Structure-property relations on exchange couplings in distorted halide-bridged Gd(III) complexes

In comparison to transition metals, the connection between the bridging geometry and the magnetic exchange coupling constant J remains vague for Gd(III)-Gd(III) magnetic couplings. However, such couplings are an important feature, for example for compounds showing a strong magnetocaloric effect. In this study, a series of Gd₂X₆ (X = F, Cl, Br, I) was systematically distorted and the magnetic coupling calculated using broken-symmetry DFT. We find an inversely exponential metal-metal distance dependence as well as the dependence on a second structural parameter, either the Gd-X distance or the Gd-X-Gd angle. We compared these structural dependencies with different DFT-features. We furthermore find that the nature of terminal ligands has neglectable influence. Using these results, we showed that such simple model complexes can be used to predict the coupling in experimentally investigated complexes with the same bridge. This lets us conclude that it may be possible to effectively extract reasonable exchange coupling constants and Spin-Hamiltonians for larger Gd(III)-clusters.