Ce^III (2), and Pr^III (3)) have been successfully synthesized by straightforward “self assembly” processes starting from a 1 : 4 ratio of the saturated Dawson precursor [α-P₂W₁₈O₆₂]⁶⁻ and Ln ions in aqueous solution, which were further characterized by elemental analyses, X-ray powder diffraction (XRPD), IR spectra, thermogravimetric (TG) analyses, electrospray ionization mass spectrometry (ESI-MS) and single-crystal X-ray diffraction. The common feature of 1–3 is that they all consist of the trimeric triangular [(α₂-P₂W₁₇O₆₁)Ln(H₂O)₄]₃²¹⁻ subunit, as we know, the trimeric [(α₂-P₂W₁₇O₆₁)Ln(H₂O)₄]₃²¹⁻ polyoxoanion is firstly discovered. Furthermore, all three compounds can further generate three dimensional channel architectures through Na⁺ cations. Meanwhile, the multinuclear solution ³¹P NMR spectrum of 1 at 300 K in D₂O has been investigated, the results are further demonstrated by the technologies of ESI-MS.