Design and structural characterization of the all-metal aromatic sandwich species [Bi3Au3Bi3]3−: insight from density functional theory

Abstract

The synthesis of the first all-metal aromatic sandwich by Pan et al. (J. Am. Chem. Soc., 2015, 137, 10954) was an important breakthrough in chemistry and is indicative of the possible existence of other similar complexes. In this study, an all-metal aromatic sandwich species with D_3h symmetry, [Bi₃Au₃Bi₃]³⁻, was designed and investigated via density functional theory. Analysis of the bonding nature indicated that the Bi–Bi bond is a nonpolar σ covalent bond, which is mainly attributed to the p orbitals of Bi atoms; the Bi–Au bond is a polar σ covalent bond, which mainly consists of 6s AOs of Au and 6p_z AOs of Bi; and the Au–Au bond has a typical aurophilic interaction dominated by 5s_Au→6p_Au character. Furthermore, charge decomposition analysis indicated an intermolecular electron transfer between cyclo-Bi₃ and cyclo-Au₃ that explained the weak Jahn–Teller effect in cyclo-Bi₃. In addition, the large E_gap and small ΔE^avg_R indicated the stability and potential application of the species as a semiconductor material. Nucleus-independent chemical shift values and molecular orbital analysis indicated that cyclo-Bi₃ constitutes uncommon multiple aromaticity (both σ and π aromaticities), and cyclo-Au₃ has conflicting aromaticity (σ and δ aromaticity and weak π antiaromaticity).