Electronic Structure and Optical Properties of the Thiolate-Protected Au₂₈(SMe)₂₀ Cluster

The recently reported crystal structure of the Au₂₈(TBBT)₂₀ cluster (TBBT: <i>p</i>-<i>tert</i>-butylbenzenethiolate) is analyzed with (time-dependent) density functional theory (TD-DFT). Bader charge analysis reveals a novel trimeric Au₃(SR)₄ binding motif. The cluster can be formulated as Au₁₄(Au₂(SR)₃)₄(Au₃(SR)₄)₂. The electronic structure of the Au₁₄⁶⁺ core and the ligand-protected cluster were analyzed, and their stability can be explained by formation of distorted eight-electron superatoms. Optical absorption and circular dichroism (CD) spectra were calculated and compared to the experiment. Assignment of handedness of the intrinsically chiral cluster is possible