Synthesis and UHV-STM observation of the Td-symmetric Lu metallofullerene: Lu2@C76(Td)

Endohedral metallofullerenes (EMFs) are novel derivatives of fullerenes that can encapsulate metal atoms or clusters in their inner space.[1] Owing to their extraordinary properties attributed to significant electron transfer from the metal atoms to the fullerene cage, [2] EMFs have attracted wide interests since the discovery of fullerenes.[3] For instance, lanthanide metallofullerenes have been suggested for use as encapsulated contrasting agents for magnetic resonance imaging. [4] In EMFs, the internal metal atoms always donate electrons to the fullerene cage and carry considerable positive charges. It is interesting and highly significant to investigate the possible formation of metal-metal bonds between these metal atoms in EMFs. [5][6][7] From a theoretical point of view, the study of metal-metal bonds in EMFs gives an in-depth perspective of the metal-metal interaction and provides an approach for further experimental and theoretical explorations of metal-metal interactions. [6,8] On the other hand, in contrast to the fact that several kinds of metal-metal bonds have been studied, in other fields, [9] up to now only rare examples of metal-metal bonds are reported in fullerene chemistry.[7] Furthermore, the presence of metal-metal bonds produces unique structures and fascinating electronic properties of EMFs, which may extend their promising applications in electronics, magnetism, and photovoltaics. [7,10] Most importantly, previous studies have indicated that the encapsulated metal atoms can move around in fullerene cage at room temperature.[11] This dynamic motion makes it possible to design these EMFs as functional molecular devices with new magnetic and electronic properties. [12] It is also an interesting question whether other novel dynamic motion of the encapsulated metals exists in fullerene cage.Lots of efforts have been devoted to metal-metal bonds in EMFs during the past decades, but only a few single metal-metal bonds have been found and confirmed. [6][7][8][13][14][15] In fact, Stevenson et al. suggested the presence of a Sc À Sc bond between the shortest Sc À Sc distance with a newly experimentally determined structure of Sc 4 O 2 @C 80 .[14] Two kinds of metal-metal bonds have been found between Y atoms so far: one two-electron bond in the Y 2 @C 82 , [7] and another long single-electron bond in Y 2 @C 79 N.[15] In addition, a single-electron bond between Tb atoms was also proposed in Tb 2 @C 79 N.[15]Herein we present a thorough investigation on a newly isolated dimetallofullerene Lu 2 @C 76 , [16] and find that the two lutetium atoms prefer to bind together to form an unprecedented single metal-metal bond, in a formal valence state of [Lu 2 ] 4 + @C 76 4À by means of combined quantum chemical and statistical thermodynamic approaches. More interestingly, it is shown that the Lu atoms can hop rapidly between six equivalent configurations in the fullerene cage at room temperature, giving rise to a trajectory as a tetrahedron in C 76 (T d ). Systematic calculations on the di-, tetra-, he...

Section: àcontrasting

confidence: 61%

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confidence: 99%

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confidence: 99%

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Can a Metal–Metal Bond Hop in the Fullerene Cage?

Yang

Zhao

Ōsawa

2011

“…These features are very similart o those reported for Lu 2 @C 76 ,w hichs uggestsa ni denticalc age structure shared by the two endohedral fullerenes. [32] On the other hand, these absorption features are essentially different from those of DySc 2 N@C s (17490)-C 76 ,w hich indicates am ajor difference in the cage symmetry and the charge transfer between the clusters and outside carbon cages. [47] On the basis of absorption onset at 1587 nm, the optical bandgapo ft his compound was estimated to be 0.79 eV.B yu sing 1.0 eV as the limit to distinguish large-and small-bandgap fullerenes, we can assign this isomer of Sc 2 O@T d (19151)-C 76 as as mall-bandgap fullerene.…”

Section: Sc Nmr Spectroscopymentioning

confidence: 96%

“…[9] Among them,t he T d -C 76 carbon cage, which features the third highest symmetry after I h and I symmetry,h as attracted great interest. [32] Nevertheless,t hough several theoretical and spectroscopics tudies have been devoted to the characterization of T d -C 76 ,b esides af unctionalized C s -(T d -C 76 (CF 3 ) 12 ), [33] Lu 2 @T d -C 76 is the only discovered species so far. [32,[34][35][36] Moreover,t he studies of Lu 2 @T d -C 76 did not provide ad etailed structural analysis because of the lack of unambiguous single-crystal X-ray characterization.…”

Section: Introductionmentioning

confidence: 99%

Sc₂O@T_d(19151)‐C₇₆: Hindered Cluster Motion inside a Tetrahedral Carbon Cage Probed by Crystallographic and Computational Studies

Yang

Hao

Abella

et al. 2015

A new cluster fullerene, Sc2 O@Td (19151)-C76 , has been isolated and characterized by mass spectrometry, UV/Vis/NIR absorption, (45) Sc NMR spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction. The crystallographic analysis unambiguously assigned the cage structure as Td (19151)-C76 , which is the first tetrahedral fullerene cage characterized by single-crystal X-ray diffraction. This study also demonstrated that the Sc2 O cluster has a much smaller ScOSc angle than that of Sc2 O@Cs (6)-C82 and the Sc2 O unit is fully ordered inside the Td (19151)-C76 cage. Computational studies further revealed that the cluster motion of the Sc2 O is more restrained in the Td (19151)-C76 cage than that in the Cs (6)-C82 cage. These results suggest that cage size affects not only the shapes but also the cluster motion inside fullerene cages.

La₂@C_s(17 490)‐C₇₆: A New Non‐IPR Dimetallic Metallofullerene Featuring Unexpectedly Weak Metal–Pentalene Interactions

Suzuki¹,

Mizorogi²,

Yang³

et al. 2013

Although all the pure-carbon fullerene isomers above C60 reported to date comply with the isolated pentagon rule (IPR), non-IPR structures, which are expected to have different properties from those of IPR species, are obtainable either by exohedral modification or by endohedral atom doping. This report describes the isolation and characterization of a new endohedral metallofullerene (EMF), La2@C76, which has a non-IPR fullerene cage. The X-ray crystallographic result for the La2@C76/[Ni(II)(OEP)] (OEP=octaethylporphyrin) cocrystal unambiguously elucidated the C(s)(17,490)-C76 cage structure, which contains two adjacent pentagon pairs. Surprisingly, multiple metal sites were distinguished from the X-ray data, which implies dynamic behavior for the two La(3+) cations inside the cage. This dynamic behavior was also corroborated by variable-temperature (139)La NMR spectroscopy. This phenomenon conflicts with the widely accepted idea that the metal cations in non-IPR EMFs invariably coordinate strongly with the negatively charged fused-pentagon carbons, thereby providing new insights into modern coordination chemistry. Furthermore, our electrochemical and computational studies reveal that La2@C(s)(17,490)-C76 has a larger HOMO-LUMO gap than other dilanthanum-EMFs with IPR cage structures, such as La2@D(3h)(5)-C78 and La2@I(h)(7)-C80, which implies that IPR is no longer a strict rule for EMFs.