[Tb₄(OH)₄]-Cuboid Complex Dianion Stabilized with Six Carboxylate Bridges and Four Diketonate Caps

A cubane-like complex dianion [Tb₄(OH)₄(tfa)₆(hfac)₄]²⁻ was synthesized, accompanied by two counter cations of [Ni(hfac)(2pyIN)₂]⁺, where Htfa, Hhfac, and 2pyIN stand for trifluoroacetic acid, 1,1,1,5,5,5-hexafluoropentane-2,4-dione, and 4,4,5,5-tetramethyl-2-pyridylimidazolin-1-oxyl, respectively. In the complex anion, each Tb ion was capped with hfac, and each Tb···Tb diagonal was bridged with tfa, thus forming an approximate Td symmetry, though the whole molecular formula was crystallographically independent in an orthorhombic Pbca space group. The ionic charge was −2 in total. The magnetic study revealed that the complex ions were magnetically isolated from each other. Practically no 4f–4f superexchange interaction was operative, while the 2p–3d ferromagnetic coupling seemed to be appreciable, as anticipated from the proposed magnetostructural relationship.