A Series of Banana-Shaped 3d-4f Heterometallic Cluster Substituted Polyoxometalates: Syntheses, Crystal Structures, and Magnetic Properties.

Four seven-nuclearity 3d-4f heterometallic cluster {FeLnO} substituted polyoxometalates (HPz)KFeLn(μ-O)(B-α-GeWO)(GeWO)· xHO (1-Ln, Pz = piperazine, Ln = Tb, Dy, Ho, Er for x = 27, 25, 25, 24, respectively) have been hydrothermally prepared and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectrometry, thermogravimetric analyses, elemental analyses, and electrospray ionization mass spectrometry. Single-crystal X-ray diffraction analyses revealed that 1-Ln contain an unprecedented banana-shaped polyanion constructed from an iron-lanthanide heterometallic {FeLnO} cluster, two trilacunary {B-α-GeWO} units, and one hexalacunary {GeWO} fragment. The magnetic susceptibility surveying proved the presence of antiferromagnetic coupling in 1-Ln.