Rotaxane-Like Dysprosium(III) Triiodide Single-Molecule Magnets with Tunable Air Stability and Record Energy Barrier

High-performance and air-stable single-molecule magnets (SMMs) can offer great convenience for the fabrication of information storage devices. However, the controversial requisition of high stability and magnetic axiality is hard to balance for lanthanide based SMMs. Here we show a family of rotaxane-like dysprosium(III) triiodide complexes possessing hexagonal-bipyramidal (pseudo-D6h symmetry) local coordination geometry with tunable air stability and effective energy barrier for magnetization reversal (Ueff). The three complexes share the common formulae of [Dy(18-C-6)L2][I3] (18-C-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane; L = I, 1; L = OtBu 2 and L = 1-AdO 3). 1 is highly unstable in the air. 2 can survive in the air for less than one hour, while 3 remains unchanged in the air for more than one week. This is roughly in accordance to the percentage of buried volumes of the axial ligands. More strikingly, 2 and 3 show progressive enhancement of Ueff and 3 exhibits a record high Ueff of 2427(19) K, which significantly contributes to the 100 seconds blocking temperature up to 11 K for yttrium-diluted sample, setting a new benchmark for air-stable SMMs.