Chemisorption-induced two- to three-dimensions structural transformations in gold pentamer (CO)(n)Au5(-) (n =0-5).

Understanding the geometry structures of gold clusters, especially with adsorbates, is essential for designing highly active gold nanocatalysts. Here, CO chemisorption onto the Au5(-) cluster is investigated using the density functional calculations. It is found that chemisorption of CO molecules can induce previously unreported two- to three-dimensions (3D) structural changes. Even a single CO chemisorption induces a major structural change to explain the huge blue-shift in photoelectron spectroscopy (PES). The apex site in the parent Au5(-) cluster is not always the most preferred site for the chemisorption, and two bridged adsorption CO molecules are observed in the lowest-energy (CO)3Au5(-) cluster. A clear splitting is observed in the first PES of (CO)4Au5 (-), and calculated planar and 3D geometries are likely coexisting in the cluster beam. The fifth CO adsorption leads to the structural transformation of Au5 skeleton to create more apex sites to accommodate five CO molecules. The structural properties, together with the vertical electron detachment energy (VDE) and binding energies calculations indicate that the chemisorption-saturated number is 5.