Abstract
Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln2@C80(CH2Ph) dimetallofullerenes (Ln2 = Y2, Gd2, Tb2, Dy2, Ho2, Er2, TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal–metal bonding orbital. Tb2@C80(CH2Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln2@C80(CH2Ph) is redox active, enabling electrochemical tuning of the magnetism.
Highlights
Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets
Lanthanides are well-known for their large atomic moments and magnetic anisotropies, and embedding discrete lanthanide ions in molecular environments leads to nanomagnets exhibiting magnetic bistability and slow relaxation of magnetization on a single molecule level[1,2]
In this work we explore the limiting case of this concept in which the role of a radical bridge is played by a single unpaired electron, residing on the lanthanide-lanthanide bonding orbital and coupling the lanthanide spins inside a fullerene
Summary
Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. The lanthanide spins are glued together by very strong exchange interactions between 4f moments and a single electron residing on the metal–metal bonding orbital. Lanthanides are well-known for their large atomic moments and magnetic anisotropies, and embedding discrete lanthanide ions in molecular environments leads to nanomagnets exhibiting magnetic bistability and slow relaxation of magnetization on a single molecule level[1,2]. Combination of several magnetic centers within one molecule may lead to high-spin ground states and can largely suppress quantum tunneling, which is the main low-temperature relaxation mechanism for single-ion magnets in zero magnetic field
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