Magnetic Exchange Coupling in Radical-Bridged Lanthanide Complexes.

-bridged complex arises from direct exchange where virtual electron hopping is greatly hindered by localized d-orbitals. The finding thus explains the experimentally observed ferromagnetic coupling in a large number of gadolinium-transition metal complexes as well as observed antiferromagnetic coupling in the aromatic radical-bridged lanthanide complexes. Extending to radical-bridged dysprosium complexes, multiconfigurational spin-orbit calculations capture the full anisotropic exchange coupling, enabling the construction of effective exchange and crystal field Hamiltonians. The computed low-energy spectra and magnetic properties show close agreement with the experiment, clarifying the distinct ferro- versus antiferromagnetic ground states. This study provides a unified framework for quantifying and interpreting exchange in radical-bridged lanthanides, thereby advancing predictive design strategies for molecular magnetism.