Redox-active metal–metal bonds between lanthanides in dimetallofullerenes

Popov, Alexey A.

doi:10.1016/j.coelec.2017.12.003

Cited by 19 publications

(22 citation statements)

References 49 publications

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“…More importantly,f or Er 2 @C s (6)-C 82 ,E r 2 @C 3v (8)-C 82 ,a nd Er 2 @C 2v (9)-C 86 ,t he first oxidation potentials exhibit pronounced metal-dependence in contrast to the first reduction potential by comparing to those of M 2 @C s (6)-C 82 (M = Lu, Y), M 2 @C 3v (8)-C 82 (M = Lu, Y), and Lu@C 2v (9)-C 86 ,r espectively, indicatingt hat the MÀMb ondingM Oi si ndeed the redox-activeH OMO of di-EMFs whereas the LUMO is based on the cage as illustrated by Popov et al [30] Accordingly,l ike the LuÀLu bond in Lu 2 @C 2n (2n = 82-86), [12a] the TETC bond is identified safely for the ErÀEr bond in Er 2 @C s (6)-C 82 ,E r 2 @C 3v (8)-C 82 ,a nd Er 2 @C 2v (9)-C 86 by the electrochemical investigations herein. Moreover,F igure S7 (in the Supporting Information) illustrates the calculated frontier molecular orbitals of Er 2 @C 1 (12)-C 84 .The molecule could exhibit metal-based oxidationa sw ell, whereas the first reduction may mainly involve the fullerene cage owing to the first reduction potentiala tÀ1.00 Vand the small difference between the first and the second reduction potentials (0.45 V), which accords well with the conclusions proposed by Popov et al based on the systematic investigations of redox-activem etal-metal bonds between lanthanides in di-EMFs.…”

Section: Resultsmentioning

confidence: 99%

“…Moreover,F igure S7 (in the Supporting Information) illustrates the calculated frontier molecular orbitals of Er 2 @C 1 (12)-C 84 .The molecule could exhibit metal-based oxidationa sw ell, whereas the first reduction may mainly involve the fullerene cage owing to the first reduction potentiala tÀ1.00 Vand the small difference between the first and the second reduction potentials (0.45 V), which accords well with the conclusions proposed by Popov et al based on the systematic investigations of redox-activem etal-metal bonds between lanthanides in di-EMFs. [30]…”

Section: Resultsmentioning

confidence: 99%

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Crystallographic and Theoretical Investigations of Er₂@C_2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Shen

Yang

et al. 2019

Chemistry A European J

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Successful isolation and characterization of a series of Er‐based dimetallofullerenes present valuable insights into the realm of metal–metal bonding. These species are crystallographically identified as Er2@Cs(6)‐C82, Er2@C3v(8)‐C82, Er2@C1(12)‐C84, and Er2@C2v(9)‐C86, in which the structure of the C1(12)‐C84 cage is unambiguously characterized for the first time by single‐crystal X‐ray diffraction. Interestingly, natural bond orbital analysis demonstrates that the two Er atoms in Er2@Cs(6)‐C82, Er2@C3v(8)‐C82, and Er2@C2v(9)‐C86 form a two‐electron‐two‐center Er−Er bond. However, for Er2@C1(12)‐C84, with the longest Er⋅⋅⋅Er distance, a one‐electron‐two‐center Er−Er bond may exist. Thus, the difference in the Er⋅⋅⋅Er separation indicates distinct metal bonding natures, suggesting a distance‐dependent bonding behavior for the internal dimetallic cluster. Additionally, electrochemical studies suggest that Er2@C82–86 are good electron donors instead of electron acceptors. Hence, this finding initiates a connection between metal–metal bonding chemistry and fullerene chemistry.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Crystallographic and Theoretical Investigations of Er₂@C_2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Shen

Yang

et al. 2019

Chemistry A European J

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“…Importantly, although the Ln 2 dimer is protected by the fullerene, it is not completely isolated from the environment. The carbon cage remains transparent for electrons 65,66 , and {Ln 2 } compounds exhibit lanthanide-based redox-activity. In the first reduction step, the Ln–Ln bonding orbital is populated by a second electron, thus allowing to change the valence state from Ln +2.5 to Ln +2 .…”

Section: Discussionmentioning

confidence: 99%

Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal–metal bond

et al. 2019

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Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4 f 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 Ln 2 @C 80 (CH 2 Ph) dimetallofullerenes (Ln 2 = Y 2 , Gd 2 , Tb 2 , Dy 2 , Ho 2 , Er 2 , TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4 f moments and a single electron residing on the metal–metal bonding orbital. Tb 2 @C 80 (CH 2 Ph) 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 Ln 2 @C 80 (CH 2 Ph) is redox active, enabling electrochemical tuning of the magnetism.

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Section: Valence State Of Lanthanides In Metallofullerenesmentioning

confidence: 99%

Single-Electron Lanthanide-Lanthanide Bonds Inside Fullerenes toward Robust Redox-Active Molecular Magnets

et al. 2019

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ConspectusA characteristic phenomenon of lanthanide–fullerene interactions is the transfer of metal valence electrons to the carbon cage. With early lanthanides such as La, a complete transfer of six valence electrons takes place for the metal dimers encapsulated in the fullerene cage. However, the low energy of the σ-type Ln–Ln bonding orbital in the second half of the lanthanide row limits the Ln2 → fullerene transfer to only five electrons. One electron remains in the Ln–Ln bonding orbital, whereas the fullerene cage with a formal charge of −5 is left electron-deficient. Such Ln2@C80 molecules are unstable in the neutral form but can be stabilized by substitution of one carbon atom by nitrogen to give azafullerenes Ln2@C79N or by quenching the unpaired electron on the fullerene cage by reacting it with a chemical such as benzyl bromide, transforming one sp2 carbon into an sp3 carbon and yielding the monoadduct Ln2@C80(CH2Ph). Because of the presence of the Ln–Ln bonding molecular orbital with one electron, the Ln2@C79N and Ln2@C80(R) molecules feature a unique single-electron Ln–Ln bond and an unconventional +2.5 oxidation state of the lanthanides.In this Account, which brings together metallofullerenes, molecular magnets, and lanthanides in unconventional valence states, we review the progress in the studies of dimetallofullerenes with single-electron Ln–Ln bonds and highlight the consequences of the unpaired electron residing in the Ln–Ln bonding orbital for the magnetic interactions between Ln ions. Usually, Ln···Ln exchange coupling in polynuclear lanthanide compounds is weak because of the core nature of 4f electrons. However, when interactions between Ln centers are mediated by a radical bridge, stronger coupling may be achieved because of the diffuse nature of radical-based orbitals. Ultimately, when the role of a radical bridge is played by a single unpaired electron in the Ln–Ln bonding orbital, the strength of the exchange coupling is increased dramatically. Giant exchange coupling in endohedral Ln2 dimers is combined with a rather strong axial ligand field exerted on the lanthanide ions by the fullerene cage and the excess electron density localized between two Ln ions. As a result, Ln2@C79N and Ln2@C80(CH2Ph) compounds exhibit slow relaxation of magnetization and exceptionally high blocking temperatures for Ln = Dy and Tb. At low temperatures, the [Ln3+–e–Ln3+] fragment behaves as a single giant spin. Furthermore, the Ln–Ln bonding orbital in dimetallofullerenes is redox-active, which allows its population to be changed by electrochemical reactions, thus changing the magnetic properties because the change in the number of electrons residing in the Ln–Ln orbital affects the magnetic structure of the molecule.

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Redox-active metal–metal bonds between lanthanides in dimetallofullerenes

Cited by 19 publications

References 49 publications

Crystallographic and Theoretical Investigations of Er₂@C_2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Crystallographic and Theoretical Investigations of Er₂@C_2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal–metal bond

Single-Electron Lanthanide-Lanthanide Bonds Inside Fullerenes toward Robust Redox-Active Molecular Magnets

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Redox-active metal–metal bonds between lanthanides in dimetallofullerenes

Cited by 19 publications

References 49 publications

Crystallographic and Theoretical Investigations of Er2@C2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Crystallographic and Theoretical Investigations of Er2@C2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal–metal bond

Single-Electron Lanthanide-Lanthanide Bonds Inside Fullerenes toward Robust Redox-Active Molecular Magnets

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Crystallographic and Theoretical Investigations of Er₂@C_2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature

Crystallographic and Theoretical Investigations of Er₂@C_2 n (2 n=82, 84, 86): Indication of Distance‐Dependent Metal–Metal Bonding Nature