Unique Bonding Properties of the Au36(SR)24 Nanocluster with FCC-Like Core

The recent discovery on the total structure of Au-36(SR)(24), which was converted from biicosahedral Au-38(SR)(24), represents a surprising finding of a face-centered cubic (FCC)-like core structure in small gold-thiolate nano clusters Prior to this finding, the FCC feature was only expected for larger (nano)crystalline gold. Herein, we report results on the unique bonding properties of Au-36(SR)(24) that are associated with its FCC like core structure. Temperature dependent X-ray absorption spectroscopy (XAS) measurements at the Au L-3-edge, in association with ab initio calculations, show that the local structure and electronic behavior of Au-36(SR)(24) are of more molecule like nature, whereas its icosahedral counterparts such as Au-38(SR)(24) and Au-25(SR)(18) are more metal-like. Moreover, site specific S K-edge XAS studies indicate that the bridging motif for Au-36(SR)(24) has different bonding behavior from the staple motif from Au-38(SR)(24). Our findings highlight the important role of "pseudo"-Au-4 units within the FCC like Au-28 core in interpreting the bonding properties of Au-36(SR)(24) and suggest that FCC like structure in gold thiolate nanoclusters should be treated differently from its bulk counterpart.