title: How Can We Understand Au8 Cores and Entangled Ligands of Selenolate- and Thiolate-Protected Gold Nanoclusters Au24(ER)20 and Au20(ER)16 (E = Se, S; R = Ph, Me)? A Theoretical Study.
abstract: The geometries and electronic structures of selenolate-protected Au nanoclusters, Au24(SeR)20 and Au20(SeR)16, and their thiolate analogues are theoretically investigated with DFT and SCS-MP2 methods, to elucidate the electronic structure of their unusual Au8 core and the reason why they have the unusual entangled "staple-like" chain ligands. The Au8 core is understood to be an [Au4](2+) dimer in which the [Au4](2+) species has a tetrahedral geometry with a closed-shell singlet ground state. The SCS-MP2 method successfully reproduced the distance between two [Au4](2+) moieties, but the DFT with various functionals failed it, suggesting that the dispersion interaction is crucial between these two [Au4](2+) moieties. The SCS-MP2-calculated formation energies of these nanocluster compounds indicate that the thiolate staple-like chain ligands are more stable than the selenolate ones, but the Au8 core more strongly coordinates with the selenolate staple-like chain ligands than with the thiolate ones. Though Au20(SeR)16 has not been reported yet, its formation energy is calculated to be large, suggesting that this compound can be synthesized as a stable species if the concentration of Au(SeR) is well adjusted. The aurophilic interactions between the staple-like chain ligands and between the Au8 core and the staple-like chain ligand play an important role for the stability of these compounds. Because of the presence of this autophilic interaction, Au24(SeR)20 is more stable than Au20(SeR)16 and the unusual entangled ligands are involved in these compounds.
authors.affiliation: †Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8245, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Takagi
authors.affiliation: ‡Institute for Molecular Science (IMS), Okazaki 444-8585, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ishimura
authors.affiliation: †Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8245, Japan.
authors.forename: Masafuyu
authors.initials: M
authors.lastname: Matsui
authors.affiliation: †Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8245, Japan.|‡Institute for Molecular Science (IMS), Okazaki 444-8585, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Fukuda
authors.affiliation: §RIKEN Advanced Institute for Computational Science (AICS), Kobe 657-0047, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Matsui
authors.affiliation: §RIKEN Advanced Institute for Computational Science (AICS), Kobe 657-0047, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Nakajima
authors.affiliation: †Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8245, Japan.|‡Institute for Molecular Science (IMS), Okazaki 444-8585, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ehara
authors.affiliation: †Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Kyoto 615-8245, Japan.|∥Fukui Institute for Fundamental Chemistry (FIFC), Kyoto University, Kyoto 606-8103, Japan.|⊥CREST, Japan Science and Technology Agency (JST), Tokyo 102-0076, Japan.
authors.forename: Shigeyoshi
authors.initials: S
authors.lastname: Sakaki