The recently reported crystal structure of the Au₂₈(TBBT)₂₀ cluster (TBBT: para-tert-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.

We predict and analyze density-functional theory (DFT) -based structures for the recently isolated Au₄₀(SR)₂₄ cluster. Combining structural information extracted from ligand-exchange reactions, circular dichroism and transmission electron microscopy leads us to propose two families of low-energy structures that have a chiral Au-S framework on the surface. These families have a common geometrical motif where a non-chiral Au₂₆ bi-icosahedral cluster core is protected by 6 RS-Au-SR and 4 RS-Au-SR-Au-SR oligomeric units, analogously to the “Divide and Protectâ€� motif of known clusters Au₂₅(SR)18^-/0, Au₃₈(SR)₂₄ and Au₁₀₂(SR)₄₄. The strongly prolate shape of the proposed Au₂₆ core is supported by transmission electron microscopy. Density-of-state-analysis shows that the electronic structure of Au₄₀(SR)₂₄ can be interpreted in terms of a dimer of two 8-electron superatoms, where the 8 shell electrons are localized at the two icosahedral halves of the metal core. The calculated optical and chiroptical characteristics of the optimal chiral structure are in a fair agreement with the reported data for Au₄₀(SR)₂₄.