Significant Roles of a Particularly Stable Two-Center Two-Electron Lu–Lu σ Bond in Lu₂@C₈₆: Electronic Structure of Lu and Radius of Lu²⁺

Abstract

There is still dispute over the stability of endohedral metallofullerenes (EMFs) M2C2n , and recently, multiform lutetium-based dimetallofullerenes have been dropped in experiments. The thermodynamic stabilities of Lu2C86 EMFs are revealed by density functional theory (DFT) in conjunction with statistical thermodynamic analyses. Inevitably, besides the experimentally reported Lu2@C 2v (63751)-C86, Lu2@C s (63750)-C86, and Lu2@C s (63757)-C86, other three metal carbide clusterfullerenes, Lu2C2@D 2d (51591)-C84, Lu2C2@C 1(51383)-C84, and Lu2C2@C s (id207430)-C84, rather than Lu2@C86 are first characterized as thermodynamically stable isomers of Lu2C86. Specially, the C s (id207430)-C84 is a newly non-classical fullerene containing one heptagon, which is stabilized via encaging Lu2C2. Another interesting phenomenon is that the outer fullerene cages of thermodynamically stable Lu2C82–88 molecules are geometrically connected through C2 addition/loss and Stone-Wales (SW) transformation, suggesting a special relationship between thermodynamic stabilities and geometries of Lu2C82–88 EMFs. Furthermore, the electronic configurations of (Lu2)4+@C86 4– and (Lu2C2)4+@C84 4– were confirmed. A significantly stable two-center two-electron (2c-2e) Lu–Lu σ single bond is formed in Lu2@C86. By comparing M–M bonds in M2@C 2v (63751)-C86 (M = Sc, Y, La, and Lu), two significant factors, the valence atomic orbital (ns) of metal atoms and radius of M2+, are found to determine the stability of the M–M bond in the C 2v (63751)-C86. Additionally, the simulated UV–vis–NIR spectra of thermodynamically stable Lu2C86 isomers were simulated, which further disclose their electronic features.

Stabilities, Geometries, Electronic Structures, and Conversion Rules of Carbide Cluster Metallofullerenes

“…We calculated statistically thermodynamic abundance of the isomers of the series within the fullerene‐formation temperature. For example, the stability of di‐EMFs Lu 2 C 86 , [67] Lu 2 C 84 , [68] and La 2 C 96 [90] has been successfully predicted (Figure 3). Due to the high thermodynamic stability, the several CCMFs, including Lu 2 C 2 @ C s (39715)‐C 82 , Lu 2 C 2 @ C 2 v (39718)‐C 82 , and Lu 2 C 2 @ C 2 v (39717)‐C 82 , [68] have been predicted as possible products in experiment.…”

“…Particularly, both the classical fullerenes with only pentagon and hexagon and several nonclassical fullerenes with one heptagon or tetragon can be stabilized as CCMFs. The first example of an endohedral carbide fullerene with a heptagon on the carbon cage is Sc 2 C 2 @ C s (hept)‐C 88 , [37] followed by the isolation and characterization of non‐classical Lu 2 C 2 @ C s (207430)‐C 84 [67] . This shows the importance of non‐classical fullerenes in CCMFs.…”

“…In most conventional M 2 @C 2 n , the M 2 cluster formally transfers four electrons to the fullerene cage, while each metal atom contributes one electron to form a two‐center two‐electron (2c–2e) M−M σ‐bond [67] . When the M 2 cluster is in large fullerene cage, there is also a two‐center one‐electron (2c–1e) M−M bond, such as 2c–1e La−La bond in La 2 @ C 2 (153476)‐C 94 and La 2 @ C s (153480)‐C 94 [91] .…”

An unprecedented C80 cage that violates the isolated pentagon rule

“…PBE has been previously proved as a suitable functional for lutetium-based metallofullerenes. 37 Statistic thermodynamic analysis including the entropy-enthalpy effect was carried out to determine the thermodynamically stable Lu 2 O@C 80 isomers based on PBE/6-31G(d)∼SDD. Furthermore, single point calculations were conducted for thermodynamically stable Lu 2 O@C 80 isomers on PBE/6-311G(d,p)∼def2TZVP, where 6-311G(d,p) was for carbon and oxygen atoms and the def2TZVP basis set with a small-core relativistic pseudopotential (14s13p10d8f6g)/[6s6p5d4f3g] was for lutetium atoms.…”

Ultraviolet Photodetectors Based on Dimetallofullerene Lu2@Cs(6)-C82 Nanorods

“…In this work, we report the exploration of a single Lu 2 @ C s (6)-C 82 nanorod ultraviolet photodetector. The prior studies have succeeded in the synthesis and characterization of Lu 2 @ C s (6)-C 82 and focused on the metal–metal bonding behavior in the fullerene cages. , However, the synthesis of single-crystalline materials and their studies in the fields of optoelectronics have not yet been explored. Herein, a liquid–liquid interfacial precipitation (LLIP) method was applied to obtain uniform single-crystalline Lu 2 @ C s (6)-C 82 nanorods with carbon disulfide (CS 2 ) as the good solvent and isopropanol (IPA) as the antisolvent, respectively.…”