Solution-Phase Structure and Bonding of Au₃₈(SR)₂₄ Nanoclusters from X-ray Absorption Spectroscopy

Understanding the atomic structure and structure−property relationship of Au−thiolate clusters is essential for advancing their fundamental studies and applications. However, a precise determination of the solution-phase structure and bonding of these clusters, albeit of its paramount importance in synthesis, processing, and applications, is still lacking. We report here solution-phase X-ray absorption spectroscopy (XAS) studies of thiolate-protected Au 38 nanoclusters. A significant bond expansion associated with an increase of Au d-electron density of states (DOS) has been observed upon solvation of Au 38 in toluene. These findings are accounted for by projected DOS calculations, which further illustrate the unique electronic behavior of Au 38 from a site-specific perspective. The impact of these findings on tuning the properties of Au−thiolate clusters is also discussed.