SMM Behavior Tuned by an Exchange Coupling LEGO Approach for Chimeric Compounds: First 2p-3d-4f Heterotrispin Complexes with Different Metal Ions Bridged by One Aminoxyl Group

Coordination compounds containing three different spin carriers (2p, 3d, and 4f), with the general formula [MIIDyIII(LH)(hfac)5] (M = Co, Ni, Mn, Zn), have been obtained using Mannich ligands decorated with a nitronyl–nitroxide fragment. The synthetic approach is general and leads to binuclear 3d–4f complexes, the two metal ions being bridged by one aminoxyl group and by one oxygen atom arising from a hfac– ligand. Triangular spin topology affords significant 2p–3d, 3d–4f, and 2p–4f exchange interactions. For the [CoIIDyIIIRad] derivative obtained using a nitronyl–nitroxide chiral ligand, a high energy barrier (∼200 cm–1) and a slow relaxation behavior below 30 K were found and rationalized by ab initio calculations. The improvement of magnetic properties comes from the synergy of optimal single ions properties and exchange couplings contributions where the CoII–Rad interaction becomes the leading one. The role played by this interaction is clearly proved by the investigation of the magnetic properties of the [ZnIIDyIIIRad] derivative, with a much lower energy barrier (12.7 cm–1) and by the lack of SMM behavior of the previously reported [CoIIDyIIIRad] compound ( Chem. Commun. 2017, 53, 6504), with a linear topology of spin carriers and a negligible CoII–Rad interaction.