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

Four seven-nuclearity 3d-4f heterometallic cluster {Fe 6 LnO 28 } substituted polyoxometalates (HPz) 11 K 4 Fe 6 Ln(μ 3 -O) 2 (B-α-GeW 9 O 34 ) 2 (GeW 6 O 26 )· x H 2 O ( 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 {Fe 6 LnO 28 } cluster, two trilacunary {B-α-GeW 9 O 34 } units, and one hexalacunary {GeW 6 O 26 } fragment. The magnetic susceptibility surveying proved the presence of antiferromagnetic coupling in 1-Ln .