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

Fupin Liu,Marco Rosenkranz,Bernd Büchner,Nataliya A Samoylova,Denis S Krylov,Alexey A Popov,Anja U B Wolter,Stanislav M Avdoshenko,Aram Kostanyan,Thomas Greber,Lukas Spree

doi:10.1038/ncomms16098

Fupin Liu, Marco Rosenkranz + Show 9 more

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https://doi.org/10.1038/ncomms16098

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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 Y2@C80 and Dy2@C80 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 Dy2@C80(CH2Ph) with a record-high 100 s blocking temperature of 18 K. All magnetic moments in Dy2@C80(CH2Ph) are parallel and couple ferromagnetically to form a single spin unit of 21 μB 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.

Highlights

Increasing the temperature at which molecules behave as single-molecule magnets is a serious challenge in molecular magnetism
In this work we describe elusive M2@C80-Ih (M 1⁄4 Y, Dy) species obtained as air-stable chemical derivatives, benzyl monoadducts M2@C80(CH2Ph)
In this work, we synthesized the single-molecule magnet with half-occupied Dy–Dy bonding orbital, Dy2@C80(CH2Ph)

Summary

Introduction

Increasing the temperature at which molecules behave as single-molecule magnets is a serious challenge in molecular magnetism. Endohedral metallofullerenes Y2@C80 and Dy2@C80 are obtained in the form of air-stable benzyl monoadducts Both feature an unpaired electron trapped between metal ions, forming a single-electron metal-metal bond. Giant exchange interactions between lanthanide ions and the unpaired electron result in single-molecule magnetism of Dy2@C80(CH2Ph) with a record-high 100 s blocking temperature of 18 K. Metal atoms in EMFs transfer their valence electrons to carbon cages[25], the M–M bonding molecular orbital (MO) with spd-hybrid character is one of the frontier MOs in dimetallofullerenes[24]. On the other side of the lanthanide row, La has a high energy of the (6 s)sg[2] MO in the La2 dimer and in La-dimetallofullerenes the electrons are fully transferred from this MO to a carbon cage, leading to the La3 þ state without La–La bonding[27]. For Y or lanthanides with higher energy of the M–M bonding MO than in La2, computations by Shinohara and colleagues[28] showed that the

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