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1.
Nat Commun ; 10(1): 571, 2019 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-30718550

RESUMO

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.

2.
Angew Chem Int Ed Engl ; 57(1): 277-281, 2018 01 02.
Artigo em Inglês | MEDLINE | ID: mdl-29119650

RESUMO

The endohedral fullerene Y3 N@C80 exhibits luminescence with reasonable quantum yield and extraordinary long lifetime. By variable-temperature steady-state and time-resolved luminescence spectroscopy, it is demonstrated that above 60 K the Y3 N@C80 exhibits thermally activated delayed fluorescence with maximum emission at 120 K and a negligible prompt fluorescence. Below 60 K, a phosphorescence with a lifetime of 192±1 ms is observed. Spin distribution and dynamics in the triplet excited state is investigated with X- and W-band EPR and ENDOR spectroscopies and DFT computations. Finally, electroluminescence of the Y3 N@C80 /PFO film is demonstrated opening the possibility for red-emitting fullerene-based organic light-emitting diodes (OLEDs).

3.
Nanoscale ; 9(23): 7977-7990, 2017 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-28574078

RESUMO

Lanthanide-lanthanide bonds are exceptionally rare, and dimetallofullerenes provide a unique possibility to stabilize and study these unusual bonding patterns. The presence of metal-metal bonds and consequences thereof for the electronic properties of M2@C82 (M = Sc, Er, Lu) are addressed by electrochemistry, electron paramagnetic resonance, SQUID magnetometry and other spectroscopic techniques. A simplified non-chromatographic separation procedure is developed for the isolation of Er2@C82 (Cs(6) and C3v(8) cage isomers) and Sc2@C82 (C3v(8) isomer) from fullerene mixtures. Sulfide clusterfullerenes Er2S@C82 with Cs(6) and C3v(8) fullerene cages are synthesized for the first time. The metal-metal bonding orbital of the spd hybrid character in M2@C82 is shown to be the highest occupied molecular orbital, which undergoes reversible single-electron oxidation with a metal-dependent oxidation potential. Sulfide clusterfullerenes with a fullerene-based HOMO have more positive oxidation potentials. The metal-based oxidation of Sc2@C82-C3v is confirmed by the EPR spectrum of the cation radical [Sc2@C82-C3v]+ generated by chemical oxidation in solution. The spectrum exhibits an exceptionally large a(45Sc) hyperfine coupling constant of 199.2 G, indicating a substantial 4s contribution to the metal-metal bonding orbital. The cationic salt [Er2@C82-C3v]+SbCl6- is prepared, and its magnetization behavior is compared to that of pristine Er2@C82-C3v and Er2S@C82-C3v. The formation of the single-electron Er-Er bond in the cation dramatically changes the coupling between magnetic moments of Er ions.

4.
Angew Chem Int Ed Engl ; 54(45): 13411-5, 2015 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-26350440

RESUMO

The use of methane as a reactive gas dramatically increases the selectivity of the arc-discharge synthesis of M-Ti-carbide clusterfullerenes (M=Y, Nd, Gd, Dy, Er, Lu). Optimization of the process parameters allows the synthesis of Dy2TiC@C80-I and its facile isolation in a single chromatographic step. A new type of cluster with an endohedral acetylide unit, M2TiC2@C80, is discovered along with the second isomer of M2TiC@C80. Dy2TiC@C80-(I,II) and Dy2TiC2@C80-I are shown to be single-molecule magnets (SMM), but the presence of the second carbon atom in the cluster Dy2TiC2@C80 leads to substantially poorer SMM properties.

5.
Chemistry ; 18(31): 9691-8, 2012 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-22745152

RESUMO

The synthesis, isolation and spectroscopic characterization of holmium-based mixed metal nitride clusterfullerenes Ho(x) Sc(3-x) N@C(80) (x=1, 2) are reported. Two isomers of Ho(x) Sc(3-x) N@C(80) (x=1, 2) were synthesized by the reactive gas atmosphere method and isolated by multistep recycling HPLC. The isomeric structures of Ho(x) Sc(3-x) N@C(80) (x=1, 2) were characterized by laser-desorption time-of-flight (LD-TOF) mass spectrometry and UV/Vis/NIR, FTIR and Raman spectroscopy. A comparative study of M(x) Sc(3-x) N@C(80) (M=Gd, Dy, Lu, Ho) demonstrates the dependence of their electronic and vibrational properties on the encaged metal. Despite the distinct perturbation induced by 4f(10) electrons, we report the first paramagnetic (13) C NMR study on Ho(x) Sc(3-x) N@C(80) (I; x=1, 2) and confirm I(h) -symmetric cage structure. A (45) Sc NMR study on HoSc(2) N@C(80) (I, II) revealed a temperature-dependent chemical shift in the temperature range of 268-308 K.

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