Selective arc-discharge synthesis of Dy₂S-clusterfullerenes and their isomer-dependent single molecule magnetism

Abstract

A method for the selective synthesis of sulfide clusterfullerenes Dy2S@C2n is developed. Addition of methane to the reactive atmosphere reduces the formation of empty fullerenes in the arc-discharge synthesis, whereas the use of Dy2S3 as a source of metal and sulfur affords sulfide clusterfullerenes as the main fullerene products along with smaller amounts of carbide clusterfullerenes. Two isomers of Dy2S@C82 with Cs(6) and C3v(8) cage symmetry, Dy2S@C72-Cs(10528), and a carbide clusterfullerene Dy2C2@C82-Cs(6) were isolated. The molecular structure of both Dy2S@C82 isomers was elucidated by single-crystal X-ray diffraction. SQUID magnetometry demonstrates that all of these clusterfullerenes exhibit hysteresis of magnetization, with Dy2S@C82-C3v(8) being the strongest single molecule magnet in the series. DC- and AC-susceptibility measurements were used to determine magnetization relaxation times in the temperature range from 1.6 K to 70 K. Unprecedented magnetization relaxation dynamics with three consequent Orbach processes and energy barriers of 10.5, 48, and 1232 K are determined for Dy2S@C82-C3v(8). Dy2S@C82-Cs(6) exhibits faster relaxation of magnetization with two barriers of 15.2 and 523 K. Ab initio calculations were used to interpret experimental data and compare the Dy-sulfide clusterfullerenes to other Dy-clusterfullerenes. The smallest and largest barriers are ascribed to the exchange/dipolar barrier and relaxation via crystal-field states, respectively, whereas an intermediate energy barrier of 48 K in Dy2S@C82-C3v(8) is assigned to the local phonon mode, corresponding to the librational motion of the Dy2S cluster inside the carbon cage.

Recent Progress on Endohedral Metallic Fullerenes

“…[91] EMFs based single molecule magnets have been a rapid developing research area in the recent years. [46,47,92] In 2012, Greber and Dunsch [91] found that DySc 2 N @C 80 exhibited a hysteresis of magnetization with zero-field quantum tunneling of magnetization, which was the first reported EMF based single molecule magnet. Later, they found that the ferromagnetic coupling of individual dysprosium moments in Dy 2 ScN@C 80 is even higher than that in DySc 2 N @C 80 .…”

“…However, no SMM property was found for Dy 3 N@C 80 due to the fully frustrated ferromagnetic coupling in it. [93] Popov and Yang studied the SMM properties of a series of EMFs including Dy 2 TiC 2 @C 80 , [94] Dy 2 TiC@C 80 , [94] TbNC@C 76 , [92] TbNC@C 82 , [95] Dy 2 S@C 82 [47] and Dy 2 ScN@C 80 . [93,96] They found that Dy 2 ScN @C 80 is the best single-molecule magnet among all the above-mentioned EMFs.…”

“…[44] Due to the stability and sensitivity of ESR signals, they can be applied in molecule magnets and quantum information processing. [11] Recently, clusterfullerenes, such as DySc 2 N@C 80 , [45] Dy 2 ScN@C 80 , [46] Dy 2 S@C 82 [47] and TbNC@C 82 [48] were found to have excellent SMM proper-ties. These EMFs based on single-molecule magnets were expected to have potential applications in high density information storage, quantum calculation, spintronics and some other sophisticated equipment.…”

Single‐Molecule Magnets DyM2N@C80 and Dy2MN@C80 (M=Sc, Lu): The Impact of Diamagnetic Metals on Dy3+ Magnetic Anisotropy, Dy⋅⋅⋅Dy Coupling, and Mixing of Molecular and Lattice Vibrations

“…Single‐molecule magnetism is a phenomenon involving the slow relaxation of magnetization in molecules with a bistable magnetic ground state and has been a hot topic in the field of molecular magnetism during the last decades . Indeed, some lanthanide‐clusterfullerenes exhibit single‐molecule magnetism, which is most robust in dysprosium‐clusterfullerenes –…”

There is nothing wrong with being soft: using sulfur ligands to increase axiality in a Dy(iii) single-ion magnet

“…1) which is a S-ligated single-ion magnet with hysteresis loops open up to 7 K and a magnetisation reversal barrier of U eff = 638 K, which is unprecedented in the very small family of S-ligated Dy(III) singleion magnets (see Table 1). [14][15][16][17][18][19][20] Compound 1 was isolated by using the cage-like ligand N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (HL ON3 ) (see ESI †). 21 Our synthetic strategy generates one short Dy-O bond, to direct the magnetic anisotropy, 22 and three longer Dy-N bonds.…”