Bis‐Alkoxide Dysprosium(III) Crown Ether Complexes Exhibit 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, a family of dysprosium(III) crown ether complexes possessing hexagonal‐bipyramidal (pseudo‐D6h symmetry) local coordination geometry with tunable air stability and effective energy barrier for magnetization reversal (Ueff) are shown. The three complexes share the common formula 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 a few minutes, while 3 remains unchanged in the air for more than 1 week. This is roughly in accordance with 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 s blocking temperature up to 11 K for Yttrium‐diluted sample, setting a new benchmark for solid‐state air‐stable SMMs. [ABSTRACT FROM AUTHOR]