Ligand-Assisted Assembly of a Family of 3d-4f Cluster-Templated Ln-Polyoxoniobate Cages with a Nested Cuboctahedral/Fullerene-Like Core and Ln-Dependent Magnetism

A flexible organic ligand-assisted strategy was developed to incorporate lanthanide ions into polyoxoniobate frameworks, yielding a series of Ln-containing polyoxoniobate cages (Ln-PONb cages 1-Ln) stabilized by 3d-4f heterometallic clusters. Compounds 1-Ln feature a giant anionic Ln4Nb96 supercage with an internal Ln4Nb24 cluster displaying a rare fullerene-like topology. These supercages assemble with propeller-like {LnCu₄(H₄L)₄}³⁺ cations via electrostatic interactions to form three-dimensional frameworks. Magnetic studies of 1-Ln (Ln = La, Ce, Pr, Nd) reveal that the magnetic behavior is strongly Ln³⁺-dependent: 1-Ce and 1-Nd exhibit dominant antiferromagnetic coupling, while 1-La and 1-Pr show ferromagnetic coupling. This work provides a promising strategy for constructing POM-based cage materials with unique topologies and tunable magnetic properties.