Self-assembly of lanthanide-based single-ion magnets (SIMs) into 1D networks via Re(IV)-based metalloligands

Within the research field of molecular magnetism, single-ion magnets (SIMs) are of particular interest due to their ability to retain magnetic memory at the molecular level. At the same time, one-dimensional coordination polymers enable controlled spatial arrangement of magnetic centers, making them valuable models for investigating magneto-structural correlations. Here, we report the synthesis, crystal structure, magnetic properties and theoretical calculations of a family of five one-dimensional Re(IV)-Ln(III) coordination complexes obtained by using the "complex-as-ligand" strategy and based on the pyridinedicarboxylic acid derivatives that form the [ReBr₅(3,4-pydcH₂)]^- and [ReBr₅(3,5-pydcH₂)]^- metalloligands, with general formulas (NBu₄)₂{Ln(EtOH)(dpkOEt)[ReBr₅(3,5-Hpydc)]₂}_n·3.5H₂O·MeOH [Ln = Dy(2), Tb(3)] and {Ln[ReBr₅(3,4-pydc)](dmf)₃(MeOH)}_n·dmf [Ln = Dy(4), Tb(5), Gd(6)]. Two of these Re(IV)-Ln(III) compounds-[Dy(EtOH)(dpkOEt){ReBr₅(3,5-Hpydc)}₂]_n (2) and [Dy{ReBr₅(3,4-pydc)}(dmf)₃(MeOH)]_n (4)-exhibit slow relaxation of the magnetisation, which is characteristic of SIM behaviour and accounted for ac magnetic susceptibility measurements. Structural analyses suggest that intra- and intermolecular halogen-halogen (Br⋯Br) interactions may influence the magneto-structural properties of 2-6. These findings demonstrate the potential of Re(IV)-Ln(III) hybrid systems as candidates for developing magnetically addressable molecular materials.