Spontaneous Breaking and Remaking of the RS-Au-SR Staple in Self-assembled Ethylthiolate/Au(111) Interface

The stability of the self-assembled RS-Au-SR (R = CH2CH3)/Au(111) interface at room temperature has been investigated using scanning tunneling microscopy (STM) in conjunction with density functional theory (DFT) and MD calculations. The RS-Au-SR staple, also known as Au-adatom-dithiolate, assembles into staple rows along the [11 (2) over bar] direction. STM imaging reveals that while the staple rows are able to maintain a static global structure, individual staples within the row are subjected to constant breaking and remaking of the Au-SR bond. The C2S-Au-SC2/Au(111) interface is under a dynamic equilibrium and it is far from rigid. DFT/MD calculations show that a transient RS-Au-Au-SR complex can be formed when a free Au atom is added to the RS-Au-SR staple. The relatively high reactivity of the RS-Au-SR staple at room temperature could explain the reactivity of thiolate-protected Au nanoclusters, such as their ability to participate in ligand exchange and intercluster reactions.