Facile interchange of 3d and 4f ions in single-molecule magnets: stepwise assembly of [Mn4 ], [Mn3Ln] and [Mn2Ln2 ] cages within calix[4]arene scaffolds.

The central Mn(II) ions in a series of calix[4]arene-stabilised butterflies can be sequentially replaced with Ln(III) ions, maintaining the structural integrity of the molecule but transforming its magnetic properties. The replacement of Mn(II) for Gd(III) allows for the examination of the transferability of spin-Hamiltonian parameters within the family as well as permitting their reliable determination. The introduction of the 4f ions results in weaker intramolecular magnetic exchange, an increase in the number of low-lying excited states, and an increase in magnetisation relaxation, highlighting the importance of exchange over single-ion anisotropy for the observation of SMM behaviour in this family of complexes. The presence of the [TM(II/III) (TBC[4])(OH)(solvent)] metalloligand (TM=transition metal, TBC=p-tBu-calix[4]arene) suggests that magnetic calix[n]arene building blocks can be employed to encapsulate a range of different "guests" within structurally robust "hosts".