Breaking Symmetry Relaxes Structural and Magnetic Restraints, Suppressing QTM in Enantiopure Butterfly Fe 2 Dy 2 SMMs

The {Fe 2 Dy 2 } butterfly systems can show single molecule magnet (SMM) behaviour, the nature of which depends on details of the electronic structure, as previously demonstrated for the [Fe 2 Dy 2 (μ 3 ‐OH) 2 (Me‐teaH) 2 (O 2 CPh) 6 ] compound, where the [N,N‐bis‐(2‐hydroxyethyl)‐amino]‐2‐propanol (Me‐teaH 3 ) ligand is usually used in its racemic form. Here, we describe the consequences for the SMM properties by using enantiopure versions of this ligand and present the first homochiral 3d/4 f SMM, which could only be obtained for the S enantiomer of the ligand for [Fe 2 Dy 2 (μ 3 ‐OH) 2 (Me‐teaH) 2 (O 2 CPh) 6 ] since the R enantiomer underwent significant racemisation. To investigate this further, we prepared the [Fe 2 Dy 2 (μ 3 ‐OH) 2 (Me‐teaH) 2 (O 2 CPh) 4 (NO 3 ) 2 ] version, which could be obtained as the RS ‐, R ‐ and S ‐compounds. Remarkably, the enantiopure versions show enhanced slow relaxation of magnetisation. The use of the enantiomerically pure ligand suppresses QTM, leading to the conclusion that use of enantiopure ligands is a “gamechanger” by breaking the cluster symmetry and altering the intimate details of the coordination cluster's molecular structure.