Electrode-Supported Endohedral Metallofullerenes: Insights into the Confined Internal Dynamics

Endohedral metallofullerenes show great promise as molecular-scale memory units due to their robust architecture and protective capability for encapsulated atoms. However, the flat potential-energy surface within the cage often results in a severe disorder of encapsulated atoms. Here, we focused on prototypical systems involving Li@C60 on metallic surfaces, emphasizing the electrode's confinement effect on caged dynamics. We demonstrated that the varying interfacial stabilities induced by Li motion predominantly depend on the synergetic effect of van der Waals forces and covalent bonds rather than the previously assumed electrostatic interactions. We unveiled that the repulsion effect between encapsulated atom and the metal electrode primarily arises from the antibonding states between the metal states below the Fermi level and the degenerated frontier orbitals from HOMO-4 to HOMO. By manipulating orbital interactions, we observed an ordered arrangement of the encapsulated atom on Rec-Pt(111) at room temperature. Furthermore, our findings underscore the disruptive influence of electric fields on the stability of distinct Li positions, a phenomenon closely tied to the dipole moment induced by Li motion. This research provides a new perspective on the confined internal dynamics of endohedral metallofullerenes by manipulating cage-electrode interactions, contributing to precisely controlled molecular electronics.

Overlooked Effects of La-4f Orbitals in Endohedral Metallofullerenes

For endohedral metallofullerenes (EMFs), a central issue is how to correctly describe the intracluster and metal-cage interactions, which are critical for understanding their structures, stabilities, and various properties. In this work, density functional theory calculations were carried out for 13 La-based EMFs covering all four reported types and a rather wide cage size range (C₃₂-C₁₀₄). The results reveal that the usually core-like lanthanide 4f subshell may play a critical role in the structural characteristics, energetic stabilities, frontier orbital energy levels, metal charges, and chemical reactivities of these endofullerenes. Regardless of the encapsulated forms, the La-4f contributions to the chemical bonding and structural stability increase with the reduced cage sizes because of the gradually enhanced cage confinement. The combination of metal-to-nonmetal charge transfer and compression of the cage cavity exposes and effectively activates the otherwise chemically inert 4f orbitals. By disclosing the important role of long-neglected metal orbitals inside fullerenes, the current work not only deepens our understanding of EMFs, but also provides new insights into the chemical bondings in general confined spaces at the subnanometer scale.

Computational mining of endohedral C70 electrides: tri-metal alkali and alkaline-earth encapsulation

Based on the atoms in molecules analysis, electron localization functions, and nonlinear optical property analysis, M3@C70 (M = Li, Be, Mg, Ca) fullerenes are identified as electrides.

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

There is still dispute over the stability of endohedral metallofullerenes (EMFs) M₂C_2n, 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@C₁(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 Lu₂C_82-88 molecules are geometrically connected through C₂ addition/loss and Stone-Wales (SW) transformation, suggesting a special relationship between thermodynamic stabilities and geometries of Lu₂C_82-88 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.

Lithium–bromine exchange reaction on C60: first theoretical proposal of a stable singlet fullerene carbene without the heteroatom

A stable singlet fullerene carbene without heteroatom is firstly proposed, and two indexes are firstly suggested to estimate the occurrence of carbene insertion or addition. The interaction between LiBr and carbon atom in LiBr-compounds is explored.