Tailoring the Structure of 58-Electron Gold Nanoclusters: Au103S2(S-Nap)41 and Its Implications

We report the synthesis and crystal structure determination of a gold nanocluster with 103 gold atoms protected by 2 sulfidos and 41 thiolates (i.e., 2-naphthalene-thiolates, S-Nap), denoted as Au103S2(S-Nap)(41). The crystallographic, analysis reveals that the thiolate ligands on the nanocluster form local tetramers by intracluster interactions of C-H center dot center dot center dot pi and pi center dot center dot center dot pi stacking. The herringbone pattern formation via intercluster interactions is also observed, which leads to a linearly connected zigzag pattern in the single crystal. The kernel of the nanocluster is a Marks decahedron of Au-79, which is the same as the kernel of the previously reported Au-102(PMBA)(44) (pMBA =-SPh-p-COOH); this is a surprise given the much bulkier naphthalene-based ligand than pMBA, indicating the robustness of the decahedral structure as well as the 58-electron configuration. Despite the same kernel, the surface structure of Au-103 is quite different from that of Au-102, indicating the major role of ligands in constructing the surface structure. Other implications from Au-103 and Au-102 include (i) both nanoclusters show similar HOMO LUMO gap energy (i.e., E-g approximate to 0.45 eV), indicating the kernel is decisive for E-g while the surface is less critical; and (ii) significant differences are observed in the excited-state lifetimes by transient absorption spectroscopy analysis, revealing the kernel-to-surface relaxation pathway of electron dynamics. Overall, this work demonstrates the ligand-effected modification of the gold-thiolate interface independent of the kernel structure, which in turn allows one to map out the respective roles of kernel and surface in determining the electronic and optical properties of the 58e nanoclusters.