Photoelectron spectroscopy of aromatic compound clusters of the B12 all-boron benzene: B12Au− and B12(BO)−

Abstract

We report a photoelectron spectroscopy and density-functional theory study of the B₁₂Au⁻ and B₁₃O⁻ clusters and their neutrals, which are shown to be six π electron aromatic compounds between the quasi-planar all-boron B₁₂ benzene-analogue and a monovalent Au or BO ligand. Electron affinities of B₁₂Au and B₁₃O are measured to be 3.48 ± 0.04 and 3.90 ± 0.04 eV, respectively. Structural searches are performed for B₁₂Au⁻ and B₁₃O⁻, which are compared with the isovalent B₁₂H⁻ cluster. The global minima of B₁₂Au⁻ and B₁₃O⁻ both feature an almost intact B₁₂ cluster with the Au and BO ligands bonded to its periphery, respectively. For B₁₂Au⁻, a low-lying isomer is also identified, which is only 0.4 kcal mol⁻¹ above the global minimum, in agreement with the experimental observation of a weakly populated isomer in the cluster beam of B₁₂Au⁻. These aromatic compound clusters provide new examples for the Au/H isolobal analogy and the boronyl (BO) chemistry.