[Au₁₂(SR)₆]²⁻, As Smaller 8‐Electron Gold Nanocluster Retaining an SP³‐Core. Evaluation of Bonding and Optical Properties from Relativistic DFT Calculations

Abstract

Exploring the versatility of atomically precise clusters is a relevant issue in the design of functional nanostructures. Superatomic clusters offer an ideal framework to gain further understanding of the different distinctive size-dependent physical and chemical properties. Here, we propose [Au (SR) ] as a minimal 8-electron superatom related to the prototypical [Au (SR) ] cluster, depicting half of its core-mass (2.3 kDa vs 5.0 kDa). The [Au (SMe) ] cluster fulfills a 1S 1P electronic configuration, with a distorted tetrahedral Au core further viewed as an SP -hybridized superatom. The distinctive optical properties show a blue-shift for the first relevant 1P→1D transition, in comparison to [Au (SR) ] . In addition, chiroptical activity is observed, denoting intrinsic core chirality. We expect that our results can shed light into the variation of the molecular properties according to the size-dependent properties, and serve as guidelines for further experimental exploration of minimal or ultrasmall nanoclusters.

Bonding and properties of superatoms. Analogs to atoms and molecules and related concepts from superatomic clusters

“…[100] Recently, Muñoz-Castro and Saillard, proposed a small 8-e cluster given by Au 12 (SR) 6 2− , which exhibits a inner SP3-core. [101] In addition to the structural evaluation, electronic, optical, and chiroptical properties were calculated. Such species are desirable for the understanding of the size-dependent properties displayed by ligandprotected gold clusters, finding plausible candidates for explorative synthetic efforts (Figure 4).…”

“…Tlahuice‐Flores explored several candidates for two families of small thiolated gold clusters given by [Au n (SR) m ] + ( n = 12‐15, m = 9‐12) and Au n (SR) m ( n = 16‐20, m = 12‐16), displaying a 2‐e and 4‐e electronic shell structures (Figure ) . Recently, Muñoz‐Castro and Saillard, proposed a small 8‐e cluster given by Au 12 (SR) 6 2− , which exhibits a inner SP3‐core . In addition to the structural evaluation, electronic, optical, and chiroptical properties were calculated.…”

Evidence for the Superatom–Superatom Bonding from Bond Energies

“…47−51 A recent study reveals the 8e ligand-protected [Au 12 (SR) 6 ] 2 cluster with the sp 3 core, which exhibits the special bonding and optical properties. 52 The SVB model reveals various bonding patterns between superatoms depending on the shape of orbitals. However, bond energy corresponding to the bond order is another key parameter for chemical bonding which has not been discussed for superatomic molecules before.…”

Superatomic Orbital Splitting in Coinage Metal Nanoclusters

“…Cheng and Yang suggested a superatom-network (SAN) constructed by similar subclusters. Following Mulliken’s methodology, through analyzing linear combination of subcluster’s superatomic orbitals, Cheng and Yang (super valence bond (SVB)), Mingos, Muñoz-Castro, and Saillard et al investigated the bonding among subclusters of superatomic molecules with density function theory (DFT), − in which the superatomic molecular orbitals from these subclusters can also be understood as the whole cluster’s superatomic orbitals. Another example is “shell by shell” structures proposed by Teo and Yang , in the jelliumatic shell model (JSM).…”