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Magnetic hysteresis and strong ferromagnetic coupling of sulfur-bridged Dy ions in clusterfullerene Dy₂S@C₈₂.

ABSTRACT: Two isomers of metallofullerene Dy₂S@C₈₂ with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature. Analysis of the level crossing events for different orientations of a magnetic field showed that even in powder samples, the hysteresis steps caused by quantum tunneling of magnetization can provide precise information on the strength of intramolecular Dy⋯Dy inter-actions. A comparison of different methods to determine the energy difference between ferromagnetic and antiferromagnetic states showed that sub-Kelvin hysteresis gives the most robust and reliable values. The ground state in Dy₂S@C₈₂ has ferromagnetic coupling of Dy magnetic moments, whereas the state with antiferromagnetic coupling in C _s and C _3v cage isomers is 10.7 and 5.1 cm^-1 higher, respectively. The value for the C _s isomer is among the highest found in metallofullerenes and is considerably larger than that reported in non-fullerene dinuclear molecular magnets. Magnetization relaxation times measured in zero magnetic field at sub-Kelvin temperatures tend to level off near 900 and 3200 s in C _s and C _3v isomers. These times correspond to the quantum tunneling relaxation mechanism, in which the whole magnetic moment of the Dy₂S@C₈₂ molecule flips at once as a single entity.

SUBMITTER: Krylov D

PROVIDER: S-EPMC7116581 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Magnetic hysteresis and strong ferromagnetic coupling of sulfur-bridged Dy ions in clusterfullerene Dy2S@C82.

Krylov Denis D Velkos Georgios G Chen Chia-Hsiang CH Büchner Bernd B Kostanyan Aram A Greber Thomas T Avdoshenko Stanislav M SM Popov Alexey A AA

Inorganic chemistry frontiers 20200729 19

Two isomers of metallofullerene Dy2S@C82 with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature. Analysis of the level crossing events for different orientations of a magnetic field showed that even in powder samples, the hysteresis steps caused by quantum tunneling of magnetization can provide precise information on the strength of intramolecular Dy⋯Dy inter-actions. A comparison of different methods to determine the energy ...[more]

PMID: 33442482

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Project description:Chemical functionalization of endohedral metallofullerenes (EMFs) is essential for the application of these novel carbon materials. Actinide EMFs, a new EMF family member, have presented unique molecular and electronic structures but their chemical properties remain unexplored. Here, for the first time, we report the chemical functionalization of actinide EMFs, in which the photochemical reaction of Th@C 3v(8)-C82 and U@C 2v(9)-C82 with 2-adamantane-2,3'-[3H]-diazirine (AdN2, 1) was systematically investigated. The combined HPLC and MALDI-TOF analyses show that carbene addition by photochemical reaction afforded three isomers of Th@C 3v(8)-C82Ad and four isomers of U@C 2v(9)-C82Ad (Ad = adamantylidene), presenting notably higher reactivity than their lanthanide analogs. Among these novel EMF derivatives, Th@C 3v(8)-C82Ad(I, II, III) and U@C 2v(9)-C82Ad(I, II, III) were successfully isolated and were characterized by UV-vis-NIR spectroscopy. In particular, the molecular structures of first actinide fullerene derivatives, Th@C 3v(8)-C82Ad(I) and U@C 2v(9)-C82Ad(I), were unambiguously determined by single crystal X-ray crystallography, both of which show a [6,6]-open cage structure. In addition, isomerization of Th@C 3v(8)-C82Ad(II), Th@C 3v(8)-C82Ad(III), U@C 2v(9)-C82Ad(II) and U@C 2v(9)-C82Ad(III) was observed at room temperature. Computational studies suggest that the attached carbon atoms on the cages of both Th@C 3v(8)-C82Ad(I) and U@C 2v(9)-C82Ad(I) have the largest negative charges, thus facilitating the electrophilic attack. Furthermore, it reveals that, compared to their lanthanide analogs, Th@C 3v(8)-C82 and U@C 2v(9)-C82 have much closer metal-cage distance, increased metal-to-cage charge transfer, and strong metal-cage interactions stemming from the significant contribution of extended Th-5f and U-5f orbitals to the occupied molecular orbitals, all of which give rise to their unusual high reactivity. This study provides first insights into the exceptional chemical properties of actinide endohedral fullerenes, which pave ways for the future functionalization and application of these novel EMF compounds.

Dataset Information

Magnetic hysteresis and strong ferromagnetic coupling of sulfur-bridged Dy ions in clusterfullerene Dy₂S@C₈₂.

Publications

Magnetic hysteresis and strong ferromagnetic coupling of sulfur-bridged Dy ions in clusterfullerene Dy<sub>2</sub>S@C<sub>82</sub>.

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