Structure of Au_(15)(SR)_(13) and Its Implication for the Origin of the Nucleus in Thiolated Gold Nanoclusters

摘要

Au_(15)(SR)_(13) is the smallest stable thiolated gold nanoduster experimentally identified so far, and its elusive structure may hold the key to the origin of the nucleus in the formation of thiolated gold nanoclusters. By an extensive exploration of possible isomers by density functional theory, we arrive at a novel structure for Au_(15)(SR)_(13) with high stability and whose optical absorption characteristics match those of the experiment. Different from the previous structures and the prevailing working hypothesis about the construction of thiolated gold nanoclusters, the Au_(15)(SR)_(13) model features a cyclic [Au(I)-SR] pentamer interlocked with one staple trimer motif protecting the tetrahedral Au_4 nucleus, together with another trimer motif. This structure suggests that Au_(15)(SR)_(13) is a transitional composition from an [Au(I)-SR]_x polymer such as Au_(10)(SR)_(10) to larger Au_n(SR)_m (n > m) clusters that have only the staple motifs and that the nucleation process starts from the Au_4 core.