Asymmetric dinuclear lanthanide complexes from in situ ligand dimerization: non-equivalent 4f sites and magnetic relaxation dynamics

Two isostructural dinuclear Dy2 and Tb2 complexes were synthesized via an unexpected in-situ metal-assisted ligand dimerization reaction of (tert-butoxy-(phenyl)methyl)-dipyridine-imidazole. This process generates an asymmetric bridging ligand while simultaneously assembling dinuclear species with distinct coordination environments.  The Dy2 compound exhibits slow relaxation of the magnetization dominated by Raman-like and Orbach-type contributions under an applied dc field. In contrast, the Tb2 analogue exhibits only weak out-of-phase ac signals, mainly associated with fast relaxation processes. These results establish a direct synthetic route to asymmetric 4f architectures and offer a promising synthetic strategy for generating molecular systems with non-equivalent magnetic centers.