Sc₂O@C_2v(5)-C₈₀: Dimetallic Oxide Cluster Inside a C₈₀ Fullerene Cage

Abstract

A new oxide cluster fullerene, Sc2O@C(2v)(5)-C80, has been isolated and characterized by mass spectrometry, UV-vis-NIR absorption spectroscopy, cyclic voltammetry, (45)Sc NMR, DFT calculations, and single crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage symmetry was assigned to C(2v)(5)-C80 and suggests that the Sc2O cluster is ordered inside the cage. The crystallographic data further reveals that the Sc1-O-Sc2 angle is much larger than that found in Sc2O@T(d)(19151)-C76 but almost comparable to that in Sc2O@Cs(6)-C82, suggesting that the endohedral Sc2O unit is flexible and can display large variation in the Sc-O-Sc angle, which depends on the size and shape of the cage. Computational studies show that there is a formal transfer of four electrons from the Sc2O unit to the C80 cage, i.e., (Sc2O)(4+)@(C80)(4-), and the HOMO and LUMO are mainly localized on the C80 framework. Moreover, thermal and entropic effects are seen to be relevant in the isomer selection. Comparative studies between the recently reported Sc2C2@C(2v)(5)-C80 and Sc2O@C(2v)(5)-C80 reveal that, despite their close structural resemblance, subtle differences exist on the crystal structures, and the clusters exert notable impact on their spectroscopic properties as well as interactions between the clusters and corresponding cages.

Crystallographic characterization of Lu2C2n (2n = 76–90): cluster selection by cage size

“…Finally, the molecular structures of Lu 2 C 2 n (2 n = 76, 78, 80, 84, 86, 88, 90) isomers were unambiguously determined by single-crystal X-ray diffraction (XRD) crystallography to be Lu 2 @ T d (2)-C 76 , Lu 2 @ D 3h (5)-C 78 , Lu 2 @ C 2v (5)-C 80 , Lu 2 @ C 2v (7)-C 84 , Lu 2 @ C s (8)-C 86 , Lu 2 @ C s (15)-C 86 , Lu 2 @ C 1 (26)-C 88 , Lu 2 C 2 @ C 2v (9)-C 86 , Lu 2 C 2 @ C s (32)-C 88 and Lu 2 C 2 @ D 2 (35)-C 88 , respectively, taking advantage of the high-quality of the co-crystals of Lu 2 C 2 n /Ni II (OEP) (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrin dianion). Although Lu 2 @ T d (2)-C 76 was first isolated and confirmed to have a T d -symmetric cage according to 13 C NMR spectroscopic studies in combination with scanning tunneling microscopy results,44 and D 3h (5)-C 78 , C 2v (5)-C 80 , C 2v (9)-C 86 and D 2 (35)-C 88 cages were obtained and crystallographically characterized for EMFs possessing the same cage symmetry, such as Sc 2 O@ D 3h (5)-C 78 ,45 Sc 2 O@ C 2v (5)-C 80 ,12 Sc 2 C 2 @ C 2v (9)-C 86 (ref. 36) and Sm 2 @ D 2 (35)-C 88 ,40 it is noteworthy that the cages of C 2v (7)-C 84 , C s (8)-C 86 , C s (15)-C 86 , C 1 (26)-C 88 and C s (32)-C 88 have never been experimentally reported before in spite of the fact that Sc 2 O@ C 2v (7)-C 84 was theoretically predicted without further experimental evidence 46…”

“…Putting metal atoms or metallic clusters into fullerenes has generated a new class of novel hybrid molecules, defined as endohedral metallofullerenes (EMFs), possessing novel structures and fascinating properties which are different from those of empty fullerenes 1–4. During the last three decades, EMFs containing different metallic clusters, including metal nitride (M 3 N),5,6 metal carbide (M 2 C 2 /M 3 C 2 /M 4 C 2 ),7–9 metal sulfide (M 2 S),10,11 metal oxide (M 2 O/M 4 O 2 /M 4 O 3 )12–14 and metal cyanide (M 3 CN/MCN)15–17 clusters, have been structurally characterized in addition to the conventional EMFs containing only metal atoms (M/M 2 /M 3 ) 18–20…”

Crystallographic characterization of Y2C2n (2n = 82, 88–94): direct Y–Y bonding and cage-dependent cluster evolution

“…[4][5][6] Traditional EMFs are those encapsulating one or two metal atoms, which transfer a certain number of electrons to the cage. 7,8 When multiple metal ions are introduced into the cages, a non-metal element is generally required to stabilize the whole cluster to form species such as a metal carbide, [9][10][11] nitride, 12,13 sulphide, 14 oxide [15][16][17] and even cyanide. 18,19 In principle, the positively charged metal ions suffer from strong Coulomb repulsion inside fullerene cages.…”

Pivotal Role of Nonmetal Atoms in the Stabilities, Geometries, Electronic Structures, and Isoelectronic Chemistry of Sc3X@C80 (X = C, N, and O)

“…Great efforts have been devoted to cluster‐EMFs owing to their peculiar structures and promising applications in various fields such as biomedicine and energy conversion, after the successful synthesis and isolation of the first cluster‐EMF Sc 3 N@C 80 by Stevenson et al . Afterward, an increasing number of cluster‐EMFs have been constantly investigated, such as Sc 3 N@C 2n (2n = 68, 78, and 82), Gd x Sc 3−x N@C 2n (2n = 78–86; x = 0, 1, 2, and 3), Gd x Lu 3− x N@C 80 ( x = 0, 1, 2, and 3), Sc 2 C 2 @C 2n (2n = 68, 72, 74, and 80–88), Sc 2 O@C 2n (2n = 70 and 76–82), Sc 3 O@C 80 , Sc 2 S@C 2n (70, 72, and 82), YNC@C 76 , Sc 3 CH@C 80 , and Sc 3 NC@C 2n (2n = 78 and 80) . It is evident that the effect, deriving from the metal atoms of inner moieties for M x Sc 3− x N@C 80 ( x = 0, 1, and 2), has been extensively concerned .…”