title: [Sb4Au4Sb4](2-): A designer all-metal aromatic sandwich.
abstract: We report on the computational design of an all-metal aromatic sandwich, [Sb4Au4Sb4](2-). The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb4](+)[Au4](4-)[Sb4](+), showing ionic bonding characters with electron transfers in between the Sb4/Au4/Sb4 layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ← Au back-donation occur, redistributing electrons from the Sb4/Au4/Sb4 layers to the interlayer Sb-Au-Sb edges, which effectively lead to four Sb-Au-Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb4](+) ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ∼1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts.
authors.affiliation: Nanocluster Laboratory, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
authors.forename: Wen-Juan
authors.initials: WJ
authors.lastname: Tian
authors.affiliation: Department of Chemistry, Xinzhou Teachers University, Xinzhou 034000, China.
authors.forename: Jin-Chang
authors.initials: JC
authors.lastname: Guo
authors.affiliation: Department of Chemical Engineering, Binzhou University, Binzhou 256603, China.
authors.forename: Da-Zhi
authors.initials: DZ
authors.lastname: Li
authors.affiliation: Nanocluster Laboratory, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
authors.forename: Xue-Rui
authors.initials: XR
authors.lastname: You
authors.affiliation: Nanocluster Laboratory, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
authors.forename: Ying-Jin
authors.initials: YJ
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
authors.forename: Zhong-Ming
authors.initials: ZM
authors.lastname: Sun
authors.affiliation: Nanocluster Laboratory, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
authors.forename: Hua-Jin
authors.initials: HJ
authors.lastname: Zhai