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 formula (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.