Heterodimerization via the Covalent Bonding of Ta@Si₁₆ Nanoclusters and C₆₀ Molecules

Abstract

Initial products prepared via the surface immobilization of Ta-atom-encapsulated Si 16 cage (Ta@Si 16 ) nanoclusters on solid surfaces terminated with monolayer films of C 60 molecules were investigated using scanning tunneling microscopy (STM). The STM results indicated that marked aggregation and desorption of surface-immobilized Ta@Si 16 nanoclusters were not induced, even after thermal annealing at ∼500 K, whereas the local vertical and lateral positions of the Ta@Si 16 nanoclusters with respect to neighboring adsorption sites in the C 60 film were modified. This local positional transition occurred on C 60 monolayer films weakly bonded (via van der Waals forces) to substrates such as highly oriented pyrolytic graphite (HOPG) but did not occur on C 60 monolayer films covalently bonded to substrates such as Si(111)7 × 7. These results indicated that the heterodimer consisting of a Ta@Si 16 nanocluster and a C 60 molecule, Ta@Si 16 −C 60 , was formed as an initial product via covalent bonding, which inhibited wide-range surface migration of the Ta@Si 16 nanoclusters but allowed them to locally change their positions via thermally activated precessional motion. In addition, the transition temperature of the local positional shift was found to decrease as the area density of the surface-immobilized Ta@Si 16 nanoclusters increased, indicating that the barrier height of the precessional motion of the Ta@Si 16 −C 60 heterodimer was decreased due to accumulation of the elastic strain energy generated in the C 60 films.

Charge Transfer Complexation of Ta-Encapsulating Ta@Si16 Superatom with C60

“…Based on the principle of 68 electron shell closure, 12−14 the Ta@Si 16 nanocluster exhibits an alkali-like superatomic behavior, which promotes the release of one electron to produce the electronically stabilized monocation (Ta@Si 16 ) + . From the stoichiometric viewpoint, indeed, previous STM results have shown that the uppermost C 60 molecules provided a favorable adsorption site at deposition densities approximating 1 ML, 20 suggesting that Ta@Si 16 interacted with C 60 in a one-to-one manner. Since C 60 displays high electron acceptability, 34 the deposited Ta@Si 16 may be stabilized by formation of a superatomic CT complex of (Ta@Si 16 ) + C 60 − .…”

“…Nakaya et al have recently observed an individual alkali-like Ta@Si 16 nanocluster on ordered electron-acceptable C 60 molecular film by scanning tunneling microscopy (STM), consistent with nanocluster immobilization. Furthermore, Ta@Si 16 readily forms the stoichiometric one-to-one Ta@Si 16 C 60 complex on C 60 films. , However, its exact chemical state, which is crucial for the treatment of M@Si 16 nanocluster-based CT complexes stabilized by counter molecules, remains unclear.…”

Li8Si8, Li10Si9, and Li12Si10: Assemblies of Lithium‐Silicon Aromatic Units

“…In this respect, it is worth mentioning the transition metal (M) encapsulating silicon super atoms, M@Si 16 , which have been probed in the gas‐phase molecular beam, and predicted by quantum chemical calculations, but not yet isolated [51] . However, the structure of surface‐immobilized M@Si 16 clusters has been elucidated using scanning probe microscopy and photoelectron spectroscopy, glimpsing a way toward future functional materials in the solid state [51–53] …”

Structural evolution and bonding of phosphorus-doped silicon clusters SinPm−/0/+ with n = 1–10, m = 1, 2

“…For example, MSi 16 clusters (M = Sc, Ti and V), which are of high symmetry and stability, were theoretically predicted to form stable hetero-oligomers ScSi 16 -VSi 16 and ScSi 16 -TiSi 16 -VSi 16 [19]. Additionally, TaSi 16 cluster can contact with C 60 cluster through covalence bond and thereby form TaSi 16 -C 60 dimer [20]. On basis of BeSi 12 hexagonal prism, a metalsilicon tubular structure was synthetized [21].…”