Polyhedral {Ag} and {Ag} Clusters: Synthesis, Structural Characterization and Third-Order Nonlinear Optical Properties.

Two polyhedral silver-thiolate clusters, [S@Ag(Tab)(MeCN)](PF) (Ag) and [Ag(Tab)(DMF)](PF) (Ag), were synthesized by using electroneutral Tab species as protective ligands (Tab=4-(trimethylammonio)benzenethiolate, DMF=N,N-dimethylformamide, MeCN=acetonitrile). Ag has a decahedral shape composed of eight pentagon {Ag} units and two square {Ag} units. The structure of Ag is a cuboctahedron, a classical Archimedean structure composed of six triangular faces and eight square faces. The former configuration is discovered in silver-thiolate cluster for the first time, possibly benefited from the more flexible coordination between the Tab ligand and Ag facilitated by the electropositive -N(CH) substituent group. Third-order nonlinear optical studies show that both clusters in DMF exhibit reverse saturate absorption response under the irradiation of 532 nm laser.