Assembly of tetra-nuclear YbIII-containing selenotungstate clusters: synthesis, structures, and magnetic properties

Two tetra-nuclear Yb-III-incorporated selenotungstate clusters, Keggin (C2H8N)(6)Na-14[Yb4Se6W44O160(H2O)(12)]center dot 40H(2)O (1) and Wells-Dawson (C2H8N)(4)Na-14[Yb4Se6W45O159(OH)(6)(H2O)(11)]center dot 38H(2)O (2), have been isolated through a pH-controlled assembly, which exhibit the first Yb-III-containing polyoxotungstates with selenium heteroatoms. Their assemblies rely on the structure-directing effects of SeO32- anion templates to give rise to available Se-containing Keggin-/Wells-Dawson-type motifs. Both compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, power X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) as well as electrospray ionization mass spectrometry (ESI-MS). Furthermore, systematic magnetic studies revealed that 1 exhibits field-induced single-molecule magnetic behavior with a pre-exponential factor of tau(0) = 6.60(7) x 10(-8) s and a relaxation energy barrier of Delta E/k(B) = 39.44(2) K, while 2 only displays antiferromagnetic interactions between the ytterbium centers.

Automated summary

Two novel tetra-nuclear Yb-III-incorporated selenotungstate clusters were isolated through pH-controlled assembly, showing the first Yb-III-containing polyoxotungstates with selenium heteroatoms. Compound 1 exhibited field-induced single-molecule magnetic behavior, while compound 2 displayed antiferromagnetic interactions between ytterbium centers.