Single molecule magnet with an unpaired electron trapped between two lanthanide ions inside a fullerene

TLDR

Increasing the temperature at which molecules behave as single‑molecule magnets is a serious challenge in molecular magnetism. One way to address this problem is to create molecules with strongly coupled lanthanide ions. In this work, endohedral metallofullerenes Y₂@C₈₀ and Dy₂@C₈₀ are obtained as air‑stable benzyl monoadducts, each featuring an unpaired electron trapped between metal ions to form a single‑electron metal‑metal bond. Giant exchange interactions between lanthanide ions and the trapped electron give Dy₂@C₈₀(CH₂Ph) single‑molecule magnetism with a record‑high 100‑s blocking temperature of 18 K, a 613 K magnetization‑reversal barrier, and a ferromagnetically coupled 21 μB spin unit with a dysprosium‑electron exchange constant of 32 cm⁻¹.

Abstract

Abstract Increasing the temperature at which molecules behave as single-molecule magnets is a serious challenge in molecular magnetism. One of the ways to address this problem is to create the molecules with strongly coupled lanthanide ions. In this work, endohedral metallofullerenes Y 2 @C 80 and Dy 2 @C 80 are obtained in the form of air-stable benzyl monoadducts. Both feature an unpaired electron trapped between metal ions, thus forming a single-electron metal-metal bond. Giant exchange interactions between lanthanide ions and the unpaired electron result in single-molecule magnetism of Dy 2 @C 80 (CH 2 Ph) with a record-high 100 s blocking temperature of 18 K. All magnetic moments in Dy 2 @C 80 (CH 2 Ph) are parallel and couple ferromagnetically to form a single spin unit of 21 μ B with a dysprosium-electron exchange constant of 32 cm −1 . The barrier of the magnetization reversal of 613 K is assigned to the state in which the spin of one Dy centre is flipped.