Toward Controlling the Electronic Structures of Chemically Modified Superatoms of Gold and Silver

Abstract

Atomically precise gold/silver clusters protected by organic ligands L, [(Au/Ag)xLy]z, have gained increasing interest as building units of functional materials because of their novel photophysical and physicochemical properties. The properties of [(Au/Ag)xLy]z are intimately associated with the quantized electronic structures of the metallic cores, which can be viewed as superatoms from the analogy of naked Au/Ag clusters. Thus, establishment of the correlation between the geometric and electronic structures of the superatomic cores is crucial for rational design and improvement of the properties of [(Au/Ag)xLy]z. This review article aims to provide a qualitative understanding on how the electronic structures of [(Au/Ag)xLy]z are affected by geometric structures of the superatomic cores with a focus on three factors: size, shape, and composition, on the basis of single‐crystal X‐ray diffraction data. The knowledge accumulated here will constitute a basis for the development of ligand‐protected Au/Ag clusters as new artificial elements on a nanometer scale.

Ligand-protected gold/silver superatoms: current status and emerging trends

“…2 shows the icosahedral and decahedral (Au/Ag) X (n*e) cores found in representative Au/Ag MPCs: Au 4 (2e), Au 11 (8e), Au 13 (8e), Ag 13 (8e), Ag 32 (18e), Ag 28 (20e), Ag 38 (20e), Au 79 (58e) and Ag 103 (58e). 41 The n* values of these cores agree with those predicted for spherical superatoms. Therefore, these isolated Au/Ag MPCs with spherical shapes can be viewed as chemically-modified Au/Ag superatoms with closed electronic structures.…”

Controlled Dimerization and Bonding Scheme of Icosahedral M@Au12 (M=Pd, Pt) Superatoms

“… [4] Cluster 1 has a bi‐icosahedral Pd 2 Au 21 core, in which two Pd dopants exclusively occupy the centers of individual icosahedral moieties (Figure 1 a). This result supports the previous theoretical predictions [18, 20, 21, 24] and reflects the ubiquitous nature of the preferential site of group 10 element in the Au superatoms [2, 15–24, 30] . Clusters 2 and 3 consist of the bi‐icosahedral PdPtAu 21 and Pt 2 Au 21 cores, respectively, protected by six Au 2 (PET) 3 and three Au 1 (PET) 2 units (Figures 1 b and c).…”

“…Namely, the Pd 2 Au 21 core of 1 is in the singlet spin state, in contrast to the triplet state for O 2 . We conclude that the electron configurations of MM′Au 21 differ significantly from that of O 2 , in contrast to the close correspondence between those of Au 23 and F 2 [11, 13, 17] …”

“…The position of Pt dopant could not be determined unambiguously because of the similarity of the electron density between Au and Pt. However, the reported structures of related systems such as [PtAu 24 (SR) 18 ] 0 and [PtAu 24 (C≡CR) 18 ] 2− led us to conclude that the Pt dopant occupies the central position of the icosahedral units [15–17, 21–24, 30, 33–36] . In summary, the cores of 1 – 3 are homo‐ and hetero‐dimers of Pd@Au 12 and Pt@Au 12 icosahedrons.…”

“…Alternatively, the Au 23 (14e) core can be viewed as a dimer of icosahedral Au 13 (7e) by sharing an Au 3 facet according to the super valence bond (SVB) model [11, 12] . The electron configuration is expressed as (1Σ) 2 (1Σ*) 2 (1Π) 4 (2Σ) 2 (1Π*) 4 , where individual orbitals are made by bonding and antibonding interactions of 1S and 1P superatomic orbitals (SOs) of Au 13 (7e) [3, 11–17] . In terms of electron configuration, the Au 23 (14e) core is analogous to a F 2 molecule.…”