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 Au-28(TBBT)(20), where TBBT = 4-tert-butylbenzenethiolate. It exhibits a rod-like Au-20 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 Au-28(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-D-2 symmetry). The enantiomers were separated by chiral HPLC and characterized by circular dichroism spectroscopy.