Oblate versus Prolate Electron Density of Lanthanide Ions: A Design Criterion for Engineering Toroidal Moments? A Case Study on {LnIII6} (Ln=Tb, Dy, Ho and Er) Wheels

We report four new complexes based on a {Ln(6)(III)} wheel structure, three of which possess a net toroidal magnetic moment. The four examples consist of {Tb-6(III)} and {Ho-6(III)} wheels, which are rare examples of non Dy-III based complexes possessing a toroidal magnetic ground state, and a {Dy-6(III)} complex which improves its toroidal structure upon lowering the crystallographic symmetry from trigonal (R3 ? ) to triclinic (P1 ? ). Notably the toroidal moment is lost for the trigonal {Er-6(III)} analogue. This suggests the possibility of utilizing the popular concept of oblate and prolate electron density of the ground state M-J levels of lanthanide ions to engineer toroidal moments.