Chiral Structure of Thiolate-Protected 28-Gold-Atom Nanocluster Determined by X‑ray Crystallography

We report the crystal structure of a new nanocluster formulated as Au₂₈(TBBT)₂₀, where TBBT = 4<i>-tert-</i>butylbenzenethiolate. It exhibits a rod-like Au₂₀ kernel consisting of two interpenetrating cuboctahedra. The kernel is protected by four dimeric “staples” (-SR-Au-SR-Au-SR-) and eight bridging thiolates (-SR-). The unit cell of Au₂₈(TBBT)₂₀ single crystals contains a pair of enantiomers. The origin of chirality is primarily rooted in the rotating arrangement of the four dimeric staples as well as the arrangement of the bridging thiolates (quasi-<i>D</i>₂ symmetry). The enantiomers were separated by chiral HPLC and characterized by circular dichroism spectroscopy