Syntheses and Structures of One- and Two-Dimensional Organic−Inorganic Hybrid Rare Earth Derivatives Based on Monovacant Keggin-Type Polyoxotungstates

Three novel organic−inorganic hybrid monovacant Keggin-type silicotungstates and germanotungstates containing
lanthanideIII cations with 1D and 2D infinitely extended structures, [Sm(H2O)6]0.25[Sm(H2O)5]0.25H0.5{Sm(H2O)7[Sm(H2O)2(DMSO)(α-SiW11O39)]}·4.5H2O (DMSO = dimethyl sulfoxide) (1), [Dy(H2O)4]0.25[Dy(H2O)6]0.25H0.5{Dy(H2O)7[Dy(H2O)2(DMSO)(α-GeW11O39)]}·5.25H2O (2), and H{[Sm(H2O)5.5(DMF)0.5]2[Sm(H2O)2(DMF)][Sm(H2O)3(α-SiW11O39)]2} (DMF = N,N-dimethyl
formamide) (3), have been synthesized in aqueous solution under moderate conditions and further characterized by elemental analyses,
inductively coupled plasma (ICP) analyses, IR, UV spectra, and X-ray diffraction. Compounds 1 and 2 reveal the one-dimensional
chain infinitely extended structure, while compound 3 represents the first example of a two-dimensional network structure formed
by the monovacant Keggin-type [α-SiW11O39]8- chain through the linkage of rare earth metal−organic coordination cations. From
thermogravimetric (TG/DTA) analyses, the polyanion frameworks of 1 and 2 retain a comparatively good thermal stability. Variable
temperature magnetic susceptibility indicates that compounds 1 and 3 obey the Curie−Weiss law in the higher temperature region
from 130 to 300 K, while in the lower temperature region from 2 to 130 K they show the occurrence of strong spin−orbital coupling
interactions and very weak ferromagnetic responses.